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electrochemistry | Electrochemistry -gold recovery | https://chemistry.stackexchange.com/questions/145552/electrochemistry-gold-recovery | <p>I was wondering how to answer a question I got from my students about the possible recovery of gold from solution. We just finished the reaction between silver ions and copper metal and they wondered why copper wouldn't displace gold from solution in an electrochemical reaction. The redox potentials suggest that it... | <p>Short Answer: Yes, based on the electrochemical/reactivity series, it is possible to percipitate gold from solution using metals higher on the series like copper or zinc. However, it isn't done often because gold is highly unreactive, and when gold salts are formed, they are formed deliberately under atypical condit... | 262 |
electrochemistry | Can I use one alkaline battery to recharge another? | https://chemistry.stackexchange.com/questions/883/can-i-use-one-alkaline-battery-to-recharge-another | <p>Unfortunately, I don't have batteries to waste to test this myself, but I am curious... </p>
<p>Let's say you have two identical batteries. AA Duracell.</p>
<p>Now let's say you run one of the batteries through an LED until the LED starts emitting at half the intensity it was emitting at when you first started (ef... | <p>First, some batteries are rechargeable, but some are not. However, even if we talk about rechargeable one, then
1) some degradation during recharge usually occurs
2) deep equality will require very long time to achieve</p>
| 263 |
electrochemistry | Electrolysis: Water to Hydrogen gas? | https://chemistry.stackexchange.com/questions/4803/electrolysis-water-to-hydrogen-gas | <p>I recently conducted an experiment where I electrolyzed a solution of sodium chloride. I was using a copper coin as the anode, and I observed a pale blue precipitate in the cup when I was done with the experiment. I then deduced the following:</p>
<p>The chloride ions get oxidized at the anode: </p>
<p>$$\ce{2Cl- ... | <p>In answer to your last statement about the formation of Hydrogen. The actual amount of hydronium ions doesn't matter because it is at equilibrium ($\ce{H2O <=> OH- + H+}$) and so once you use an $\ce{H+}$ you'll simply have more $\ce{H2O}$ dissociate into $\ce{OH-}$ and $\ce{H+}$ (Le Chatlier states) so if you... | 264 |
electrochemistry | Is there anything in the literature that supports revolutionary claims for this "new" sulfuric-acid battery? | https://chemistry.stackexchange.com/questions/5109/is-there-anything-in-the-literature-that-supports-revolutionary-claims-for-this | <p>I've got the following from a <a href="http://megglobal.com/commitment.html" rel="nofollow noreferrer">supposed new energy-storage technologist</a>. It's supposed to be a fancy new cheap, high-powered, highly scalable battery. I want to know if this is known chemistry, and if there's anything genuinely revolutionary... | <p>There is nothing in the chemistry of what they describe that is different in any way to a conventional Lead-Acid battery. What they really seem to claim is improvement in materials in the battery not to change the electrochemistry but to improve other aspects of battery operation. <a href="http://megglobal.com/about... | 265 |
electrochemistry | In a battery what would happen if you had a perfectly uniform and pure cathode? | https://chemistry.stackexchange.com/questions/5446/in-a-battery-what-would-happen-if-you-had-a-perfectly-uniform-and-pure-cathode | <p>I have been watching some videos on how batteries work and they seem to talk about the cathode being the most important. I also watched another video a long time ago and while my memory is blurred it talked about impurities in the cathode being the only reason the electrical charge doesn't flow constantly. While I f... | <p>I don't think that's accurate. Even the universe doesn't have an "unlimited supply of electrons".</p>
<p>Impurities in the cathode likely give rise to internal resistance inside the battery (among other things), leading to deviation from an ideal cell. I would guess that as your cathode approached purity, ... | 266 |
electrochemistry | What are high throw solutions? | https://chemistry.stackexchange.com/questions/6072/what-are-high-throw-solutions | <p>I am trying to make a copper sulfate electroplating solution. I came across a <a href="http://www2.bren.ucsb.edu/~dturney/port/papers/Modern%20Electroplating/02.pdf" rel="nofollow">document</a> (Schlesinger and Paunovic 2011) which mentions the amount of copper sulfate that should be added to water to create such a ... | <p><a href="http://www.plating.com/platingtechnical/poorthrowingpower.htm">This page</a> suggests that throwing power is the ability to coat a surface evenly regardless of current density differences, and thus to produce an even plating thickness across the whole of a surface.</p>
<p>A solution with high throwing powe... | 267 |
electrochemistry | During electrolysis, why are the products attracted to the cathode? | https://chemistry.stackexchange.com/questions/6773/during-electrolysis-why-are-the-products-attracted-to-the-cathode | <p>Take the electrolysis of Lead(II) bromide:</p>
<p>We can write it as two half-reactions:</p>
<p>$$\ce{Pb^{2+}(l) + 2e^{-} \rightarrow Pb(l)}$$</p>
<p>$$\ce{Br^{-} \rightarrow Br + e^{-}}$$</p>
<p>In the electrolysis reaction, lead is formed at the cathode and bromine is liberated at the anode. But why is it so? ... | <p>You have to think about what exactly a cathode and anode are. You are falling victim to this: </p>
<p><em>A widespread misconception is that anode polarity is always positive (+). This is often incorrectly inferred from the correct fact that in all electrochemical devices, negatively charged anions move towards the... | 268 |
electrochemistry | Balanced reactions at the anode and cathode | https://chemistry.stackexchange.com/questions/7726/balanced-reactions-at-the-anode-and-cathode | <p>A current of 2.25 A is applied to $\ce{NiCl2}$ solution</p>
<p>A. Write the balanced half reaction that takes place at the anode
B. Write the balanced half reaction that takes place at the cathode</p>
<p>Can someone check if my answers seem logical? I'm not quite sure if I did the problem correctly</p>
<p>Anode:... | <p>At the <strong>A</strong>-node you <strong>O</strong>-xidize, at the <strong>C</strong>-athode you <strong>R</strong>-educe. (Vowel to vowel, consonant to consonant.)</p>
<p>Following this, you will have to generate electrons at the anode, which doesn't happen with your reaction.</p>
<p>What reaction will happen d... | 269 |
electrochemistry | What happens to the hydroxide anion during the electroreduction of water? | https://chemistry.stackexchange.com/questions/8180/what-happens-to-the-hydroxide-anion-during-the-electroreduction-of-water | <p>The reduction of water at a cathode is represented by the following equation:</p>
<p>Cathode (reduction): $\ce{2 H2O_{(l)} + 2e^{−} → H2_{(g)} + 2 OH^{-}_{(aq)}}$</p>
<p>If this is done in a divided cell, what would happen to the $\ce{OH-}$ anions? The hydrogen gas would accumulate and bubble would form. Would the... | <p>You only show one a half-reaction, reduction at the cathode. Write the other half-reaction, oxidation at the anode to give oxygen. A real world water electrolysis cell requires a salt electrolyte for conductivity. $\ce{NaCl}$ could be electrolyzed to $\ce{Cl2}$ and $\ce{Na}$, the latter reacting with water to giv... | 270 |
electrochemistry | Electrolytic cell chemical composition during/after charging? | https://chemistry.stackexchange.com/questions/9206/electrolytic-cell-chemical-composition-during-after-charging | <p>I have a pot with some (bottled) water and added (sea) salt. It has a pencil (graphite) and tin foil (aluminum). The pencil is connected to the positive outlet of a solar panel and the tinfoil is connected to the negative outlet of the solar panel (effectively 'charging' the electrolytic cell).</p>
<p>To ensure I d... | <p>Voltage determines the kind of reactions, amperage determines the amounts. The positive graphite electrode is the oxidizing anode. It will evolve oxygen and chlorine and be eroded to carbon dioxide, carbon monoxide, and chloro-organics. The negative aluminum electrode is the reducing cathode. It will reduce Na+ ... | 271 |
electrochemistry | Electrochemistry lye quality | https://chemistry.stackexchange.com/questions/9214/electrochemistry-lye-quality | <p>With the following setup: plastic container, water (impure), pencil (anode), tin foil (aluminum, cathode) and solar panels supplying electrical charge (roughly 36v at about 400-800ma), with the intention of producing lye via electrochemistry:</p>
<p>1) Would it be possible to produce the right kind of lye to a leve... | 272 | |
electrochemistry | how to determine the relative differences in activity between metals | https://chemistry.stackexchange.com/questions/9855/how-to-determine-the-relative-differences-in-activity-between-metals | <p>I am doing a lab for school and I do not know what this question is asking. In this lab we are making electrochemical cells from different metals. </p>
| <p>You have a standard pot of liquid electrolyte into which are dipped non-touching same-spaced paired strips of different clean metals. The external circuit between the strips is a sensitive voltmeter (with extremely high electrical resistance - hard by zero current flow). You measure the potential (noting direction... | 273 |
electrochemistry | Voltaic and electrolytic cells | https://chemistry.stackexchange.com/questions/10203/voltaic-and-electrolytic-cells | <p>Why more attractive metals will be oxidized? Aren't they being reduced, because they attract and receive electrons from negative polyatomic ions? So they will be anodes, where oxidization occurs. Why anodes are negative in voltaic cells and positive in electrolytic cells? Same for cathodes.</p>
| <p>Metals want to lose electrons and become positively charged. When the metal loses the electron, it is called oxidation. The substance that gets the electron is reduced.</p>
<p>Oxidation could occur at the anode if it takes electrons from a metal (i.e. $Fe^{2+}$ to $Fe^{3+}$). </p>
<p>Anodes are negative in voltaic... | 274 |
electrochemistry | How does the diffusion coefficient of a species affect the limiting current for a RDE voltammagram? | https://chemistry.stackexchange.com/questions/10686/how-does-the-diffusion-coefficient-of-a-species-affect-the-limiting-current-for | <p>And how do I find the diffusion coefficient from a Levich plot?</p>
