texts: What old chemistry textbooks are good until present day?

texts:
I have found old chemistry textbooks like Walter Moore's Physical Chemistry and Morrison&Boyd's Organic Chemistry to be really good source of information, as good as actual reference textbooks.

What other books do you recommend, regardless the area, that still useful nowadays despite its age?

The reason I ask this is because the language used by these authors seems to be different from today, and I find it to be a pleasant reading.


texts: I'm not sure what the answer is, all of my friends and my chemistry teacher said it is A, I think it is obvious that the graph is talking about 2 catalysts so it could be D. But I have no idea what the E_a thing is, I've tried googling it to no avail. I got this question on an advanced Chemistry test. One thing for sure, it is not B because the word "additional" isn't there. And another thing, we can't say that one is the graph of the molecule without a catalyst and the other is its graph with a catalyst because according to the graph that would mean that sometimes the molecule without a catalyst is more active than without a catalyst which is obviously wrong.


texts: Can any other common reagent other than than H3PO4 cause this conversion?

texts: Can any other common reagent other than than $\ce{H3PO4}$ cause this conversion? What about (conc) $\ce{H2SO4}$ or (conc) $\ce{HNO3}$ or (conc) $\ce{HCl}$?


texts: Are the hydrogen atoms of 2-methylindane homotopic, enantiotopic, diastereotopic or unrelated?

texts:
I'm very confused. According to the answer key, the circled hydrogens of 2-methylindane (2-methyl-2,3-dihydro-1H-indene) are diastereotopic. I thought they were enantiotopic.

My thought process is the following. They aren't homotopic because replacing one of them with another atom would create a chiral center. Due to them creating a chiral center, I thought it was enantiotopic.

I thought that for it to be diastereoptopic, the carbon with the methyl group off of it would have to be chiral as well, but I don't think it is chiral. The molecule is symmetrical off both sides. Does diastereotopic rely on that carbon being chiral after the new atom replaced the hydrogen? If so, then I understand.

I was under the assumption that the state of that carbon must be chiral before the hydrogen is even replaced.


texts: Relationship between surface energy of liquid and solid states

texts:
I have been experimenting with different kinds of hot-melt (hot glue) adhesives. I have been comparing EVA to acrylic on various substrates. In comparing the two I have found the acrylic to be significantly superior in the strength of the bond, yet it is much more gummy when dry. I want to know how the surface energy of the liquid hot glue compares to the surface energy of the dried adhesive. Furthermore any insight as to why acrylic adhesives (of all kinds) seem to provide such tenacious bonds in general would be appreciated.
In general, What is the relationship between surface tension and surface energy between the liquid and solid states of a material?


texts: How to find molecular charge of fragments using quantum calculations?

texts:
Assume in a software like Avogadro, I put molecules A and B in a specific distance and I know they will involve in a charge transfer reaction ( as Marcus Theory outer sphere transfer ). Then I run a calculation package as Gaussian or GAMESS.

Now I want to see if any charge has moved from A to B.  One approach is to measure their charges and see if they are partially charged.

The problem is that I don't know how to find that molecular partial charge in a selected part of the system in such softwares (like I select a part of the system on the screen and see its charge )

One approach I found is in Avogadro: View>properties > atom properties and find the charge of each single atom and then add the selected atoms together , but it is very very time consuming in larger systems. I am pretty sure there must be a more effective method.


texts: Why do tealights burn violently when nearly burnt out

texts:
I'm not entirely sure if this is the right place for this question, but I decided that it's better than physics.se (and I had no other ideas). I hope this is a good match, otherwise please move the question where it would belong. :)

I often use a mildly scented tealight in my apartment to cover the lingering smell of food. I usually light them using a matchstick, and sometimes I would toss the matchsticks into the tealight after lighting it up.

Usually, the matchstick would burn out after a short while, and for most of the life of the tealight nothing interesting happens. However, when the tealight is very close to burning out with the remains of the matchstick inside, it starts burning very violently, with the flame forming fantastic shapes (it looks like the whole remaining volume of the wax is burning).

Once the flame was so violent it broke the heat resistant glass container I kept it in (I was careless and I let the side of the cup touch a thinner part of the glass, rather than just the bottom).

