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Initial mass of cathode = 1.0 g Final mass of cathode = 1.6 g Change in mass of cathode = 0.60 g (i)Determine the change in mass at the anode. Explain your answer. Mass decrease = 0.6g. Electrode ionization take place where the cathode increase in mass form the erosion of the anode (ii)Calculate the quantity of electricity required to deposit one mole of copper.(Cu =63.5) Q =It => 2 x 15 x 60 = 1800 coulombs Method 1 0.60 g of copper ->1800 coulombs 63.5 g -> 63.5 x 1800 = 190500 Coulombs 0.60 Method 2 Moles of Copper = Mass => 0.60 = 9.4488 x10 -3 moles Molar mass 63.5 9.4488 x10 -3 moles -> 1800 coulombs 1 Mole -> 1 x 1800 coulombs = 190500.381 coulombs 9.4488 x10 -3 moles (iii)Determine the oxidation number of copper produced at the cathode and hence the formula of its nitrate (V)salt (1 Faraday = 96500 Coulombs) 96500 Coulombs -> 1 Faraday 190500.381 coulombs -> 190500.381 coulombs x 1 96500 Coulombs = 1.9741 Faradays => 2F(whole number) Charge of copper = 2+ = Oxidation number => Valency of copper = 2 hence chemical formula of nitrate (V)salt = Cu (NO3)2
1 22.0.0 METALS (20 LESSONS) a)Introduction to metals The rationale of studying metals cannot be emphasized.Since ages, the world over, metals like gold and silver have been used for commercial purposes. The periodicity of alkali and alkaline earth metals was discussed in year 2 of secondary school education. This topic generally deals with: (a)Natural occurrence of the chief ores of the most useful metals for industrial /commercial purposes. (b)Extraction of these metals from their ores for industrial/ commercial purposes. (c)industrial/ commercial uses of these metals. (d)main physical and chemical properties /characteristic of the metals.
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(b)Extraction of these metals from their ores for industrial/ commercial purposes. (c)industrial/ commercial uses of these metals. (d)main physical and chemical properties /characteristic of the metals. The metals given detailed emphasis here are; Sodium, Aluminium, Iron, Zinc, Lead and Copper. 2 The main criteria used in extraction of metals is based on its position in the electrochemical/reactivity series and its occurrence on the earth’s crust. 1.SODIUM a) Natural occurrence Sodium naturally occurs as: (i)Brine-a concentrated solution of sodium chloride(NaCl(aq)) in salty seas and oceans. (ii)Rock salt-solid sodium chloride(NaCl(s) (iii)Trona-sodium sesquicarbonate(NaHCO3.Na2CO3.2H2O) especially in lake Magadi in Kenya. (iv)Chile saltpeter-sodium nitrate(NaNO3) Position on the earth’s crust If near the surface ,open cast mining / quarrying is used If deep on the earth’s crust deep mining is used If the ore is low grade oil, water, and air is blown forming a froth(froth flotation) to concentrate The ore first roasted if it is a carbonate or sulphide of Zinc, Iron, Tin, Lead, and Copper to form the oxide Electrolysis of the ore is used for reactive metals; Potassium, Sodium, Magnesium, Calcium, Aluminium The oxide is reduced using carbon/ carbon(II) oxide in a furnace if it is made of Zinc ,Tin, Lead ,Copper and Iron
3 b)(i) Extraction of Sodium from brine/Manufacture of Sodium hydroxide/The flowing mercury cathode cell/ TheCaster-Keller process I.Raw materials (i) Brine-concentrated solution of sodium chloride (NaCl (aq)) from salty seas and oceans. (ii)Mercury (iii)Water from river/lakes II. Chemical processes Salty lakes, seas and oceans contain large amount of dissolved sodium chloride (NaCl (aq)) solution. This solution is concentrated to form brine which is fed into an electrolytic chamber made of suspended Carbon graphite/titanium as the anode and a continuous flow of Mercury as the cathode.Note Mercury is the only naturally occurring known liquid metal at room temperature and pressure Questions I. Write the equation for the decomposition of the electrolyte during the electrolytic process.
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Chemical processes Salty lakes, seas and oceans contain large amount of dissolved sodium chloride (NaCl (aq)) solution. This solution is concentrated to form brine which is fed into an electrolytic chamber made of suspended Carbon graphite/titanium as the anode and a continuous flow of Mercury as the cathode.Note Mercury is the only naturally occurring known liquid metal at room temperature and pressure Questions I. Write the equation for the decomposition of the electrolyte during the electrolytic process. H2O(l) H+(aq) + OH-(aq) NaCl(aq) Na+(aq) + Cl-(aq) II. Name the ions present in brine that moves to the: (i)Mercury cathode; H+(aq) , Na+(aq) (ii)Titanium/graphite; OH-(aq), Cl-(aq) III. Write the equation for the reaction that take place during the electrolytic process at the; Cathode; 2Na+(aq) + 2e 2Na(s) Anode; 2Cl-(aq) Cl2(g) + 2e Note (i)Concentration of 2Cl-(aq) ions is higher than OH- ions causing overvoltage thus blocking OH- ions from being discharged at the anode. (ii)Concentration of Na+(aq) ions is higher than H+ ions causing overvoltage thus blocking H+ ions from being discharged at the cathode. 4 IV. Name the products of electrolysis in the flowing mercury-cathode cell. (i)Mercury cathode; Sodium metal as grey soft metal/solid (ii)Titanium/graphite; Chlorine gas as a pale green gas that turns moist blue/red litmus papers red then bleaches both. Chlorine gas is a very useful by-product in; (i)making (PVC)polyvinylchloride(polychloroethene) pipes. (ii)chlorination/sterilization of water to kill germs. (iii)bleaching agent (iv)manufacture of hydrochloric acid. Sodium produced at the cathode immediately reacts with the mercury at the cathode forming sodium amalgam(NaHg) liquid that flow out of the chamber. Na(s) + Hg(l) Na Hg (l) Sodium amalgam is added distilled water and reacts to form sodium hydroxide solution, free mercury and Hydrogen gas.
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(iii)bleaching agent (iv)manufacture of hydrochloric acid. Sodium produced at the cathode immediately reacts with the mercury at the cathode forming sodium amalgam(NaHg) liquid that flow out of the chamber. Na(s) + Hg(l) Na Hg (l) Sodium amalgam is added distilled water and reacts to form sodium hydroxide solution, free mercury and Hydrogen gas. 2Na Hg (l) + 2H2O(l) 2NaOH (aq) + 2Hg(l) + H2(g) Hydrogen gas is a very useful by-product in; (i)making ammonia gas in the Haber process (ii)manufacture of hydrochloric acid (iii)in weather balloons to forecast weather (iv)as rocket fuel As the electrolysis of brine continues, the concentration of Cl-ions decreases and oxygen gas start being liberated. Continuous feeding of the electrolyte is therefore very necessary. III.Uses of sodium hydroxide The sodium hydroxide produced is very pure and is used mainly in: (i)Making soapy and soapless detergents. (ii)making cellulose acetate/rayon IV. Diagram showing the Manufacture of Sodium hydroxide from the flowing Mercury-cathode cell. 5 3 V. Environmental effects of Manufacture of Sodium hydroxide from the flowing Mercury-cathode cell. 1.Most of the Mercury used at the cathode is recycled ; (i)to reduce the cost because mercury is expensive (ii)to reduce pollution because mercury kills marine life. (iii)because it causes chromosomal/genetic mutation to human beings. 2.Chlorine produced at the anode; (i)has a pungent irritating smell that causes headache to human beings. (ii)bleaches any wet substance. (iii)dissolves water to form both hydrochloric acid and chloric(I)acid Both cause marine pollution and stomach upsets. b)(ii) Extraction of sodium from rock salt/The Downs cell/process
6 I. Raw materials (i)Rock salt/solid sodium chloride (ii)calcium(II)chloride II. Chemical processes. Rock salt/ solid sodium chloride is heated to molten state in a chamber lined with fire bricks on the outside. Sodium chloride has a melting point of about 800oC.
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Chemical processes. Rock salt/ solid sodium chloride is heated to molten state in a chamber lined with fire bricks on the outside. Sodium chloride has a melting point of about 800oC. A little calcium (II) chloride is added to lower the melting point of the electrolyte to about 600oC. The molten electrolyte is the electrolyzed in a carbon graphite anode suspended at the centre and surrounded by steel cathode. Questions I. Write the equation for the decomposition of the electrolyte during the electrolytic process. NaCl(l) Na+(l) + Cl-(l) Note: In absence of water, the ions are in liquid state. II. Name the ions present in molten rock salt that move to the; (i)Steel cathode -Na+(l) (ii)Carbon graphite anode- Cl-(l) III. Write the equation for the reaction that take place during the electrolytic process at the; (i)Steel cathode 2Na+(l) + 2e 2Na(l) (ii)Carbon graphite anode 2Cl-(l) Cl2(g) + 2e IV. Name the products of electrolysis in the Downs cell at; (i)Cathode: Grey solid Sodium metal is less dense than the molten electrolyte and therefore float on top of the cathode to be periodically tapped off. (ii)Anode: Pale green chlorine gas that turns moist/damp/wet blue/red litmus papers red then bleaches/decolorizes both. Chlorine gas is again a very useful by-product in; (i)making (PVC)polyvinylchloride(polychloroethene) pipes. (ii)chlorination/sterilization of water to kill germs. (iii)bleaching agent (iv)manufacture of hydrochloric acid. 7 A steel diaphragm/gauze is suspended between the electrodes to prevent recombination of sodium at the cathode and chlorine gas at the anode back to sodium chloride. III. Diagram showing the Downs cell/process for extraction of sodium IV. Uses of sodium. 1.Sodium vapour is used as sodium lamps to give a yellow light in street lighting.
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Diagram showing the Downs cell/process for extraction of sodium IV. Uses of sodium. 1.Sodium vapour is used as sodium lamps to give a yellow light in street lighting. 2.Sodium is used in making very useful sodium compounds like; (i)Sodium hydroxide(NaOH) (ii)Sodium cyanide(NaCN) (iii)Sodium peroxide(Na2O2) (iv)Sodamide(NaNH2) 3.An alloy of Potassium and Sodium is used as coolant in nuclear reactors. V. Environmental effects of Downs cell. 1.Chlorine produced at the anode;
8 (i)has a pungent irritating smell that causes headache to human beings. (ii)bleaches any wet substance. (iii)dissolves water to form both hydrochloric acid and chloric(I)acid Both cause marine pollution and stomach upsets. 2.Sodium metal rapidly react with traces of water to form alkaline Sodium hydroxide(NaOH(aq))solution. This raises the pH of rivers/lakes killing aquatic lifein case of leakages. VI. Test for presence of Na. If a compound has Na+ ions in solid/molten/aqueous state then it changes a non-luminous clear/colourless flame to a yellow coloration but does not burn Experiment Scoop a portion of sodium chloride crystals/solution in a clean metallic spatula. Introduce it to a clear /colourless Bunsen flame. Observation Inference Yellow coloration Na+ Practice (i)Calculate the time taken in hours for 230kg of sodium to be produced in the Downs cell when a current of 120kA is used. (ii)Determine the volume of chlorine released to the atmosphere.
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10 (a)Calculate the concentration of the resulting solution in moles per litre. (b)The volume of gaseous products formed at s.t.p(1 mole of gas =22.4 dm3 at s.t.p) Chemical equation at Caster-Keller tank 2Na(s) + 2H2O(l) -> 2NaOH(aq) + H2 (g) Mole ratio Na:NaOH = 2 : 2 => 1:1 Moles Na =10000moles=10000moles of NaOH 25000dm3 ->10000moles of NaOH 1dm3 -> 10000 x 1 = 0.4M / 0.4 moles/dm3 25000 Mole ratio Na: H2 (g) = 2 : 1 Moles Na = 10000moles = 5000moles of H2 (g) Volume of H2 (g) = moles x molar gas volume at s.t.p => 5000moles x 22.4 dm3 =120,000dm3 (iv)The solution formed was further diluted with water for a titration experiment. 25.0 cm3 of the diluted solution required 20.0cm3 of 0.2M sulphuric(VI)acid for complete neutralization. Calculate the volume of water added to the diluted solution before titration.
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(b)The volume of gaseous products formed at s.t.p(1 mole of gas =22.4 dm3 at s.t.p) Chemical equation at Caster-Keller tank 2Na(s) + 2H2O(l) -> 2NaOH(aq) + H2 (g) Mole ratio Na:NaOH = 2 : 2 => 1:1 Moles Na =10000moles=10000moles of NaOH 25000dm3 ->10000moles of NaOH 1dm3 -> 10000 x 1 = 0.4M / 0.4 moles/dm3 25000 Mole ratio Na: H2 (g) = 2 : 1 Moles Na = 10000moles = 5000moles of H2 (g) Volume of H2 (g) = moles x molar gas volume at s.t.p => 5000moles x 22.4 dm3 =120,000dm3 (iv)The solution formed was further diluted with water for a titration experiment. 25.0 cm3 of the diluted solution required 20.0cm3 of 0.2M sulphuric(VI)acid for complete neutralization. Calculate the volume of water added to the diluted solution before titration. Chemical equation 2NaOH(aq) + H2SO4(aq) -> Na2SO4(aq) + H2O(l) Moles ratio NaOH : H2SO4 = 2 : 1 Moles ratio H2SO4 = molarity x volume => 0.2M x 20 1000 1000 =4.0 x 10-3 moles Moles NaOH = 2 x 4.0 x 10-3 moles= 8.0 x 10-3 moles Molarity of NaOH= Moles x 1000=> 8.0 x 10-3 moles x 1000 volume 25 =0.16 molesdm-3 /M Volume used during dilution C1V1 = C2V2 => 0.4M x V1 = 0.16 M x 25
11 = 0.16 M x 25 = 10cm3 0.4 (a) Below is a simplified diagram of the Downs Cell used for the manufacture of sodium.
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25.0 cm3 of the diluted solution required 20.0cm3 of 0.2M sulphuric(VI)acid for complete neutralization. Calculate the volume of water added to the diluted solution before titration. Chemical equation 2NaOH(aq) + H2SO4(aq) -> Na2SO4(aq) + H2O(l) Moles ratio NaOH : H2SO4 = 2 : 1 Moles ratio H2SO4 = molarity x volume => 0.2M x 20 1000 1000 =4.0 x 10-3 moles Moles NaOH = 2 x 4.0 x 10-3 moles= 8.0 x 10-3 moles Molarity of NaOH= Moles x 1000=> 8.0 x 10-3 moles x 1000 volume 25 =0.16 molesdm-3 /M Volume used during dilution C1V1 = C2V2 => 0.4M x V1 = 0.16 M x 25
11 = 0.16 M x 25 = 10cm3 0.4 (a) Below is a simplified diagram of the Downs Cell used for the manufacture of sodium. Study it and answer the questions that follow (i)What material is the anode made of? Give a reason (2 mks) Carbon graphite/Titanium This because they are cheap and inert/do not influence/affect the products of electrolysis (ii) What precaution is taken to prevent chlorine and sodium from re- combination? ( 1 mks) Using a steel gauze/diaphragm separating the cathode from anode (iii) Write an ionic equation for the reaction in which chlorine gas is formed ( 1mk) 2Cl-(l) -> Cl2(g) + 2e (b) In the Downs process, (used for manufacture of sodium), a certain salt is added to lower the melting point of sodium chloride from about 8000C to about 6000C.
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Study it and answer the questions that follow (i)What material is the anode made of? Give a reason (2 mks) Carbon graphite/Titanium This because they are cheap and inert/do not influence/affect the products of electrolysis (ii) What precaution is taken to prevent chlorine and sodium from re- combination? ( 1 mks) Using a steel gauze/diaphragm separating the cathode from anode (iii) Write an ionic equation for the reaction in which chlorine gas is formed ( 1mk) 2Cl-(l) -> Cl2(g) + 2e (b) In the Downs process, (used for manufacture of sodium), a certain salt is added to lower the melting point of sodium chloride from about 8000C to about 6000C. (i) Name the salt that is added (1mk) Calcium chloride (ii) State why it is necessary to lower the temperature(1mk) To reduce the cost of production
12 (c) Explain why aqueous sodium chloride is not suitable as an electrolyte for the manufacture of sodium in the Downs process( 2mk) The sodium produced react explosively/vigorously with water in the aqueous sodium chloride (d) Sodium metal reacts with air to form two oxide. Give the formulae of two oxides ( 1mk) Na2O Sodium oxide(in limited air) Na2O2 Sodium peroxide(in excess air) 2.ALUMINIUM a)Natural occurrence Aluminium is the most common naturally occurring metal. It makes 7% of the earths crust as: (i)Bauxite ore- Hydrated aluminium oxide(Al2O3.2H2O) (ii)Mica ore-Potassium aluminium silicate(K2Al2Si6O16) (iii)China clay ore- aluminium silicate (Al2Si6O16) (iv)Corrundum-Anhydrous aluminium oxide(Al2O3) b)Extraction of aluminium from Bauxite/Halls cell/process) The main ore from which aluminium is extracted is Bauxite ore- hydrated aluminium oxide(Al2O3.2H2O). The ore is mined by open-caste mining method/quarrying where it is scooped together with silica/sand/silicon(IV)oxide (SiO2) and soil/ iron(III)oxide (Fe2O3) as impurities.
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Give the formulae of two oxides ( 1mk) Na2O Sodium oxide(in limited air) Na2O2 Sodium peroxide(in excess air) 2.ALUMINIUM a)Natural occurrence Aluminium is the most common naturally occurring metal. It makes 7% of the earths crust as: (i)Bauxite ore- Hydrated aluminium oxide(Al2O3.2H2O) (ii)Mica ore-Potassium aluminium silicate(K2Al2Si6O16) (iii)China clay ore- aluminium silicate (Al2Si6O16) (iv)Corrundum-Anhydrous aluminium oxide(Al2O3) b)Extraction of aluminium from Bauxite/Halls cell/process) The main ore from which aluminium is extracted is Bauxite ore- hydrated aluminium oxide(Al2O3.2H2O). The ore is mined by open-caste mining method/quarrying where it is scooped together with silica/sand/silicon(IV)oxide (SiO2) and soil/ iron(III)oxide (Fe2O3) as impurities. The mixture is first dissolved in hot concentrated sodium/potassium hydroxide solution. The alkalis dissolve both bauxite and silicon(IV)oxide. This is because bauxite is amphotellic while silicon(IV)oxide is acidic. Iron(III)oxide (Fe2O3) is filtered of /removed as a residue. Carbon(IV)oxide is bubbled into the filtrate to precipitate aluminium (III) hydroxide (Al(OH)3) as residue. The aluminium (III) hydroxide (Al(OH)3) residue is filtered off. Silicon (IV)oxide remain in the solution as filtrate. Aluminium (III) hydroxide (Al(OH)3) residue is then heated to form pure aluminium (III)oxide(Al2O3) 2Al(OH)3 (s) Al2O3 (s) + 3H2O(l)
13 Pure aluminium (III)oxide (Al2O3) has a very high melting point of 2015oC. Alot of energy is required to melt the oxide.
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Silicon (IV)oxide remain in the solution as filtrate. Aluminium (III) hydroxide (Al(OH)3) residue is then heated to form pure aluminium (III)oxide(Al2O3) 2Al(OH)3 (s) Al2O3 (s) + 3H2O(l)
13 Pure aluminium (III)oxide (Al2O3) has a very high melting point of 2015oC. Alot of energy is required to melt the oxide. It is therefore dissolved first in molten cryolite /sodium hexafluoroaluminate (III)/Na3AlF6 to lower the melting point to about 800oC. The molten electrolyte is put in the Hall cell made up of a steel tank lined with carbon graphite and an anode suspended into the electrolyte. During the electrolysis: (i)At the cathode; 4Al3+(l) + 12e 4Al(l) (ii) At the anode; 6O2-(l) 3O2(g) + 12e Aluminium is denser than the electrolyte therefore sink to the bottom of the Hall cell. At this temperature ,the Oxygen evolved/produced at the anode reacts with carbon anode to form carbon(IV)oxide gas that escape to the atmosphere. C(s) + O2(g) CO2(g) The anode thus should be continuously replaced from time to time. Flow chart summary of extraction of aluminium from Bauxite Bauxite(Al2O3.2H2O) ore with impurities Fe2O3 and SiO2 Powdered mixture Crush (increase surface area) Hot concentrated sodium hydroxide
14 c) Diagram showing the Hall cell / process for extraction of Bauxite Iron(III)oxide- Fe2O3 as residue Sodium aluminate (NaAl(OH)4) and sodium silicate (Na2SiO3) as filtrate Carbon(IV)oxide Aluminium hydroxide (Al(OH)3) as residue Sodium silicate (Na2SiO3) Aluminium (III) Oxide Roast at 1000oC Cryolite Electrolysis Oxygen gas at anode Pure aluminium sinks in Hall cell
15 d)Uses of aluminium (i) In making aeroplane parts, buses, tankers, furniture because aluminium is very light.
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At this temperature ,the Oxygen evolved/produced at the anode reacts with carbon anode to form carbon(IV)oxide gas that escape to the atmosphere. C(s) + O2(g) CO2(g) The anode thus should be continuously replaced from time to time. Flow chart summary of extraction of aluminium from Bauxite Bauxite(Al2O3.2H2O) ore with impurities Fe2O3 and SiO2 Powdered mixture Crush (increase surface area) Hot concentrated sodium hydroxide
14 c) Diagram showing the Hall cell / process for extraction of Bauxite Iron(III)oxide- Fe2O3 as residue Sodium aluminate (NaAl(OH)4) and sodium silicate (Na2SiO3) as filtrate Carbon(IV)oxide Aluminium hydroxide (Al(OH)3) as residue Sodium silicate (Na2SiO3) Aluminium (III) Oxide Roast at 1000oC Cryolite Electrolysis Oxygen gas at anode Pure aluminium sinks in Hall cell
15 d)Uses of aluminium (i) In making aeroplane parts, buses, tankers, furniture because aluminium is very light. (ii)Making duralumin-an alloy which is harder and has a higher tensile strength (iii)Making utensils,sauce pans,spoons because it is light and good conductor of electricity. (iv)Making overhead electric cables because it is light,ductile and good conductor of electricity. (iv)Used in the thermite process for production of Manganese, Chromium amd Titanium. e) Environmental effects of extracting aluminium from Bauxite. Carbon(IV)oxide gas that escape to the atmosphere is a green house gas that causes global warming. Bauxite is extracted by open caste mining that causes soil/environmental degradation. 16 f) Test for presence of Al3+ If an ore is suspected to contain Al3+ it is; (i)added hot concentrated sulphuric(VI)/Nitric(V)acid to free the ions present. (ii)the free ions are then added a precipitating reagent like 2M sodium hydroxide /2M aqueous ammonia.