| <p>I would recommend you take a look at the book Electrochemical Methods fundamentals and applications.</p>
<p>For the Koutecý-Levich equation (totally irreversible one-step, one-electron reaction):</p>
<p>$\Large \frac{1}{i}=\frac{1}{i_K}+\frac{1}{i_{l,c}}=\frac{1}{i_K}+\frac{1}{0.62nFAD^{2/3}\omega^{1/2}\nu^{-1/6}C... | 275 |
electrochemistry | What does the slope of a Levich plot represent? | https://chemistry.stackexchange.com/questions/10688/what-does-the-slope-of-a-levich-plot-represent | <p>I know that the limiting current is proportional to the square root of the rotation speed, but what does the slope of the plot represent?</p>
| <p>if you mean the following plot:
<img src="https://i.sstatic.net/zGGBU.jpg" alt="enter image description here"></p>
<p>(Electrochemical Methods. fundamentals and applications, p. 341). </p>
<p>If a bulk concentration is the same as the concentration at the surface of the electrode (the mass-transfer is very high) t... | 276 |
electrochemistry | Confusion regarding specific conductivity | https://chemistry.stackexchange.com/questions/10949/confusion-regarding-specific-conductivity | <p>Is there any difference between the terms specific conductivity and conductance. If yes, please explain.</p>
| <p>Let's take a wire inside cable for example. That wire's <strong>conductance</strong> is just the inverse of the resistance this cable is making when electricity passes through it. This depends on things like the length, what is made of, the maximum/minimum width of certain areas of the wire, etc.</p>
<p>On the othe... | 277 |
electrochemistry | how does electronic conductance of a metal change with density? | https://chemistry.stackexchange.com/questions/13606/how-does-electronic-conductance-of-a-metal-change-with-density | <p>The electronic conductance of a metal depends on its density.Does this mean that if we increase the density of the metal,its electronic conductance will increase?How does it happen?</p>
| <p>You cannot change the density of a metal without also changing other properties. </p>
<p>Brass is a mixture of several elements. It can have different densities depending on the mixture of the elements. I haven't researched it, but the electronic conductance would likely be different for each type of brass.</p>
<p... | 278 |
electrochemistry | In a galvanic cell, why does an electrode with a higher potential "pull" the electrons from the electrode with a lower potential? | https://chemistry.stackexchange.com/questions/15002/in-a-galvanic-cell-why-does-an-electrode-with-a-higher-potential-pull-the-ele | <p>I'm doing Grade 12 Chemistry and I'm unsure of this, taking the hydrogen electorde as having a potential of 0 volts.</p>
<p>I'll use the copper-zinc cell as an example. Just let me know if I've got the full logic right:</p>
<ol>
<li><p>Zinc has higher electronegativity, so due to the equilibrium $\ce{Zn <=> ... | <p>There are not many problems where electronegativity helps you find the answer. It is popular for some reason amongst newer chem students but it shouldn't be.</p>
<p>Here's what happens in the Daniell cell:</p>
<p>Metallic bonds in zinc are broken and zinc atoms each lose 2 electrons. Both of these processes are ... | 279 |
electrochemistry | Protonation of nitric acid | https://chemistry.stackexchange.com/questions/15760/protonation-of-nitric-acid | <p>I found that reaction: HNO3 + 4.1633363423443E-17 H3O = NO2{+} + OH{-}
Please help me understand " 4.1633363423443E-17" term.</p>
| <p>It seems to me like you were asked to balance a chemical equation and you used some computer program to do it for you instead.</p>
<p>4.1633363423443E-17 is the result of the limitations of floating point arithmetic (ie that computers only have finite precision). The real answer should be 0 (which you could have fi... | 280 |
electrochemistry | Electrochemical potentials | https://chemistry.stackexchange.com/questions/16929/electrochemical-potentials | <p>I was carrying out an experiment into the effect of temperature changes on the standard potential of a cell. </p>
<p>$$\ce{Zn(s) +2Fe^{3+}->Zn^{2+} +2Fe^{2+}}$$
I used equi-molar concentrations of $\ce{Fe(CN)_6^{4-}}$and $\ce{Fe(CN)_6^{3-}}$. Thus the Nernst equation</p>
<p>$$\mathrm{E^{\theta}_{cell}=E_{cell}-... | <p>A few thoughts:</p>
<p>For starters, $\ce{Zn^{2+}}$ is also part of the reaction quotient, so the log term in the Nernst equation will not necessarily be zero if the hexacyanoferrate concentrations are equal, depending on the $\ce{Zn^{2+}}$ concentration:</p>
<p>$$E = E°+\frac{RT}{zF}\ln\frac{[\ce{Zn^2+}][\ce{Fe^2... | 281 |
electrochemistry | in the electrolysis of H₂SO₄ solution, when the concentration is increased why does the current increase even when OH⁻ ions reduce? | https://chemistry.stackexchange.com/questions/23495/in-the-electrolysis-of-h%e2%82%82so%e2%82%84-solution-when-the-concentration-is-increased-why-d | <p>During the electrolysis of $\ce{H2SO4}$, $\ce {OH-}$ ions are more reactive than $\ce {SO4^{2-} }$ ions and so they dissociate. as $\ce {OH-}$ ions dissociate, they are the negative ions that carry current. So when the concentration of $\ce {H2SO4}$ is increased, the concentration of $\ce {OH-}$ ions actually reduce... | <p>Near room temperature, considering solutions of water and sulphuric acid, the maximum conductivity is at about 30% sulfuric acid. For pure water or pure sulfuric acid the conductivity is orders of magnitude lower. </p>
<p>In pure water, there are only $10^{-7}$M of $\ce{H+}$ and $\ce{OH-}$ to carry current. </p>... | 282 |
electrochemistry | Can we make a rusting battery | https://chemistry.stackexchange.com/questions/23720/can-we-make-a-rusting-battery | <p>Since in rusting (oxidation) of Iron, transfer of 4 electrons takes place is it possible to use this reaction under catalytic conditions to create a simple electric cell, even if it just gave a millivolt of potential.</p>
<p>$\ce {Fe + H2O -> FeOH3 + H2}$</p>
<p>Considering that we have complete control over th... | <p>Sure! A nickel-iron battery uses the oxidation of iron at the negative plate to produce about half the voltage. Though invented by Jungner, it's often called an Edison battery. See <a href="http://en.wikipedia.org/wiki/Nickel%E2%80%93iron_battery" rel="nofollow">http://en.wikipedia.org/wiki/Nickel%E2%80%93iron_batte... | 283 |
electrochemistry | offset in measuring decomposition potentials | https://chemistry.stackexchange.com/questions/24188/offset-in-measuring-decomposition-potentials | <p>as far as I've understood to measure the decomposition potential of an electrolyte using a galvanic cell we just put two electrodes, connect them to a battery, and vary the external potential till when we observe a current. The potential at which the current starts to grow linearly is the decomposition potential of ... | <p>Ok I will answer your last question first. If you have two identical electrodes(i.e. same electrode material), the cell potential will be zero and there won't be any issues there.</p>
<p>You have to use inert electrodes so that you are not measuring the dissolution of the electrode itself.</p>
<p>The one part I a... | 284 |
electrochemistry | Why is chloridric acid used in salt bridges? | https://chemistry.stackexchange.com/questions/25010/why-is-chloridric-acid-used-in-salt-bridges | <p>I've been planning an experiment on how to make galvanic cells and during my research I came across an article in which chloridric acid was used, along with a soluble salt and agar-agar, in salt bridges.
Since then, I've been wondering why chloridric acid was added to agar-agar.</p>
<p>Thanks in advence. </p>
| <p>Any ionic solution can function as a salt bridge. Having it acid based helps with the fast conduction paths of H+ in water.</p>
<p>The critical question is the leak rate. Any salt bridge will leak some amount of the ions into the solution. Good ones leak less, bad ones leak more. </p>
<p>So if you cannot tolerate ... | 285 |
electrochemistry | An electric potential is generated when a liquid moves with respect to a solid (streaming potential). Is the reverse true? | https://chemistry.stackexchange.com/questions/26284/an-electric-potential-is-generated-when-a-liquid-moves-with-respect-to-a-solid | <p>Streaming potential is an electrochemical phenomenon that a that relates
electric currents with the relative movement of solid and liquid phases in contact with
each other.</p>
<p>So when a liquid moves past a solid a potential is generated. The equations for the values of the potential and current generated can be... | <p>Your assumption is correct. <em>Electrokinetic pumps</em> use a potential difference across an osmotic membrane, i.e. through narrow channels, the inverse of flow causing a streaming potential difference. There are other aspects of the phenomena such as <em>electrophoresis</em>, <em>capillary osmosis</em> etc.; see:... | 286 |
electrochemistry | How is streaming potential measured? | https://chemistry.stackexchange.com/questions/26287/how-is-streaming-potential-measured | <p><a href="http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1548283&tag=1" rel="nofollow">This paper</a> describes the measurement of streaming potential using a potential divider configuration. However it is unclear where the potential difference is created. From the diagram it appears that it is created acros... | 287 | |
electrochemistry | How to use salt spray data in real environments? | https://chemistry.stackexchange.com/questions/26452/how-to-use-salt-spray-data-in-real-environments | <p>I want to convert resultant hours of salt spray corrosion test to estimated values in years for real life environments such as marine. In other words, How could I predict the result of real life tests using salt spray data?</p>
| <p><em>Note that I'm not an expert in this field and wikipedia itself is not a scientifically relevant primary source</em>. The latter might however be different for sources cited there.</p>
<p><strong>In short, you seemingly better shouldn't.</strong></p>
<p>It seems that the German wikipedia article on the <a href=... | 288 |
electrochemistry | The feasibility of the electrochemical cell. | https://chemistry.stackexchange.com/questions/27035/the-feasibility-of-the-electrochemical-cell | <p>This is the question extracted from my country high school level' exam.
