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How to calculate the concentration based on dilution of a stock solution? |
In all of my physical chemistry books I find the same expression for estimating the equilibrium constant of a reaction at a non-standard temperature. The derivation starts with $R \ln K_\text{eq} = -\Delta g^\circ/T = -(\Delta h^\circ/T - \Delta s^\circ)$. Then one takes the temperature derivative of each side assuming... |
Is perioxide bleaching (H2O2) suitable for treating bast fibres? I read that to be succesful it needs to be combined with chlorine bleaching. Because of the end usage, I don't want to use this kind of bleaching. |
Perioxide bleaching for bast fibres? |
Is peroxide bleaching ($\ce{H2O2}$) suitable for treating bast fibres? I read that to be successful, it needs to be combined with chlorine bleaching. Because of the end usage, I don't want to use this kind of bleaching. |
Peroxide bleaching for bast fibres? |
How to remove Sn from Sn60Cu40 alloy? |
I'm modelling a small set of proline analogues - extra functional groups, sulphur in the ring. Using Gaussian / DMACRYS.
--functional B3LYP EmpiricalDispersion=GD3BJ --basis_set 6-311G**
or
-fun B3LYP EmpiricalDispersion=GD3BJ -bas 6-311G**
1. Would EmpiricalDispersion=GD3BJ go under -fun, or would ... |
Is it possible for 'n' to ever be negative? Trying to figure out where I went wrong on some thing and want to rule that out. |
Is the 'n' in $\Delta$ $\rm G = -nFE$, ever negative? |
I'm modelling a small set of proline analogues - extra functional groups, sulphur in the ring. Using Gaussian / DMACRYS.
--functional B3LYP EmpiricalDispersion=GD3BJ --basis_set 6-311G**
or
-fun B3LYP EmpiricalDispersion=GD3BJ -bas 6-311G**
1. Would EmpiricalDispersion=GD3BJ go under -fun, or would ... |
Problem: A buffer was made by mixing 500 mL of 1 M (mol/L) acetic acid and 500 mL of 0.5 M calcium acetate.
What are the resulting concentrations of acetic acid (henceforth called AcH), $Ca^{2+}$ and acetate (henceforth called $Ac^{-}$, and what is the resulting pH? $K_a$(acetic acid) = $1.75\times10^{-5}.$
My at... |
I am reading *The Selfish Gene* by Richard Dawkins.
I am on chapter two.
-----
He speaks of the observation of the formation of amino-acids when you simulate environmental conditions of primordial earth.
`UV light + water + carbon dioxide + methane + ammonia + a couple of weeks time = amino-acids`
I u... |
Problem: A buffer was made by mixing 500 mL of 1 M (mol/L) acetic acid and 500 mL of 0.5 M calcium acetate.
What are the resulting concentrations of acetic acid (henceforth called $\ce{AcH}$), $\ce{Ca^2+}$ and acetate (henceforth called $\ce{Ac- }$, and what is the resulting pH? $K_\text{a}$(acetic acid) = $1.75\tim... |
Is the 'n' in Delta G = -nFE, ever negative? |
I bought a phosphate buffer from Sigma/Fluka (73212-1L) containing potassium dihydrogen phosphate ($\ce{KH_2PO_4}$) and disodium hydrogen phosphate ($\ce{Na_2HPO_4}$).
It is at pH 8.0 but they do not provide the phosphate concentration. Can I determine it from pH via titration?
This table shows the concentration... |
I haven’t quite reached the point where I can read a full-fledged text on chemical kinetics and thermodynamics yet, so bear with me, please.
I’m wondering why a value like $K_\text{eq} = \frac{[\ce{NO}]^2[\ce{O2}]}{[\ce{NO2}]^2}$ wouldn't have units of M?
|
How do you get from 2,3-dimethylcyclopentanol to 1,2-dimethylcyclopent-1-ene?