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Bauxite is extracted by open caste mining that causes soil/environmental degradation. 16 f) Test for presence of Al3+ If an ore is suspected to contain Al3+ it is; (i)added hot concentrated sulphuric(VI)/Nitric(V)acid to free the ions present. (ii)the free ions are then added a precipitating reagent like 2M sodium hydroxide /2M aqueous ammonia. Observation Inference White precipitate in excess 2M NaOH(aq) Pb2+ , Al3+, Zn2+ White precipitate in excess 2M NH3(aq) Pb2+ , Al3+ No black precipitate on adding Na2S(aq) Al3+ No white precipitate on adding either NaCl(aq),HCl(aq),H2SO4(aq),Na2SO4(aq) Al3+ Practice 1.An unknown rock X was discovered in Ukraine. Test with dilute sulphuric (VI)acid shows rapid effervescence with production of a colourless gas A that forms a white precipitate with lime water and colourless solution B. On adding 3cm3 of 2M sodium hydroxide, a white precipitate C is formed that dissolves to form a colourless solution D on adding more sodium hydroxide. On adding 2M aqueous ammonia, a white precipitate E is formed which persist in excess aqueous ammonia.On which on adding 5cm3 of 1M Lead(II)nitrate(V) to F a white precipitate G is formed which remains on heating. Identify: A Hydrogen/H2 B Aluminium sulphate(VI)/Al2(SO4) 3 C Aluminium hydroxide/ Al(OH4) 3 D Tetrahydroxoaluminate(III)/ [Al(OH4) 3] - E Aluminium hydroxide/ Al(OH) 3 F Aluminium chloride/ AlCl3
17 2.Aluminium is obtained from the ore with the formula Al2O3. 2H2O. The ore is first heated and refined to obtain pure aluminium oxide (Al2O3). The oxide is then electrolysed to get Aluminium and oxygen gas using carbon anodes and carbon as cathode.
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2H2O. The ore is first heated and refined to obtain pure aluminium oxide (Al2O3). The oxide is then electrolysed to get Aluminium and oxygen gas using carbon anodes and carbon as cathode. Give the common name of the ore from where aluminium is extracted from ½ mark What would be the importance of heating the ore first before refining it?1 mark To remove the water of crystallization The refined ore has to be dissolved in cryolite first before electrolysis. Why is this necessary? 1½ mark To lower the melting point of aluminium oxide from about 2015oC to 900oC so as to lower /reduce cost of production Why are the carbon anodes replaced every now and then in the cell for electrolysing aluminium oxide? 1 mark Oxygen produced at anode react with carbon to form carbon(IV)oxide gas that escape State two uses of aluminium In making aeroplane parts, buses, tankers, utensils, sauce pans,spoons Making overhead electric cables Making duralumin
18 3. IRON a)Natural occurrence Iron is the second most common naturally occurring metal. It makes 4% of the earths crust as: (i)Haematite(Fe2O3) (ii)Magnetite(Fe3O4) (iii)Siderite(FeCO3) b)The blast furnace for extraction of iron from Haematite and Magnetite a)Raw materials: (i)Haematite(Fe2O3) (ii)Magnetite(Fe3O4) (iii)Siderite(FeCO3) (iv)Coke/charcoal/ carbon (v)Limestone b)Chemical processes: Iron is usually extracted from Haematite (Fe2O3), Magnetite(Fe3O4) Siderite (FeCO3).These ores contain silicon(IV)oxide(SiO2) and aluminium(III)oxide (Al2O3) as impurities. When extracted from siderite, the ore must first be roasted in air to decompose the iron(II)Carbonate to Iron(II)oxide with production of carbon(IV)oxide gas: FeCO3(s) FeO(s) + CO2(g) Iron(II)oxide is then rapidly oxidized by air to iron(III)oxide(Haematite).
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IRON a)Natural occurrence Iron is the second most common naturally occurring metal. It makes 4% of the earths crust as: (i)Haematite(Fe2O3) (ii)Magnetite(Fe3O4) (iii)Siderite(FeCO3) b)The blast furnace for extraction of iron from Haematite and Magnetite a)Raw materials: (i)Haematite(Fe2O3) (ii)Magnetite(Fe3O4) (iii)Siderite(FeCO3) (iv)Coke/charcoal/ carbon (v)Limestone b)Chemical processes: Iron is usually extracted from Haematite (Fe2O3), Magnetite(Fe3O4) Siderite (FeCO3).These ores contain silicon(IV)oxide(SiO2) and aluminium(III)oxide (Al2O3) as impurities. When extracted from siderite, the ore must first be roasted in air to decompose the iron(II)Carbonate to Iron(II)oxide with production of carbon(IV)oxide gas: FeCO3(s) FeO(s) + CO2(g) Iron(II)oxide is then rapidly oxidized by air to iron(III)oxide(Haematite). 4FeO(s) + O2(g) 2Fe2O3(s) Haematite (Fe2O3), Magnetite(Fe3O4), coke and limestone are all then fed from top into a tall (about 30metres in height) tapered steel chamber lined with refractory bricks called a blast furnace. The furnace is covered with inverted double cap to prevent/reduce amount of any gases escaping . Near the base/bottom, blast of hot air at about 1000K (827oC) is driven/forced into the furnace through small holes called Tuyeres. As the air enters ,it reacts with coke/charcoal/carbon to form carbon(IV)oxide gas. This reaction is highly exothermic. C(s)+ O2(g) CO2 (g) ∆H = -394kJ
19 This raises the temperature at the bottom of the furnace to about 2000K(1650oC).As Carbon(IV)oxide gas rises up the furnace it reacts with more coke to form carbon(II)oxide gas.This reaction is endothermic.
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As the air enters ,it reacts with coke/charcoal/carbon to form carbon(IV)oxide gas. This reaction is highly exothermic. C(s)+ O2(g) CO2 (g) ∆H = -394kJ
19 This raises the temperature at the bottom of the furnace to about 2000K(1650oC).As Carbon(IV)oxide gas rises up the furnace it reacts with more coke to form carbon(II)oxide gas.This reaction is endothermic. CO2 (g) + C(s) 2CO (g) ∆H = +173kJ Carbon(II)oxide gas is a strong reducing agent that reduces the ores at the upper parts of the furnace where temperatures are about 750K(500oC) i.e. For Haematite; Fe2O3 (s) + 3CO(g) 2Fe(s) + CO2(g) For Magnetite; Fe3O4 (s) + 4CO(g) 3Fe(s) + 4CO2(g) Iron is denser than iron ore. As it falls to the hotter base of the furnace it melts and can easily be tapped off. Limestone fed into the furnace decomposes to quicklime/calcium oxide and produce more carbon(IV)oxide gas. CaCO3(s) CaO(s) + CO2(g) Quicklime/calcium oxide reacts with the impurities silicon(IV)oxide(SiO2) and aluminium(III)oxide(Al2O3)in the ore to form calcium silicate and calcium aluminate. CaO(s) + SiO2(s) CaSiO3 (l) CaO(s) + Al2O3(s) Ca Al2O4 (l) Calcium silicate and calcium aluminate mixture is called slag.Slag is denser than iron ore but less dense than iron therefore float on the pure iron. It is tapped at different levels to be tapped off for use in: (i)tarmacing roads (ii) cement manufacture (iii)as building construction material (c)Uses of Iron Iron obtained from the blast furnace is hard and brittle. It is called Pig iron. It is remelted, added scrap steel then cooled. This iron is called cast iron. Iron is mainly used to make: (i)gates ,pipes, engine blocks, rails, charcoal iron boxes,lamp posts because it is cheap.
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It is remelted, added scrap steel then cooled. This iron is called cast iron. Iron is mainly used to make: (i)gates ,pipes, engine blocks, rails, charcoal iron boxes,lamp posts because it is cheap. 20 (ii)nails, cutlery, scissors, sinks, vats, spanners,steel rods, and railway points from steel. Steel is an alloy of iron with carbon, and/or Vanadium, Manganese, Tungsten, Nickel ,Chromium. It does not rust/corrode like iron. e) Environmental effects of extracting Iron from Blast furnace (i)Carbon(IV)oxide(CO2) gas is a green house gas that causes/increases global warming if allowed to escape/leak from the furnace. (ii)Carbon(II)oxide(CO)gas is a highly poisonous/toxic odourless gas that can kill on leakage. It is preferentially absorbed by the haemoglobin in mammals instead of Oxygen to form a stable compound that reduce free hemoglobin in the blood. (iii) Haematite (Fe2O3), Magnetite(Fe3O4) and Siderite (FeCO3) are extracted through quarrying /open cast mining that cause soil / environmental degradation . 21 f) Test for the presence of Iron Iron naturally exist in its compound as Fe2+ /Fe3+ If an ore is suspected to contain Fe2+ /Fe3+ it is; (i)added hot concentrated sulphuric(VI)/Nitric(V)acid to free the ions present. (ii)the free ions are then added a precipitating reagent like 2M sodium hydroxide /2M aqueous ammonia which forms; I) an insoluble green precipitate in excess of 2M sodium hydroxide /2M aqueous ammonia if Fe2+ ions are present. I) an insoluble brown precipitate in excess of 2M sodium hydroxide /2M aqueous ammonia if Fe2+ ions are present.
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21 f) Test for the presence of Iron Iron naturally exist in its compound as Fe2+ /Fe3+ If an ore is suspected to contain Fe2+ /Fe3+ it is; (i)added hot concentrated sulphuric(VI)/Nitric(V)acid to free the ions present. (ii)the free ions are then added a precipitating reagent like 2M sodium hydroxide /2M aqueous ammonia which forms; I) an insoluble green precipitate in excess of 2M sodium hydroxide /2M aqueous ammonia if Fe2+ ions are present. I) an insoluble brown precipitate in excess of 2M sodium hydroxide /2M aqueous ammonia if Fe2+ ions are present. Observation Inference green precipitate in excess 2M NaOH(aq) Fe2+ green precipitate in excess 2M NH3(aq) Fe2+ brown precipitate in excess 2M NaOH(aq) Fe3+ brown precipitate in excess 2M NH3(aq) Fe3+ Practice questions
22 4.COPPER a)Natural occurrence Copper is found as uncombined element/metal on the earths crust in Zambia, Tanzania, USA and Canada .The chief ores of copper are: (i)Copper pyrites(CuFeS2) (ii)Malachite(CuCO3.Cu(OH)2) (iii)Cuprite(Cu2O) b)Extraction of copper from copper pyrites. Copper pyrites are first crushed into fine powder. The powdered ore is the added water and oil. The purpose of water is to dissolve hydrophilic substances/particle. The purpose of oil is to make cover copper ore particle so as to make it hydrophobic Air is blown through the mixture. Air creates bubbles that stick around hydrophobic copper ore. The air bubbles raise through buoyancy small hydrophobic copper ore particles to the surface. A concentrated ore floats at the top as froth. This is called froth flotation. The concentrated ore is then skimmed off.The ore is then roasted in air to form copper(I)sulphide ,sulphur(IV)oxide and iron (II) oxide.
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A concentrated ore floats at the top as froth. This is called froth flotation. The concentrated ore is then skimmed off.The ore is then roasted in air to form copper(I)sulphide ,sulphur(IV)oxide and iron (II) oxide. 2CuFeS2(s) + 4O2(g) Cu2S(s) + 3SO2(g) + 2FeO(s) Limestone (CaCO3) and silicon(IV)oxide (SiO2) are added and the mixture heated in absence of air.Silicon(IV)oxide (SiO2) reacts with iron (II) oxide to form Iron silicate which constitutes the slag and is removed. FeO(s) + SiO2(s) FeSiO3(s) The slag separates off from the copper(I)sulphide. Copper(I)sulphide is then heated in a regulated supply of air where some of it is converted to copper (I) oxide. 2Cu2S (s) + 3O2(g) 2Cu2S(s) + 2SO2(g) The mixture then undergo self reduction in which copper(I)oxide is reduced by copper(I)sulphide to copper metal. Cu2S (s) + 2Cu2O (s) 6Cu (s) + SO2(g) The copper obtained has Iron, sulphur and traces of silver and gold as impurities.It is therefore about 97.5% pure. It is refined by electrolysis/electrolytic method. During the electrolysis of refining copper, the impure copper is made the anode and a small pure strip is made the cathode. Electrode ionization takes place where: At the anode;
23 Cu(s) Cu2+ (aq) + 2e Note: Impure copper anode dissolves/erodes into solution and decreases in size. At the Cathode; Cu2+ (aq) + 2e Cu(s) Note: The copper ions in the electrolyte(CuSO4) are reduced and deposited as copper metal at the cathode. The copper obtained is 99.98% pure. Valuable traces of silver and gold collect at the bottom of the electrolytic cell as sludge. It is used to finance the extraction of copper pyrites.
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The copper obtained is 99.98% pure. Valuable traces of silver and gold collect at the bottom of the electrolytic cell as sludge. It is used to finance the extraction of copper pyrites. (c)Flow chart summary of extraction of copper from Copper pyrites Copper pyrites(CuFeS2) ore with impurities Fe2O3 and SiO2 Froth Crush (increase surface area) Oil Concentration chamber 1st roasting chamber Silicon(IV) oxide Smelting furnace 2nd roasting furnace Calcium aluminate (CaAl2O4)slag Limestone Sulphur(IV)Oxide Iron Silicate (FeSiO3)Slag Water Excess air Limited air Sulphur(IV)Oxide Self reduction Impure copper Rocky impurities Cu2S Cu2S, Cu2O Electrolysis using Copper electrodes
24 Electrolytic purification of impure copper d) Uses of copper Copper is mainly used in: (i)making low voltage electric cables,contact switches, cockets and plugs because it is a good conductor of electricity. (ii)Making solder because it is a good thermal conductor. (iii)Making useful alloys e.g. -Brass is an alloy of copper and Zinc(Cu/Zn) -Bronze is an alloy of copper and Tin(Cu/Sn) -German silver is an alloy of copper ,Zinc and Nickel(Cu/Zn/Ni) (iv)Making coins and ornaments. e) Environmental effects of extracting copper from Copper pyrites (i)Sulphur(IV)oxide is a gas that has a pungent poisonous smell that causes head ache to human in high concentration. (ii)Sulphur(IV)oxide gas if allowed to escape dissolves in water /rivers/rain to form weak sulphuric(IV)acid lowering the pH of the water leading to marine pollution, accelerated corrosion/rusting of metals/roofs and breathing problems to human beings. Anode; Impure Copper eroded. Cathode; Pure Copper deposited. 25 (iii)Copper is extracted by open caste mining leading to land /environmental /soil degradation.
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Anode; Impure Copper eroded. Cathode; Pure Copper deposited. 25 (iii)Copper is extracted by open caste mining leading to land /environmental /soil degradation. f) Test for the presence of copper in an ore Copper naturally exist in its compound as Cu2+ /Cu+ Copper (I) / Cu+ is readily oxidized to copper(II)/ Cu2+ If an ore is suspected to contain Cu2+ /Cu+ it is; (i)added hot concentrated sulphuric(VI)/Nitric(V)acid to free the ions present. (ii)the free ions are then added a precipitating reagent; 2M sodium hydroxide /2M aqueous ammonia which forms; I) an insoluble blue precipitate in excess of 2M sodium hydroxide if Cu2+ ions are present. I) an insoluble blue precipitate in 2M aqueous ammonia that dissolve to royal/deep blue solution in excess if Cu2+ ions are present. Observation Inference blue precipitate in excess 2M NaOH(aq) Cu2+ blue precipitate,dissolve to royal/deep blue solution in excess 2M NH3(aq) Cu2+ g)Sample questions Copper is extracted from copper pyrites as in the flow chart outlined below. Study it and answer the questions that follow
26 5.ZINC and LEAD a)Natural occurrence Zinc occurs mainly as: (i)Calamine-Zinc carbonate(ZnCO3) (ii)Zinc blende-Zinc sulphide(ZnS) Lead occurs mainly as Galena-Lead(II)Sulphide mixed with Zinc blende: b)Extraction of Zinc/Lead from Calamine ,Zinc blende and Galena. During extraction of Zinc , the ore is first roasted in air: For Calamine Zinc carbonate decompose to Zinc oxide and carbon(IV) oxide gas. ZnCO3(s) ZnO(s) + CO2(g) Zinc blende does not decompose but reacts with air to form Zinc oxide and sulphur(IV) oxide gas. Galena as a useful impurity also reacts with air to form Lead(II) oxide and sulphur(IV) oxide gas.
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During extraction of Zinc , the ore is first roasted in air: For Calamine Zinc carbonate decompose to Zinc oxide and carbon(IV) oxide gas. ZnCO3(s) ZnO(s) + CO2(g) Zinc blende does not decompose but reacts with air to form Zinc oxide and sulphur(IV) oxide gas. Galena as a useful impurity also reacts with air to form Lead(II) oxide and sulphur(IV) oxide gas. 2ZnS(s) + 3O2(g) 2ZnO(s) + 2SO2(g) (Zinc blende) 2PbS(s) + 3O2(g) 2PbO(s) + 2SO2(g) (Galena) The oxides are mixed with coke and limestone/Iron(II)oxide/ Aluminium (III) oxide and heated in a blast furnace. At the furnace temperatures limestone decomposes to quicklime/CaO and produce Carbon(IV)oxide gas. CaCO3(s) CaO(s) + CO2 (g) Carbon(IV)oxide gas reacts with more coke to form the Carbon(II)oxide gas. C(s) + CO2 (g) 2CO (g) Both Carbon(II)oxide and carbon/coke/carbon are reducing agents. 27 The oxides are reduced to the metals by either coke or carbon (II)oxide. ZnO(s) + C(s) Zn(g) + CO (g) PbO(s) + C(s) Pb(l) + CO (g) PbO(s) + CO(s) Pb(l) + CO2 (g) PbO(s) + CO(s) Pb(g) + CO2 (g) At the furnace temperature: (i)Zinc is a gas/vapour and is collected at the top of the furnace. It is condensed in a spray of molten lead to prevent reoxidation to Zinc oxide. On further cooling , Zinc collects on the surface from where it can be tapped off (ii)Lead is a liquid and is ale to trickle to the bottom of the furnace from where it is tapped off. Quicklime/CaO, Iron(II)Oxide, Aluminium(III)oxide are used to remove silica/silicon(IV)oxide as silicates which float above Lead preventing its reoxidation back to Lead(II)Oxide.
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It is condensed in a spray of molten lead to prevent reoxidation to Zinc oxide. On further cooling , Zinc collects on the surface from where it can be tapped off (ii)Lead is a liquid and is ale to trickle to the bottom of the furnace from where it is tapped off. Quicklime/CaO, Iron(II)Oxide, Aluminium(III)oxide are used to remove silica/silicon(IV)oxide as silicates which float above Lead preventing its reoxidation back to Lead(II)Oxide. CaO(s) + SiO2(s) CaSiO3(s/l) (Slag-Calcium silicate) FeO(s) + SiO2(s) FeSiO3(s/l) (Slag-Iron silicate) Al2O3(s) + SiO2(s) Al2SiO4(s/l) (Slag-Aluminium silicate) c)Flow chart on extraction of Zinc from Calamine ,Zinc blende. Zinc ore (calamine /Zinc blende Powdered ore Froth flotation Roasting chamber Oil Water CO2 from calamine SO2 from Zinc blende Reduction chamber Iron/aluminium/ Limestone Coke Slag (Iron silicate/ aluminium silicate/calcium Condenser Filtration Gl ikWater
28 d) Flow chart on extraction of Lead from Galena e) Uses of Lead Lead is used in: (i)making gun-burettes. (ii)making protective clothes against nuclear (alpha rays/particle) radiation in a nuclear reactor. (iii)Mixed with tin(Sn) to make solder alloy f) Uses of Zinc Zinc is used in: Lead ore/Galena Powdered ore Froth flotation Roasting chamber oil Water Reduction chamber Iron/Limestone coke SO2(g) Slag(Iron silicate) Condenser Filtration LEAD VAPOUR Zinc residue
29 (i)Galvanization-when iron sheet is dipped in molten Zinc ,a thin layer of Zinc is formed on the surface.Since Zinc is more reactive than iron ,it reacts with elements of air(CO2/ O2 / H2O) to form basic Zinc carbonate(ZnCO3.Zn(OH)2).This sacrificial method protects iron from corrosion/rusting. (ii)As negative terminal and casing in dry/Laclanche cells. (iii)Making brass alloy with copper(Cu/Zn) g) Environmental effects of extracting Zinc and Lead.