So it asks to discuss the feasibility of the electrochemical cell to carry out electrolysis of an aqueous solution of sodium chloride at standard condition.</p>
<p>Al(s)/Al(aq)//Cu(aq)/Cu</p>
<p>My question is how I should start to answer thi... | 289 | |
electrochemistry | Reverse electro-plating byproducts | https://chemistry.stackexchange.com/questions/27126/reverse-electro-plating-byproducts | <p>Following <a href="https://byo.com/stories/issue/item/3113-etch-your-kettle-projects" rel="nofollow">this plan</a>, I am wondering what the byproducts of this method are? At the site with the q-tip, the solution turned a bright yellow, with the q-tip turning a dark yellow, almost red. Holding the q-tip in place for ... | <p>The yellow colour in solution is likely from iron ions from the metal being oxidized and dissolved:
$$\ce{Fe_{(s)} + 2e- -> Fe^{2+}_{(aq)}}$$ (Probably $\ce{Fe^3+}$, too)</p>
<p>The gas bubbles/smoke is the product of the other half of the reaction, the reduction of something in your solution. Because you have ... | 290 |
electrochemistry | Why does an increase in temperature decrease the electrode potential? | https://chemistry.stackexchange.com/questions/28036/why-does-an-increase-in-temperature-decrease-the-electrode-potential | <p>According to the Nernst equation, the electrode potential $E$ is
$$E = E^\circ - \frac{RT}{nF}\ln\frac{[\ce{M}]}{[\ce{M^{$n$+}}]}$$</p>
<p>Question is, why? Assuming a simple galvanic cell, we know that in general if the temperature is increased, there should be more collisions of the solution with the electrode, r... | 291 | |
electrochemistry | How is a car battery recharged? | https://chemistry.stackexchange.com/questions/28634/how-is-a-car-battery-recharged | <p>When recharging a lead-acid battery, how are the terminals of the battery connected to the voltage source. I mean, do we connect the positive terminal of the battery to the negative terminal of the source and vice versa? Or does the positive go with the positive and the negative with the negative? Also, are the elec... | <p>The polarities are not reversed, basically current always flows from the positive to negative terminal (opposite the flow of electrons by definition). When a battery is discharged, the voltage difference across its terminals will drop. When you then connect the charger with the full voltage across the terminals of t... | 292 |
electrochemistry | Transistors: How does the gate work? | https://chemistry.stackexchange.com/questions/28820/transistors-how-does-the-gate-work | <p>Two questions: </p>
<p>First, how does the gate provide a positive charge by running a current through it? I really just don't see how this positive charge could be achieved, unless you had some sort of battery in the gate itself and attached a wire to donate some of the electrons flowing through to the cathode of ... | <p>The gate of a FET works much like the grid of a radio tube (valve). The gate is insulated from source and drain; the only current flow (if the insulator were perfect) is to charge the intrinsic gate capacitance. Even a MOSFET has <em>some</em> leakage, but it's pico- or femtoamperes. See <a href="https://electronics... | 293 |
electrochemistry | Does the relationship equation between standard cell potential and equilibrium constant violate potential's intensive properties? | https://chemistry.stackexchange.com/questions/28954/does-the-relationship-equation-between-standard-cell-potential-and-equilibrium-c | <p>The equation: </p>
<p>$$E^{。}_{cell}= \frac{RT}{nF}\ln K_{eq}$$</p>
<p>We all know cell potential is intensive, not affected by the amount, Because: $volt=\frac{joule}{coulomb}$. Both joule and coulomb will be doubled altogether.</p>
<p>But as seen from the equation, cell potential is affected by the number of el... | <p>No, there is no violation of "intensivity". The reason is that $K_{eq}$ depends on $n$, and changes in one cancel the other out.</p>
<p>For example, consider the electrolysis of water:</p>
<ol>
<li>$$\ce{2H2O_{(l)} -> 2H2_{(g)} + O2_{(g)}}$$</li>
</ol>
<p>The equilibrium constant for this reaction is $K_{1}=\... | 294 |
electrochemistry | Why can some redox half-reactions be combined and some cannot? | https://chemistry.stackexchange.com/questions/28995/why-can-some-redox-half-reactions-be-combined-and-some-cannot | <p>I mean by "combining" is to make a new half-reaction equation and not an overall equation for a reaction in whole.</p>
<p>For instance, I was trying to arrive at the following half-reaction:</p>
<p>$\ce{MnO2(s) + 4H+(aq) + 2e- -> Mn^{2+}(aq) + 2H2O(l)}\quad E^\circ= 1.23\,\mathrm{V}$</p>
<p>by combining</p>
<... | <p>In general, you cannot simply subtract electrode potentials like this to find the potential of another half-reaction. They have to be weighted by $n$ (the stoichiometric coefficient of $\ce{e-}$). In cases where your method works, it is only because $n$ is coincidentally the same for both half-reactions you are comb... | 295 |
electrochemistry | Why does the cathode have to be made out Cu in a Zn-Cu voltaic cell? | https://chemistry.stackexchange.com/questions/28732/why-does-the-cathode-have-to-be-made-out-cu-in-a-zn-cu-voltaic-cell | <p>The classic voltaic cell has a <span class="math-container">$\ce{Zn}$</span> anode and <span class="math-container">$\ce{Cu}$</span> cathode. The reduction half reaction occurring at the cathode combines aqueous copper ions and electrons supplied by the anode to form solid <span class="math-container">$\ce{Cu}$</spa... | <p>You could certain have a zinc-copper cell in which copper was not the cathode material. Graphite or silver or whatever could be the electrode material instead. But once you close the circuit:</p>
<ol>
<li>Current flows</li>
<li>Cu is deposited as a metal solid on the electrode surface, whatever it is made out of... | 296 |
electrochemistry | What is the meaning of signs in electrode potentials? | https://chemistry.stackexchange.com/questions/31921/what-is-the-meaning-of-signs-in-electrode-potentials | <h2>Question</h2>
<p>Suppose you have a cell set up between a copper metal/copper(II) ion electrode and a reference electrode.</p>
<p>Under standard conditions, the emf of this cell was −0.07 V. The standard electrode potential of the copper metal / copper(II) ion electrode is +0.34 V. Hence the standard electrode po... | <p>Chapter 14 of Harris' Quantitative Chemical Analysis has a helpful section entitled, <em>an intuitive way to think about cell potentials.</em> Here's the corresponding graphic:</p>
<p><img src="https://i.sstatic.net/J7XRq.gif" alt="enter image description here"> </p>
<p>In this case, the author is describing a Ga... | 297 |
electrochemistry | Is this product description wrong and a simple battery and not a fuel cell? | https://chemistry.stackexchange.com/questions/32907/is-this-product-description-wrong-and-a-simple-battery-and-not-a-fuel-cell | <p>I won this <a href="http://rads.stackoverflow.com/amzn/click/B007V5TEMW">"toy"</a> at a science fair...
Now I have to make a short presentation about it in school.
On the package description they describe its energy source as "fuel cell"...
It consists out of a metal plate(magnesium), a black metal plate with a bla... | <p>Your analysis seems correct, i.e. it is only a <a href="https://en.wikipedia.org/wiki/Fuel_cell">fuel cell</a> if the <em>magnesium is being oxidized by the air</em>. You can prove if that is the case, and do so as part of your classroom demonstration, by excluding any air, and therefore oxygen, from the fuel cell.<... | 298 |
electrochemistry | Electrode Potential Half Reactions | https://chemistry.stackexchange.com/questions/34268/electrode-potential-half-reactions | <p>Does flipping a reaction as written change the sign of the value of E or is it a completely different value? </p>
<p>For example if I have the value for the half reaction $\ce{Cl2 + 2e- -> 2Cl-}$ but need the value for the opposite reaction ($\ce{2Cl- -> Cl2 + 2e-}$), do I just put a negative sign and treat i... | <p>Yes, you are correct - just flip the sign. As quoted from <a href="http://chemwiki.ucdavis.edu/Analytical_Chemistry/Electrochemistry/Voltaic_Cells/The_Cell_Potential" rel="nofollow">the venerable UC Davis ChemWiki</a>:</p>
<blockquote>
<p>To determine oxidation electrodes, the reduction equation can simply be fli... | 299 |
stoichiometry | Stoichiometry of alkane-perchlorate reaction | https://chemistry.stackexchange.com/questions/44119/stoichiometry-of-alkane-perchlorate-reaction | <blockquote>
<p>What are the products of an alkane and a perchlorate reaction?</p>
<p>e.g., making the alkane methane and the perchlorate anhydrous for simplicity:</p>
</blockquote>
<p><strong>My effort</strong>:</p>
<p><span class="math-container">$$\ce{Mg(ClO4)2 + 4CH4 -> MgCl2 + 4CO2}$$</span></p>
<p>leaves 16H f... | <p>I think that there is some $\ce{H2O}$ as product:
$$\ce{2Mg(ClO4)2 + 4CH4 -> 2MgCl2 + 4CO2 + 8H2O}%edit$$</p>
| 300 |
stoichiometry | Moles of Diatomic Molecules | https://chemistry.stackexchange.com/questions/53609/moles-of-diatomic-molecules | <p>Does "Mole of Iodine" or any other element that normally appears as diatomic molecules refer to a mole of single atoms (<span class="math-container">$6.02\times 10^{23}$</span> iodine atoms) or a mole of the molecules (<span class="math-container">$6.02\times 10^{23}$</span> molecules of <span class="math-... | <p>When we ask, for example, "how many moles of Iodine (or Oxygen or Hydrogen) is contained in 100g?" It ALWAYS refers to the molecule (e.g. I2, O2, H2 etc). Therefore, the number of 6.02 x 10^23 refers to the number of molecules, not atomes of Iodine and therefore you actually have 12.04 x 10^23 atomes of Iodine conta... | 301 |
stoichiometry | Which of the following samples contains the largest number of atoms? | https://chemistry.stackexchange.com/questions/59761/which-of-the-following-samples-contains-the-largest-number-of-atoms | <blockquote>
<p>Which of the following samples contains the largest number of atoms?</p>
<p>a. 2.0 moles of <span class="math-container">$\ce{H3PO4}$</span><br />
b. 3.0 moles of <span class="math-container">$\ce{H2SO3}$</span><br />
c. 4.0 moles of <span class="math-container">$\ce{HNO3}$</span><br />
d. 6... | <p>Geeze, NaCl has 1 mole of Na and 1 mole of Cl per mole of NaCl. So that is 2 moles of atoms per mole of NaCl. </p>
<p>$\ce{K2SO4}$ has 2 moles of potassium, 1 mole of S and 4 moles of O per mole of $\ce{K2SO4}$. So that is 7 moles of atoms per mole $\ce{K2SO4}$. </p>
<p>You don't need to convert to atoms using Avo... | 302 |
stoichiometry | Stoichiometry and percentage concentration | https://chemistry.stackexchange.com/questions/135405/stoichiometry-and-percentage-concentration | <p>10 g of Mg(NO3)2 was dissolved in 120 g of water. The result is a solution with a
density of 1.12 g / ml. Determine the percentage concentration
(in %) and the molar concentration (in mol/L) of the resulting
solution</p>
| <p>As you are new to this forum I want to welcome you but nevertheless I would kindly ask you to <em>first</em> make your own research on a problem you have and <em>then</em> ask your question providing some information on what you do not understand. Your question seems to be a homework which you only copied without an... | 303 |
stoichiometry | Why use 1.008 g/mol instead of 1.0079 g/mol calculating the number of moles in 75.0 g H_2 molecules? | https://chemistry.stackexchange.com/questions/136321/why-use-1-008-g-mol-instead-of-1-0079-g-mol-calculating-the-number-of-moles-in-7 | <p>Why are figures removed from the calculation for values that are known in more detail? E.g. if you want to calculate the number of moles in 75.0 g H2 molecules. Why should one here use
for the relative atomic mass/molar mass of H 1,008 u or g/mol instead of 1,0079 u or g/mol?