I know the -OH group leaves as water (being protonated by acid) forming a carbocation. Then the weak nucleophile (water) attacks the beta-hydrogen to form what I think is 2,3-dimethylcyclopent-1-ene. But why is it 1,2-dimethylcyclopent-1-... |
What is the significance of 273.16 K? |
Can pseudochirality be considered when 3 or 4 groups on the C atom are the same? |
I'm familiar with the sea model of metals. What I'm curious about is: exactly how many electrons are lost by the iron, to be absorbed into the sea of electrons? For a general metal, how many electrons are lost to the sea of electrons?
Thanks |
In solid Iron, what is the charge of the positive atom? |
I have a polymethine molecule with let's say 9 C atoms.
H-CH=CH-CH=CH-CH=CH-CH=CH-CH3
How can I calculate the length of the whole molecule?
I need this number to compute the wavelengths the molecule will absorb (model of linear potential well).
So what are the average bond lengths and bond angles in this m... |
How to determine bond length and angle in a conjugated pi-system (polymethine)? |
> So what are the average bond lengths and bond angles in this molecule
> and how are they calculated?
1,3-butadiene should serve as a reasonable model for your work.
![enter image description here][1]
We can find the bond lengths in the literature. The carbon-carbon double bond length is 1.338 Å, typi... |
Whenever I brush teeth, there are some kind of bubbles sticking inside the cavity and that's uncomfortable, it should be SLS as found on the internet. Does anyone know how do I get rid of those bubbles things easily?
Eat\Drink sth ? Tell me if anything is wrong.
Any help would be appreciated, thanks. |
What non-poisonous chemicals can get rid of SLS effectively? |
Whenever I brush teeth, there are some kind of bubbles sticking inside the cavity and that's uncomfortable, it should be SLS as found on the internet. Does anyone know how do I get rid of those bubbles things easily?
Eat\Drink sth ? Tell me if anything is wrong.
Any help would be appreciated, thanks.
Addiction : SLS... |
I was wondering if there was a known algorithm which could calculate simple reaction products - not anything organic, but things like
NaBr + LiF -> NaF + LiBr
While these are quite easily to be worked out mentally, I cannot think of an easy way in which these reaction products could be predicted. Is there some so... |
Calculating reaction products programmatically? |
> So what are the average bond lengths and bond angles in this molecule
> and how are they calculated?
1,3-butadiene should serve as a reasonable model for your work.
![enter image description here][1]
We can find the bond lengths in the literature. The carbon-carbon double bond length is 1.338 Å, typi... |
**Setup**
I found in [Szabo, Quantum chemistry][1] page 88, these two ways to calculate the energy of the basal state:
$$E_0= \sum_a^N \langle a|h|a\rangle + \frac{1}{2} \sum_a^N \sum_b^N \langle ab||ab\rangle $$
and
$$E_0= \sum_a^N \langle a|h|a\rangle + \sum_a^N \sum_{b>a}^N \langle ab||ab\rangle $$
**... |
Why are 2 ways to calculate the energy of a basal state? |
I have a polymethine molecule with let's say 9 C atoms.
H-CH=CH-CH=CH-CH=CH-CH=CH-CH3
How can I calculate the length of the whole molecule?
I need this number to compute the wavelengths the molecule will absorb (model of linear potential well).