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(iii)Mixed with tin(Sn) to make solder alloy f) Uses of Zinc Zinc is used in: Lead ore/Galena Powdered ore Froth flotation Roasting chamber oil Water Reduction chamber Iron/Limestone coke SO2(g) Slag(Iron silicate) Condenser Filtration LEAD VAPOUR Zinc residue
29 (i)Galvanization-when iron sheet is dipped in molten Zinc ,a thin layer of Zinc is formed on the surface.Since Zinc is more reactive than iron ,it reacts with elements of air(CO2/ O2 / H2O) to form basic Zinc carbonate(ZnCO3.Zn(OH)2).This sacrificial method protects iron from corrosion/rusting. (ii)As negative terminal and casing in dry/Laclanche cells. (iii)Making brass alloy with copper(Cu/Zn) g) Environmental effects of extracting Zinc and Lead. (i) Lead and Lead salts are carcinogenic/causes cancer (ii)Carbon(IV)oxide is a green house gas that causes/accelerate global warming. (iii)Carbon(II)oxide is a colourless odourless poisonous /toxic gas that combines with haemoglobin in the blood to form stable carboxyhaemoglobin reducing free haemoglobin leading to death. (iv) Sulphur(IV)oxide is a gas that has a pungent poisonous smell that causes headache to human if in high concentration. (v)Any leakages in Sulphur(IV)oxide gas escapes to the water bodies to form weak sulphuric(VI)acid lowering the pH of the water. This causes marine pollution /death of aquatic life, accelerated rusting/corrosion of metals/roofs and breathing problems to human beings. h) Test for presence of Zinc/ Lead. If an ore is suspected to contain Zinc/Lead it is: I.added hot concentrated Nitric(V)acid to free the ions present. Note: Concentrated Sulphuric(VI)acid forms insoluble PbSO4 thus cannot be used to free the ions in Lead salts. II.the free ions are then added a precipitating reagent mostly 2M sodium hydroxide or 2M aqueous ammonia with the formation of; (i)a soluble precipitate in excess of 2M sodium hydroxide if Zn2+, Pb2+, Al3+ions are present.
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If an ore is suspected to contain Zinc/Lead it is: I.added hot concentrated Nitric(V)acid to free the ions present. Note: Concentrated Sulphuric(VI)acid forms insoluble PbSO4 thus cannot be used to free the ions in Lead salts. II.the free ions are then added a precipitating reagent mostly 2M sodium hydroxide or 2M aqueous ammonia with the formation of; (i)a soluble precipitate in excess of 2M sodium hydroxide if Zn2+, Pb2+, Al3+ions are present. (ii)a white precipitate that dissolves to form a colorless solution in excess 2M aqueous ammonia if Zn2+ions are present. (iii)an insoluble white precipitate in excess 2M aqueous ammonia if Pb2+, Al3+ions are present. (iv) Pb2+ ions form a white precipitate when any soluble SO42-, SO32-, CO32-, Cl-, is added while Al3+ ions do not form a white precipitate
30 (v) Pb2+ ions form a yellow precipitate when any soluble I-(e.g. Potassium/sodium Iodide) is added while Al3+ ions do not form a yellow precipitate. (vi) Pb2+ ions form a black precipitate when any soluble S-(e.g.
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(iv) Pb2+ ions form a white precipitate when any soluble SO42-, SO32-, CO32-, Cl-, is added while Al3+ ions do not form a white precipitate
30 (v) Pb2+ ions form a yellow precipitate when any soluble I-(e.g. Potassium/sodium Iodide) is added while Al3+ ions do not form a yellow precipitate. (vi) Pb2+ ions form a black precipitate when any soluble S-(e.g. Potassium/sodium sulphide) is added while Al3+ ions do not form a black precipitate.i.e; Observation Inference White precipitate in excess 2M NaOH (aq) Zn2+, Pb2+, Al3+ ions White precipitate that dissolves to form a colourless solution in excess 2M NH3(aq) Zn2+ ions White precipitate in excess 2M NH3(aq) Pb2+, Al3+ ions White precipitate on adding about 4 drops of either Na2CO3(aq), Na2SO3(aq), Na2SO4(aq), H2SO4(aq), HCl(aq), NaCl(aq) Pb2+ions Yellow precipitate on adding about 4 drops of of KI(aq).NaI (aq) Pb2+ ions Black precipitate on adding aout 4 drops of Na2S(aq)/K2S(aq) Pb2+ ions
31 6.GENERAL SUMMARY OF METALS a) Summary methods of extracting metal from their ore The main criteria used in extraction of metals is based on its position in the electrochemical/reactivity series and its occurrence on the earth’s crust. Position on the earth’s crust If near the surface use open cast mining / quarrying If deep on the earth’s crust use deep mining Add oil, water, and blow air to form froth to concentrate the ore if it is a low grade Roast the ore first if it is a carbonate / sulphide of Zinc, Iron, Tin, Lead, and copper to form the oxide Electrolyse the ore if it is made of reactive metals; Potassium, Sodium, Magnesium, Calcium, Aluminium Reduce the oxide using carbon in a furnace if it is made of Zinc ,Tin, Lead ,Copper and Iron
32 b) Summary of extraction of common metal.
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(vi) Pb2+ ions form a black precipitate when any soluble S-(e.g. Potassium/sodium sulphide) is added while Al3+ ions do not form a black precipitate.i.e; Observation Inference White precipitate in excess 2M NaOH (aq) Zn2+, Pb2+, Al3+ ions White precipitate that dissolves to form a colourless solution in excess 2M NH3(aq) Zn2+ ions White precipitate in excess 2M NH3(aq) Pb2+, Al3+ ions White precipitate on adding about 4 drops of either Na2CO3(aq), Na2SO3(aq), Na2SO4(aq), H2SO4(aq), HCl(aq), NaCl(aq) Pb2+ions Yellow precipitate on adding about 4 drops of of KI(aq).NaI (aq) Pb2+ ions Black precipitate on adding aout 4 drops of Na2S(aq)/K2S(aq) Pb2+ ions
31 6.GENERAL SUMMARY OF METALS a) Summary methods of extracting metal from their ore The main criteria used in extraction of metals is based on its position in the electrochemical/reactivity series and its occurrence on the earth’s crust. Position on the earth’s crust If near the surface use open cast mining / quarrying If deep on the earth’s crust use deep mining Add oil, water, and blow air to form froth to concentrate the ore if it is a low grade Roast the ore first if it is a carbonate / sulphide of Zinc, Iron, Tin, Lead, and copper to form the oxide Electrolyse the ore if it is made of reactive metals; Potassium, Sodium, Magnesium, Calcium, Aluminium Reduce the oxide using carbon in a furnace if it is made of Zinc ,Tin, Lead ,Copper and Iron
32 b) Summary of extraction of common metal. Metal Chief ore/s Chemical formula of ore Method of extraction Main equation during extraction Sodium Rock salt NaCl(s) Downs process Through electrolysis of molten NaCl (CaCl2 lower m.pt from 800oC-> 600oC) Cathode: 2Na+(l) + 2e -> 2Na(l) Anode: 2Cl-(l) -> Cl2(g) + 2e Sodium/ sodium hydroxide Brine NaCl(aq) Flowing mercury cathode cell Through electrolysis of concentrated NaCl(aq) Cathode: 2Na+(aq)+2e ->2Na(aq) Anode: 2Cl-(aq) -> Cl2(g) + 2e Aluminium Bauxite Al2O3.2H2O Halls process Through electrolysis of molten Al2O3.
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Potassium/sodium sulphide) is added while Al3+ ions do not form a black precipitate.i.e; Observation Inference White precipitate in excess 2M NaOH (aq) Zn2+, Pb2+, Al3+ ions White precipitate that dissolves to form a colourless solution in excess 2M NH3(aq) Zn2+ ions White precipitate in excess 2M NH3(aq) Pb2+, Al3+ ions White precipitate on adding about 4 drops of either Na2CO3(aq), Na2SO3(aq), Na2SO4(aq), H2SO4(aq), HCl(aq), NaCl(aq) Pb2+ions Yellow precipitate on adding about 4 drops of of KI(aq).NaI (aq) Pb2+ ions Black precipitate on adding aout 4 drops of Na2S(aq)/K2S(aq) Pb2+ ions
31 6.GENERAL SUMMARY OF METALS a) Summary methods of extracting metal from their ore The main criteria used in extraction of metals is based on its position in the electrochemical/reactivity series and its occurrence on the earth’s crust. Position on the earth’s crust If near the surface use open cast mining / quarrying If deep on the earth’s crust use deep mining Add oil, water, and blow air to form froth to concentrate the ore if it is a low grade Roast the ore first if it is a carbonate / sulphide of Zinc, Iron, Tin, Lead, and copper to form the oxide Electrolyse the ore if it is made of reactive metals; Potassium, Sodium, Magnesium, Calcium, Aluminium Reduce the oxide using carbon in a furnace if it is made of Zinc ,Tin, Lead ,Copper and Iron
32 b) Summary of extraction of common metal. Metal Chief ore/s Chemical formula of ore Method of extraction Main equation during extraction Sodium Rock salt NaCl(s) Downs process Through electrolysis of molten NaCl (CaCl2 lower m.pt from 800oC-> 600oC) Cathode: 2Na+(l) + 2e -> 2Na(l) Anode: 2Cl-(l) -> Cl2(g) + 2e Sodium/ sodium hydroxide Brine NaCl(aq) Flowing mercury cathode cell Through electrolysis of concentrated NaCl(aq) Cathode: 2Na+(aq)+2e ->2Na(aq) Anode: 2Cl-(aq) -> Cl2(g) + 2e Aluminium Bauxite Al2O3.2H2O Halls process Through electrolysis of molten Al2O3. (Cryolite lower m.pt from 2015oC -> 800oC) Cathode: 4Al3+(l) + 12e -> 4Al(l) Anode: 6O2-(l) -> 3O2(g) + 12e Iron Haematite Magnetite Fe2O3 Fe3O4 Blast furnace Reduction of the ore by carbon(II)oxide Fe2O3(s)+ 3CO(g) 2Fe(l) +3CO2(g) Fe3O4(s)+ 4CO(g) 3Fe(l) +4CO2(g) Copper Copper pyrites CuFeS2 Roasting the ore in air to get Cu2S.
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Position on the earth’s crust If near the surface use open cast mining / quarrying If deep on the earth’s crust use deep mining Add oil, water, and blow air to form froth to concentrate the ore if it is a low grade Roast the ore first if it is a carbonate / sulphide of Zinc, Iron, Tin, Lead, and copper to form the oxide Electrolyse the ore if it is made of reactive metals; Potassium, Sodium, Magnesium, Calcium, Aluminium Reduce the oxide using carbon in a furnace if it is made of Zinc ,Tin, Lead ,Copper and Iron
32 b) Summary of extraction of common metal. Metal Chief ore/s Chemical formula of ore Method of extraction Main equation during extraction Sodium Rock salt NaCl(s) Downs process Through electrolysis of molten NaCl (CaCl2 lower m.pt from 800oC-> 600oC) Cathode: 2Na+(l) + 2e -> 2Na(l) Anode: 2Cl-(l) -> Cl2(g) + 2e Sodium/ sodium hydroxide Brine NaCl(aq) Flowing mercury cathode cell Through electrolysis of concentrated NaCl(aq) Cathode: 2Na+(aq)+2e ->2Na(aq) Anode: 2Cl-(aq) -> Cl2(g) + 2e Aluminium Bauxite Al2O3.2H2O Halls process Through electrolysis of molten Al2O3. (Cryolite lower m.pt from 2015oC -> 800oC) Cathode: 4Al3+(l) + 12e -> 4Al(l) Anode: 6O2-(l) -> 3O2(g) + 12e Iron Haematite Magnetite Fe2O3 Fe3O4 Blast furnace Reduction of the ore by carbon(II)oxide Fe2O3(s)+ 3CO(g) 2Fe(l) +3CO2(g) Fe3O4(s)+ 4CO(g) 3Fe(l) +4CO2(g) Copper Copper pyrites CuFeS2 Roasting the ore in air to get Cu2S. Heating Cu2S ore in regulated supply of air.
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Metal Chief ore/s Chemical formula of ore Method of extraction Main equation during extraction Sodium Rock salt NaCl(s) Downs process Through electrolysis of molten NaCl (CaCl2 lower m.pt from 800oC-> 600oC) Cathode: 2Na+(l) + 2e -> 2Na(l) Anode: 2Cl-(l) -> Cl2(g) + 2e Sodium/ sodium hydroxide Brine NaCl(aq) Flowing mercury cathode cell Through electrolysis of concentrated NaCl(aq) Cathode: 2Na+(aq)+2e ->2Na(aq) Anode: 2Cl-(aq) -> Cl2(g) + 2e Aluminium Bauxite Al2O3.2H2O Halls process Through electrolysis of molten Al2O3. (Cryolite lower m.pt from 2015oC -> 800oC) Cathode: 4Al3+(l) + 12e -> 4Al(l) Anode: 6O2-(l) -> 3O2(g) + 12e Iron Haematite Magnetite Fe2O3 Fe3O4 Blast furnace Reduction of the ore by carbon(II)oxide Fe2O3(s)+ 3CO(g) 2Fe(l) +3CO2(g) Fe3O4(s)+ 4CO(g) 3Fe(l) +4CO2(g) Copper Copper pyrites CuFeS2 Roasting the ore in air to get Cu2S. Heating Cu2S ore in regulated supply of air. Reduction of Cu2O by Cu2S 2CuFeS2 (s)+ 4O2(g) -> Cu2S(s)+3SO2(g) +2FeO(s) 2Cu2S (s)+ 3O2(g) -> 2Cu2O(s)+2SO2(g) Cu2S (s)+ 2Cu2O(s) -> 6Cu(s)+ SO2(g) Zinc Calamine ZnCO3 Roasting the ore in air to get ZnO ZnCO3(s)-> ZnO(s) + CO2(g)
33 Blast furnace /reduction of the oxide by Carbon(II)Oxide/Carbon 2ZnS(s) +3O2(g) -> 2ZnO(s) + 2SO2(g) ZnO(s) + CO(g)-> Zn(s) + CO2(g) Lead Galena PbS Blast furnaceReduction of the oxide by carbon(II)oxide /Carbon PbO(s) + CO(g)-> Pb(s) + CO2(g) c) Common alloys of metal.
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(Cryolite lower m.pt from 2015oC -> 800oC) Cathode: 4Al3+(l) + 12e -> 4Al(l) Anode: 6O2-(l) -> 3O2(g) + 12e Iron Haematite Magnetite Fe2O3 Fe3O4 Blast furnace Reduction of the ore by carbon(II)oxide Fe2O3(s)+ 3CO(g) 2Fe(l) +3CO2(g) Fe3O4(s)+ 4CO(g) 3Fe(l) +4CO2(g) Copper Copper pyrites CuFeS2 Roasting the ore in air to get Cu2S. Heating Cu2S ore in regulated supply of air. Reduction of Cu2O by Cu2S 2CuFeS2 (s)+ 4O2(g) -> Cu2S(s)+3SO2(g) +2FeO(s) 2Cu2S (s)+ 3O2(g) -> 2Cu2O(s)+2SO2(g) Cu2S (s)+ 2Cu2O(s) -> 6Cu(s)+ SO2(g) Zinc Calamine ZnCO3 Roasting the ore in air to get ZnO ZnCO3(s)-> ZnO(s) + CO2(g)
33 Blast furnace /reduction of the oxide by Carbon(II)Oxide/Carbon 2ZnS(s) +3O2(g) -> 2ZnO(s) + 2SO2(g) ZnO(s) + CO(g)-> Zn(s) + CO2(g) Lead Galena PbS Blast furnaceReduction of the oxide by carbon(II)oxide /Carbon PbO(s) + CO(g)-> Pb(s) + CO2(g) c) Common alloys of metal. Alloy name Constituents of the alloy Uses of the alloy Brass Copper and Zinc Making scews and bulb caps Bronze Copper and Tin Making clock springs,electrical contacts and copper coins Soldier Lead and Tin Soldering, joining electrical contacts because of its low melting points and high thermal conductivity Duralumin Aluminium, Copper and Magnesium Making aircraft , utensils ,windows frames because of its light weight and corrosion resistant. Steel Iron, Carbon ,Manganese and other metals Railway lines , car bodies girders and utensils.
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Reduction of Cu2O by Cu2S 2CuFeS2 (s)+ 4O2(g) -> Cu2S(s)+3SO2(g) +2FeO(s) 2Cu2S (s)+ 3O2(g) -> 2Cu2O(s)+2SO2(g) Cu2S (s)+ 2Cu2O(s) -> 6Cu(s)+ SO2(g) Zinc Calamine ZnCO3 Roasting the ore in air to get ZnO ZnCO3(s)-> ZnO(s) + CO2(g)
33 Blast furnace /reduction of the oxide by Carbon(II)Oxide/Carbon 2ZnS(s) +3O2(g) -> 2ZnO(s) + 2SO2(g) ZnO(s) + CO(g)-> Zn(s) + CO2(g) Lead Galena PbS Blast furnaceReduction of the oxide by carbon(II)oxide /Carbon PbO(s) + CO(g)-> Pb(s) + CO2(g) c) Common alloys of metal. Alloy name Constituents of the alloy Uses of the alloy Brass Copper and Zinc Making scews and bulb caps Bronze Copper and Tin Making clock springs,electrical contacts and copper coins Soldier Lead and Tin Soldering, joining electrical contacts because of its low melting points and high thermal conductivity Duralumin Aluminium, Copper and Magnesium Making aircraft , utensils ,windows frames because of its light weight and corrosion resistant. Steel Iron, Carbon ,Manganese and other metals Railway lines , car bodies girders and utensils. Nichrome Nichrome and Chromium Provide resistance in electric heaters and ovens German silver Copper,Zinc and Nickel Making coins d) Physical properties of metal. Metals form giant metallic structure joined by metallic bond from electrostatic attraction between the metallic cation and free delocalized electrons. This makes metals to have the following physical properties: (i)High melting and boiling points The giant metallic structure has a very close packed metallic lattice joined by strong electrostatic attraction between the metallic cation and free delocalized electrons.The more delocalized electrons the higher the melting/boiling points e.g. Aluminium has a melting point of about 2015oC while that of sodium is about 98oC.This is mainly because aluminium has more/three delocalized electrons than sodium/has one.
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Metals form giant metallic structure joined by metallic bond from electrostatic attraction between the metallic cation and free delocalized electrons. This makes metals to have the following physical properties: (i)High melting and boiling points The giant metallic structure has a very close packed metallic lattice joined by strong electrostatic attraction between the metallic cation and free delocalized electrons.The more delocalized electrons the higher the melting/boiling points e.g. Aluminium has a melting point of about 2015oC while that of sodium is about 98oC.This is mainly because aluminium has more/three delocalized electrons than sodium/has one. Aluminium has a boiling point of about 2470oC while that of sodium is about 890oC.This is mainly because aluminium has more/three delocalized electrons than sodium/has one. 34 (ii)High thermal and electrical conductivity All metals are good thermal and electrical conductors as liquid or solids. The more delocalized electrons the higher the thermal and electrical conductivity. e.g. Aluminium has an electrical conductivity of about 3.82 x 19-9 ohms per metre. Sodium has an electrical conductivity of about 2.18 x 19-9 ohms per metre. (iii)Shiny/Lustrous The free delocalized electrons on the surface of the metal absorb, vibrate and then scatter/re-emit/lose light energy. All metals are therefore usually shades of grey in colour except copper which is shiny brown.e.g. Zinc is bluish grey while iron is silvery grey. (iv)High tensile strength The free delocalized electrons on the surface of the metal atoms binds the surface immediately when the metal is coiled/folded preventing it from breaking /being brittle. (v)Malleable. Metals can be made into thin sheet. The metallic crystal lattice on being beaten/pressed/hammered on two sides extend its length and width/bredth and is then immediately bound by the delocalized electrons preventing it from breaking/being brittle. (vi)Ductile. Metals can be made into thin wires. The metallic crystal lattice on being beaten/pressed/hammered on all sides extend its length is then immediately bound by the delocalized electrons preventing it from breaking/being brittle.
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(vi)Ductile. Metals can be made into thin wires. The metallic crystal lattice on being beaten/pressed/hammered on all sides extend its length is then immediately bound by the delocalized electrons preventing it from breaking/being brittle. Revision questions 1.Given some soil , dilute sulphuric(VI)acid,mortar,pestle,filter paper,filter funnel and 2M aqueous ammonia,describe with explanation,how you would show that the soil contain Zinc. Place the soil sample in the pestle. Crush using the mortar to reduce the particle size/increase its surface area. Add dilute sulphuric(VI)acid to free the ions in soil sample. Filter to separate insoluble residue from soluble filtrate To filtrate,add three drops of aqueous ammonia as precipitating reagent. A white precipitate of Zn(OH)2, Pb(OH)2 or Al(OH)3 is formed Add excess aqueous ammonia to the white precipitate. If it dissolves the Zn2+ ions are present. Zn(OH)2 react with excess ammonia to form soluble [Zn(OH)4]2+ complex. 2.In the extraction of aluminium,the oxide is dissolved in cryolite. (i)What is the chemical name of cryolite? Sodium hexafloroaluminate/Na3AlF6
35 (ii)What is the purpose of cryolite? To lower the melting point of the electrolyte/Aluminium oxide from about 2015oC to 900oC (iii)Name the substance used for similar purpose in the Down cell Calcium chloride/CaCl2 (iv)An alloy of sodium and potassium is used as coolant in nuclear reactors.Explain. Nuclear reactors generate a lot of heat energy. sodium and potassium alloy reduce/lower the high temperature in the reactors. (v)Aluminium metal is used to make cooking utensils in preference to other metals.Explain. Aluminium (i) is a very good conductor of electricity because it has three delocalized electrons in its metallic structure (ii)is cheap,malleable,ductile and has high tensile strength (iii)on exposure to fire/heat form an impervious layer that prevent it from rapid corrosion. 3.Study the scheme below and use it to answer the questions that follow.
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(v)Aluminium metal is used to make cooking utensils in preference to other metals.Explain. Aluminium (i) is a very good conductor of electricity because it has three delocalized electrons in its metallic structure (ii)is cheap,malleable,ductile and has high tensile strength (iii)on exposure to fire/heat form an impervious layer that prevent it from rapid corrosion. 3.Study the scheme below and use it to answer the questions that follow. (a)Identify: (i)solid residue L Iron(III)Oxide/Fe2O3 (ii)Solid N Aluminium hydroxide /Al(OH)3
36 (iii)Filtrate M Sodium tetrahydroxoaluminate/ NaAl(OH)4 and sodium silicate/ NaSiO3 (iv)Solid P Aluminium oxide/ Al2O3 (v)Gas Q Oxygen/O2 (vi)Process K1 Filtration (vii)Process K2 Electrolysis (b)Write the equation for the reaction taking place in the formation of solid P from solid N 2Al(OH)3 -> Al2O3 (s) + 3H2O(l) (c)Name a substance added to solid N before process Process K2 take place. Cryolite/Sodium tetrahydroxoaluminate/ NaAl(OH)4 (d)State the effect of evolution of gas Q on (i)process K2 Oxygen produced at the anode reacts with the carbon anode to form carbon(IV) oxide which escape. The electrolytic process needs continuous replacement of the carbon anode. (ii)the environment Oxygen produced at the anode reacts with the carbon anode to form carbon(IV) oxide which escape to the atmosphere.CO2 is a green house gas that cause global warming. (e)An aluminium manufacturing factory runs for 24 hours. If the total mass of aluminium produced is 27000kg, (i)Calculate the current used. (Faraday constant=96500Coulombs, Al=27.0).