What is the purpose of this?
In addition... | <p>In my experience, mostly cause we don't care.</p>
<p>In my lab if I'm measuring 3mL - 12mL of a liquid I use a syringe that only has lines on the syringe every 0.2mL. So if I were to be measuring, say, 9mL, I would only have about 2 <a href="https://en.wikipedia.org/wiki/Significant_figures" rel="nofollow noreferrer... | 304 |
stoichiometry | Equation for reaction of tin and iodine to produce tin(IV) iodide | https://chemistry.stackexchange.com/questions/35309/equation-for-reaction-of-tin-and-iodine-to-produce-tiniv-iodide | <blockquote>
<p>Tin(IV) iodide is prepared by direct combination of the elements.
Add 2.00 g of granulated tin to a solution of 6.35 g of iodine. Write an equation for this reaction.</p>
</blockquote>
<p>Attempt:</p>
<p><strong>1.</strong> Determine the amount of tin using <strong>moles = mass/molar mass</strong>. This... | <p>The balanced chemical equation is independent of the amounts of each reactant added. In this case we can easily deduce the equation to be: $$\ce{Sn + 2I2 -> SnI4}$$</p>
<p>What the given masses tell us is that there is excess tin being added. We can see this because the $\ce{Sn:I2}$ ratio added is $1:1.5$ wherea... | 305 |
stoichiometry | What is the liquid which has the most hydrogen atoms per volume? | https://chemistry.stackexchange.com/questions/138783/what-is-the-liquid-which-has-the-most-hydrogen-atoms-per-volume | <p>What is the liquid which has the most hydrogen atoms per volume at STP ?
Is there anything better than water?</p>
<p><a href="https://chemistry.stackexchange.com/questions/117073/most-dense-hydrogen-containing-composition">This answer</a> does not answer this question because none of the compounds listed in it are l... | <p><strong>Hydrazine has more hydrogen atoms per mL than water</strong></p>
<p>Some simple calculations give the moles of hydrogen per mL in some possible alternative liquids. Taking into account density and molecular mass we get the following results:</p>
<p>Water 0.056 mol/mL 2 Hydrogens -> 0.11 mol H/mL
Hydrazine... | 306 |
stoichiometry | How much grams oxygen is in 7 gram magnesiumnitrate? Mg(NO3)2 | https://chemistry.stackexchange.com/questions/141359/how-much-grams-oxygen-is-in-7-gram-magnesiumnitrate-mgno32 | <p>I calculated this:
molar mass (M) of Mg(NO3)2 is 148,32 (24,3 + 2<em>14,01 + 6</em>16)
so when there is 7 grams Mg(NO3)2 there is 0,0472 mol (7/148,32)</p>
<p>But how do i find out how much of that is oxygen? Do i just divide by 8 and multiply by 6? (because 8 atoms of with 6 are oxygen)</p>
| <p>No. Each mole of the compound contains 6 moles of oxygen atoms, and has a mass of about 6 * 16 grams. You don’t have a mole, so use proportional reasoning to determine the actual mass in the sample.</p>
<p>To help to understand why it is simply a factor 6 and does not depend on the total number of atoms in the compo... | 307 |
stoichiometry | Find the molecular formula of a gas | https://chemistry.stackexchange.com/questions/143757/find-the-molecular-formula-of-a-gas | <p>The problem is:</p>
<blockquote>
<p>A quantity of <span class="math-container">$\pu{35.2 g}$</span> if a certain hydrocarbon gas, occupies <span class="math-container">$\pu{13.2 L}$</span>, measured at <span class="math-container">$\pu{1 atm}$</span> and at <span class="math-container">$\pu{323 K}$</span>. Knowing t... | 308 | |
stoichiometry | Calcium carbonate and hydrogen phosphate producing calcium phosphate, carbon dioxide, and water | https://chemistry.stackexchange.com/questions/5018/calcium-carbonate-and-hydrogen-phosphate-producing-calcium-phosphate-carbon-dio | <p>How does the balanced reaction look for these compounds? I found that phosphoric acid instead of hydrogen phosphate creates a much easier problem, but the teacher said hydrogen phosphate and I can't seem to balance it.</p>
| <p>Most likely that your teacher meant to say phosphoric acid ($\ce{H3PO4}$) rather than the hydrogen phosphate anion ($\ce{HPO4^{2-}}$) so lets go with that.</p>
<p>$$\ce{ 3CaCO3 + 2H3PO4 -> Ca3(PO4)2 + 3CO2 + 3H2O}$$ </p>
<p>In reality the carbon dioxide and water would exist in an equilibrium state with carboni... | 309 |
stoichiometry | Stoichiometry: efficiency | https://chemistry.stackexchange.com/questions/6640/stoichiometry-efficiency | <p>My book gives me the following problem:
"A mixture of $125.0 g$ $\ce{N2}$ and $32.0 g$ $\ce{H2}$ reacts to $36.5 g$ $\ce{NH3}$. Calculate the efficiency."</p>
<p>My method to do this is - one I learned from my teacher, to put every given molecule's amount of substance (moles) in a table with 3 steps: start (S), gon... | <p>Yes, that is completely correct. Let me summarize the approach.</p>
<p>If you look at the chemical reaction:
$$\ce{N2 + 3H2 \rightarrow 2 NH3}$$</p>
<p>You can see that you can, at best, make 2 mole of $\ce{NH3}$ per mole of $\ce{N2}$ (for the case here where $\ce{H2}$ is abundant). Given that you have $4.46\; mol... | 310 |
stoichiometry | Amount of substance produced in chemical reaction | https://chemistry.stackexchange.com/questions/6716/amount-of-substance-produced-in-chemical-reaction | <p>If $15.0\ \mathrm{mol}$ of nitrogen are reacted with $30.0\ \mathrm{mol}$ of hydrogen, how much ammonia will be produced?</p>
<p>$$\ce{N2 + 3H2 -> 2NH3}$$</p>
<p>What I’ve tried is the following: </p>
<p>$$\dfrac{n(\ce{N2})}{n(\ce{H2})}=\dfrac{1}{3}=\dfrac{15.0\ \mathrm{mol}}{x}$$</p>
<p>$$\dfrac{n(\ce{N2})}{... | <p>In the reaction:</p>
<p>$$\ce{N_2 + 3H_2 \to 2NH_3}$$</p>
<p>If 15 moles of $\ce{N_2}$ is used along with 30 moles of $\ce{H_2}$, then $\ce{H_2}$ will be the limiting reagent (Reactant which is consumed completely). This is because 15 moles of $\ce{N_2}$ will need 45 moles of $\ce{H_2}$ ($15 \times 3$, by the bala... | 311 |
stoichiometry | Units in stoichiometry | https://chemistry.stackexchange.com/questions/7727/units-in-stoichiometry | <p>$$C_x H_y O_z$$ </p>
<p>1.What are the units of x,y,z.I've read that they're termed as 'stoichiometric coefficients'.</p>
<p>2.What is the unit of mass proportion of carbon(c) in the fuel?</p>
<p>$$c=\frac{M_{carbon}}{M_{fuel}} .x$$</p>
| <p>The stoichiometric coefficients is something else than you suggest.</p>
<p><a href="https://www.boundless.com/chemistry/definition/stoichiometric-coefficient/" rel="nofollow noreferrer">stoichiometric coefficients</a>:</p>
<p>The number of molecules of a given component that participate in the reaction as written.</... | 312 |
stoichiometry | Calculating mass of krypton from mole fraction | https://chemistry.stackexchange.com/questions/7899/calculating-mass-of-krypton-from-mole-fraction | <blockquote>
<p>There are two gases in a container: krypton and carbon dioxide. If the mass of the gases is 35 grams, and total pressure of the container is 0.708 atm, and the pressure of krypton is 0.250 atm. What is the mass of the krypton?</p>
</blockquote>
<p>I've found the mole fraction of krypton is 0.3531. Fi... | <p>Let $m_{\ce{CO2}}$ be the mass of carbon dioxide and $m_{\ce{Kr}}$ be the mass of krypton in the vessel. These two are related by:</p>
<p>$$m_{\ce{CO2}}+m_{\ce{Kr}}=35\ \text{g}\ \ \ \ \ (1)$$</p>
<p>If we can get a second equation in both variables, you can solved the system for each variable.</p>
<p>You were ab... | 313 |
stoichiometry | Laws of Chemical Combination | https://chemistry.stackexchange.com/questions/9958/laws-of-chemical-combination | <p>I'm doing revision questions and want to double check something. The opening information reads: </p>
<blockquote>
<p>Two chlorides of iron were prepared. One was prepared by reacting iron with dry chlorine
gas. 4.50 g of iron reacted with chlorine gas to produce 13.01 g of the chloride.