So what are the average bond lengths and bond angles in this m... |
**Setup**
I found in [Szabo, Quantum chemistry][1] page 88, these two ways to calculate the energy of a state:
$$E_0= \sum_a^N \langle a|h|a\rangle + \frac{1}{2} \sum_a^N \sum_b^N \langle ab||ab\rangle $$
and
$$E_0= \sum_a^N \langle a|h|a\rangle + \sum_a^N \sum_{b>a}^N \langle ab||ab\rangle $$
**Question... |
**Setup**
I found in [Szabo, Quantum chemistry][1] page 88, these two ways to calculate the energy of the ground state:
$$E_0= \sum_a^N \langle a|h|a\rangle + \frac{1}{2} \sum_a^N \sum_b^N \langle ab||ab\rangle $$
and
$$E_0= \sum_a^N \langle a|h|a\rangle + \sum_a^N \sum_{b>a}^N \langle ab||ab\rangle $$
*... |
Why are 2 ways to calculate the energy of the ground state? |
I was wondering if there was a known algorithm which could calculate simple reaction products - not anything organic, but things like
$$\ce{NaBr + LiF -> NaF + LiBr}$$
While these are quite easily to be worked out mentally, I cannot think of an easy way in which these reaction products could be predicted. Is ther... |
I have no idea what is meant by the "basal state", but both formulas have exactly the same meaning. They are just two different ways of *not double counting* the Coulomb and the exchange interactions. In principle, the goal can be achieved in two ways:
- double counting in the first place and then dividing by two (... |
I have no idea what is meant by the "basal state", but both formulas have exactly the same meaning. They are just two different ways of *not double counting* the Coulomb and the exchange interactions. In principle, the goal can be achieved in two ways:
- double counting in the first place and then dividing by two (... |
Both formulas have exactly the *same meaning*. They are just two different ways of *not double counting* the Coulomb and the exchange interactions. In principle, the goal can be achieved in two ways:
- double counting in the first place and then dividing by two (first formula);
- counting wisely so that there is ... |
I dont know if this is really applicable but I want to add a custom force ( say F(x,y,z) ) to some atoms in my geometry optimization. Is there any way to add such forces to the DFT or Molecular Mechanics calculations? ( preferably GAMESS or Gaussian for QC or Avogadro for MM ).
**It can be also done as Molecular Me... |
I am computational graduate student in biochemistry. I took organic chemistry, and I am reading a paper about instability and decay of DNA. The author says:
"The chemical price paid for the greatly increased resistance of the nucleic acid phosphodiester bond (gained by removal of the sugar 2'-OH group) is the labil... |
As explained in [pH Paradoxes: Demonstrating That It Is Not True
That pH ≡ -log\[H+\]][1] Journal of Chemical Education Vol. 83 pages 752-757.
pH = -log (hydrogen ion activity).
and "pH of 7.6 M HCl is about -1.85 (not -0.88)"
So how far off is -log (5) = -0.69 from the real answer?
From [this table of ac... |
$$\ce{HCO3- (aq) + H2O(l) <=> H2CO3(aq) +OH- (aq)}$$
I do not understand why this makes an Arrhenius base and why it doesn't form:
$$\ce{HCO3- (aq) + H2O(l) <=> CO3^2- (aq) +H3O+ (aq)}$$
Could someone explain this to me? |
Both of these equations are valid, as $\ce{HCO3-}$ is amphoteric (i.e. both an acid and a base).
To answer your question, one has to consider that the $\mathrm{p}K_\text{a}$ value for $\ce{H2CO3}$ is 6.37 and that for $\ce{HCO3-}$ is 10.32. So if we started from "pure" $\ce{HCO3-}$ (let's assume sodium bicarbonate)... |
As explained in [pH Paradoxes: Demonstrating That It Is Not True
That pH ≡ -log\[H+\]][1] Journal of Chemical Education Vol. 83 pages 752-757.
pH = -log (hydrogen ion activity).
and "pH of 7.6 M HCl is about -1.85 (not -0.88)"
So how far off is -log (5) = -0.69 from the real answer?
From [this table of ac... |
PBP vs TBP geometry? |
Why are the axial bond lengths greater than those of the equatorial bonds in a trigonal bi-pyramid (TBP) geometry molecule; but the opposite is true for pentagonal bi-pyramid (PBP) geometry molecules? I think that it might have something to do with the angles between the bonds, so I thought of a possible explanation.
... |
Ok, this is probably an insane question but I may as well ask:
I broke a cfl in my home (so elemental mercury is present in a small amount) and wiped up some of the mess with a clorox wipe.
The wipe in question contains dimethyl benzyl ammonium choride and dimethyl ethylbenzyl ammonium chloride.
I'm not chemical-p... |
How do you get from 2,3-dimethylcyclopentanol to 1,2-dimethylcyclopent-1-ene?