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(e)An aluminium manufacturing factory runs for 24 hours. If the total mass of aluminium produced is 27000kg, (i)Calculate the current used. (Faraday constant=96500Coulombs, Al=27.0). (ii)assuming all the gas produced react with 200kg of anode ,calculate the loss in mass of the electrode.(Molar gas volume at room temperature = 24dm3,C=12.0) Working Equation at Cathode Al3+(l) + 3e -> Al(l) 27g Al -> 3 Faradays = 3 x 96500C (27000kg x 1000) g -> (27000kg x 1000) g x 3 x 96500C 27g =289500000000 Coulombs
37 Current = Quantity of electricity =>289500000000 Coulombs Time in seconds 24 x 60 x 60 3350690Ampheres Working Equation at Anode 2O2-(l) + 4e -> O2(g) 4 Faradays -> 4 x 96500C24dm3 O2(g) - 289500000000 Coulombs -> 289500000000 Coulombs x 24dm3 4 x 96500C 18,000,000dm3 Chemical equation at anode O2(g) + C (s) -> CO2(g) Method 1 24dm3 of O2(g) -> 12.0g Carbon 18,000,000dm3 of O2(g) -> 18,000,000dm3 x 12 = 9000000g = 9000kg 24dm3 1000g Loss in mass of the carbon graphite anode = 9000kg NB:Mass of the carbon graphite anode remaining =27000kg - 9000kg =18000kg The flow chart below shows the extraction of iron metal.Use it to answer the questions that follow.
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If the total mass of aluminium produced is 27000kg, (i)Calculate the current used. (Faraday constant=96500Coulombs, Al=27.0). (ii)assuming all the gas produced react with 200kg of anode ,calculate the loss in mass of the electrode.(Molar gas volume at room temperature = 24dm3,C=12.0) Working Equation at Cathode Al3+(l) + 3e -> Al(l) 27g Al -> 3 Faradays = 3 x 96500C (27000kg x 1000) g -> (27000kg x 1000) g x 3 x 96500C 27g =289500000000 Coulombs
37 Current = Quantity of electricity =>289500000000 Coulombs Time in seconds 24 x 60 x 60 3350690Ampheres Working Equation at Anode 2O2-(l) + 4e -> O2(g) 4 Faradays -> 4 x 96500C24dm3 O2(g) - 289500000000 Coulombs -> 289500000000 Coulombs x 24dm3 4 x 96500C 18,000,000dm3 Chemical equation at anode O2(g) + C (s) -> CO2(g) Method 1 24dm3 of O2(g) -> 12.0g Carbon 18,000,000dm3 of O2(g) -> 18,000,000dm3 x 12 = 9000000g = 9000kg 24dm3 1000g Loss in mass of the carbon graphite anode = 9000kg NB:Mass of the carbon graphite anode remaining =27000kg - 9000kg =18000kg The flow chart below shows the extraction of iron metal.Use it to answer the questions that follow. (a)Identify: (i)gas P Carbon(IV)oxide/CO2 (ii)Solid Q
38 Carbon/coke/charcoal (iii)Solid R Carbon/coke/charcoal (iv)Solid V Limestone/calcium carbonate/CaCO3 (v)Solid S Iron/Fe (b)Write the chemical equation for the reaction for the formation of: (i)Solid S Fe2O3(s) + 3CO(g) -> 2Fe(s) + 3CO2(g) (ii)Carbon(II)oxide C(s) + CO2 (g) -> 2CO (g) (iii)Slag SiO2(s) + CaO(s) -> CaSiO3(s) Al2O3 (s) + CaO(s) -> Ca Al2O4(s) (iv)Gas P C(s) + O2 (g) -> CO2 (g) (c)State two uses of: (i)Solid S Iron is used in making: (i)gates ,pipes, engine blocks, rails, charcoal iron boxes, lamp posts because it is cheap.
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(Faraday constant=96500Coulombs, Al=27.0). (ii)assuming all the gas produced react with 200kg of anode ,calculate the loss in mass of the electrode.(Molar gas volume at room temperature = 24dm3,C=12.0) Working Equation at Cathode Al3+(l) + 3e -> Al(l) 27g Al -> 3 Faradays = 3 x 96500C (27000kg x 1000) g -> (27000kg x 1000) g x 3 x 96500C 27g =289500000000 Coulombs
37 Current = Quantity of electricity =>289500000000 Coulombs Time in seconds 24 x 60 x 60 3350690Ampheres Working Equation at Anode 2O2-(l) + 4e -> O2(g) 4 Faradays -> 4 x 96500C24dm3 O2(g) - 289500000000 Coulombs -> 289500000000 Coulombs x 24dm3 4 x 96500C 18,000,000dm3 Chemical equation at anode O2(g) + C (s) -> CO2(g) Method 1 24dm3 of O2(g) -> 12.0g Carbon 18,000,000dm3 of O2(g) -> 18,000,000dm3 x 12 = 9000000g = 9000kg 24dm3 1000g Loss in mass of the carbon graphite anode = 9000kg NB:Mass of the carbon graphite anode remaining =27000kg - 9000kg =18000kg The flow chart below shows the extraction of iron metal.Use it to answer the questions that follow. (a)Identify: (i)gas P Carbon(IV)oxide/CO2 (ii)Solid Q
38 Carbon/coke/charcoal (iii)Solid R Carbon/coke/charcoal (iv)Solid V Limestone/calcium carbonate/CaCO3 (v)Solid S Iron/Fe (b)Write the chemical equation for the reaction for the formation of: (i)Solid S Fe2O3(s) + 3CO(g) -> 2Fe(s) + 3CO2(g) (ii)Carbon(II)oxide C(s) + CO2 (g) -> 2CO (g) (iii)Slag SiO2(s) + CaO(s) -> CaSiO3(s) Al2O3 (s) + CaO(s) -> Ca Al2O4(s) (iv)Gas P C(s) + O2 (g) -> CO2 (g) (c)State two uses of: (i)Solid S Iron is used in making: (i)gates ,pipes, engine blocks, rails, charcoal iron boxes, lamp posts because it is cheap. (ii)nails, cutlery, scissors, sinks, vats, spanners, steel rods, and railway points from steel.
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(ii)assuming all the gas produced react with 200kg of anode ,calculate the loss in mass of the electrode.(Molar gas volume at room temperature = 24dm3,C=12.0) Working Equation at Cathode Al3+(l) + 3e -> Al(l) 27g Al -> 3 Faradays = 3 x 96500C (27000kg x 1000) g -> (27000kg x 1000) g x 3 x 96500C 27g =289500000000 Coulombs
37 Current = Quantity of electricity =>289500000000 Coulombs Time in seconds 24 x 60 x 60 3350690Ampheres Working Equation at Anode 2O2-(l) + 4e -> O2(g) 4 Faradays -> 4 x 96500C24dm3 O2(g) - 289500000000 Coulombs -> 289500000000 Coulombs x 24dm3 4 x 96500C 18,000,000dm3 Chemical equation at anode O2(g) + C (s) -> CO2(g) Method 1 24dm3 of O2(g) -> 12.0g Carbon 18,000,000dm3 of O2(g) -> 18,000,000dm3 x 12 = 9000000g = 9000kg 24dm3 1000g Loss in mass of the carbon graphite anode = 9000kg NB:Mass of the carbon graphite anode remaining =27000kg - 9000kg =18000kg The flow chart below shows the extraction of iron metal.Use it to answer the questions that follow. (a)Identify: (i)gas P Carbon(IV)oxide/CO2 (ii)Solid Q
38 Carbon/coke/charcoal (iii)Solid R Carbon/coke/charcoal (iv)Solid V Limestone/calcium carbonate/CaCO3 (v)Solid S Iron/Fe (b)Write the chemical equation for the reaction for the formation of: (i)Solid S Fe2O3(s) + 3CO(g) -> 2Fe(s) + 3CO2(g) (ii)Carbon(II)oxide C(s) + CO2 (g) -> 2CO (g) (iii)Slag SiO2(s) + CaO(s) -> CaSiO3(s) Al2O3 (s) + CaO(s) -> Ca Al2O4(s) (iv)Gas P C(s) + O2 (g) -> CO2 (g) (c)State two uses of: (i)Solid S Iron is used in making: (i)gates ,pipes, engine blocks, rails, charcoal iron boxes, lamp posts because it is cheap. (ii)nails, cutlery, scissors, sinks, vats, spanners, steel rods, and railway points from steel. Steel is an alloy of iron with carbon, and/or Vanadium, Manganese, Tungsten, Nickel ,Chromium.
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(a)Identify: (i)gas P Carbon(IV)oxide/CO2 (ii)Solid Q
38 Carbon/coke/charcoal (iii)Solid R Carbon/coke/charcoal (iv)Solid V Limestone/calcium carbonate/CaCO3 (v)Solid S Iron/Fe (b)Write the chemical equation for the reaction for the formation of: (i)Solid S Fe2O3(s) + 3CO(g) -> 2Fe(s) + 3CO2(g) (ii)Carbon(II)oxide C(s) + CO2 (g) -> 2CO (g) (iii)Slag SiO2(s) + CaO(s) -> CaSiO3(s) Al2O3 (s) + CaO(s) -> Ca Al2O4(s) (iv)Gas P C(s) + O2 (g) -> CO2 (g) (c)State two uses of: (i)Solid S Iron is used in making: (i)gates ,pipes, engine blocks, rails, charcoal iron boxes, lamp posts because it is cheap. (ii)nails, cutlery, scissors, sinks, vats, spanners, steel rods, and railway points from steel. Steel is an alloy of iron with carbon, and/or Vanadium, Manganese, Tungsten, Nickel ,Chromium. It does not rust/corrode like iron. (ii)Slag (i) tarmacing roads (ii) cement manufacture (iii) as building construction material 3.You are provided with sulphuric(VI)acid ,2M aqueous ammonia and two ores suspected to contain copper and iron. Describe with explanation how you would differentiate the two ores. Crush the two ores separately in using a mortar and pestle to reduce the particle size/increase the surface area. Add sulphuric(VI)acid to separate portion of the ore. Filter. 39 To a portion of the filtrate,add three drops of 2M aqueous ammonia then axcess Results A green precipitate insoluble in excess 2M aqueous ammonia confirms the ore contain Fe2+ ion. A brown precipitate insoluble in excess 2M aqueous ammonia confirms the ore contain Fe3+ ion. A blue precipitate that dissolve in excess 2M aqueous ammonia to form a deep/royal blue solution confirms the ore contain Cu2+ ion. 4.
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A brown precipitate insoluble in excess 2M aqueous ammonia confirms the ore contain Fe3+ ion. A blue precipitate that dissolve in excess 2M aqueous ammonia to form a deep/royal blue solution confirms the ore contain Cu2+ ion. 4. Use the flow chart below showing the extraction of Zinc metal to answer the questions that follow (a)Name: (i)two ores from which Zinc can be extracted Calamine(ZnCO3) Zinc blende(ZnS) (ii)two possible identity of gas P Sulphur(IV)oxide(SO2) from roasting Zinc blende Carbon(IV)oxide(CO2) from decomposition of Calamine. (b)Write a possible chemical equation taking place in the roasting chamber. 2ZnS(s) + 3O2 (g) -> 2ZnO(s) + 2SO2(g) ZnCO3(s) -> ZnO(s) + CO2(g) (c)Explain the effect of the by-product of the roating on the environment. Sulphur (IV)oxide from roasting Zinc blende is an acidic gas that causes “acid rain” on dissolving in rain water. Carbon(IV)oxide(CO2) from decomposition of Calamine is a green house gas that causes global warming. (d)(i)Name a suitable reducing agent used in the furnace during extraction of Zinc. Carbon(II)oxide
40 (ii)Write a chemical equation for the reduction process ZnO(s) + CO(g) -> Zn(s) + CO2(g) (e)(i)Before electrolysis, the products from roasting is added dilute sulphuric (VI)acid. Write the equation for the reaction with dilute sulphuric(VI)acid. ZnO(s) + H2SO4 (aq) -> Zn SO4(aq) + H2(g) (ii)During the electrolysis for extraction of Zinc,state the I. Anode used Aluminium sheet II.
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Write the equation for the reaction with dilute sulphuric(VI)acid. ZnO(s) + H2SO4 (aq) -> Zn SO4(aq) + H2(g) (ii)During the electrolysis for extraction of Zinc,state the I. Anode used Aluminium sheet II. Cathode used Lead plate coated with silver (ii)Write the equation for the electrolysis for extraction of Zinc at the: I.Cathode; Zn2+(aq) + 2e -> Zn(s) II.Anode; 4OH-(aq) -> 2H2O(l) + O2(s) + 4e (f)(i)What is galvanization Dipping Iron in molten Zinc to form a thin layer of Zinc to prevent iron from rusting. (ii)Galvanized iron sheet rust after some time. Explain The thin layer of Zinc protect Iron from rusting through sacrificial protection. When all the Zinc has reacted with elements of air, Iron start rusting. (g)State two uses of Zinc other than galvanization. Making brass(Zinc/copper alloy) Making german silver(Zinc/copper/nickel alloy) As casing for dry cells/battery (h)Calculate the mass of Zinc that is produced from the reduction chamber if 6400kg of Calamine ore is fed into the roaster.
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When all the Zinc has reacted with elements of air, Iron start rusting. (g)State two uses of Zinc other than galvanization. Making brass(Zinc/copper alloy) Making german silver(Zinc/copper/nickel alloy) As casing for dry cells/battery (h)Calculate the mass of Zinc that is produced from the reduction chamber if 6400kg of Calamine ore is fed into the roaster. Assume the process is 80% efficient in each stage(Zn=64.0,C=12.0,O=16.0) Molar mass ZnCO3(s) =124g Molar mass Zn = 64g Molar mass ZnO = 80g Chemical equation ZnCO3(s) -> ZnO(s) + CO2(g) Method 1 124g ZnCO3 => 80g ZnO
41 (6400kg x1000)g ZnCO3 => (6400 x1000) x 80 = 512,000,000 g of ZnO 124 100% => 512,000,000 g of ZnO 80% => 80 x 512,000,000 g = 409600000g of ZnO 100 Chemical equation ZnO(s) + CO(g) -> Zn(s) + CO2(g) 80g ZnO(s) => 64g Zn(s) 409600000g of ZnO => 409600000g x 64 = 327680000 g Zn 80 100% => 327680000 g Zn 80% => 80 x 327680000 g Zn = 262144000g of Zn 100 Mass of Zinc produced = 262144000g of Zn 5.An ore is suspected to bauxite. Describe the process that can be used to confirm the presence of aluminium in the ore. Crush the ore to fine powder to increase surface area/reduce particle size. Add hot concentrated sulphuric(VI)/nitric(V) acid to free the ions. Filter. Retain the filtrate Add excess aqueous ammonia to a sample of filtrate. A white precipitate confirms presence of either Al3+ or Pb2+. Add sodium sulphate,dilute sulphuric(VI)to another portion of filtrate.
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Retain the filtrate Add excess aqueous ammonia to a sample of filtrate. A white precipitate confirms presence of either Al3+ or Pb2+. Add sodium sulphate,dilute sulphuric(VI)to another portion of filtrate. No white precipitate confirms presence of Al3+ Or Add potassium iodide to another portion of filtrate. No yellow precipitate confirms presence of Al3+ 6.The flow chart below illustrate the industrial extraction of Lead metal
42 (a)(i)Name the chief ore that is commonly used in this process Galena(PbS) (ii)Explain what take place in the roasting furnace
23.0.0 ORGANIC CHEMISTRY II (ALKANOLS AND ALKANOIC ACIDS) (20 LESSONS) B.ALKANOLS(Alcohols) (A) INTRODUCTION.
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Add sodium sulphate,dilute sulphuric(VI)to another portion of filtrate. No white precipitate confirms presence of Al3+ Or Add potassium iodide to another portion of filtrate. No yellow precipitate confirms presence of Al3+ 6.The flow chart below illustrate the industrial extraction of Lead metal
42 (a)(i)Name the chief ore that is commonly used in this process Galena(PbS) (ii)Explain what take place in the roasting furnace
23.0.0 ORGANIC CHEMISTRY II (ALKANOLS AND ALKANOIC ACIDS) (20 LESSONS) B.ALKANOLS(Alcohols) (A) INTRODUCTION. Alkanols belong to a homologous series of organic compounds with a general formula CnH2n +1 OH and thus -OH as the functional group .The 1st ten alkanols include n General / molecular formular Structural formula IUPAC name 1 CH3OH H – C –O - H │ H Methanol 2 CH3 CH2OH H H Ethanol
2 C2H5 OH H C – C –O - H │ H H 3 CH3 (CH2)2OH C3H7 OH H H H H C – C - C –O - H │ H H H Propanol 4 CH3 (CH2)3OH C4H9 OH H H H H H C – C - C - C –O - H │ H H H H Butanol 5 CH3(CH2)4OH C5H11 OH H H H H H H C – C - C- C- C –O - H │ H H H H H Pentanol 6 CH3(CH2)5OH C6H13 OH H H H H H H H C – C - C- C- C– C - O - H │ H H H H H H Hexanol 7 CH3(CH2)6OH C7H15 OH H H H H H H H H C – C - C- C- C– C –C- O - H │ H H H H H H H Heptanol 8 CH3(CH2)7OH C8H17 OH H H H H H H H H H C – C - C- C- C– C –C- C -O - H │ H H H H H H H H Octanol
3 9 CH3(CH2)8OH C9H19 OH H H H H H H H H H H C – C - C- C- C– C –C- C –C- O - H │ H H H H H H H H H Nonanol 10 CH3(CH2)9OH C10H21 OH H H H H H H H H H H H C – C - C- C- C– C –C- C –C- C-O - H │ H H H H H H H H H H Decanol Alkanols like Hydrocarbons( alkanes/alkenes/alkynes) form a homologous series where: (i)general name is derived from the alkane name then ending with “-ol” (ii)the members have –OH as the fuctional group (iii)they have the same general formula represented by R-OH where R is an alkyl group.
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No white precipitate confirms presence of Al3+ Or Add potassium iodide to another portion of filtrate. No yellow precipitate confirms presence of Al3+ 6.The flow chart below illustrate the industrial extraction of Lead metal
42 (a)(i)Name the chief ore that is commonly used in this process Galena(PbS) (ii)Explain what take place in the roasting furnace
23.0.0 ORGANIC CHEMISTRY II (ALKANOLS AND ALKANOIC ACIDS) (20 LESSONS) B.ALKANOLS(Alcohols) (A) INTRODUCTION. Alkanols belong to a homologous series of organic compounds with a general formula CnH2n +1 OH and thus -OH as the functional group .The 1st ten alkanols include n General / molecular formular Structural formula IUPAC name 1 CH3OH H – C –O - H │ H Methanol 2 CH3 CH2OH H H Ethanol
2 C2H5 OH H C – C –O - H │ H H 3 CH3 (CH2)2OH C3H7 OH H H H H C – C - C –O - H │ H H H Propanol 4 CH3 (CH2)3OH C4H9 OH H H H H H C – C - C - C –O - H │ H H H H Butanol 5 CH3(CH2)4OH C5H11 OH H H H H H H C – C - C- C- C –O - H │ H H H H H Pentanol 6 CH3(CH2)5OH C6H13 OH H H H H H H H C – C - C- C- C– C - O - H │ H H H H H H Hexanol 7 CH3(CH2)6OH C7H15 OH H H H H H H H H C – C - C- C- C– C –C- O - H │ H H H H H H H Heptanol 8 CH3(CH2)7OH C8H17 OH H H H H H H H H H C – C - C- C- C– C –C- C -O - H │ H H H H H H H H Octanol
3 9 CH3(CH2)8OH C9H19 OH H H H H H H H H H H C – C - C- C- C– C –C- C –C- O - H │ H H H H H H H H H Nonanol 10 CH3(CH2)9OH C10H21 OH H H H H H H H H H H H C – C - C- C- C– C –C- C –C- C-O - H │ H H H H H H H H H H Decanol Alkanols like Hydrocarbons( alkanes/alkenes/alkynes) form a homologous series where: (i)general name is derived from the alkane name then ending with “-ol” (ii)the members have –OH as the fuctional group (iii)they have the same general formula represented by R-OH where R is an alkyl group. (iv) each member differ by –CH2 group from the next/previous.
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No yellow precipitate confirms presence of Al3+ 6.The flow chart below illustrate the industrial extraction of Lead metal
42 (a)(i)Name the chief ore that is commonly used in this process Galena(PbS) (ii)Explain what take place in the roasting furnace
23.0.0 ORGANIC CHEMISTRY II (ALKANOLS AND ALKANOIC ACIDS) (20 LESSONS) B.ALKANOLS(Alcohols) (A) INTRODUCTION. Alkanols belong to a homologous series of organic compounds with a general formula CnH2n +1 OH and thus -OH as the functional group .The 1st ten alkanols include n General / molecular formular Structural formula IUPAC name 1 CH3OH H – C –O - H │ H Methanol 2 CH3 CH2OH H H Ethanol
2 C2H5 OH H C – C –O - H │ H H 3 CH3 (CH2)2OH C3H7 OH H H H H C – C - C –O - H │ H H H Propanol 4 CH3 (CH2)3OH C4H9 OH H H H H H C – C - C - C –O - H │ H H H H Butanol 5 CH3(CH2)4OH C5H11 OH H H H H H H C – C - C- C- C –O - H │ H H H H H Pentanol 6 CH3(CH2)5OH C6H13 OH H H H H H H H C – C - C- C- C– C - O - H │ H H H H H H Hexanol 7 CH3(CH2)6OH C7H15 OH H H H H H H H H C – C - C- C- C– C –C- O - H │ H H H H H H H Heptanol 8 CH3(CH2)7OH C8H17 OH H H H H H H H H H C – C - C- C- C– C –C- C -O - H │ H H H H H H H H Octanol
3 9 CH3(CH2)8OH C9H19 OH H H H H H H H H H H C – C - C- C- C– C –C- C –C- O - H │ H H H H H H H H H Nonanol 10 CH3(CH2)9OH C10H21 OH H H H H H H H H H H H C – C - C- C- C– C –C- C –C- C-O - H │ H H H H H H H H H H Decanol Alkanols like Hydrocarbons( alkanes/alkenes/alkynes) form a homologous series where: (i)general name is derived from the alkane name then ending with “-ol” (ii)the members have –OH as the fuctional group (iii)they have the same general formula represented by R-OH where R is an alkyl group. (iv) each member differ by –CH2 group from the next/previous. (v)they show a similar and gradual change in their physical properties e.g.