The other chloride was... | <blockquote>
<p>Two chlorides of iron were prepared.</p>
</blockquote>
<p>I do <strong>not</strong> read that as: $\ce{FeCl_{n}}$ was prepared by two different methods, but as:</p>
<ol>
<li>Reacting iron with dry chlorine gas yields $\ce{FeCl_{n}}$</li>
<li>Reacting iron with hydrogen chloride yields $\ce{FeCl_{m}}... | 314 |
stoichiometry | Reactions involving trimethylaluminium Al2Me6 | https://chemistry.stackexchange.com/questions/10135/reactions-involving-trimethylaluminium-al2me6 | <p>I need to write balanced equations describing the following reactions:</p>
<ul>
<li>one mole of $\ce{Al2Me6}$ with two moles of water</li>
<li>excess of $\ce{Al2Me6}$ with silicon dioxide</li>
<li>excess of $\ce{Al2Me6}$ with tin(IV) chloride</li>
</ul>
<p>My answer so far:</p>
<ul>
<li>a) $\ce{2H2O + Al2Me6 ->... | <p>For a): Many organometallic compounds are easily hydrolyzed to the respective hydrocarbons and metal (hydr)oxides. In this case, the products are $\ce{CH4}$ and more likely $\ce{Al2O3}$, because the formation of $\ce{Al(OH)3}$ requires more moles of water. </p>
<p>Reactions b) and c) should be transmetallations whe... | 315 |
stoichiometry | what's the mass of the original sample (g)? | https://chemistry.stackexchange.com/questions/13751/whats-the-mass-of-the-original-sample-g | <p>here is a question that i don't know how it is solved :</p>
<p>A sample that is 75 % chloride by mass is dissolved in water and treated with an excess of AgNO3. If the mass of the AgCl precipitate that forms is 2.013 g, what was the mass of the original sample?</p>
<p>I hope you give me the the proper way of solvi... | <p>It is first of all important to recognise that all the chloride in the original sample will precipitate upon treatment with excess AgNO3. This will give you a starting point, which is a measurable amount of AgCl.</p>
<p>The molecular mass of AgCl = (107.87+35.45)=143.32g</p>
<p>Therefore, the proportion of chlorid... | 316 |
stoichiometry | Use the given information to write the formula of this compound | https://chemistry.stackexchange.com/questions/13752/use-the-given-information-to-write-the-formula-of-this-compound | <p>the question says :</p>
<p>Two elements, A and B, combine to form two binary compounds. In the first
compound, 3.5 g of A combines with 8.00 g of B. In the second compound,
5.0 g of A combines with 17.1 g of B. If the formula of the first compound is
AB2, then the formula of the second compound would be ?</p>
<p>I... | <p>For a molecule AB2, 3.5g of A represents one molar fraction, and 8.00g B represents 2 molar fractions (or 4.0+4.0). Therefore, a direct ratio can be given as 3.5:4.0, or 1:1.14. This means a molecule A<sub>n</sub>B<sub>m</sub> will give a mass ratio for A:B of n:1.14xm</p>
<p>For a molecule AB, for every 1g of A, ... | 317 |
stoichiometry | A sample of copper(II) sulfate pentahydrate (CuSO4·5H2O) contains 0.360 g of water. What is the total number of atoms in the compound | https://chemistry.stackexchange.com/questions/13769/a-sample-of-copperii-sulfate-pentahydrate-cuso4-5h2o-contains-0-360-g-of-wat | <p>A sample of copper(II) sulfate pentahydrate (CuSO4·5H2O) contains 0.360 g of water.
What is the total number of atoms in the compound</p>
<p>what's the idea of this question?</p>
<p>what i know is that atoms number is found by multiplying the Avogadro number by the mol's number</p>
<p>??</p>
| <p>You have to calculate the amount of substance with the mass of water.</p>
<p>$n[H_2O]=\frac{m}{M}=\frac{0.360\,g}{18\,g} \cdot mol = 0.02\, mol$</p>
<p>$1~ n[CuSO_4\cdot 5 H_2O] = 5~n[H_2O]$</p>
<p>$1~ n[CuSO_4\cdot 5 H_2O] = 0.004\, mol$</p>
<p>In 0.004 mol copper sulfate pentahydrate you have 0.36 g water.</p>... | 318 |
stoichiometry | Given the mass of precipitate, how can I calculate the relative amount of the original dissolved compounds? | https://chemistry.stackexchange.com/questions/18756/given-the-mass-of-precipitate-how-can-i-calculate-the-relative-amount-of-the-or | <blockquote>
<p>A simple mixture of $\ce{NaCl}$ and $\ce{NaBr}$ weighing $0.180~ \mathrm{g}$ is treated with $\ce{AgNO3}$ solution to give $0.3715~ \mathrm{g}$ of precipitate. Calculate the content of $\ce{NaCl}$ and $\ce{NaBr}$ in the mixture.</p>
</blockquote>
<p>The answer given in book are $\ce{NaCl}$ = $0.0682~... | <p>x = number of moles of chloride
y = number of moles of bromide</p>
<p>Since you know the mass of the original $\ce{NaCl}$/$\ce{NaBr }$mixture and the molar masses of $\ce{NaCl}$ and $\ce{NaBr}$, you can write an equation of the form:</p>
<p>$58.44 \pu{\frac{g}{mol}}~ x + 102.89 \pu{\frac{g}{mol}}~ y = 0.180~ \pu{g... | 319 |
stoichiometry | What does "a metallic oxide has 40 % oxygen" mean? | https://chemistry.stackexchange.com/questions/18939/what-does-a-metallic-oxide-has-40-oxygen-mean | <blockquote>
<p><strong>Question</strong><br>
If a metallic oxide has $40\,\%$ oxygen, find the equivalent weight of
the metal.</p>
</blockquote>
<p>This amounts to finding the atomic weight of the metal and the charge on the cation (in effect identifying the metal itself). </p>
<p>I didn't know how to do this,... | <p>Your question is a good one, and no, you can't assume that the metal is $\ce{MO}$ necessarily. However, you can find the equivalent weight of the metal without <em>any</em> assumptions about its formula. </p>
<p>The equivalent weight of a metal combining with oxygen is the mass that reacts with 8g of oxygen. We ... | 320 |
stoichiometry | Limiting reactant and percent yield | https://chemistry.stackexchange.com/questions/19555/limiting-reactant-and-percent-yield | <p>If 2.30 mol of sodium reacts with 1.95 mol of water, how many moles of sodium hydroxide are produced? </p>
<p>Would it be 2.3 mol NaOH?</p>
| <p>The first step is to figure out a reaction equation.</p>
<p>[I'm assuming elemental] sodium reacts with water violently because it releases a lot of energy when its only valence electron gets ripped apart. It creates \ce{NaOH} and \ce{H2}.</p>
<p>$\ce{Na + H2O -> NaOH + H2}$</p>
<p>We need to balance this.</p>... | 321 |
stoichiometry | How to find the molar mass of an unknown metal carbonate through a gas evolution reaction? | https://chemistry.stackexchange.com/questions/24246/how-to-find-the-molar-mass-of-an-unknown-metal-carbonate-through-a-gas-evolution | <p>As part of a pre-lab exercise in Chemistry, we went through the necessary calculations to identify an unknown metal in a metal carbonate. The method was gas evolution by means of hydrochloric acid (see equation below). </p>
<p><span class="math-container">$$\ce{HCl + M2CO3 -> MCl + CO2 + H2O}$$</span></p>
<p>Th... | <blockquote>
<p>$$\ce{HCl + M2CO3 -> MCl + CO2 + H2O}$$</p>
</blockquote>
<p>Since you already figured out, that there is a one-to-one ratio of carbonate to carbon dioxide, you can simply write
$$n(\ce{CO2}) = n(\ce{M2CO3}).$$</p>
<p>With the formula for the Molar mass,
$$M(\ce{M2CO3}) = \frac{m(\ce{M2CO3})}{n(\... | 322 |
stoichiometry | Limiting Reagent Stoichiometry | https://chemistry.stackexchange.com/questions/24656/limiting-reagent-stoichiometry | <p>What mass of precipitate forms when a solution containing 6.24 g of potassium sulfide is reacted with a solution containing 19.2 g of barium nitrate?</p>
<p>I have already identified the limiting reagent $\left(\text{K}_2 \text{S}\right)$ as well as the mass of the precipitate.</p>
<p>My question, however, is: why... | <p>So basically this problem is bad and incomplete (they tend to be at this level) in that it doesn't give you the concentrations/volumes of the reagents/solutions, so we end up making several assumptions. First of all, <strong>precipitates cannot be aqueous</strong>, by definition they are solids. So the way you end u... | 323 |
stoichiometry | Atomic mass ratios - Is the problem providing enough info? | https://chemistry.stackexchange.com/questions/25027/atomic-mass-ratios-is-the-problem-providing-enough-info | <blockquote>
<p>One gram of Hydrogen reacts with exactly (almost) 8 grams of oxygen to produce $\ce{H2O}$. Another single gram of Hydrogen reacts with 16 grams of Oxygen to produce $\ce{H2O2}$. </p>
</blockquote>
<p>Can the ratio $\frac{m_O}{m_H}$ be determined from this information? If not, what else do chemists ne... | <p>Are you asking whether we can figure out the ratio of the mass of an oxygen atom to a hydrogen atom from this information? If so, then the answer is yes, assuming that you know that $\ce{H2O}$ and $\ce{H2O2}$ are the formulas for each compound, and that atoms exist and are indivisible in chemical reactions.</p>
<p>... | 324 |
stoichiometry | calculate the final concentration of this equation | https://chemistry.stackexchange.com/questions/26726/calculate-the-final-concentration-of-this-equation | <p>A student mixed 260ml of 1.2 M lead(II) nitrate with 300ml of 1.90M potassium iodide. What is the final concentration of $\ce{NO3^{-}}$ ?</p>
<p>the answer is 1.11M , but he used the moles of lead(II) nitrate to find out the moles of $\ce{NO3^{-}}$ ,, and I think he should had used the moles of potassium iodide sin... | <blockquote>
<p>[…] he should had used the moles of potassium iodide since it is the limiting reactant.</p>
</blockquote>
<ul>
<li>Did any reaction take place upon mixing solutions of $\ce{Pb(NO3)2}$ and $\ce{KI}$?</li>
<li>If so, did the reaction change the number of moles of $\ce{NO3-}$ in solution by preci... | 325 |
stoichiometry | Why not to consider hydrogen and oxygen moles to determine an empirical formula | https://chemistry.stackexchange.com/questions/26848/why-not-to-consider-hydrogen-and-oxygen-moles-to-determine-an-empirical-formula | <p>A question says:</p>
<p>Find the empirical formula of an organic compound from the following composition:</p>
<p>34.62% C, 3.88% H, 61.50% O.</p>
<p>The answer is $\ce{C3H4O4}$.