I know the -OH group leaves as water (being protonated by acid) forming a carbocation. Then the weak nucleophile (water) attacks the beta-hydrogen to form what I think is 2,3-dimethylcyclopent-1-ene. But why is it 1,2-dimethylcyclopent-1-... |
I broke a CFL in my home (so elemental mercury is present in a small amount) and wiped up some of the mess with a clorox wipe.
The wipe in question contains dimethyl benzyl ammonium chloride and dimethyl ethylbenzyl ammonium chloride.
I'm not chemical-phobic, but can someone please tell me, I didn't accidentally ex... |
Can dimethylmercury originate from cleaning up a broken thermometer with disposable wet wipes? |
What are the resonance structures of 3-aminocyclohex-2-en-1-ylium? |
The resonance structures and how to construct them for 3-aminocyclohex-2-en-1-ylium are shown below. The second structure in your question is none of them, as it is a different molecule: cyclohexa-1,3-dien-1-amine. For this molecule it is also possible to construct a resonance structure, as also shown below.
![reson... |
I am familiar with the idea that rate law must be determined experimentally. I am also familiar with the fact that there is experimental evidence showing that there is no formulated way for coming up with the rate law besides just experimentation.
My question is: why isn't the rate law of
$$ aA + bB \rightarrow... |
Why must rate law be experimentally? |
I want to know if there is any free open source tool available for Gasteiger-Hückel charge calculation? I know it is available on Sylbyl but is there any other(free) way to calculate these charges for small molecules?
|
Any free tool for Calculating Gasteiger-Hückel charges? |
I would like to add another shade to the already quite excellent answer of ron.
I will use donor-acceptor complexes, like Lewis acid base adducts, as case in point. Probably one of the simplest and most popular is the ammonia and borane adduct. I consider the structures below to be the most accepted ones, with prob... |
I will remove the pectin from hemp fibres with Bioprep 3000L pectinase. How can I measure the % of pectin before and after for loose fibres? I only found a way to measure it for fabric, but I will perform this test on just loose hemp fibres. |
SO3 molecule has three double bonded oxygen to the central sulfur atom.
![enter image description here][1]
Sulfur has sp2 hybridization and it has 6 outer electrons which make the bonds with the oxygen.
So shouldn't the BO be 2?
[1]: https://i.stack.imgur.com/I0QVj.png |
Why is SO3 bond order 1.33 and not 2? |
$\ce{SO3}$ molecule has three double bonded oxygen to the central sulfur atom.
![enter image description here][1]
Sulfur has sp2 hybridization and it has 6 outer electrons which make the bonds with the oxygen.<br>
So shouldn't the bond order be 2?
[1]: https://i.stack.imgur.com/I0QVj.png |
I have a polymethine molecule with let's say 9 $\ce{C}$ atoms.
$\ce{H-CH=CH-CH=CH-CH=CH-CH=CH-CH3}$
How can I calculate the length of the whole molecule?
I need this number to compute the wavelengths the molecule will absorb (model of linear potential well).
So what are the average bond lengths and bond an... |
Which is the least stable trihlide of nitrogen and why?
I have two conflicting theories, one is that Fluorine-fluorine electron repulsion will make $\ce{NF3}$ least stable and another is steric reasons of Iodine which give $\ce{NI3}$ as the answer.
Which is correct? |
Which is the least stable trihalide of nitrogen and why?
I have two conflicting theories, one is that fluorine-fluorine electron repulsion will make $\ce{NF3}$ least stable and another is steric reasons of iodine which give $\ce{NI3}$ as the answer.
Which is correct? |
Which is the least stable trihalide of nitrogen? |
$\ce{SO3}$ molecule has three double bonded oxygen to the central sulfur atom.
Sulfur has $\ce{sp^2}$ hybridization and it has 6 outer electrons which make the bonds with the oxygen.
So shouldn't the bond order be 2?
<img src="https://i.stack.imgur.com/I0QVj.png" width="150">
[1]: https://i.stack.i... |
Why is the bond order in the SO₃ molecule 1.33 and not 2? |
*Note that I do not have professional experience in the textile industry!*
Supposed that the stems have been (mechanically) treated, and the "bark" is removed, the *ruthenium red method* should work.