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Alkanols belong to a homologous series of organic compounds with a general formula CnH2n +1 OH and thus -OH as the functional group .The 1st ten alkanols include n General / molecular formular Structural formula IUPAC name 1 CH3OH H – C –O - H │ H Methanol 2 CH3 CH2OH H H Ethanol
2 C2H5 OH H C – C –O - H │ H H 3 CH3 (CH2)2OH C3H7 OH H H H H C – C - C –O - H │ H H H Propanol 4 CH3 (CH2)3OH C4H9 OH H H H H H C – C - C - C –O - H │ H H H H Butanol 5 CH3(CH2)4OH C5H11 OH H H H H H H C – C - C- C- C –O - H │ H H H H H Pentanol 6 CH3(CH2)5OH C6H13 OH H H H H H H H C – C - C- C- C– C - O - H │ H H H H H H Hexanol 7 CH3(CH2)6OH C7H15 OH H H H H H H H H C – C - C- C- C– C –C- O - H │ H H H H H H H Heptanol 8 CH3(CH2)7OH C8H17 OH H H H H H H H H H C – C - C- C- C– C –C- C -O - H │ H H H H H H H H Octanol
3 9 CH3(CH2)8OH C9H19 OH H H H H H H H H H H C – C - C- C- C– C –C- C –C- O - H │ H H H H H H H H H Nonanol 10 CH3(CH2)9OH C10H21 OH H H H H H H H H H H H C – C - C- C- C– C –C- C –C- C-O - H │ H H H H H H H H H H Decanol Alkanols like Hydrocarbons( alkanes/alkenes/alkynes) form a homologous series where: (i)general name is derived from the alkane name then ending with “-ol” (ii)the members have –OH as the fuctional group (iii)they have the same general formula represented by R-OH where R is an alkyl group. (iv) each member differ by –CH2 group from the next/previous. (v)they show a similar and gradual change in their physical properties e.g. boiling and melting points.
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(iv) each member differ by –CH2 group from the next/previous. (v)they show a similar and gradual change in their physical properties e.g. boiling and melting points. (vi)they show similar and gradual change in their chemical properties. B. ISOMERS OF ALKANOLS. Alkanols exhibit both structural and position isomerism. The isomers are named by using the following basic guidelines: (i)Like alkanes , identify the longest carbon chain to be the parent name. (ii)Identify the position of the -OH functional group to give it the smallest /lowest position. (iii) Identify the type and position of the side branches. Practice examples of isomers of alkanols (i)Isomers of propanol C3H7OH CH3CH2CH2OH - Propan-1-ol OH CH3CHCH3 - Propan-2-ol
4 Propan-2-ol and Propan-1-ol are position isomers because only the position of the –OH functional group changes. (ii)Isomers of Butanol C4H9OH CH3 CH2 CH3 CH2 OH Butan-1-ol CH3 CH2 CH CH3 OH Butan-2-ol CH3 CH3 CH3 CH3 OH 2-methylpropan-2-ol Butan-2-ol and Butan-1-ol are position isomers because only the position of the -OH functional group changes. 2-methylpropan-2-ol is both a structural and position isomers because both the position of the functional group and the arrangement of the atoms in the molecule changes.
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Practice examples of isomers of alkanols (i)Isomers of propanol C3H7OH CH3CH2CH2OH - Propan-1-ol OH CH3CHCH3 - Propan-2-ol
4 Propan-2-ol and Propan-1-ol are position isomers because only the position of the –OH functional group changes. (ii)Isomers of Butanol C4H9OH CH3 CH2 CH3 CH2 OH Butan-1-ol CH3 CH2 CH CH3 OH Butan-2-ol CH3 CH3 CH3 CH3 OH 2-methylpropan-2-ol Butan-2-ol and Butan-1-ol are position isomers because only the position of the -OH functional group changes. 2-methylpropan-2-ol is both a structural and position isomers because both the position of the functional group and the arrangement of the atoms in the molecule changes. (iii)Isomers of Pentanol C5H11OH CH3 CH2 CH2CH2CH2 OH Pentan-1-ol (Position isomer) CH3 CH2 CH CH3 OH Pentan-2-ol (Position isomer) CH3 CH2 CH CH2 CH3 OH Pentan-3-ol (Position isomer) CH3 CH3 CH2 CH2 C CH3
5 OH 2-methylbutan-2-ol (Position /structural isomer) CH3 CH3 CH2 CH2 C CHOH CH3 2,2-dimethylbutan-1-ol (Position /structural isomer) CH3 CH3 CH2 CH C CH3 CH3 OH 2,3-dimethylbutan-1-ol (Position /structural isomer) (iv)1,2-dichloropropan-2-ol CClH2 CCl CH3 OH (v)1,2-dichloropropan-1-ol CClH2 CHCl CH2 OH (vi) Ethan1,2-diol H H HOCH2CH2OH H-O - C - C – O-H H H (vii) Propan1,2,3-triol H OH H HOCH2CHOHCH2OH H-O - C- C – C – O-H H H H C. LABORATORY PREPARATION OF ALKANOLS.
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2-methylpropan-2-ol is both a structural and position isomers because both the position of the functional group and the arrangement of the atoms in the molecule changes. (iii)Isomers of Pentanol C5H11OH CH3 CH2 CH2CH2CH2 OH Pentan-1-ol (Position isomer) CH3 CH2 CH CH3 OH Pentan-2-ol (Position isomer) CH3 CH2 CH CH2 CH3 OH Pentan-3-ol (Position isomer) CH3 CH3 CH2 CH2 C CH3
5 OH 2-methylbutan-2-ol (Position /structural isomer) CH3 CH3 CH2 CH2 C CHOH CH3 2,2-dimethylbutan-1-ol (Position /structural isomer) CH3 CH3 CH2 CH C CH3 CH3 OH 2,3-dimethylbutan-1-ol (Position /structural isomer) (iv)1,2-dichloropropan-2-ol CClH2 CCl CH3 OH (v)1,2-dichloropropan-1-ol CClH2 CHCl CH2 OH (vi) Ethan1,2-diol H H HOCH2CH2OH H-O - C - C – O-H H H (vii) Propan1,2,3-triol H OH H HOCH2CHOHCH2OH H-O - C- C – C – O-H H H H C. LABORATORY PREPARATION OF ALKANOLS. For decades the world over, people have been fermenting grapes juice, sugar, carbohydrates and starch to produce ethanol as a social drug for relaxation. 6 In large amount, drinking of ethanol by mammals /human beings causes mental and physical lack of coordination. Prolonged intake of ethanol causes permanent mental and physical lack of coordination because it damages vital organs like the liver. Fermentation is the reaction where sugar is converted to alcohol/alkanol using biological catalyst/enzymes in yeast. It involves three processes: (i)Conversion of starch to maltose using the enzyme diastase.
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Prolonged intake of ethanol causes permanent mental and physical lack of coordination because it damages vital organs like the liver. Fermentation is the reaction where sugar is converted to alcohol/alkanol using biological catalyst/enzymes in yeast. It involves three processes: (i)Conversion of starch to maltose using the enzyme diastase. (C6H10O5)n (s) + H2O(l) --diastase enzyme --> C12H22O11(aq) (Starch) (Maltose) (ii)Hydrolysis of Maltose to glucose using the enzyme maltase. C12H22O11(aq)+ H2O(l) -- maltase enzyme -->2 C6H12O6(aq) (Maltose) (glucose) (iii)Conversion of glucose to ethanol and carbon(IV)oxide gas using the enzyme zymase. C6H12O6(aq) -- zymase enzyme --> 2 C2H5OH(aq) + 2CO2(g) (glucose) (Ethanol) At concentration greater than 15% by volume, the ethanol produced kills the yeast enzyme stopping the reaction. To increases the concentration, fractional distillation is done to produce spirits (e.g. Brandy=40% ethanol). Methanol is much more poisonous /toxic than ethanol. Taken large quantity in small quantity it causes instant blindness and liver, killing the consumer victim within hours. School laboratory preparation of ethanol from fermentation of glucose Measure 100cm3 of pure water into a conical flask. Add about five spatula end full of glucose. Stir the mixture to dissolve. Add about one spatula end full of yeast. Set up the apparatus as below. 7 Preserve the mixture for about three days. D.PHYSICAL AND CHEMICAL PROPERTIES OF ALKANOLS Use the prepared sample above for the following experiments that shows the characteristic properties of alkanols (a) Role of yeast Yeast is a single cell fungus which contains the enzyme maltase and zymase that catalyse the fermentation process. (b) Observations in lime water. A white precipitate is formed that dissolve to a colourless solution later. Lime water/Calcium hydroxide reacts with carbon(IV)0xide produced during the fermentation to form insoluble calcium carbonate and water.
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(b) Observations in lime water. A white precipitate is formed that dissolve to a colourless solution later. Lime water/Calcium hydroxide reacts with carbon(IV)0xide produced during the fermentation to form insoluble calcium carbonate and water. More carbon (IV)0xide produced during fermentation react with the insoluble calcium carbonate and water to form soluble calcium hydrogen carbonate. Ca(OH)2(aq) + CO2 (g) -> CaCO3(s) H2O(l) + CO2 (g) + CaCO3(s) -> Ca(HCO3) 2 (aq) (c)Effects on litmus paper Experiment
8 Take the prepared sample and test with both blue and red litmus papers. Repeat the same with pure ethanol and methylated spirit. Sample Observation table Substance/alkanol Effect on litmus paper Prepared sample Blue litmus paper remain blue Red litmus paper remain red Absolute ethanol Blue litmus paper remain blue Red litmus paper remain red Methylated spirit Blue litmus paper remain blue Red litmus paper remain red Explanation Alkanols are neutral compounds/solution that have characteristic sweet smell and taste. They have no effect on both blue and red litmus papers. (d)Solubility in water. Experiment Place about 5cm3 of prepared sample into a clean test tube Add equal amount of distilled water. Repeat the same with pure ethanol and methylated spirit. Observation No layers formed between the two liquids. Explanation Ethanol is miscible in water.Both ethanol and water are polar compounds . The solubility of alkanols decrease with increase in the alkyl chain/molecular mass. The alkyl group is insoluble in water while –OH functional group is soluble in water. As the molecular chain becomes longer ,the effect of the alkyl group increases as the effect of the functional group decreases. e)Melting/boiling point. Experiment Place pure ethanol in a long boiling tube .Determine its boiling point. Observation Pure ethanol has a boiling point of 78oC at sea level/one atmosphere pressure. Explanation The melting and boiling point of alkanols increase with increase in molecular chain/mass . 9 This is because the intermolecular/van-der-waals forces of attraction between the molecules increase. More heat energy is thus required to weaken the longer chain during melting and break during boiling.
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Explanation The melting and boiling point of alkanols increase with increase in molecular chain/mass . 9 This is because the intermolecular/van-der-waals forces of attraction between the molecules increase. More heat energy is thus required to weaken the longer chain during melting and break during boiling. f)Density Density of alkanols increase with increase in the intermolecular/van-der-waals forces of attraction between the molecule, making it very close to each other. This reduces the volume occupied by the molecule and thus increase the their mass per unit volume (density). Summary table showing the trend in physical properties of alkanols Alkanol Melting point (oC) Boiling point (oC) Density gcm-3 Solubility in water Methanol -98 65 0.791 soluble Ethanol -117 78 0.789 soluble Propanol -103 97 0.803 soluble Butanol -89 117 0.810 Slightly soluble Pentanol -78 138 0.814 Slightly soluble Hexanol -52 157 0.815 Slightly soluble Heptanol -34 176 0.822 Slightly soluble Octanol -15 195 0.824 Slightly soluble Nonanol -7 212 0.827 Slightly soluble Decanol 6 228 0.827 Slightly soluble g)Burning Experiment Place the prepared sample in a watch glass. Ignite. Repeat with pure ethanol and methylated spirit. Observation/Explanation Fermentation produce ethanol with a lot of water(about a ratio of 1:3)which prevent the alcohol from igniting. Pure ethanol and methylated spirit easily catch fire / highly flammable. They burn with an almost colourless non-sooty/non-smoky blue flame to form carbon(IV) oxide (in excess air/oxygen)or carbon(II) oxide (limited air) and water. Ethanol is thus a saturated compound like alkanes.
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Pure ethanol and methylated spirit easily catch fire / highly flammable. They burn with an almost colourless non-sooty/non-smoky blue flame to form carbon(IV) oxide (in excess air/oxygen)or carbon(II) oxide (limited air) and water. Ethanol is thus a saturated compound like alkanes. 10 Chemica equation C2 H5OH(l) + 3O2 (g) -> 3H2O(l) + 2CO2 (g) ( excess air) C2 H5OH(l) + 2O2 (g) -> 3H2O(l) + 2CO (g) ( limited air) 2CH3OH(l) + 3O2 (g) -> 4H2O(l) + 2CO2 (g) ( excess air) 2 CH3OH(l) + 2O2 (g) -> 4H2O(l) + 2CO (g) ( limited air) 2C3 H7OH(l) + 9O2 (g) -> 8H2O(l) + 6CO2 (g) ( excess air) C3 H7OH(l) + 3O2 (g) -> 4H2O(l) + 3CO (g) ( limited air) 2C4 H9OH(l) + 13O2 (g) -> 20H2O(l) + 8CO2 (g) ( excess air) C4 H9OH(l) + 3O2 (g) -> 4H2O(l) + 3CO (g) ( limited air) Due to its flammability, ethanol is used; (i) as a fuel in spirit lamps (ii) as gasohol when blended with gasoline (h)Formation of alkoxides Experiment Cut a very small piece of sodium. Put it in a beaker containing about 20cm3 of the prepared sample in a beaker. Test the products with litmus papers. Repeat with absolute ethanol and methylated spirit.
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Put it in a beaker containing about 20cm3 of the prepared sample in a beaker. Test the products with litmus papers. Repeat with absolute ethanol and methylated spirit. Sample observations Substance/alkanol Effect of adding sodium Fermentation prepared sample (i)effervescence/fizzing/bubbles (ii)colourless gas produced that extinguish burning splint with explosion/ “Pop” sound (iii)colourless solution formed (iv)blue litmus papers remain blue (v)red litmus papers turn blue Pure/absolute ethanol/methylated spirit (i)slow effervescence/fizzing/bubbles (ii)colourless gas slowly produced that extinguish burning splint with explosion/ “Pop” sound (iii)colourless solution formed (iv)blue litmus papers remain blue (v)red litmus papers turn blue Explanations
11 Sodium/potassium reacts slowly with alkanols to form basic solution called alkoxides and producing hydrogen gas. If the alkanol has some water the metals react faster with the water to form soluble hydroxides/alkalis i.e.
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Repeat with absolute ethanol and methylated spirit. Sample observations Substance/alkanol Effect of adding sodium Fermentation prepared sample (i)effervescence/fizzing/bubbles (ii)colourless gas produced that extinguish burning splint with explosion/ “Pop” sound (iii)colourless solution formed (iv)blue litmus papers remain blue (v)red litmus papers turn blue Pure/absolute ethanol/methylated spirit (i)slow effervescence/fizzing/bubbles (ii)colourless gas slowly produced that extinguish burning splint with explosion/ “Pop” sound (iii)colourless solution formed (iv)blue litmus papers remain blue (v)red litmus papers turn blue Explanations
11 Sodium/potassium reacts slowly with alkanols to form basic solution called alkoxides and producing hydrogen gas. If the alkanol has some water the metals react faster with the water to form soluble hydroxides/alkalis i.e. Sodium + Alkanol -> Sodium alkoxides + Hydrogen gas Potassium + Alkanol -> Potassium alkoxides + Hydrogen gas Sodium + Water -> Sodium hydroxides + Hydrogen gas Potassium + Water -> Potassium hydroxides + Hydrogen gas Examples 1.Sodium metal reacts with ethanol to form sodium ethoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2OH(l) + 2Na(s) -> 2CH3CH2ONa (aq) + H2 (s) 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) 2.Potassium metal reacts with ethanol to form Potassium ethoxide Potassium metal reacts with water to form Potassium Hydroxide 2CH3CH2OH(l) + 2K(s) -> 2CH3CH2OK (aq) + H2 (s) 2H2O(l) + 2K(s) -> 2KOH (aq) + H2 (s) 3.Sodium metal reacts with propanol to form sodium propoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2 CH2OH(l) + 2Na(s) -> 2CH3CH2 CH2ONa (aq) + H2 (s) 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) 4.Potassium metal reacts with propanol to form Potassium propoxide Potassium metal reacts with water to form Potassium Hydroxide 2CH3CH2 CH2OH(l) + 2K(s) -> 2CH3CH2 CH2OK (aq) + H2 (s) 2H2O(l) + 2K(s) -> 2KOH (aq) + H2 (s) 5.Sodium metal reacts with butanol to form sodium butoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2 CH2 CH2OH(l) + 2Na(s) -> 2CH3CH2 CH2 CH2ONa (aq) + H2 (s) 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) 6.Sodium metal reacts with pentanol to form sodium pentoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2 CH2 CH2 CH2OH(l)+2Na(s) -> 2CH3CH2 CH2 CH2 CH2ONa (aq) + H2 (s)
12 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) (i)Formation of Esters/Esterification Experiment Place 2cm3 of ethanol in a boiling tube.
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Sample observations Substance/alkanol Effect of adding sodium Fermentation prepared sample (i)effervescence/fizzing/bubbles (ii)colourless gas produced that extinguish burning splint with explosion/ “Pop” sound (iii)colourless solution formed (iv)blue litmus papers remain blue (v)red litmus papers turn blue Pure/absolute ethanol/methylated spirit (i)slow effervescence/fizzing/bubbles (ii)colourless gas slowly produced that extinguish burning splint with explosion/ “Pop” sound (iii)colourless solution formed (iv)blue litmus papers remain blue (v)red litmus papers turn blue Explanations
11 Sodium/potassium reacts slowly with alkanols to form basic solution called alkoxides and producing hydrogen gas. If the alkanol has some water the metals react faster with the water to form soluble hydroxides/alkalis i.e. Sodium + Alkanol -> Sodium alkoxides + Hydrogen gas Potassium + Alkanol -> Potassium alkoxides + Hydrogen gas Sodium + Water -> Sodium hydroxides + Hydrogen gas Potassium + Water -> Potassium hydroxides + Hydrogen gas Examples 1.Sodium metal reacts with ethanol to form sodium ethoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2OH(l) + 2Na(s) -> 2CH3CH2ONa (aq) + H2 (s) 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) 2.Potassium metal reacts with ethanol to form Potassium ethoxide Potassium metal reacts with water to form Potassium Hydroxide 2CH3CH2OH(l) + 2K(s) -> 2CH3CH2OK (aq) + H2 (s) 2H2O(l) + 2K(s) -> 2KOH (aq) + H2 (s) 3.Sodium metal reacts with propanol to form sodium propoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2 CH2OH(l) + 2Na(s) -> 2CH3CH2 CH2ONa (aq) + H2 (s) 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) 4.Potassium metal reacts with propanol to form Potassium propoxide Potassium metal reacts with water to form Potassium Hydroxide 2CH3CH2 CH2OH(l) + 2K(s) -> 2CH3CH2 CH2OK (aq) + H2 (s) 2H2O(l) + 2K(s) -> 2KOH (aq) + H2 (s) 5.Sodium metal reacts with butanol to form sodium butoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2 CH2 CH2OH(l) + 2Na(s) -> 2CH3CH2 CH2 CH2ONa (aq) + H2 (s) 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) 6.Sodium metal reacts with pentanol to form sodium pentoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2 CH2 CH2 CH2OH(l)+2Na(s) -> 2CH3CH2 CH2 CH2 CH2ONa (aq) + H2 (s)
12 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) (i)Formation of Esters/Esterification Experiment Place 2cm3 of ethanol in a boiling tube. Add equal amount of ethanoic acid.To the mixture add carefully 2drops of concentrated sulphuric(VI)acid.
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If the alkanol has some water the metals react faster with the water to form soluble hydroxides/alkalis i.e. Sodium + Alkanol -> Sodium alkoxides + Hydrogen gas Potassium + Alkanol -> Potassium alkoxides + Hydrogen gas Sodium + Water -> Sodium hydroxides + Hydrogen gas Potassium + Water -> Potassium hydroxides + Hydrogen gas Examples 1.Sodium metal reacts with ethanol to form sodium ethoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2OH(l) + 2Na(s) -> 2CH3CH2ONa (aq) + H2 (s) 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) 2.Potassium metal reacts with ethanol to form Potassium ethoxide Potassium metal reacts with water to form Potassium Hydroxide 2CH3CH2OH(l) + 2K(s) -> 2CH3CH2OK (aq) + H2 (s) 2H2O(l) + 2K(s) -> 2KOH (aq) + H2 (s) 3.Sodium metal reacts with propanol to form sodium propoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2 CH2OH(l) + 2Na(s) -> 2CH3CH2 CH2ONa (aq) + H2 (s) 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) 4.Potassium metal reacts with propanol to form Potassium propoxide Potassium metal reacts with water to form Potassium Hydroxide 2CH3CH2 CH2OH(l) + 2K(s) -> 2CH3CH2 CH2OK (aq) + H2 (s) 2H2O(l) + 2K(s) -> 2KOH (aq) + H2 (s) 5.Sodium metal reacts with butanol to form sodium butoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2 CH2 CH2OH(l) + 2Na(s) -> 2CH3CH2 CH2 CH2ONa (aq) + H2 (s) 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) 6.Sodium metal reacts with pentanol to form sodium pentoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2 CH2 CH2 CH2OH(l)+2Na(s) -> 2CH3CH2 CH2 CH2 CH2ONa (aq) + H2 (s)
12 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) (i)Formation of Esters/Esterification Experiment Place 2cm3 of ethanol in a boiling tube. Add equal amount of ethanoic acid.To the mixture add carefully 2drops of concentrated sulphuric(VI)acid. Warm/Heat gently.