It was found by using the mass (percentages) divided by the molar mass of each element.</p>
<p>But they didn't consider the (2moles) of... | <blockquote>
<p>The answer is $\ce{C3H4O4}$. It was found by using the mass (percentages) divided by the molar mass of each element. </p>
</blockquote>
<p>Exactly! That's the way to do it.</p>
<blockquote>
<p>But they didn't consider the (2moles) of hydrogen and oxygen in calculations. Why? In this case it will b... | 326 |
stoichiometry | the molecular formula of an unknown hydrocarbon | https://chemistry.stackexchange.com/questions/27046/the-molecular-formula-of-an-unknown-hydrocarbon | <p>A student analysed a hydrocarbon X and found it to be containing 43g carbon and 7.2g hydrogen.The relative molecular mass of X was found to be 42.What is the molecular formula of X?</p>
| <p>$43\ \mathrm g$ of carbon for $7.2\ \mathrm g$ hydrogen.<br>
Molar mass of carbon is $12\ \mathrm{g/mol}$ and that of hydrogen is $1\ \mathrm{g/mol}$.</p>
<p>Hence there are $\frac{43\ \mathrm g}{12\ \mathrm{g/mol}} = 3.58\ \mathrm{mol} \approx 3.6\ \mathrm{mol}$ of carbon for every $\frac{7.2\ \mathrm g}{1\ \mathr... | 327 |
stoichiometry | Dimensional Analysis in Chemistry | https://chemistry.stackexchange.com/questions/29711/dimensional-analysis-in-chemistry | <p>I was once told on this site that it was incorrect form to use units that specify the chemical being referred to in dimensional analysis. For example: </p>
<p>$$150.~\mathrm{g}~~\ce{KNO3} \cdot \frac{1~\mathrm{mol}~~\ce{KNO3}}{101.103~\mathrm{g}~~\ce{KNO3}} \cdot{} \frac{1~\mathrm{mol}~~\ce{C7H4O}}{6~\mathrm{mol}~~... | <p>The way I would perform the dimensional analysis you give in your question would be slightly different. That is mainly due to the fact that I don't consider chemical names or formulae as units, but as designators.</p>
<p>As an aside, I think you were starting from a question like the following:</p>
<blockquote>
... | 328 |
stoichiometry | What is the amount of nitrate ions in 20 g of Fe(NO3)3? | https://chemistry.stackexchange.com/questions/33040/what-is-the-amount-of-nitrate-ions-in-20-g-of-feno33 | <blockquote>
<p>What is the amount of nitrate ions in <span class="math-container">$20.0\:\mathrm{g}$</span> of <span class="math-container">$\ce{Fe(NO3)3}$</span>?</p>
</blockquote>
<p>The chemical formula for the nitrate ion is <span class="math-container">$\ce{NO3}$</span>, I think.</p>
<p>The molar mass of <spa... | <p>The molar mass of iron (III) nitrate is $m(\ce{Fe(NO3)3}\approx 242~\mathrm{g\, mol^{-1}}$. Pay close attention to the unit.</p>
<p>You correctly calculated the amount of substance of iron (III) nitrate to be $n(\ce{Fe(NO3)3}= 0.0826~\mathrm{mol}$</p>
<p>Now you should ask yourself the question: How many nitrate i... | 329 |
stoichiometry | Calculate molar mass of a compound from a given molecular mass | https://chemistry.stackexchange.com/questions/35257/calculate-molar-mass-of-a-compound-from-a-given-molecular-mass | <p>The mass of one molecule of a compound is $2.19\times10^{-22}\ \mathrm g$. What is the molar mass of the compound?</p>
<p>My attempt:
Using the formula <strong>moles=mass/molar mass</strong>, I found how to calculate molar mass using the formula <strong>molar mass=moles/mass</strong>.
Therefore, I was under the imp... | <p>To get the molar mass of your mystery compound, make use of the fact that there are $N_{\rm A}$ (Avogadro's number) of molecules of it in one mole of it. </p>
<p>To solve the problem, we multiply the molecular mass (given) by Avogadro's number (known) to get the mass of one mole of the mystery compound:</p>
<p>$${... | 330 |
stoichiometry | Calculating change in enthalpy of combustion of 1.12g of hexane | https://chemistry.stackexchange.com/questions/36923/calculating-change-in-enthalpy-of-combustion-of-1-12g-of-hexane | <p>I will calculate the change in enthalpy of combustion of 1.12g of hexane.</p>
<p><strong>1)</strong> Calculate the energy transferred to 200g of water using the equation: <em>J = mass of water in grams (<strong>200g</strong>) x specific heat capacity of water (<strong>4.18 J/gK</strong>) x temperature increase in K... | <p>I can't figure out exactly what you are trying to calculate, but if you want to know how much energy is created when burning 1.15 g of hexane by measuring an temperature increase of water, then this is the right way:</p>
<p>1.) 0.2 kg Water was icreased by 24 °C:
U = 0.2 kg * 4187 J/(kgK) * 24 K = 20,100 J = 20.100... | 331 |
stoichiometry | How to calculate the number of water molecules of a hydrate based on mass loss upon heating? | https://chemistry.stackexchange.com/questions/37592/how-to-calculate-the-number-of-water-molecules-of-a-hydrate-based-on-mass-loss-u | <blockquote>
<p>A <span class="math-container">$\pu{4.250 g}$</span> sample of <span class="math-container">$\ce{Na2SO4.nH2O}$</span> the sample loses <span class="math-container">$\pu{2.388 g}$</span> upon heating. What is <span class="math-container">$n$</span> for this hydrate?</p>
</blockquote>
<p>Do I first det... | <ol>
<li>Determine what the <span class="math-container">$\pu{2.388 g}$</span> is.
<blockquote class="spoiler">
<p> It's the amount of water lost from the crystal structure, assuming the sample was heated enough for this purpose.</p>
</blockquote></li>
<li>What does 'mole' mean? Isn't it just an indicator of the n... | 332 |
stoichiometry | Calculate water hardness from grams of CaCO3 | https://chemistry.stackexchange.com/questions/37944/calculate-water-hardness-from-grams-of-caco3 | <p>We have to figure out what the water hardness in mg/L or ppm is for a $\pu{20ml}$ solution of $\pu{0.400M}$ $\ce{CaCl2}$. </p>
<p>We learned that the formula for hardness is mg/L of calcium carbonate per liter. I started by calculating that there would be $\pu{0.801 g}$ of $\ce{CaCO3}$ precipitate if reacted with $... | <p>Unless I'm missing something, I don't see the problem with your working either. Perhaps check whether you got the original concentration of $\ce{CaCl2}$ given in the problem right (the volume of the solution does not affect your final answer). The given answer may well be wrong, it's irritating but it does happen.</... | 333 |
stoichiometry | Stoichiometry in Gas-Solid Flow System | https://chemistry.stackexchange.com/questions/39498/stoichiometry-in-gas-solid-flow-system | <p>I am a bit confused on how to account for the stoichiometry of a reaction as follows:</p>
<p>$$\ce{A}(s) + \delta \ce{B}(g) \ce{->} \ce{C}(s) + \delta \ce{D}(g)$$</p>
<p>The solid $\ce{A}$ is stationary in the reactor, and gas $\ce{B}$ flows through it with known inlet molar flow rate. Since 1 mol of $\ce{A}$ p... | 334 | |
stoichiometry | Stoichiometric calculations for the combustion of octane | https://chemistry.stackexchange.com/questions/40921/stoichiometric-calculations-for-the-combustion-of-octane | <p>The equation for the burning of octane:</p>
<p>$$\ce{2C8H18 + 25O2 -> 16CO2 + 18H2O}$$</p>
<ol>
<li>How do i find the number of moles of carbon dioxide which is produced when one mole of octane burns ?</li>
<li>How do i find , at what volume , at STP , is occupied by the number of moles determined in the answe... | <p>This is a homework problem, so I'll not spell the answer outright, but try and give as much as I would if you came to me in office hours.</p>
<ol>
<li><p>Your equation tells you what the ratio of moles of $\ce{C8H18}$ to moles of $\ce{CO2}$. For every two moles of octane burned, how many moles of $\ce{CO2}$ are pr... | 335 |
stoichiometry | Validity of rationale for balancing chemical equations | https://chemistry.stackexchange.com/questions/41390/validity-of-rationale-for-balancing-chemical-equations | <p>The reason given for balancing chemical equations is the law of conservation of mass. They say that we balance equations with keeping in mind that atoms of every element included in the reaction must be equal on both sides of equations. And they just add some coefficients for this purpose. </p>
<p>But I apprehend w... | <p>When you write the equation</p>
<p>$$\ce{H2 + O2 -> H2O}$$</p>
<p>you are implicitly saying that the stoichiometric coefficient of every substance is $1$. It is like writing the equation $a + b = c$. By not having coefficients in front of $a$, $b$, or $c$, you are implying that $1a + 1b = 1c$ and not $2a + 3b =... | 336 |
stoichiometry | Why weren't the moles of oxygen calculated the same way as C? | https://chemistry.stackexchange.com/questions/46408/why-werent-the-moles-of-oxygen-calculated-the-same-way-as-c | <blockquote>
<p>Combustion analysis of a $\rm1.500~g$ sample of ascorbic acid yields $4.023\rm~g$ of $\ce{CO2}$ and $\rm0.96~g$ of $\ce{H2O}$. What is the empirical formula of ascorbic acid?</p>
</blockquote>
<p>Actually my question is that in many solutions I saw it's solved like that:</p>
<p>In $\ce{CO2}$ the mol... | <p>You have done combustion analysis, so you have introduced a large amount of oxygen to the ascorbic acid sample. Because of this, you can't know how much of the oxygen in the $\ce{CO2}$ and $\ce{H2O}$ you produced actually came from the acid sample and how much came from the atmosphere.</p>