Why does this happen?


texts: Formation of Calcite from Calcium carbonate

texts:
So, in lab we are forming the different polymorphs of calcium carbonate. It required us to age the sample that was prepared for the formation of calcite for one week. This sample mixture was suspended in water. Whilst the other samples that were prepared for vaterite and aragonite were immediately washed/filtered.
Why do you need to age a calcite sample for a week?


texts: Why are the electronegativities of transition metals so similar to each other?

texts: I was wondering why the electronegativity among transition metals are so similar. I can't find anything on the internet, just vague answers about the d orbitals that don't seem to provide a sufficient justification.


texts: Is a buffer solution really inactive beyond a range of pKa±1?

texts: I have learnt from several books that the range of a buffer solution is always from $\ce{pH = pKa - 1}$ to $\ce{pH = pKa + 1}$. But is there any solid reason to this and any exception?


texts: when do we consider the moles in bomb calorimeter?

texts:
When dealing with different problems in thermodynamics
I noticed that some of the problem consider the number of moles in calculating the heat absorbed or released, whereas some don't and they deal with the heat,capacity,difference in temperature WITHOUT considering the number of moles

example1:       1 gram of a sample burns in .....
they divide the grams over the molar mass to get the moles, then multiply by the enthalpy and solve for the needed.

example2:       1 gram of a sample burns in ....
they get one one of (q,C,delta H) directly without considering the number of moles.

what's the difference?


texts:
I am trying to accomplish the very famous magnetic Ferrofluid in a bottle aka office desk toy.

Before anyone suggest to buy online, I would like to make it myself and learn the whole process VS store bought item.

here is a short video of it

Grade 11 chemistry was the last time I studied chemistry.

I would like to create the similar/same toy

My first question is: is ferrofliud thick liquid you can just buy online or do you have to make it yourself using ink toner or magnetic powder etc

I tried making it  using ink toner powder mixing it with vegetable oil. The results were not the best but worth a shot, it ended up thick blob and alot of particles it was not clear at all and very hard to see through it.

for the clear liquid I used 50% cleaning alcohol,
i tried using water before and it just ended up making the whole glass black.    So in short this is the measurements I used and once again I apologize if I forgot to mention anything.  I used black ink toner mixed it with vegetable oil, ink toner 10 grams vegetable oil 20ml, and 100ml was cleaning alcohol

Alot of people suggest use magnetic powder instead of ink toner what do you recommend? What different liquids should I be using so it does not mix and stays clear.  Some people suggest online make sure you only use water without minerals and iron and many other liquids


texts: Calculating pH of weak base and strong acid: Why is K(a) not required?

texts:
Question: 35mL of 1.5M $\ce{HCN}$, a weak acid(K(a)= $6.2*10^{-10}$) is mixed with 25mL of 2.5M $\ce{KOH}$. Calculate the pH of final solution.

The solution given in my textbook is as follows:-

$\ce{KOH}$ completely dissociates to give 0.062 mol $\ce{OH-}$(The $\ce{K+}$ becomes irrelevant)
0.052 mol of $\ce{HCN}$

3.The equation is $\ce{HCN + OH- ⇌ CN- + H2O}$

So 0.062-0.052 mol=0.01 mol of $\ce{OH-}$ is left over
so 0.01 mol/(0.035l+0.025l)=0.17M of $\ce{OH-}$

6.pOH=0.76 so pH=13.24

7.Also, $\ce{CN-}$ is a weak base relative to $\ce{OH-}$ so we consider it negligible in the calculation.

Finally, it says that K(a) was not required and it was just to distract.

However, I think K(a) is actually required because $\ce{HCN + OH- ⇌ CN- + H2O}$ is a reversible reaction and I don't understand how all of the 0.052 mol of $\ce{HCN}$ can react with $\ce{OH-}$(and in turn, 0.01 mol of $\ce{OH-}$ is left) when there is also a backward reaction producing $\ce{OH-}$ and $\ce{HCN}$ back.

Please help.


texts: Finding the equivalent point of a weak polyprotic acid when reacted with a strong base

texts:
I have a graph of a titration of a weak polyprotic acid with a strong base.
I graphed $\mathrm {pH}$ versus amount of strong base added.
Now since the acid is polyprotic, how do I determine which equivalence point is the final one?
Also not sure how to find the initial concentration of the weak acid? I know the volume I put in, as well as the volume of strong base at any given time.


texts:
When you report Einstein units do you capitalize it? Since we're using it in the context of a unit (and not a name) is capitalization necessary?