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Sodium + Alkanol -> Sodium alkoxides + Hydrogen gas Potassium + Alkanol -> Potassium alkoxides + Hydrogen gas Sodium + Water -> Sodium hydroxides + Hydrogen gas Potassium + Water -> Potassium hydroxides + Hydrogen gas Examples 1.Sodium metal reacts with ethanol to form sodium ethoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2OH(l) + 2Na(s) -> 2CH3CH2ONa (aq) + H2 (s) 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) 2.Potassium metal reacts with ethanol to form Potassium ethoxide Potassium metal reacts with water to form Potassium Hydroxide 2CH3CH2OH(l) + 2K(s) -> 2CH3CH2OK (aq) + H2 (s) 2H2O(l) + 2K(s) -> 2KOH (aq) + H2 (s) 3.Sodium metal reacts with propanol to form sodium propoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2 CH2OH(l) + 2Na(s) -> 2CH3CH2 CH2ONa (aq) + H2 (s) 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) 4.Potassium metal reacts with propanol to form Potassium propoxide Potassium metal reacts with water to form Potassium Hydroxide 2CH3CH2 CH2OH(l) + 2K(s) -> 2CH3CH2 CH2OK (aq) + H2 (s) 2H2O(l) + 2K(s) -> 2KOH (aq) + H2 (s) 5.Sodium metal reacts with butanol to form sodium butoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2 CH2 CH2OH(l) + 2Na(s) -> 2CH3CH2 CH2 CH2ONa (aq) + H2 (s) 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) 6.Sodium metal reacts with pentanol to form sodium pentoxide Sodium metal reacts with water to form sodium Hydroxide 2CH3CH2 CH2 CH2 CH2OH(l)+2Na(s) -> 2CH3CH2 CH2 CH2 CH2ONa (aq) + H2 (s)
12 2H2O(l) + 2Na(s) -> 2NaOH (aq) + H2 (s) (i)Formation of Esters/Esterification Experiment Place 2cm3 of ethanol in a boiling tube. Add equal amount of ethanoic acid.To the mixture add carefully 2drops of concentrated sulphuric(VI)acid. Warm/Heat gently. Pour the mixture into a beaker containing about 50cm3 of cold water.
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Add equal amount of ethanoic acid.To the mixture add carefully 2drops of concentrated sulphuric(VI)acid. Warm/Heat gently. Pour the mixture into a beaker containing about 50cm3 of cold water. Smell the products. Repeat with methanol Sample observations Substance/alkanol Effect on adding equal amount of ethanol/concentrated sulphuric(VI)acid Absolute ethanol Sweet fruity smell Methanol Sweet fruity smell Explanation Alkanols react with alkanoic acids to form a group of homologous series of sweet smelling compounds called esters and water. This reaction is catalyzed by concentrated sulphuric(VI)acid in the laboratory. Alkanol + Alkanoic acid –Conc. H2SO4-> Ester + water Naturally esterification is catalyzed by sunlight. Each ester has a characteristic smell derived from the many possible combinations of alkanols and alkanoic acids that create a variety of known natural(mostly in fruits) and synthetic(mostly in juices) esters . Esters derive their names from the alkanol first then alkanoic acids. The alkanol “becomes” an alkyl group and the alkanoic acid “becomes” alkanoate hence alkylalkanoate. e.g. Ethanol + Ethanoic acid -> Ethylethanoate + Water Ethanol + Propanoic acid -> Ethylpropanoate + Water Ethanol + Methanoic acid -> Ethylmethanoate + Water Ethanol + butanoic acid -> Ethylbutanoate + Water Propanol + Ethanoic acid -> Propylethanoate + Water Methanol + Ethanoic acid -> Methyethanoate + Water Methanol + Decanoic acid -> Methyldecanoate + Water Decanol + Methanoic acid -> Decylmethanoate + Water
13 During the formation of the ester, the “O” joining the alkanol and alkanoic acid comes from the alkanol. R1 -COOH + R2 –OH -> R1 -COO –R2 + H2O e.g. 1. Ethanol reacts with ethanoic acid to form the ester ethyl ethanoate and water. Ethanol + Ethanoic acid --Conc.
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1. Ethanol reacts with ethanoic acid to form the ester ethyl ethanoate and water. Ethanol + Ethanoic acid --Conc. H2SO4 -->Ethylethanoate + Water C2H5OH (l) + CH3COOH(l) --Conc. H2SO4 --> CH3COO C2H5(aq) +H2O(l) CH3CH2OH (l)+ CH3COOH(l) --Conc. H2SO4 --> CH3COOCH2CH3(aq) +H2O(l) 2. Ethanol reacts with propanoic acid to form the ester ethylpropanoate and water. Ethanol + Propanoic acid --Conc. H2SO4 -->Ethylethanoate + Water C2H5OH (l)+ CH3 CH2COOH(l) --Conc. H2SO4 -->CH3CH2COO C2H5(aq) +H2O(l) CH3CH2OH (l)+ CH3 CH2COOH(l) --Conc. H2SO4 --> CH3 CH2COOCH2CH3(aq) +H2O(l) 3. Methanol reacts with ethanoic acid to form the ester methyl ethanoate and water. Methanol + Ethanoic acid --Conc. H2SO4 -->Methylethanoate + Water CH3OH (l) + CH3COOH(l) --Conc. H2SO4 --> CH3COO CH3(aq) +H2O(l) 4. Methanol reacts with propanoic acid to form the ester methyl propanoate and water. Methanol + propanoic acid --Conc. H2SO4 -->Methylpropanoate + Water CH3OH (l)+ CH3 CH2COOH(l) --Conc. H2SO4 --> CH3 CH2COO CH3(aq) +H2O(l) 5. Propanol reacts with propanoic acid to form the ester propylpropanoate and water. Propanol + Propanoic acid --Conc.
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H2SO4 --> CH3 CH2COO CH3(aq) +H2O(l) 5. Propanol reacts with propanoic acid to form the ester propylpropanoate and water. Propanol + Propanoic acid --Conc. H2SO4 -->Ethylethanoate + Water C3H7OH (l)+ CH3 CH2COOH(l) --Conc. H2SO4 -->CH3CH2COO C3H7(aq) +H2O(l) CH3CH2 CH2OH (l)+ CH3 CH2COOH(l) --Conc. H2SO4 --> CH3 CH2COOCH2 CH2CH3(aq) +H2O(l) (j)Oxidation Experiment Place 5cm3 of absolute ethanol in a test tube.Add three drops of acidified potassium manganate(VII).Shake thoroughly for one minute/warm.Test the solution mixture using pH paper. Repeat by adding acidified potassium dichromate(VII). Sample observation table Substance/alkanol Adding acidified KMnO4/K2Cr2O7 pH of resulting solution/mixture Nature of resulting solution/mixture Pure ethanol (i)Purple colour of pH= 4/5/6 Weakly acidic
14 KMnO4decolorized (ii) Orange colour of K2Cr2O7turns green. pH = 4/5/6 Weakly acidic Explanation Both acidified KMnO4 and K2Cr2O7 are oxidizing agents(add oxygen to other compounds.
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Repeat by adding acidified potassium dichromate(VII). Sample observation table Substance/alkanol Adding acidified KMnO4/K2Cr2O7 pH of resulting solution/mixture Nature of resulting solution/mixture Pure ethanol (i)Purple colour of pH= 4/5/6 Weakly acidic
14 KMnO4decolorized (ii) Orange colour of K2Cr2O7turns green. pH = 4/5/6 Weakly acidic Explanation Both acidified KMnO4 and K2Cr2O7 are oxidizing agents(add oxygen to other compounds. They oxidize alkanols to a group of homologous series called alkanals then further oxidize them to alkanoic acids.The oxidizing agents are themselves reduced hence changing their colour: (i) Purple KMnO4 is reduced to colourless Mn2+ (ii)Orange K2Cr2O7is reduced to green Cr3+ The pH of alkanoic acids show they have few H+ because they are weak acids i.e Alkanol + [O] -> Alkanal + [O] -> alkanoic acid NB The [O] comes from the oxidizing agents acidified KMnO4 or K2Cr2O7 Examples 1.When ethanol is warmed with three drops of acidified KMnO4 there is decolorization of KMnO4 Ethanol + [O] -> Ethanal + [O] -> Ethanoic acid CH3CH2OH + [O] -> CH3CH2O + [O] -> CH3COOH 2.When methanol is warmed with three drops of acidified K2Cr2O7 ,the orange colour of acidified K2Cr2O7 changes to green. methanol + [O] -> methanal + [O] -> methanoic acid CH3OH + [O] -> CH3O + [O] -> HCOOH 3.When propanol is warmed with three drops of acidified K2Cr2O7 ,the orange colour of acidified K2Cr2O7 changes to green.
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pH = 4/5/6 Weakly acidic Explanation Both acidified KMnO4 and K2Cr2O7 are oxidizing agents(add oxygen to other compounds. They oxidize alkanols to a group of homologous series called alkanals then further oxidize them to alkanoic acids.The oxidizing agents are themselves reduced hence changing their colour: (i) Purple KMnO4 is reduced to colourless Mn2+ (ii)Orange K2Cr2O7is reduced to green Cr3+ The pH of alkanoic acids show they have few H+ because they are weak acids i.e Alkanol + [O] -> Alkanal + [O] -> alkanoic acid NB The [O] comes from the oxidizing agents acidified KMnO4 or K2Cr2O7 Examples 1.When ethanol is warmed with three drops of acidified KMnO4 there is decolorization of KMnO4 Ethanol + [O] -> Ethanal + [O] -> Ethanoic acid CH3CH2OH + [O] -> CH3CH2O + [O] -> CH3COOH 2.When methanol is warmed with three drops of acidified K2Cr2O7 ,the orange colour of acidified K2Cr2O7 changes to green. methanol + [O] -> methanal + [O] -> methanoic acid CH3OH + [O] -> CH3O + [O] -> HCOOH 3.When propanol is warmed with three drops of acidified K2Cr2O7 ,the orange colour of acidified K2Cr2O7 changes to green. Propanol + [O] -> Propanal + [O] -> Propanoic acid CH3CH2 CH2OH + [O] -> CH3CH2 CH2O + [O] -> CH3 CH2COOH 4.When butanol is warmed with three drops of acidified K2Cr2O7 ,the orange colour of acidified K2Cr2O7 changes to green. Butanol + [O] -> Butanal + [O] -> Butanoic acid CH3CH2 CH2 CH2OH + [O] ->CH3CH2 CH2CH2O +[O] -> CH3 CH2COOH
15 Air slowly oxidizes ethanol to dilute ethanoic acid commonly called vinegar.
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methanol + [O] -> methanal + [O] -> methanoic acid CH3OH + [O] -> CH3O + [O] -> HCOOH 3.When propanol is warmed with three drops of acidified K2Cr2O7 ,the orange colour of acidified K2Cr2O7 changes to green. Propanol + [O] -> Propanal + [O] -> Propanoic acid CH3CH2 CH2OH + [O] -> CH3CH2 CH2O + [O] -> CH3 CH2COOH 4.When butanol is warmed with three drops of acidified K2Cr2O7 ,the orange colour of acidified K2Cr2O7 changes to green. Butanol + [O] -> Butanal + [O] -> Butanoic acid CH3CH2 CH2 CH2OH + [O] ->CH3CH2 CH2CH2O +[O] -> CH3 CH2COOH
15 Air slowly oxidizes ethanol to dilute ethanoic acid commonly called vinegar. If beer is not tightly corked, a lot of carbon(IV)oxide escapes and there is slow oxidation of the beer making it “flat”. (k)Hydrolysis /Hydration and Dehydration I. Hydrolysis/Hydration is the reaction of a compound/substance with water. Alkenes react with water vapour/steam at high temperatures and high pressures in presence of phosphoric acid catalyst to form alkanols.i.e.
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(k)Hydrolysis /Hydration and Dehydration I. Hydrolysis/Hydration is the reaction of a compound/substance with water. Alkenes react with water vapour/steam at high temperatures and high pressures in presence of phosphoric acid catalyst to form alkanols.i.e. Alkenes + Water - H3PO4 catalyst-> Alkanol Examples (i)Ethene is mixed with steam over a phosphoric acid catalyst at 300oC temperature and 60 atmosphere pressure to form ethanol Ethene + water ---60 atm/300oC/ H3PO4 --> Ethanol H2C =CH2 (g) + H2O(l) --60 atm/300oC/ H3PO4 --> CH3 CH2OH(l) This is the main method of producing large quantities of ethanol instead of fermentation (ii) Propene + water ---60 atm/300oC/ H3PO4 --> Propanol CH3C =CH2 (g) + H2O(l) --60 atm/300oC/ H3PO4 --> CH3 CH2 CH2OH(l) (iii) Butene + water ---60 atm/300oC/ H3PO4 --> Butanol CH3 CH2 C=CH2 (g) + H2O(l) --60 atm/300oC/ H3PO4 --> CH3 CH2 CH2 CH2OH(l) II. Dehydration is the process which concentrated sulphuric(VI)acid (dehydrating agent) removes water from a compound/substances. Concentrated sulphuric(VI)acid dehydrates alkanols to the corresponding alkenes at about 180oC. i.e Alkanol --Conc. H2 SO4/180oC--> Alkene + Water Examples 1. At 180oC and in presence of Concentrated sulphuric(VI)acid, ethanol undergoes dehydration to form ethene. Ethanol ---180oC/ H2SO4 --> Ethene + Water CH3 CH2OH(l) --180oC/ H2SO4 --> H2C =CH2 (g) + H2O(l) 2. Propanol undergoes dehydration to form propene.
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At 180oC and in presence of Concentrated sulphuric(VI)acid, ethanol undergoes dehydration to form ethene. Ethanol ---180oC/ H2SO4 --> Ethene + Water CH3 CH2OH(l) --180oC/ H2SO4 --> H2C =CH2 (g) + H2O(l) 2. Propanol undergoes dehydration to form propene. Propanol ---180oC/ H2SO4 --> Propene + Water CH3 CH2 CH2OH(l) --180oC/ H2SO4 --> CH3CH =CH2 (g) + H2O(l) 3. Butanol undergoes dehydration to form Butene. Butanol ---180oC/ H2SO4 --> Butene + Water CH3 CH2 CH2CH2OH(l) --180oC/ H2SO4 --> CH3 CH2C =CH2 (g) + H2O(l) 3. Pentanol undergoes dehydration to form Pentene. Pentanol ---180oC/ H2SO4 --> Pentene + Water
16 CH3 CH2 CH2 CH2 CH2OH(l)--180oC/ H2SO4-->CH3 CH2 CH2C =CH2 (g)+H2O(l) (l)Similarities of alkanols with Hydrocarbons I. Similarity with alkanes Both alkanols and alkanes burn with a blue non-sooty flame to form carbon(IV)oxide(in excess air/oxygen)/carbon(II)oxide(in limited air) and water. This shows they are saturated with high C:H ratio. e.g. Both ethanol and ethane ignite and burns in air with a blue non-sooty flame to form carbon(IV)oxide(in excess air/oxygen)/carbon(II)oxide(in limited air) and water.
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This shows they are saturated with high C:H ratio. e.g. Both ethanol and ethane ignite and burns in air with a blue non-sooty flame to form carbon(IV)oxide(in excess air/oxygen)/carbon(II)oxide(in limited air) and water. CH2 CH2OH(l) + 3O2(g) -Excess air-> 2CO2 (g) + 3H2 O(l) CH2 CH2OH(l) + 2O2(g) -Limited air-> 2CO (g) + 3H2 O(l) CH3 CH3(g) + 3O2(g) -Excess air-> 2CO2 (g) + 3H2 O(l) 2CH3 CH3(g) + 5O2(g) -Limited air-> 4CO (g) + 6H2 O(l) II. Similarity with alkenes/alkynes Both alkanols(R-OH) and alkenes/alkynes(with = C = C = double and – C = C- triple ) bond: (i)decolorize acidified KMnO4 (ii)turns Orange acidified K2Cr2O7 to green. Alkanols(R-OH) are oxidized to alkanals(R-O) ant then alkanoic acids(R-OOH). Alkenes are oxidized to alkanols with duo/double functional groups. Examples 1.When ethanol is warmed with three drops of acidified K2Cr2O7 the orange of acidified K2Cr2O7 turns to green. Ethanol is oxidized to ethanol and then to ethanoic acid. Ethanol + [O] -> Ethanal + [O] -> Ethanoic acid CH3CH2OH + [O] -> CH3CH2O + [O] -> CH3COOH 2.When ethene is bubbled in a test tube containing acidified K2Cr2O7 ,the orange of acidified K2Cr2O7 turns to green. Ethene is oxidized to ethan-1,2-diol. Ethene + [O] -> Ethan-1,2-diol. H2C=CH2 + [O] -> HOCH2 -CH2OH III. Differences with alkenes/alkynes Alkanols do not decolorize bromine and chlorine water.
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Ethene + [O] -> Ethan-1,2-diol. H2C=CH2 + [O] -> HOCH2 -CH2OH III. Differences with alkenes/alkynes Alkanols do not decolorize bromine and chlorine water. Alkenes decolorizes bromine and chlorine water to form halogenoalkanols Example
17 When ethene is bubbled in a test tube containing bromine water,the bromine water is decolorized. Ethene is oxidized to bromoethanol. Ethene + Bromine water -> Bromoethanol. H2C=CH2 + HOBr -> BrCH2 -CH2OH IV. Differences in melting and boiling point with Hydrocarbons Alkanos have higher melting point than the corresponding hydrocarbon (alkane/alkene/alkyne) This is because most alkanols exist as dimer.A dimer is a molecule made up of two other molecules joined usually by van-der-waals forces/hydrogen bond or dative bonding. Two alkanol molecules form a dimer joined by hydrogen bonding. Example In Ethanol the oxygen atom attracts/pulls the shared electrons in the covalent bond more to itself than Hydrogen. This creates a partial negative charge (δ-) on oxygen and partial positive charge(δ+) on hydrogen. Two ethanol molecules attract each other at the partial charges through Hydrogen bonding forming a dimmer. H H H H C C O H H H H H O C C H H H Dimerization of alkanols means more energy is needed to break/weaken the Hydrogen bonds before breaking/weakening the intermolecular forces joining the molecules of all organic compounds during boiling/melting. E.USES OF SOME ALKANOLS (a)Methanol is used as industrial alcohol and making methylated spirit (b)Ethanol is used: 1. as alcohol in alcoholic drinks e.g Beer, wines and spirits. 2.as antiseptic to wash woulds 3.in manufacture of vanishes, ink ,glue and paint because it is volatile and thus easily evaporate 4.as a fuel when blended with petrol to make gasohol. Hydrogen bonds Covalent bonds
18 B.ALKANOIC ACIDS (Carboxylic acids) (A) INTRODUCTION.
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as alcohol in alcoholic drinks e.g Beer, wines and spirits. 2.as antiseptic to wash woulds 3.in manufacture of vanishes, ink ,glue and paint because it is volatile and thus easily evaporate 4.as a fuel when blended with petrol to make gasohol. Hydrogen bonds Covalent bonds
18 B.ALKANOIC ACIDS (Carboxylic acids) (A) INTRODUCTION. Alkanoic acids belong to a homologous series of organic compounds with a general formula CnH2n +1 COOH and thus -COOH as the functional group .The 1st ten alkanoic acids include:
19 Alkanoic acids like alkanols /alkanes/alkenes/alkynes form a homologous series where: (i)the general name of an alkanoic acids is derived from the alkane name then ending with “–oic” acid as the table above shows. (ii) the members have R-COOH/R C-O-H as the functional group.
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Hydrogen bonds Covalent bonds
18 B.ALKANOIC ACIDS (Carboxylic acids) (A) INTRODUCTION. Alkanoic acids belong to a homologous series of organic compounds with a general formula CnH2n +1 COOH and thus -COOH as the functional group .The 1st ten alkanoic acids include:
19 Alkanoic acids like alkanols /alkanes/alkenes/alkynes form a homologous series where: (i)the general name of an alkanoic acids is derived from the alkane name then ending with “–oic” acid as the table above shows. (ii) the members have R-COOH/R C-O-H as the functional group. n General /molecular formular Structural formula IUPAC name 0 HCOOH H – C –O - H │ O Methanoic acid 1 CH3 COOH H H – C – C – O - H │ H O Ethanoic acid 2 CH3 CH2 COOH C2 H5 COOH H H H-C – C – C – O – H H H O Propanoic acid 3 CH3 CH2 CH2 COOH C3 H7 COOH H H H H- C - C – C – C – O – H H H H O Butanoic acid 4 CH3CH2CH2CH2 COOH C4 H9 COOH H H H H H - C – C - C – C – C – O – H H H H H O Pentanoic acid 5 CH3CH2 CH2CH2CH2 COOH C5 H11 COOH H H H H H H C - C – C - C – C – C – O – H H H H H H O Hexanoic acid 6 CH3CH2 CH2 CH2CH2CH2 COOH C6 H13 COOH H H H H H H H C C - C – C - C – C – C – O – H H H H H H H O Pentanoic acid
20 O (iii)they have the same general formula represented by R-COOH where R is an alkyl group. (iv)each member differ by –CH2- group from the next/previous. (v)they show a similar and gradual change in their physical properties e.g. boiling and melting point.