<p>But you do know that ... | 337 |
stoichiometry | How many atoms of Lithium are there in 14.3 grams of Lithium Fluoride? | https://chemistry.stackexchange.com/questions/47849/how-many-atoms-of-lithium-are-there-in-14-3-grams-of-lithium-fluoride | <p><strong>How many atoms of Lithium are there in 14.3 grams of Lithium Fluoride?</strong>
I can't seem to single out how many atoms of Lithium are in lithium fluoride.</p>
<p>I know that the first step is to convert 14.3 grams to moles, so 14.3 multiplied by the molar mass of LiF divided by 1 is 0.55 moles. But where... | <p>Convert 14.3 grams of Lithium Fluoride to moles which is the same for lithium and lithium fluoride since there is one atom of lithium per molecule of lithium fluoride (carry an extra significant digit to round later to 3 significant figures). </p>
<blockquote>
<p>$\mathrm{moles(Li) = \dfrac{g(LiF)}{mw(LiF)} = \df... | 338 |
stoichiometry | Maximum amount of P4 | https://chemistry.stackexchange.com/questions/48157/maximum-amount-of-p4 | <p>$\ce{2Ca3(PO4)2 +6SiO2 +10C->6CaSiO3 +P4 +10CO}$</p>
<p>What is the maximum amount of P4 that can be produced from 1.0 kg of phosphorite if the phosphorite sample is 75% $\ce{2Ca3(PO4)2}$ by mass</p>
<hr>
<p>The wording is confusing. I do not know what to do. Would you start by finding the limiting reactant? <... | <p>First you find the number of moles of $\ce{Ca3(PO4)2}$ reacting. You have 75% of 1 kg, i.e. 750 grams, of calcium phosphate. The rest of reagents are assumed to be in excess as we have to find the maximum amount of $\ce{P4}$ obtained, hence reaction should not have other limiting reagents.</p>
| 339 |
stoichiometry | Stoichiometry Assignment | https://chemistry.stackexchange.com/questions/48178/stoichiometry-assignment | <p>$\ce{2Ca3(PO4)2 +6SiO2 +10C->6CaSiO3 +P4 +10CO}$</p>
<p>What is the maximum amount of P4 that can be produced from 1.0 kg of phosphorite if the phosphorite sample is 75% $\ce{2Ca3(PO4)2}$ by mass</p>
<hr>
<p>I am confused. How do I find a maximum amount of a reaction</p>
| <p>Phosphorite is a mineral containing calcium phosphate. This particular 1kg sample has 75% percent of it by weight i.e. 750 grams. All others reagents are assumed to be in excess as you have to find the maximum p4 obtained which would be at a point where all of our mineral is used.</p>
| 340 |
stoichiometry | Variation in pressure for a gas phase reaction | https://chemistry.stackexchange.com/questions/54547/variation-in-pressure-for-a-gas-phase-reaction | <blockquote>
<p>Predict how the total pressure varies during the gas-phase reaction
$\ce{N_2}(g)+ 3 \ce{H2}(g) \rightarrow 2 \ce{NH3} (g) $ in a constant volume container. </p>
</blockquote>
<p>Reference: Atkin's Physical Chemistry, Tenth Edition, Chapter 20, Exercise 20A.1 (b) on page 870</p>
<p>My attempt at a... | 341 | |
stoichiometry | How do I find the formula of the compound given the ratio of its constituents by weight? | https://chemistry.stackexchange.com/questions/57897/how-do-i-find-the-formula-of-the-compound-given-the-ratio-of-its-constituents-by | <p>Problem : An organic compound containing carbon, nitrogen and oxygen will have a weight ratio $9:1:3$. The molecular weight of the compound is $108$. What is the formula of the compound?</p>
<p>I thought of calculating the empirical formula, but percentages are given for that, and not weight. </p>
| <p>It's an algebra problem.</p>
<p>108 = 9x + 1x + 3x</p>
<p>Solve for x.</p>
<p>Weight of carbon per molecule = 9x
Weight of nitrogen per molecule = 1x
Weight of oxygen per molecule = 3x</p>
<p>Then convert from weights to numbers (I assume you know how to do that :) ).</p>
<p>Note that the result is rather non... | 342 |
stoichiometry | What is the relation between the amu and avogadro’s number? | https://chemistry.stackexchange.com/questions/70135/what-is-the-relation-between-the-amu-and-avogadro-s-number | <p>I know that the relation between Avogadro’s number and amu is a reciprocal relationship but the relation is slightly unclear.</p>
<p>Could anyone give me more clarification?</p>
| <p>$\pu{1amu}$ is defined as one twelfth of the mass of one carbon-12 atom.</p>
<p>Avogadro's number is defined as the total number of entities in $\pu{12g}$ of carbon-12. </p>
<p>$N_\mathrm A=6.022\times10^{23}$</p>
<p>It is a measuring criteria, just like a dozen, which is used to put a number to a certain item. A... | 343 |
stoichiometry | More than one way of balancing a chemical equation | https://chemistry.stackexchange.com/questions/64202/more-than-one-way-of-balancing-a-chemical-equation | <p>My textbook had this question on balancing chemical reactions </p>
<blockquote>
<p>Ozone reacts with nitric oxide to give nitrogen dioxide and oxygen gas</p>
</blockquote>
<p>Here's how I balanced it: $$\ce{O3 + NO -> NO2 + O2}$$</p>
<p>However I realised that the equation is also balanced if I write it as: ... | <p>This happens when you have a <strong>sum of two</strong> (or more) independent reactions. You can balance each one, and then add them together in an <em>arbitrary</em> proportion. People usually run into this when trying to come up with an equation for combustion of gunpowder, where the oxidation of carbon and oxida... | 344 |
stoichiometry | How many liters of hydrogen, H2, are needed to react with 10 liters of nitrogen gas in the reaction forming ammonia? | https://chemistry.stackexchange.com/questions/64333/how-many-liters-of-hydrogen-h2-are-needed-to-react-with-10-liters-of-nitrogen | <p>How many liters of hydrogen, H2, are needed to react with 10 liters of nitrogen gas in the reaction forming ammonia?</p>
<p>$$\ce{3 H2(g) + N2(g) -> 2 NH3(g)}$$</p>
<p><strong>My try::</strong> Because we have 10 L of nitrogen gas, we have 10/22.4 moles = 0.446 moles of nitrogen gas, and thus need 0.446 * 3 = 1... | <p>You are on the right track. Dimensional Analysis is your friend:</p>
<p>$$\frac{10\,\text{L $\ce{N2}$}}{1} \cdot \frac{1\,\text{mol $\ce{N2}$}}{22.4 \,\text{L $\ce{N2}$}}\cdot \frac{3\,\text{mol $\ce{H2}$}}{1\,\text {mol $\ce{N2}$}}\cdot \frac{22.4\,\text{L $\ce{H2}$}}{1\,\text {mol $\ce{H2}$}}=\,?\,\, \text... | 345 |
stoichiometry | Help with uncertainties | https://chemistry.stackexchange.com/questions/71658/help-with-uncertainties | <p>When diluting a mixture of two reactants with lets say a 100ml of H2O, how do you add this to the uncertainties of the concentrations of the reactants? Should the relative uncertainty of the added H2O be added to the relative uncertainty of the volume in both reactants? </p>
| <p>When adding values together, you should add together their absolute uncertainties. For example, if you started with $500\pm5\mathrm{mL}$ and add $100\pm1\mathrm{mL}$, your new volume value is $600\pm6\mathrm{mL}$. </p>
<p>You would add the relative uncertainties if you are multiplying values. For example, if you st... | 346 |
stoichiometry | Equivalent weight for CaO | https://chemistry.stackexchange.com/questions/74410/equivalent-weight-for-cao | <ul>
<li>I was wondering how I'd go around calculating the equivalent weight
of CaO. From my knowledge, the EW of a compound is its (given mass
)/(valence factor, n). Since CaO has no charge and no change in<br>
the oxidation number takes place, my valence factor comes out to be
0, which I know is wrong because the c... | <p>Yes, Dev, you know the correct process of calculating EW, but the problem you are facing is how to calculate the valence factor?, right?</p>
<p>So, in this case you have to understand that EW for any compound is reaction-specific. So, you can't calculate the EW of $\ce{CaO}$ without any reaction reference.</p>
<p>... | 347 |
stoichiometry | Need help with stoichiometry problem | https://chemistry.stackexchange.com/questions/76327/need-help-with-stoichiometry-problem | <p>I'm pretty new to chemistry and I've been stuck on it for hours.</p>
<p>Question: $\pu{10g}$ of the hydroxide of a metal on ignition gave $\pu{8g}$ of oxide. The equivalent weight of the metal is:<br>
a) $\pu{136g}$<br>
b) $\pu{40g}$<br>
c) $\pu{56g}$<br>
d) $\pu{28g}$ </p>
<p>I used the law of equivalence but th... | <p>I found your numbers confusing, but I think the first equation you wrote is not correct. This is how I'd solve it:</p>
<p>Let's say we have $\mathrm{n}$ equivalents of metal in the sample, and let's call the equivalent weight of the metal $\mathrm{e}$. For the hydroxide sample, we have:</p>
<p>$n(e+17)=10$</p>
<p... | 348 |
stoichiometry | How to calculate mass produced when a given gas is burned? | https://chemistry.stackexchange.com/questions/76548/how-to-calculate-mass-produced-when-a-given-gas-is-burned | <blockquote>
<p>The equation below represents combustion of methane ($\ce{CH4}$, $\pu{16.04 g/mol}$). Balance the equation, and calculate the mass of water ($\pu{18.02 g/mol}$) formed when $\pu{40.0g}$ of methane is burned.