Example:

The measured value was reported as 10 Einstein.

or

The measured value was reported as 10 einstein.


texts: One mole of solute (NaCl) is dissolved in 1 litre water. The molarity of solution is

texts:
One mole of solute ($\ce{NaCl}$) is dissolved in $\pu{1 L}$ of water. The molarity of the solution is:
A) $\pu{<1M}$
B) $\pu{>1M}$
C) $\pu{=1M}$
D) $\pu{=2M}$

My answer: It’s a fairly simple question so, I did what anybody would do.
$\mathrm{Molarity}=\frac{\text{No. of moles}}{\text{volume of solution}}$
$\mathrm{Molarity}=1$
That is the obvious answer, and it’s probably right, but the answer given is $\pu{<1M}$. I just wanted to confirm that the answer given is right or wrong. If it is right, why?


texts: Color of Anhydrous Transition Metal Salt

texts:
Why are some anhydrous transition metal salts colored?

Here are some examples I found.

Anhydrous cobalt(II) chloride ($\ce{CoCl2}$), with sky-blue color.
Anhydrous chromium(III) chloride ($\ce{CrCl3}$), with purple color.
Anhydrous copper(II) chloride ($\ce{CuCl2}$), with yellow-brown color.

I already know that complex ion could undergo d-d transition from its unfilled d orbitals, and that's what makes them pretty-colored. (The wavelength of absorbed light corresponds to the gap in energies between d orbitals.)

But in anhydrous salt, which I think isn't a coordination compound, the d orbitals are degenerate. Thus, no energy gap and excitation could occur, no light is absorbed, and the compound would be colorless / white-colored as it reflects all wavelength.

I summarize my understanding in this problem as below.

Solution of complex ion could give color (with exception of $\ce{[Zn(H2O)6]^2+}$ and some other complex ions). e.g. $\ce{CuSO4 (aq)}$, which form $\ce{[Cu(H2O)6]^2+}$ complex ion with blue color.
Hydrated salt is indeed a coordination compound (found related question here), so it could give color. e.g. $\ce{CuSO4.5H2O (s)}$ with blue color.
Anhydrous salt, because it doesn't have any ligands coordinating with the metal ion, it's not a coordination compound. It's a mere ionic salt instead. Shouldn't it be colorless?

Is there any explanation to this case?

Note that in all compounds mentioned above, the metal ions are transition metal. We don't consider s-block metal ions such as $\ce{NaCl}$ and $\ce{MgSO4}$. (Additional question: They should be colorless, am I right?)


texts: Relative intensities are basically independent from the absolute ion abundances registered by the detector?

texts:
I am currently studying the textbook Mass Spectrometry - A Textbook, third edition, by Jürgen Gross. Chapter 1.4.4 Mass Spectrum says the following:

The most intense peak of a mass spectrum is called base peak. In most representations of mass spectral data the intensity of the base peak is normalized to 100% relative intensity. This largely helps to make mass spectra more easily comparable. The normalization can be done because the relative intensities are basically independent from the absolute ion abundances registered by the detector.

I don't understand how it makes sense to say that the relative intensities are independent from the absolute ion abundances. It seems clear to me that the contrary is true; that is, that the relative intensities are derived from the recorded absolute ion abundances registered by the detector, and so the relative intensities are dependent on the absolute ion abundances. After all, the detector records the absolute ion abundances first, and then uses these values to calculate the relatives intensities, right? I'm not sure that it would make much sense to say that it was the other way around.
I would greatly appreciate it if people would please take the time to clarify this.


texts: How does the solvent determine whether mono- or tribromination of phenol occurs?

texts:
In phenol, the $-\ce{OH}$ group activates the benzene ring towards electrophilic substitution. But why is it that the electrophilic bromination of phenol gives trisubstitution (forming 2,4,6-tribromophenol) when aqueous bromine is used, but monosubstitution (either 2- or 4-bromophenol) when a $\ce{CCl4}$ solution of bromine is used? How does the solvent control the extent of bromination?

Related but does not explain completely: How do we know whether we will get a mono substituted or tri-substituted product during electrophilic aromatic substitution?


texts:
Repulsion between shared electron pairs shapes the molecule in such a
  way that enables the pairs to be as far apart as possible.
  Furthermore, the repulsion between shared and unshared pairs forces
  bonded pairs closer to one another.  These principles of the VSEPR
  theory and orbital hybridization, in addition to Van der Waals
  forces, explain the overall shape of a molecule.

In my textbook,  however, there was little mention to how polar bonds and the partial charges they cause affect the structure of a molecule.  I would expect that poles of the same charge would repel each other and have a profound affect on molecular shape.  However, many compounds make me second guess this assumption, including $\ce{H2O}$.

Do polar bonds at all affect molecular shape? Why or why not?  If so, to what extent?


texts: Cause of imaginary part of Warburg element in EIS

texts:
In electrochemical impedance spectroscopy experiments (EIS) the diffusion of electroactive species at flat, macroscopic electrodes is commonly described by the Warburg element with the impedance expression

$$Z_W = \frac{σ}{\sqrt{w}} - i\frac{σ}{\sqrt{w}}$$

This means that the values have a phase angle of $-45^\circ$.