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(iv)each member differ by –CH2- group from the next/previous. (v)they show a similar and gradual change in their physical properties e.g. boiling and melting point. (vi)they show similar and gradual change in their chemical properties. (vii) since they are acids they show similar properties with mineral acids. (B) ISOMERS OF ALKANOIC ACIDS. Alkanoic acids exhibit both structural and position isomerism. The isomers are named by using the following basic guidelines (i)Like alkanes. identify the longest carbon chain to be the parent name. (ii)Identify the position of the -C-O-H functional group to give it the smallest O /lowest position. (iii)Identify the type and position of the side group branches. Practice examples on isomers of alkanoic acids 1.Isomers of butanoic acid C3H7COOH CH3 CH2 CH2 COOH Butan-1-oic acid CH3 H2C C COOH 2-methylpropan-1-oic acid 2-methylpropan-1-oic acid and Butan-1-oic acid are structural isomers because the position of the functional group does not change but the arrangement of the atoms in the molecule does. 2.Isomers of pentanoic acid C4H9COOH CH3CH2CH2CH2 COOH pentan-1-oic acid CH3 CH3CH2CH COOH 2-methylbutan-1-oic acid
21 CH3 H3C C COOH 2,2-dimethylpropan-1-oic acid CH3 3.Ethan-1,2-dioic acid O O HOOC- COOH // H - O – C - C – O – H 4.Propan-1,3-dioic acid O H O HOOC- CH2COOH // H - O – C – C - C – O – H H 5.Butan-1,4-dioic acid O H H O HOOC CH2 CH2 COOH H- O – C – C - C – C –O – H H H 6.2,2-dichloroethan-1,2-dioic acid HOOCCHCl2 Cl H – O - C – C – Cl O H (C) LABORATORY AND INDUSTRIAL PREPARATIONOF ALKANOIC ACIDS.
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(iii)Identify the type and position of the side group branches. Practice examples on isomers of alkanoic acids 1.Isomers of butanoic acid C3H7COOH CH3 CH2 CH2 COOH Butan-1-oic acid CH3 H2C C COOH 2-methylpropan-1-oic acid 2-methylpropan-1-oic acid and Butan-1-oic acid are structural isomers because the position of the functional group does not change but the arrangement of the atoms in the molecule does. 2.Isomers of pentanoic acid C4H9COOH CH3CH2CH2CH2 COOH pentan-1-oic acid CH3 CH3CH2CH COOH 2-methylbutan-1-oic acid
21 CH3 H3C C COOH 2,2-dimethylpropan-1-oic acid CH3 3.Ethan-1,2-dioic acid O O HOOC- COOH // H - O – C - C – O – H 4.Propan-1,3-dioic acid O H O HOOC- CH2COOH // H - O – C – C - C – O – H H 5.Butan-1,4-dioic acid O H H O HOOC CH2 CH2 COOH H- O – C – C - C – C –O – H H H 6.2,2-dichloroethan-1,2-dioic acid HOOCCHCl2 Cl H – O - C – C – Cl O H (C) LABORATORY AND INDUSTRIAL PREPARATIONOF ALKANOIC ACIDS. In a school laboratory, alkanoic acids can be prepared by adding an oxidizing agent (H+/KMnO4 or H+/K2Cr2O7)to the corresponding alkanol then warming. 22 The oxidation converts the alkanol first to an alkanal the alkanoic acid.
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2.Isomers of pentanoic acid C4H9COOH CH3CH2CH2CH2 COOH pentan-1-oic acid CH3 CH3CH2CH COOH 2-methylbutan-1-oic acid
21 CH3 H3C C COOH 2,2-dimethylpropan-1-oic acid CH3 3.Ethan-1,2-dioic acid O O HOOC- COOH // H - O – C - C – O – H 4.Propan-1,3-dioic acid O H O HOOC- CH2COOH // H - O – C – C - C – O – H H 5.Butan-1,4-dioic acid O H H O HOOC CH2 CH2 COOH H- O – C – C - C – C –O – H H H 6.2,2-dichloroethan-1,2-dioic acid HOOCCHCl2 Cl H – O - C – C – Cl O H (C) LABORATORY AND INDUSTRIAL PREPARATIONOF ALKANOIC ACIDS. In a school laboratory, alkanoic acids can be prepared by adding an oxidizing agent (H+/KMnO4 or H+/K2Cr2O7)to the corresponding alkanol then warming. 22 The oxidation converts the alkanol first to an alkanal the alkanoic acid. NB Acidified KMnO4 is a stronger oxidizing agent than acidified K2Cr2O7 General equation: R- CH2 – OH + [O] --H+/KMnO4--> R- CH –O + H2O(l) (alkanol) (alkanal) R- CH – O + [O] --H+/KMnO4--> R- C –OOH (alkanal) (alkanoic acid) Examples 1.Ethanol on warming in acidified KMnO4 is oxidized to ethanal then ethanoic acid .
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In a school laboratory, alkanoic acids can be prepared by adding an oxidizing agent (H+/KMnO4 or H+/K2Cr2O7)to the corresponding alkanol then warming. 22 The oxidation converts the alkanol first to an alkanal the alkanoic acid. NB Acidified KMnO4 is a stronger oxidizing agent than acidified K2Cr2O7 General equation: R- CH2 – OH + [O] --H+/KMnO4--> R- CH –O + H2O(l) (alkanol) (alkanal) R- CH – O + [O] --H+/KMnO4--> R- C –OOH (alkanal) (alkanoic acid) Examples 1.Ethanol on warming in acidified KMnO4 is oxidized to ethanal then ethanoic acid . CH3- CH2 – OH + [O] --H+/KMnO4--> CH3- CH –O + H2O(l) (ethanol) (ethanal) CH3- CH – O + [O] --H+/KMnO4--> CH3- C –OOH (ethanal) (ethanoic acid) 2Propanol on warming in acidified KMnO4 is oxidized to propanal then propanoic acid CH3- CH2 CH2 – OH + [O] --H+/KMnO4--> CH3- CH2 CH –O + H2O(l) (propanol) (propanal) CH3- CH – O + [O] --H+/KMnO4--> CH3- C –OOH (propanal) (propanoic acid) Industrially,large scale manufacture of alkanoic acid like ethanoic acid is obtained from: (a)Alkenes reacting with steam at high temperatures and pressure in presence of phosphoric(V)acid catalyst and undergo hydrolysis to form alkanols. i.e. Alkenes + Steam/water -- H2PO4 Catalyst--> Alkanol The alkanol is then oxidized by air at 5 atmosphere pressure with Manganese (II)sulphate(VI) catalyst to form the alkanoic acid.
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CH3- CH2 – OH + [O] --H+/KMnO4--> CH3- CH –O + H2O(l) (ethanol) (ethanal) CH3- CH – O + [O] --H+/KMnO4--> CH3- C –OOH (ethanal) (ethanoic acid) 2Propanol on warming in acidified KMnO4 is oxidized to propanal then propanoic acid CH3- CH2 CH2 – OH + [O] --H+/KMnO4--> CH3- CH2 CH –O + H2O(l) (propanol) (propanal) CH3- CH – O + [O] --H+/KMnO4--> CH3- C –OOH (propanal) (propanoic acid) Industrially,large scale manufacture of alkanoic acid like ethanoic acid is obtained from: (a)Alkenes reacting with steam at high temperatures and pressure in presence of phosphoric(V)acid catalyst and undergo hydrolysis to form alkanols. i.e. Alkenes + Steam/water -- H2PO4 Catalyst--> Alkanol The alkanol is then oxidized by air at 5 atmosphere pressure with Manganese (II)sulphate(VI) catalyst to form the alkanoic acid. Alkanol + Air -- MnSO4 Catalyst/5 atm pressure--> Alkanoic acid Example Ethene is mixed with steam over a phosphoric(V)acid catalyst,300oC temperature and 60 atmosphere pressure to form ethanol. 23 CH2=CH2 + H2O -> CH3 CH2OH (Ethene) (Ethanol) This is the industrial large scale method of manufacturing ethanol Ethanol is then oxidized by air at 5 atmosphere pressure with Manganese (II)sulphate(VI) catalyst to form the ethanoic acid. CH3 CH2OH + [O] -- MnSO4 Catalyst/5 atm pressure--> CH3 COOH (Ethanol) (Ethanoic acid) (b)Alkynes react with liquid water at high temperatures and pressure in presence of Mercury(II)sulphate(VI)catalyst and 30% concentrated sulphuric(VI)acid to form alkanals.
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Alkanol + Air -- MnSO4 Catalyst/5 atm pressure--> Alkanoic acid Example Ethene is mixed with steam over a phosphoric(V)acid catalyst,300oC temperature and 60 atmosphere pressure to form ethanol. 23 CH2=CH2 + H2O -> CH3 CH2OH (Ethene) (Ethanol) This is the industrial large scale method of manufacturing ethanol Ethanol is then oxidized by air at 5 atmosphere pressure with Manganese (II)sulphate(VI) catalyst to form the ethanoic acid. CH3 CH2OH + [O] -- MnSO4 Catalyst/5 atm pressure--> CH3 COOH (Ethanol) (Ethanoic acid) (b)Alkynes react with liquid water at high temperatures and pressure in presence of Mercury(II)sulphate(VI)catalyst and 30% concentrated sulphuric(VI)acid to form alkanals. Alkyne + Water -- Mercury(II)sulphate(VI)catalyst--> Alkanal The alkanal is then oxidized by air at 5 atmosphere pressure with Manganese (II) sulphate(VI) catalyst to form the alkanoic acid. Alkanal + air/oxygen -- Manganese(II)sulphate(VI)catalyst--> Alkanoic acid Example Ethyne react with liquid water at high temperature and pressure with Mercury (II) sulphate (VI)catalyst and 30% concentrated sulphuric(VI)acid to form ethanal. CH = CH + H2O --HgSO4--> CH3 CH2O (Ethyne) (Ethanal) This is another industrial large scale method of manufacturing ethanol from large quantities of ethyne found in natural gas. Ethanal is then oxidized by air at 5 atmosphere pressure with Manganese (II)sulphate(VI) catalyst to form the ethanoic acid. CH3 CH2O + [O] -- MnSO4 Catalyst/5 atm pressure--> CH3 COOH (Ethanal) (Oxygen from air) (Ethanoic acid) (D) PHYSICAL AND CHEMICAL PROPERTIES OF ALKANOIC ACIDS.
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CH = CH + H2O --HgSO4--> CH3 CH2O (Ethyne) (Ethanal) This is another industrial large scale method of manufacturing ethanol from large quantities of ethyne found in natural gas. Ethanal is then oxidized by air at 5 atmosphere pressure with Manganese (II)sulphate(VI) catalyst to form the ethanoic acid. CH3 CH2O + [O] -- MnSO4 Catalyst/5 atm pressure--> CH3 COOH (Ethanal) (Oxygen from air) (Ethanoic acid) (D) PHYSICAL AND CHEMICAL PROPERTIES OF ALKANOIC ACIDS. I.Physical properties of alkanoic acids
24 The table below shows some physical properties of alkanoic acids Alkanol Melting point(oC) Boiling point(oC) Density(gcm-3) Solubility in water Methanoic acid 18.4 101 1.22 soluble Ethanoic acid 16.6 118 1.05 soluble Propanoic acid -2.8 141 0.992 soluble Butanoic acid -8.0 164 0.964 soluble Pentanoic acid -9.0 187 0.939 Slightly soluble Hexanoic acid -11 205 0.927 Slightly soluble Heptanoic acid -3 223 0.920 Slightly soluble Octanoic acid 11 239 0.910 Slightly soluble Nonanoic acid 16 253 0.907 Slightly soluble Decanoic acid 31 269 0.905 Slightly soluble From the table note the following: (i) Melting and boiling point decrease as the carbon chain increases due to increase in intermolecular forces of attraction between the molecules requiring more energy to separate the molecules. (ii) The density decreases as the carbon chain increases as the intermolecular forces of attraction increases between the molecules making the molecule very close reducing their volume in unit mass. (iii) Solubility decreases as the carbon chain increases as the soluble –COOH end is shielded by increasing insoluble alkyl/hydrocarbon chain. (iv) Like alkanols ,alkanoic acids exist as dimmers due to the hydrogen bonds within the molecule. i.e..
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(iii) Solubility decreases as the carbon chain increases as the soluble –COOH end is shielded by increasing insoluble alkyl/hydrocarbon chain. (iv) Like alkanols ,alkanoic acids exist as dimmers due to the hydrogen bonds within the molecule. i.e.. 25 jgthungu@gmail.com104Hydrogen bondscovalent bondsR1C O δ-…….….…H δ+O δO δH δ+……..….O δCR2R1 and 2 are extensions of the molecule.For ethanoic acid the extension is made up of CH3 – to make the structure; jgthungu@gmail.com105For ethanoic acid the extension is made up of CH3 – to make the structure;Hydrogen bondscovalent bonds CH3CO δ-…………… H δ+O δO δH δ+…………O δCCH3Ethanoic acid has a higher melting/boiling point than ethanol .This is because ethanoic acid has two/more hydrogen bond than ethanol. II Chemical properties of alkanoic acids The following experiments shows the main chemical properties of ethanoic (alkanoic) acid. (a)Effect on litmus papers Experiment Dip both blue and red litmus papers in ethanoic acid. Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute nitric(V)acid. Sample observations Solution/acid Observations/effect on litmus papers Inference Ethanoic acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion
26 Succinic acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Citric acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Oxalic acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Tartaric acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Nitric(V)acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Explanation All acidic solutions contains H+/H3O+(aq) ions.
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(a)Effect on litmus papers Experiment Dip both blue and red litmus papers in ethanoic acid. Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute nitric(V)acid. Sample observations Solution/acid Observations/effect on litmus papers Inference Ethanoic acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion
26 Succinic acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Citric acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Oxalic acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Tartaric acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Nitric(V)acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Explanation All acidic solutions contains H+/H3O+(aq) ions. The H+ /H3O+ (aq) ions is responsible for turning blue litmus paper/solution to red (b)pH Experiment Place 2cm3 of ethaoic acid in a test tube. Add 2 drops of universal indicator solution and determine its pH. Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute sulphuric (VI)acid. Sample observations Solution/acid pH Inference Ethanoic acid 4/5/6 Weakly acidic Succinic acid 4/5/6 Weakly acidic Citric acid 4/5/6 Weakly acidic Oxalic acid 4/5/6 Weakly acidic Tartaric acid 4/5/6 Weakly acidic Sulphuric(VI)acid 1/2/3 Strongly acidic Explanations Alkanoic acids are weak acids that partially/partly dissociate to release few H+ ions in solution. The pH of their solution is thus 4/5/6 showing they form weakly acidic solutions when dissolved in water.
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Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute sulphuric (VI)acid. Sample observations Solution/acid pH Inference Ethanoic acid 4/5/6 Weakly acidic Succinic acid 4/5/6 Weakly acidic Citric acid 4/5/6 Weakly acidic Oxalic acid 4/5/6 Weakly acidic Tartaric acid 4/5/6 Weakly acidic Sulphuric(VI)acid 1/2/3 Strongly acidic Explanations Alkanoic acids are weak acids that partially/partly dissociate to release few H+ ions in solution. The pH of their solution is thus 4/5/6 showing they form weakly acidic solutions when dissolved in water. All alkanoic acid dissociate to releases the “H” at the functional group in -COOH to form the alkanoate ion; –COO- Mineral acids(Sulphuric(VI)acid, Nitric(V)acid and Hydrochloric acid) are strong acids that wholly/fully dissociate to release many H+ ions in solution. The pH of their solution is thus 1/2/3 showing they form strongly acidic solutions when dissolved in water.i.e Examples 1. CH3COOH(aq) CH3COO-(aq) + H+(aq)
27 (ethanoic acid) (ethanoate ion) (few H+ ion) 2. CH3 CH2COOH(aq) CH3 CH2COO-(aq) + H+(aq) (propanoic acid) (propanoate ion) (few H+ ion) 3. CH3 CH2 CH2COOH(aq) CH3 CH2 CH2COO-(aq) + H+(aq) (Butanoic acid) (butanoate ion) (few H+ ion) 4. HOOH(aq) HOO-(aq) + H+(aq) (methanoic acid) (methanoate ion) (few H+ ion) 5. H2 SO4 (aq) SO42- (aq) + 2H+(aq) (sulphuric(VI) acid) (sulphate(VI) ion) (many H+ ion) 6.
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CH3 CH2 CH2COOH(aq) CH3 CH2 CH2COO-(aq) + H+(aq) (Butanoic acid) (butanoate ion) (few H+ ion) 4. HOOH(aq) HOO-(aq) + H+(aq) (methanoic acid) (methanoate ion) (few H+ ion) 5. H2 SO4 (aq) SO42- (aq) + 2H+(aq) (sulphuric(VI) acid) (sulphate(VI) ion) (many H+ ion) 6. HNO3 (aq) NO3- (aq) + H+(aq) (nitric(V) acid) (nitrate(V) ion) (many H+ ion) (c)Reaction with metals Experiment Place about 4cm3 of ethanoic acid in a test tube. Put about 1cm length of polished magnesium ribbon. Test any gas produced using a burning splint. Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute sulphuric (VI) acid.
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Put about 1cm length of polished magnesium ribbon. Test any gas produced using a burning splint. Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute sulphuric (VI) acid. Sample observations Solution/acid Observations Inference Ethanoic acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that burn with “pop” sound/explosion H3O+/H+(aq)ion Succinic acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that burn with “pop” sound/explosion H3O+/H+(aq)ion Citric acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that burn with “pop” sound/explosion H3O+/H+(aq)ion Oxalic acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that burn with “pop” sound/explosion H3O+/H+(aq)ion Tartaric acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that burn with “pop” sound/explosion H3O+/H+(aq)ion
28 Nitric(V)acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that burn with “pop” sound/explosion H3O+/H+(aq)ion Explanation Metals higher in the reactivity series displace the hydrogen in all acids to evolve/produce hydrogen gas and form a salt. Alkanoic acids react with metals with metals to form alkanoates salt and produce/evolve hydrogen gas .Hydrogen extinguishes a burning splint with a pop sound/explosion. Only the “H”in the functional group -COOH is /are displaced and not in the alkyl hydrocarbon chain. Alkanoic acid + Metal -> Alkanoate + Hydrogen gas. i.e. Examples 1.
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Alkanoic acid + Metal -> Alkanoate + Hydrogen gas. i.e. Examples 1. For a monovalent metal with monobasic acid 2R – COOH + 2M -> 2R- COOM + 2H2(g) 2.For a divalent metal with monobasic acid 2R – COOH + M -> (R- COO) 2M + H2(g) 3.For a divalent metal with dibasic acid HOOC-R-COOH+ M -> MOOC-R-COOM + H2(g) 4.For a monovalent metal with dibasic acid HOOC-R-COOH+ 2M -> MOOC-R-COOM + H2(g) 5 For mineral acids (i)Sulphuric(VI)acid is a dibasic acid H2 SO4 (aq) + 2M -> M2 SO4 (aq) + H2(g) H2 SO4 (aq) + M -> MSO4 (aq) + H2(g) (ii)Nitric(V) and hydrochloric acid are monobasic acid HNO3 (aq) + 2M -> 2MNO3 (aq) + H2(g) HNO3 (aq) + M -> M(NO3 ) 2 (aq) + H2(g) Examples 1.Sodium reacts with ethanoic acid to form sodium ethanoate and produce. hydrogen gas. Caution: This reaction is explosive. CH3COOH (aq) + Na(s) -> CH3COONa (aq) + H2(g) (Ethanoic acid) (Sodium ethanoate) 2.Calcium reacts with ethanoic acid to form calcium ethanoate and produce. hydrogen gas. 2CH3COOH (aq) + Ca(s) -> (CH3COO) 2Ca (aq) + H2(g)
29 (Ethanoic acid) (Calcium ethanoate) 3.Sodium reacts with ethan-1,2-dioic acid to form sodium ethan-1,2-dioate and produce. hydrogen gas.
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hydrogen gas. 2CH3COOH (aq) + Ca(s) -> (CH3COO) 2Ca (aq) + H2(g)
29 (Ethanoic acid) (Calcium ethanoate) 3.Sodium reacts with ethan-1,2-dioic acid to form sodium ethan-1,2-dioate and produce. hydrogen gas. HOOC-COOH+ 2Na -> NaOOC - COONa + H2(g) (ethan-1,2-dioic acid) (sodium ethan-1,2-dioate) Commercial name of ethan-1,2-dioic acid is oxalic acid. The salt is sodium oxalate. 4.Magnesium reacts with ethan-1,2-dioic acid to form magnesium ethan-1,2-dioate and produce. hydrogen gas. HOOC-R-COOH+ Mg -> ( OOC - COO) Mg + H2(g) (ethan-1,2-dioic acid) (magnesium ethan-1,2-dioate) 5.Magnesium reacts with (i)Sulphuric(VI)acid to form Magnesium sulphate(VI) H2 SO4 (aq) + Mg -> MgSO4 (aq) + H2(g) (ii)Nitric(V) and hydrochloric acid are monobasic acid 2HNO3 (aq) + Mg -> M(NO3 ) 2 (aq) + H2(g) (d)Reaction with hydrogen carbonates and carbonates Experiment Place about 3cm3 of ethanoic acid in a test tube. Add about 0.5g/ ½ spatula end full of sodium hydrogen carbonate/sodium carbonate. Test the gas produced using lime water. Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute sulphuric (VI) acid.
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Add about 0.5g/ ½ spatula end full of sodium hydrogen carbonate/sodium carbonate. Test the gas produced using lime water. Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute sulphuric (VI) acid. Sample observations Solution/acid Observations Inference Ethanoic acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that forms a white precipitate with lime water H3O+/H+(aq)ion Succinic acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that forms a white precipitate with lime water H3O+/H+(aq)ion Citric acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that forms a white precipitate with lime water H3O+/H+(aq)ion Oxalic acid (i)effervescence, fizzing, bubbles H3O+/H+(aq)ion
30 (ii)colourless gas produced that forms a white precipitate with lime water Tartaric acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that forms a white precipitate with lime water H3O+/H+(aq)ion Nitric(V)acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that forms a white precipitate with lime water H3O+/H+(aq)ion All acids react with hydrogen carbonate/carbonate to form salt ,water and evolve/produce bubbles of carbon(IV)oxide and water. Carbon(IV)oxide forms a white precipitate when bubbled in lime water/extinguishes a burning splint. Alkanoic acids react with hydrogen carbonate/carbonate to form alkanoates ,water and evolve/produce bubbles of carbon(IV)oxide and water. Alkanoic acid + hydrogen carbonate -> alkanoate + water + carbon(IV)oxide Alkanoic acid + carbonate -> alkanoate + water + carbon(IV)oxide Examples 1. Sodium hydrogen carbonate reacts with ethanoic acid to form sodium ethanoate ,water and carbon(IV)oxide gas.