$$\ce{CH4(g) + O2(g) -> CO2 + H2O(g)}$$</p>
</blockquote>
<p>I have started the problem... | <p>You have already balanced the equation, so we can get the stoichiometric coefficients. From the equation we can say that 1 mole $\ce{CH4}$ gives 2 moles of $\ce{H2O}$ because their coefficients are 1 and 2, correspondigly. So 2.5 moles of $\ce{CH4}$ would give 5 moles of $\ce{H2O}$, that is $\pu{90 g}$ of $\ce{H2O}... | 349 |
reaction kinetics | Reaction kinetics of exothermic reaction | https://chemistry.stackexchange.com/questions/161619/reaction-kinetics-of-exothermic-reaction | <p>A colleague said we can’t dissolve a salt (whose solvation enthalpy is exothermic) faster if we increase the temperature (the solubility equilibrium product is not reached) because Le Chatelier‘s principle would favor the reactants.</p>
<p>For example, imagine dissolving NaOH(s) in distilled water, can’t this be acc... | <p>Typically, rates of uncatalyzed simple reactions increase with temperature. There are well-known examples where this is not the case (such as enzyme-catalyzed reactions where the enzyme denatures at high temperatures, or reactions with an intermediate that is at rapid equilibrium with the reactant in an exothermic s... | 350 |
reaction kinetics | Reaction kinetics - Organic chemistry | https://chemistry.stackexchange.com/questions/100861/reaction-kinetics-organic-chemistry | <p><a href="https://i.sstatic.net/cMItP.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/cMItP.png" alt="enter image description here"></a></p>
<p>On an exam in organic chemistry I was asked why the reaction B proceeds faster than reaction A. </p>
<p>I answered that: in reaction B, I- is a better leavin... | <p>Your answer is simply missing something. Yes, I is a better leaving group, therefore an Sn reaction of an iodide proceeds faster than the one of the chloride. But your starting material in both cases is the chloride. You first need to exchange that chloride for an iodide and that only works well if the iodide is a g... | 351 |
reaction kinetics | Reaction Kinetics and Catalyst Addition | https://chemistry.stackexchange.com/questions/86980/reaction-kinetics-and-catalyst-addition | <p>The addition of a catalyst is known to increase the rate constant of a reaction by providing an easier pathway for the reaction to occur, one with lesser activation energy. </p>
<p><em>My doubt is:</em></p>
<p>Is it possible that the addition of a catalyst, alters the <strong>order of a reaction</strong>?</p>
<p>... | 352 | |
reaction kinetics | reaction coordinate, kinetics, equilibrium in example | https://chemistry.stackexchange.com/questions/94751/reaction-coordinate-kinetics-equilibrium-in-example | <p><a href="https://i.sstatic.net/2srvk.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/2srvk.jpg" alt="enter image description here"></a></p>
<p>In this special reaction coordinate diagram with two reaction mechanisms, I tried to analyze it in two other ways, one with kinetics, another with equilibrium... | <p>You have chosen an unusual scheme in that A appears to be an intermediate as well as a reactant. If you use the simpler scheme things are easier and so rather than try to follow yours I have examined the scheme below which is very nonetheless very similar</p>
<p>$$RX\underset{k_{-1}} {\stackrel{k_1}{\leftrightharpo... | 353 |
reaction kinetics | Can Spectator Ions Affect Reaction Kinetics? | https://chemistry.stackexchange.com/questions/175496/can-spectator-ions-affect-reaction-kinetics | <p>Specifically, I am interested in the reaction of different hydroxides (in aqueous form) with <span class="math-container">$\ce{CO_2}$</span>. I would like to determine which hydroxide would conduct the reaction the fastest. My initial thought would be that spectator ions would have no effect, and since the concentra... | <p>Everything present has an effect. The question is, is it distinguishable and measurable? Your proposal has many variables to consider; here are some. The amount of hydroxide, analysis by formulation or by titration, Activity of OH-, a good pH meter can help here, solubility of the hydroxide, carbonate, and bicarbona... | 354 |
reaction kinetics | Reaction Kinetics and Stoichiometry -- Mass conservation | https://chemistry.stackexchange.com/questions/24506/reaction-kinetics-and-stoichiometry-mass-conservation | <p>This question has been bothering me for some time, and I can't seem to find a good answer online. </p>
<p>Say I have four chemical species $\ce{A}$, $\ce{B}$, $\ce{C}$, $\ce{D}$, and these four react in the following ways: </p>
<p>\begin{align}\ce{
A + A &-> B\\
A + B &-> C\\
A + C &-> D\\
A +... | <p>Reaction rates should be defined in terms of the <a href="http://en.wikipedia.org/wiki/Extent_of_reaction" rel="nofollow">Extent of reaction</a> ($\xi$) that corresponds to the number of moles (or the molarity for reactions in solution) of specie $i$ divided by the the stoichiometric number, $\nu_i$:
$$\xi = \frac{[... | 355 |
reaction kinetics | Why is temperature considered as an important factor in deciding chemical reaction kinetics? | https://chemistry.stackexchange.com/questions/67798/why-is-temperature-considered-as-an-important-factor-in-deciding-chemical-reacti | <p>According to the Arrhenius equation, the rate of reaction is proportional to $e^{-1/RT}$.</p>
<p>Here is a plot of the equation and its derivative with respect to temperature, both with respect to temperature. All constants are set to unity.</p>
<p><a href="https://i.sstatic.net/23Hut.png" rel="nofollow noreferrer... | 356 | |
reaction kinetics | Reaction kinetics, relating half life to reaction rate | https://chemistry.stackexchange.com/questions/32561/reaction-kinetics-relating-half-life-to-reaction-rate | <p><img src="https://i.sstatic.net/8fKfm.png" alt="enter image description here"></p>
<p>How do I relate the half life to the overall rate of reaction? </p>
<p>I argued that from the data, doubling the partial pressure of either reactant, keeping the other constant, will half the half life. </p>
<p>So try t1/2 =
$\... | <p>Recall the meaning of the half life $t_{1/2}$: At $t_{1/2}$, a concentration (or partial pressure) is decreased to the half of its initial value.</p>
<p><strong>It is crucial to realize that this represents exactly the $\mathbf{-\frac{dp_A}{dt}}$ in your rate equation!</strong></p>
<p>With other words, $-\frac{dp_... | 357 |
reaction kinetics | Kinetics for E1cb reactions | https://chemistry.stackexchange.com/questions/112482/kinetics-for-e1cb-reactions | <p>We were taught that the kinetics of a reaction is determined by the reactions ‘rate determining step’ which is also the slowest step of the reaction. For E1 as well as E2 reactions the slowest steps are easily determined by the mechanism and I derived the rate laws for those. </p>
<p>In the case of E1cb reactions, ... | 358 | |
reaction kinetics | Reaction kinetics exercise for hydrogen iodide synthesis | https://chemistry.stackexchange.com/questions/178022/reaction-kinetics-exercise-for-hydrogen-iodide-synthesis | <p>The rate constant for the reaction of hydrogen with iodine is <span class="math-container">$\pu{2.45E-4 M-1 s-1}$</span> at 302 °C and <span class="math-container">$\pu{0.905 M-1 s-1}$</span> at 508 °C.</p>
<p>a. calculate the activation energy and Arrhenius preexponential factor for this reaction.</p>
<p>b. What is... | <p>A mistake must have happened in your calculations, because, when I do them, I obtain :</p>
<p>ln<span class="math-container">$k_1 = - 8.314$</span>;</p>
<p>ln<span class="math-container">$k_2 = - 0.100$</span>;</p>
<p>ln<span class="math-container">$k_1$</span> - ln<span class="math-container">$k_2$</span> = <span c... | 359 |
reaction kinetics | Order of reactions in kinetics | https://chemistry.stackexchange.com/questions/30849/order-of-reactions-in-kinetics | <p>In kinetics, zero order reactions are those reactions who are independent from the concentration of the reactant or the product. So their rate is equal to the constant <strong>k</strong>. But still we build the diagram where we find the correlation between concentration and time, where the slope is negative.
Why do... | <blockquote>
<p>So their rate is equal to the constant k.</p>
</blockquote>
<p>With other words, the <strong>change</strong> of concentration over time is linear:</p>
<p>\[ \frac{d[\ce{A}]}{dt} = k\]</p>
| 360 |
reaction kinetics | Sequential Kinetics | https://chemistry.stackexchange.com/questions/27466/sequential-kinetics | <p>I was solving some problems on chemical kinetics, then I was just struck at some ques of sequential reaction kinetics. </p>
<p>Given reactions $$\ce{O_3 + Cl \rightarrow O_2 + ClO ~~~ k_1=5.2 \times 10^9~Lmol^{-1}s^{-1}}$$</p>
<p>and $$\ce{ClO + O \rightarrow O_2 + Cl ~~~ ~~~ k_2=2.6 \times 10^{10} ~Lmol^{-1}s^{... | <p>The rate constant of the overall reaction is determined by the rate constant of the RDS, Rate Determining Step.</p>
<p>The RDS is the one with the lowest rate constant. Hence in this case the overall rate of the reaction is $5.2 \times 10^9 Lmol^{-1}s^{-1}$</p>
| 361 |
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