In *Crystal-Structure of Ruthenium Red and Stereochemistry of its Pectic Stain* by *Clarence Sterling*, *Am. J. Bo... |
*Note that I do not have professional experience in the textile industry!*
Supposed that the stems have been (mechanically) treated, and the "bark" is removed, the *ruthenium red method* should work.
In *Crystal-Structure of Ruthenium Red and Stereochemistry of its Pectic Stain* by *Clarence Sterling*, *Am. J. Bo... |
I was wondering about this. What is the physics underlying the "stringy" consistency of melted cheese? That is, when the melted cheese is hot, and it is pulled apart, it forms strings of cheese.
This behavior also occurs with a number of other fluid substances. It seems to happen with polymer substances (like cheese... |
What causes "stringy" melted cheese (and similar behavior in other materials)? |
Great question, I had to do a little reading to piece together an answer as I haven't worked with sulfur oxides in quite some time:
Sources:
- Wikipedia: Sulfur Trioxide
- Shriver & Atkins, *Inorganic Chemistry*, 4th ed., p388
- [Some Yahoo Answer](https://answers.yahoo.com/question/index?qid=201209181609... |
I want to know if there is any free open source tool available for Gasteiger-Hückel charge calculation? I know it is available on Sylbyl but is there any other(free) way to calculate these charges for small molecules?
I was actually trying this paper, if any one is interested,
[How to improve docking accuracy of... |
Any free tool for Calculating Gasteiger-Hückel charges for ligands? |
Why does an more electronegative heteroatom (i.e. cl or o) increase the stretching frequency of a carbonyl?
I'd suspect its that they donate their lone pairs and we end up with a -ve charge on the oxygen in one of our resonance structures which makes the electrostatic attraction between the carbon and oxygen larger... |
Great question, I had to do a little reading to piece together an answer as I haven't worked with sulfur oxides in quite some time:
Sources:
- Wikipedia: Sulfur Trioxide
- Shriver & Atkins, *Inorganic Chemistry*, 4th ed., p388
- [Some Yahoo Answer](https://answers.yahoo.com/question/index?qid=201209181609... |
A problem in my textbook:
Solid $\ce{AgCl}$ is placed in $1$ $L$ of $0.55$ $M$ $\ce{NaCl}$. Find the mass of $\ce{AgCl}$ which dissolves.
I know the method to solve the problem. But is the problem malformed? We get an answer, say $x$ grams $\ce{AgCl}$ dissolves. But what if we placed less than $x$ grams solid $\c... |
A problem in my textbook:
> Solid $\ce{AgCl}$ is placed in $1\,\mathrm{L}$ of $0.55\,\mathrm{M}$ $\ce{NaCl}$. Find the mass of $\ce{AgCl}$ which dissolves.
I know the method to solve the problem. But is the problem malformed? We get an answer, say $x$ grams $\ce{AgCl}$ dissolves. But what if we placed less than $... |
Great question, I had to do a little reading to piece together an answer as I haven't worked with sulfur oxides in quite some time:
Sources:
- Wikipedia: Sulfur Trioxide
- Shriver & Atkins, *Inorganic Chemistry*, 4th ed., p388
- [Some Yahoo Answer](https://answers.yahoo.com/question/index?qid=201209181609... |
Great question, I had to do a little reading to piece together an answer as I haven't worked with sulfur oxides in quite some time:
Sources:
- Wikipedia: Sulfur Trioxide
- Shriver & Atkins, *Inorganic Chemistry*, 4th ed., p388
- [Some Yahoo Answer](https://answers.yahoo.com/question/index?qid=201209181609... |
What is the the full name of TAPD? Structure provided |
Why does a more electronegative heteroatom (i.e. $\ce{Cl}$ or $\ce{O}$) increase the stretching frequency of a carbonyl?
I'd suspect it's that they donate their lone pairs and we end up with a negative charge on the oxygen in one of our resonance structures which makes the electrostatic attraction between the carbo... |
The $\ce{SO3}$ molecule has three oxygen atoms double bonded to the central sulfur atom. Sulfur has $\ce{sp^2}$ hybridization and has 6 outer electrons which make the bonds with the oxygen, so shouldn’t the bond order be 2?