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Alkanoic acids react with hydrogen carbonate/carbonate to form alkanoates ,water and evolve/produce bubbles of carbon(IV)oxide and water. Alkanoic acid + hydrogen carbonate -> alkanoate + water + carbon(IV)oxide Alkanoic acid + carbonate -> alkanoate + water + carbon(IV)oxide Examples 1. Sodium hydrogen carbonate reacts with ethanoic acid to form sodium ethanoate ,water and carbon(IV)oxide gas. CH3COOH (aq) + NaHCO3 (s) -> CH3COONa (aq) + H2O(l) + CO2 (g) (Ethanoic acid) (Sodium ethanoate) 2.Sodium carbonate reacts with ethanoic acid to form sodium ethanoate ,water and carbon(IV)oxide gas. 2CH3COOH (aq) + Na2CO3 (s) -> 2CH3COONa (aq) + H2O(l) + CO2 (g) (Ethanoic acid) (Sodium ethanoate) 3.Sodium carbonate reacts with ethan-1,2-dioic acid to form sodium ethanoate ,water and carbon(IV)oxide gas. HOOC-COOH+ Na2CO3 (s) -> NaOOC - COONa + H2O(l) + CO2 (g) (ethan-1,2-dioic acid) (sodium ethan-1,2-dioate) 4.Sodium hydrogen carbonate reacts with ethan-1,2-dioic acid to form sodium ethanoate ,water and carbon(IV)oxide gas. HOOC-COOH+ 2NaHCO3 (s) -> NaOOC - COONa + H2O(l) + 2CO2 (g) (ethan-1,2-dioic acid) (sodium ethan-1,2-dioate)
31 (e)Esterification Experiment Place 4cm3 of ethanol acid in a boiling tube. Add equal volume of ethanoic acid. To the mixture, add 2 drops of concentrated sulphuric(VI)acid carefully. Warm/heat gently on Bunsen flame. Pour the mixture into a beaker containing 50cm3 of water. Smell the products.
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Warm/heat gently on Bunsen flame. Pour the mixture into a beaker containing 50cm3 of water. Smell the products. Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute sulphuric (VI) acid. Sample observations Solution/acid Observations Ethanoic acid Sweet fruity smell Succinic acid Sweet fruity smell Citric acid Sweet fruity smell Oxalic acid Sweet fruity smell Tartaric acid Sweet fruity smell Dilute sulphuric(VI)acid No sweet fruity smell Explanation Alkanols react with alkanoic acid to form the sweet smelling homologous series of esters and water.The reaction is catalysed by concentrated sulphuric(VI)acid in the laboratory but naturally by sunlight /heat.Each ester has a characteristic smell derived from the many possible combinations of alkanols and alkanoic acids. Alkanol + Alkanoic acids -> Ester + water Esters derive their names from the alkanol first then alkanoic acids. The alkanol “becomes” an alkyl group and the alkanoic acid “becomes” alkanoate hence alkylalkanoate. e.g. Ethanol + Ethanoic acid -> Ethylethanoate + Water Ethanol + Propanoic acid -> Ethylpropanoate + Water Ethanol + Methanoic acid -> Ethylmethanoate + Water Ethanol + butanoic acid -> Ethylbutanoate + Water Propanol + Ethanoic acid -> Propylethanoate + Water Methanol + Ethanoic acid -> Methyethanoate + Water Methanol + Decanoic acid -> Methyldecanoate + Water Decanol + Methanoic acid -> Decylmethanoate + Water
32 During the formation of the ester, the “O” joining the alkanol and alkanoic acid comes from the alkanol. R1 -COOH + R2 –OH -> R1 -COO –R2 + H2O Examples 1. Ethanol reacts with ethanoic acid to form the ester ethyl ethanoate and water. Ethanol + Ethanoic acid --Conc. H2SO4 -->Ethylethanoate + Water C2H5OH (l) + CH3COOH(l) --Conc.
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Ethanol reacts with ethanoic acid to form the ester ethyl ethanoate and water. Ethanol + Ethanoic acid --Conc. H2SO4 -->Ethylethanoate + Water C2H5OH (l) + CH3COOH(l) --Conc. H2SO4 --> CH3COO C2H5(aq) +H2O(l) CH3CH2OH (l)+ CH3COOH(l) --Conc. H2SO4 --> CH3COOCH2CH3(aq) +H2O(l) 2. Ethanol reacts with propanoic acid to form the ester ethylpropanoate and water. Ethanol + Propanoic acid --Conc. H2SO4 -->Ethylethanoate + Water C2H5OH (l)+ CH3 CH2COOH(l) --Conc. H2SO4 -->CH3CH2COO C2H5(aq) +H2O(l) CH3CH2OH (l)+ CH3 CH2COOH(l) --Conc. H2SO4 --> CH3 CH2COOCH2CH3(aq) +H2O(l) 3. Methanol reacts with ethanoic acid to form the ester methyl ethanoate and water. Methanol + Ethanoic acid --Conc. H2SO4 -->Methylethanoate + Water CH3OH (l) + CH3COOH(l) --Conc. H2SO4 --> CH3COO CH3(aq) +H2O(l) 4. Methanol reacts with propanoic acid to form the ester methyl propanoate and water. Methanol + propanoic acid --Conc. H2SO4 -->Methylpropanoate + Water CH3OH (l)+ CH3 CH2COOH(l) --Conc. H2SO4 --> CH3 CH2COO CH3(aq) +H2O(l) 5. Propanol reacts with propanoic acid to form the ester propylpropanoate and water. Propanol + Propanoic acid --Conc.
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H2SO4 --> CH3 CH2COO CH3(aq) +H2O(l) 5. Propanol reacts with propanoic acid to form the ester propylpropanoate and water. Propanol + Propanoic acid --Conc. H2SO4 -->Ethylethanoate + Water C3H7OH (l)+ CH3 CH2COOH(l) --Conc. H2SO4 -->CH3CH2COO C3H7(aq) +H2O(l) CH3CH2 CH2OH (l)+ CH3 CH2COOH(l) --Conc. H2SO4 --> CH3 CH2COOCH2 CH2CH3(aq) +H2O(l)
33 C. DETERGENTS Detergents are cleaning agents that improve the cleaning power /properties of water.A detergent therefore should be able to: (i)dissolve substances which water can not e.g grease ,oil, fat (ii)be washed away after cleaning. There are two types of detergents: (a)Soapy detergents (b)Soapless detergents (a) SOAPY DETERGENTS Soapy detergents usually called soap is long chain salt of organic alkanoic acids.Common soap is sodium octadecanoate .It is derived from reacting concentrated sodium hydroxide solution with octadecanoic acid(18 carbon alkanoic acid) i.e. Sodium hydroxide + octadecanoic acid -> Sodium octadecanoate + water NaOH(aq) + CH3 (CH2) 16 COOH(aq) -> CH3 (CH2) 16 COO – Na+ (aq) +H2 O(l) Commonly ,soap can thus be represented ; R- COO – Na+ where; R is a long chain alkyl group and -COO – Na+ is the alkanoate ion. In a school laboratory and at industrial and domestic level,soap is made by reacting concentrated sodium hydroxide solution with esters from (animal) fat and oil. The process of making soap is called saponification. During saponification ,the ester is hydrolyzed by the alkali to form sodium salt /soap and glycerol/propan-1,2,3-triol is produced.
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In a school laboratory and at industrial and domestic level,soap is made by reacting concentrated sodium hydroxide solution with esters from (animal) fat and oil. The process of making soap is called saponification. During saponification ,the ester is hydrolyzed by the alkali to form sodium salt /soap and glycerol/propan-1,2,3-triol is produced. Fat/oil(ester)+sodium/potassium hydroxide->sodium/potassium salt(soap)+ glycerol Fats/Oils are esters with fatty acids and glycerol parts in their structure; C17H35COOCH2 C17H35COOCH C17H35COOCH2
34 When boiled with concentrated sodium hydroxide solution NaOH; (i)NaOH ionizes/dissociates into Na+ and OH- ions (ii)fat/oil split into three C17H35COO- and one CH2 CH CH2 (iii) the three Na+ combine with the three C17H35COO- to form the salt C17H35COO- Na+ (iv)the three OH-ions combine with the CH2 CH CH2 to form an alkanol with three functional groups CH2 OH CH OH CH2 OH(propan-1,2,3-triol) C17H35COOCH2 CH2OH C17H35COOCH +NaOH -> 3 C17H35COO- Na+ + CHOH C17H35COOCH2 CH2OH Ester Alkali Soap glycerol Generally: CnH2n+1COOCH2 CH2OH CnH2n+1COOCH +NaOH -> 3 CnH2n+1COO- Na+ + CHOH CnH2n+1COOCH2 CH2OH Ester Alkali Soap glycerol R - COOCH2 CH2OH R - COOCH +NaOH -> 3R-COO- Na+ + CHOH R- COOCH2 CH2OH Ester Alkali Soap glycerol During this process a little sodium chloride is added to precipitate the soap by reducing its solubility. This is called salting out. The soap is then added colouring agents ,perfumes and herbs of choice.
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Fat/oil(ester)+sodium/potassium hydroxide->sodium/potassium salt(soap)+ glycerol Fats/Oils are esters with fatty acids and glycerol parts in their structure; C17H35COOCH2 C17H35COOCH C17H35COOCH2
34 When boiled with concentrated sodium hydroxide solution NaOH; (i)NaOH ionizes/dissociates into Na+ and OH- ions (ii)fat/oil split into three C17H35COO- and one CH2 CH CH2 (iii) the three Na+ combine with the three C17H35COO- to form the salt C17H35COO- Na+ (iv)the three OH-ions combine with the CH2 CH CH2 to form an alkanol with three functional groups CH2 OH CH OH CH2 OH(propan-1,2,3-triol) C17H35COOCH2 CH2OH C17H35COOCH +NaOH -> 3 C17H35COO- Na+ + CHOH C17H35COOCH2 CH2OH Ester Alkali Soap glycerol Generally: CnH2n+1COOCH2 CH2OH CnH2n+1COOCH +NaOH -> 3 CnH2n+1COO- Na+ + CHOH CnH2n+1COOCH2 CH2OH Ester Alkali Soap glycerol R - COOCH2 CH2OH R - COOCH +NaOH -> 3R-COO- Na+ + CHOH R- COOCH2 CH2OH Ester Alkali Soap glycerol During this process a little sodium chloride is added to precipitate the soap by reducing its solubility. This is called salting out. The soap is then added colouring agents ,perfumes and herbs of choice. School laboratory preparation of soap Place about 40 g of fatty (animal fat)beef/meat in 100cm3 beaker .Add about 15cm3 of 4.0M sodium hydroxide solution. Boil the mixture for about 15minutes.Stir the mixture .Add about 5.0cm3 of distilled water as you boil to make up for evaporation.
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The soap is then added colouring agents ,perfumes and herbs of choice. School laboratory preparation of soap Place about 40 g of fatty (animal fat)beef/meat in 100cm3 beaker .Add about 15cm3 of 4.0M sodium hydroxide solution. Boil the mixture for about 15minutes.Stir the mixture .Add about 5.0cm3 of distilled water as you boil to make up for evaporation. Boil for about another 15minutes.Add about four spatula end full of pure sodium chloride crystals. Continue stirring for another five minutes. Allow to cool. Filter of
35 /decant and wash off the residue with distilled water .Transfer the clean residue into a dry beaker. Preserve. The action of soap Soapy detergents: (i)act by reducing the surface tension of water by forming a thin layer on top of the water. (ii)is made of a non-polar alkyl /hydrocarbon tail and a polar -COO-Na+ head. The non-polar alkyl /hydrocarbon tail is hydrophobic (water hating) and thus does not dissolve in water .It dissolves in non-polar solvent like grease, oil and fat. The polar -COO-Na+ head is hydrophilic (water loving)and thus dissolve in water. When washing with soapy detergent, the non-polar tail of the soapy detergent surround/dissolve in the dirt on the garment /grease/oil while the polar head dissolve in water. Through mechanical agitation/stirring/sqeezing/rubbing/beating/kneading, some grease is dislodged/lifted of the surface of the garment. It is immediately surrounded by more soap molecules It float and spread in the water as tiny droplets that scatter light in form of emulsion making the water cloudy and shinny. It is removed from the garment by rinsing with fresh water.The repulsion of the soap head prevent /ensure the droplets do not mix.Once removed, the dirt molecules cannot be redeposited back because it is surrounded by soap molecules. Advantages and disadvantages of using soapy detergents Soapy detergents are biodegradable. They are acted upon by bacteria and rot.They thus do not cause environmental pollution. Soapy detergents have the diadvatage in that: (i)they are made from fat and oils which are better eaten as food than make soap.
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Advantages and disadvantages of using soapy detergents Soapy detergents are biodegradable. They are acted upon by bacteria and rot.They thus do not cause environmental pollution. Soapy detergents have the diadvatage in that: (i)they are made from fat and oils which are better eaten as food than make soap. (ii)forms an insoluble precipitate with hard water called scum. Scum is insoluble calcium octadecanoate and Magnesium octadecanoate formed when soap reacts with Ca2+ and Mg2+ present in hard water. Chemical equation 2C17H35COO- Na+ (aq) + Ca2+(aq) -> (C17H35COO- )Ca2+ (s) + 2Na+(aq) (insoluble Calcium octadecanote/scum) 2C17H35COO- Na+ (aq) + Mg2+(aq) -> (C17H35COO- )Mg2+ (s) + 2Na+(aq) (insoluble Magnesium octadecanote/scum) This causes wastage of soap. Potassium soaps are better than Sodium soap. Potassium is more expensive than sodium and thus its soap is also more expensive. (b)SOAPLESS DETERGENTS
36 Soapless detergent usually called detergent is a long chain salt fromed from byproducts of fractional distillation of crude oil.Commonly used soaps include: (i)washing agents (ii)toothpaste (iii)emulsifiers/wetting agents/shampoo Soapless detergents are derived from reacting: (i)concentrated sulphuric(VI)acid with a long chain alkanol e.g. Octadecanol(18 carbon alkanol) to form alkyl hydrogen sulphate(VI) Alkanol + Conc sulphuric(VI)acid -> alkyl hydrogen sulphate(VI) + Water R –OH + H2SO4 -> R –O-SO3H + H2O (ii)the alkyl hydrogen sulphate(VI) is then neutralized with sodium/potassium hydroxide to form sodium/potassium alkyl hydrogen sulphate(VI) Sodium/potassium alkyl hydrogen sulphate(VI) is the soapless detergent.
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Potassium is more expensive than sodium and thus its soap is also more expensive. (b)SOAPLESS DETERGENTS
36 Soapless detergent usually called detergent is a long chain salt fromed from byproducts of fractional distillation of crude oil.Commonly used soaps include: (i)washing agents (ii)toothpaste (iii)emulsifiers/wetting agents/shampoo Soapless detergents are derived from reacting: (i)concentrated sulphuric(VI)acid with a long chain alkanol e.g. Octadecanol(18 carbon alkanol) to form alkyl hydrogen sulphate(VI) Alkanol + Conc sulphuric(VI)acid -> alkyl hydrogen sulphate(VI) + Water R –OH + H2SO4 -> R –O-SO3H + H2O (ii)the alkyl hydrogen sulphate(VI) is then neutralized with sodium/potassium hydroxide to form sodium/potassium alkyl hydrogen sulphate(VI) Sodium/potassium alkyl hydrogen sulphate(VI) is the soapless detergent. alkyl hydrogen + Potassium/sodium -> Sodium/potassium + Water sulphate(VI) hydroxide alkyl hydrogen sulphate(VI) R –O-SO3H + NaOH -> R –O-SO3- Na+ + H2O Example Step I : Reaction of Octadecanol with Conc.H2SO4 C17H35CH2OH (aq) + H2SO4 -> C17H35CH2-O- SO3- H+ (aq) + H2O (l) octadecanol + sulphuric(VI)acid -> Octadecyl hydrogen sulphate(VI) + water Step II: Neutralization by an alkali C17H35CH2-O- SO3- H+ (aq) + NaOH -> C17H35CH2-O- SO3- Na+ (aq) + H2O (l) Octadecyl hydrogen + sodium/potassium -> sodium/potassium octadecyl+Water sulphate(VI) hydroxide hydrogen sulphate(VI) School laboratory preparation of soapless detergent Place about 20g of olive oil in a 100cm3 beaker. Put it in a trough containing ice cold water.
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Octadecanol(18 carbon alkanol) to form alkyl hydrogen sulphate(VI) Alkanol + Conc sulphuric(VI)acid -> alkyl hydrogen sulphate(VI) + Water R –OH + H2SO4 -> R –O-SO3H + H2O (ii)the alkyl hydrogen sulphate(VI) is then neutralized with sodium/potassium hydroxide to form sodium/potassium alkyl hydrogen sulphate(VI) Sodium/potassium alkyl hydrogen sulphate(VI) is the soapless detergent. alkyl hydrogen + Potassium/sodium -> Sodium/potassium + Water sulphate(VI) hydroxide alkyl hydrogen sulphate(VI) R –O-SO3H + NaOH -> R –O-SO3- Na+ + H2O Example Step I : Reaction of Octadecanol with Conc.H2SO4 C17H35CH2OH (aq) + H2SO4 -> C17H35CH2-O- SO3- H+ (aq) + H2O (l) octadecanol + sulphuric(VI)acid -> Octadecyl hydrogen sulphate(VI) + water Step II: Neutralization by an alkali C17H35CH2-O- SO3- H+ (aq) + NaOH -> C17H35CH2-O- SO3- Na+ (aq) + H2O (l) Octadecyl hydrogen + sodium/potassium -> sodium/potassium octadecyl+Water sulphate(VI) hydroxide hydrogen sulphate(VI) School laboratory preparation of soapless detergent Place about 20g of olive oil in a 100cm3 beaker. Put it in a trough containing ice cold water. Add dropwise carefully 18M concentrated sulphuric(VI)acid stirring continuously into the olive oil until the oil turns brown.Add 30cm3 of 6M sodium hydroxide solution.Stir.This is a soapless detergent. The action of soapless detergents
37 The action of soapless detergents is similar to that of soapy detergents.The soapless detergents contain the hydrophilic head and a long hydrophobic tail. i.e.
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Add dropwise carefully 18M concentrated sulphuric(VI)acid stirring continuously into the olive oil until the oil turns brown.Add 30cm3 of 6M sodium hydroxide solution.Stir.This is a soapless detergent. The action of soapless detergents
37 The action of soapless detergents is similar to that of soapy detergents.The soapless detergents contain the hydrophilic head and a long hydrophobic tail. i.e. vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv-COO-Na+ vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv-O-SO3- Na+ (long hydrophobic /non-polar alkyl tail) (hydrophilic/polar/ionic head) The tail dissolves in fat/grease/oil while the ionic/polar/ionic head dissolves in water. The tail stick to the dirt which is removed by the attraction of water molecules and the polar/ionic/hydrophilic head by mechanical agitation /squeezing/kneading/ beating/rubbing/scrubbing/scatching. The suspended dirt is then surrounded by detergent molecules and repulsion of the anion head preventing the dirt from sticking on the material garment. The tiny droplets of dirt emulsion makes the water cloudy. On rinsing the cloudy emulsion is washed away. Advantages and disadvantages of using soapless detergents Soapless detergents are non-biodegradable unlike soapy detergents. They persist in water during sewage treatment by causing foaming in rivers ,lakes and streams leading to marine /aquatic death. Soapless detergents have the advantage in that they: (i)do not form scum with hard water. (ii)are cheap to manufacture/buying (iii)are made from petroleum products but soapis made from fats/oil for human consumption. Sample revision questions 1. Study the scheme below Fat/oil KOH Boiling Sodium Chloride Filtration Filtrate Y Residue X
38 (a)Identify the process Saponification (b)Fats and oils are esters.
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(ii)are cheap to manufacture/buying (iii)are made from petroleum products but soapis made from fats/oil for human consumption. Sample revision questions 1. Study the scheme below Fat/oil KOH Boiling Sodium Chloride Filtration Filtrate Y Residue X
38 (a)Identify the process Saponification (b)Fats and oils are esters. Write the formula of the a common structure of ester C17H35COOCH2 C17H35COOCH C17H35COOCH2 (c)Write a balanced equation for the reaction taking place during boiling C17H35COOCH2 CH2OH C17H35COOCH +3NaOH -> 3 C17H35COO- Na+ + CHOH C17H35COOCH2 CH2OH Ester Alkali Soap glycerol (d)Give the IUPAC name of: (i)Residue X Potassium octadecanoate (ii)Filtrate Y Propan-1,2,3-triol (e)Give one use of fitrate Y Making paint (f)What is the function of sodium chloride To reduce the solubility of the soap hence helping in precipitating it out (g)Explain how residue X helps in washing. Has a non-polar hydrophobic tail that dissolves in dirt/grease /oil/fat Has a polar /ionic hydrophilic head that dissolves in water. 39 From mechanical agitation,the dirt is plucked out of the garment and surrounded by the tail end preventing it from being deposited back on the garment. (h)State one: (i)advantage of continued use of residue X on the environment Is biodegradable and thus do not pollute the environment (ii)disadvantage of using residue X Uses fat/oil during preparation/manufacture which are better used for human consumption. (i)Residue X was added dropwise to some water.The number of drops used before lather forms is as in the table below. Water sample A B C Drops of residue X 15 2 15 Drops of residue X in boiled water 2 2 15 (i)State and explain which sample of water is: I. Soft Sample B .Very little soap is used and no effect on amount of soap even on boiling/heating. II. Permanent hard Sample C .
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