<img src="https://i.stack.imgur.com/I0QVj.png" width="150" alt="Diagram of SO₃"> |
So while calculating for the relative yield of monochlorination for 2,3-dimethylbutane, I was counting the primary hydrogens, I counted 6, but in fact it was 12. Why is it 12? How do you find equivalent hydrogens? Since the compound is symmetrical doesn't the hydrogens on both sides be equivalent to each other?
![... |
I would like to add another shade to the already quite excellent answer of ron.
I will use donor-acceptor complexes, like Lewis acid base adducts, as case in point. Probably one of the simplest and most popular is the ammonia and borane adduct. I consider the structures below to be the most accepted ones, with prob... |
I am familiar with the idea that rate law must be determined experimentally. I am also familiar with the idea that there is no formulated way for coming up with the rate law besides just experimentation.
My question is: why isn't the rate law of:
$$ aA + bB \rightarrow \mbox{something}$$
just:
$$r = k[A]^a... |
Why must the rate law be experimentally determined? |
> Problem: A buffer was made by mixing 500 mL of 1 M (mol/L) acetic acid and 500 mL of 0.5 M calcium acetate.
What are the resulting concentrations of acetic acid, Ca2+ and acetate and what is the resulting pH? Ka(acetic acid) = 1.75×10−5
Final volume = $500+500$ mL = 1L<br>
Concentration of Acetic Acid = $\frac{... |
Can a liquid which is saturated with a single solute, dissolve a different solute, or is saturation a universal thing? I ask because I've seen that different solutes have different points (amounts) at which they become saturated in water, for example, which caused me to think that maybe each solution was perhaps indepe... |
**General Rule #1:** Most elements use only s and p orbitals to form bonds, only transition elements and heavier elements use d, f, *etc*. orbitals in bonding.
**General Rule #2:** The more s-character in a bond the shorter the bond ([reference][1]). For example
- a $\ce{C(sp^3)-C(sp^3)}$ single bond length is... |
**General Rule #1:** Most elements use only s and p orbitals to form bonds, only transition elements and heavier elements use d, f, *etc*. orbitals in bonding.
**General Rule #2:** The more s-character in a bond the shorter the bond ([reference][1]). For example
- a $\ce{C(sp^3)-C(sp^3)}$ single bond length is... |
Can a liquid which is saturated with a single solute, dissolve a different solute, or is saturation a universal thing? I ask because I've seen that different solutes have different points (amounts) at which they become saturated in water, for example, which caused me to think that maybe each solution was perhaps indepe... |
Why are the axial bond lengths greater than those of the equatorial bonds in a trigonal bi-pyramid (TBP) geometry molecule; but the opposite is true for pentagonal bi-pyramid (PBP) geometry molecules? I think that it might have something to do with the angles between the bonds, so I thought of a possible explanation.
... |
I have measured the element composition of a sample using ICP-OES, and reported my results in wt%. A study which has analyzed the same sample types, but with an electron microprobe, has reported their element concentrations in at%, which in addition are normalized to 100 %. I would like to compare my results to those i... |
From basic coordination chemistry and acid-base equilibria we understand that a metal hexa-aqua ion can be deprotonated until it's positive charge is balanced by the negative charge of the hydroxides rendering a neutral complex. We then say that this complex precipitates.
Recently in my inorganic class we studied h... |
When studying ligand substitution (at UK year 13 level), the following example has been given:
$\ce{[Cu(H2O)_6]^2+ + 2NH3 <=> [Cu(OH)_2(H2O)_6] + 2NH4^+}$
$\ce{[Cu(OH)_2(H2O)_4] + 4NH3 <=> [Cu(NH3)_4(H2O)_2]^2+ +2OH- +2H2O}$
There has been no explanation given of why the substitution is only partial, whereas the... |
Why is ligand substitution only partial with $\ce{Cu^2+}$ and $\ce{NH3}$? |
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