What is an intuitive way to understand the fact, that the Nernst-diffusion layer contributes both a real and imaginary part to the impedance of the system?

I find that it is relatively straightforward to understand that the more the diffusion layer grows, the shallower the concentration gradient gets and therefore that the current decreases. This would explain the real part. I am unsure however, where the imaginary part, or energy-storing component, fits into this picture.

It is very hard to find any information in this regard, as practically all literature treats this just as a result of the mathematical derivation of the faradaic impedance, but does not go into any kind of intuitive explanation.


texts: Does an increase in pressure always causes increase in molar concentration of each gaseous substance involved?

texts:
Question

Statement :
"An increase in pressure (caused by decrease im volume) at equilibrium results in increase in molar concentration of each gaseous susbstance  involved"

This statement is given true, so i tried this reasoning:

Since decrease in volume(V) causes increase in pressure and hence increase in no. of moles(n), so n/V increase  hence molarity increases.

Is this reasoning correct? Please give the real reason for the statement.


texts: What is the relation between partial pressure and concentration?

texts:
So, one of my books said that partial pressure plays more significance in determining the gradient than concentration. So, it said it was possible for a gas to go from high partial pressure at point A to low partial pressure at point B, even though there is low concentration at point A and high concentration at point B.

How is this even possibly? I thought partial pressure and concentration were always related.


texts:
If we are given $\ce{CH3NC}$ and told to convert it into $\ce{CH3CN}$ by doing some chemical reactions.
My attempt
According to my textbook there are no chemical reaction of isocyanide conpounds.  I tried reduction of isocyanide giving a secondary amine. Then I don't know how to convert a secondary amine to cyanide compound.
Hints are too appreciated.
Edit:
I have got a solution but I don't know whether the reaction are spontaneous.

I have written these reaction on the basis of theoretical knowledge I don't know whether they are spontaneous or not. Correct me if I am wrong somewhere.


texts: Is following graph is of a dibasic or monobasic acid?

texts:
Is the above graph is of a dibasic or monobasic acid?
There is slight hint of it being of dibasic around 15. But is it enough to conclude ? I am confused.


texts: Why does the Second Law of Thermodynamics hold true?

texts:
The Second Law of Thermodynamics states that the state of entropy of
  the entire universe, as an isolated system, will always increase over
  time. The second law also states that the changes in the entropy in
  the universe can never be negative.

According to that, $\Delta S$ of the universe should always be positive for a spontaneous reaction to occur. But what is the reason for that?

In Advanced Chemistry, Philip Matthews states:

  Pg-287  This result cannot be proved; rather it is a statement of
  experiment

While there is true reasons for every point in chemistry, I feel there should be a real reason for it rather than experimental statement. But I searched it on Google but can't to find an answer. So, can you help me to give the reason?


texts:
Do amides from primary or secondary amines ever oxidize to a double-bond on the nitrogen? For example, like from an $\mathrm{R \bbox[yellow]{\color{red}{-}}(NH)-(C=O)-R'}$ to an $\mathrm{ R \bbox[yellow]{\color{red}{=}}N-(C=O)-R'}$?

Seems like a favorable product, given the creation of that conjugated pi-bonded system! But, I can't seem to find any references to such a reaction -- would it perhaps require some kind of elimination groups on the amine as well?


texts: Is the compound CM-7 in Red Comet fire grenades azeotropic dichloromethane?

texts:
Red Comet Manufacturing changed the liquid in their fire grenades from carbon tetrachloride to something they referred to as CM-7 in 1955.

Is CM-7 the same thing as azeotropic dichloromethane? If not, what is the composition of CM-7? What are the gases given off by CM-7 when it is exposed to heat?


texts: Hot tub shock is potassium peroxymonosulfate. When added to a hot tub, it creates bubbles. It is said to oxidize organic debris in the water. What is the reaction?


texts: Are the triply-bonded carbons in pyridyne (and benzyne) sp-hybridised?

texts:
I was given this molecule (3,4-pyridyne) in a test:

I had to find out if it had any atoms which had a hybridization state other than sp2. The solution said that it doesn't have any. But aren't the triply-bonded carbon atoms sp-hybridized?

Edit:
Benzyne also has a similar structure, with a distorted triple bond -


texts: Which has a greater dipole: chloroform (CHCl3) or trichlorofluoromethane (CCl3F)?

texts: Does chloroform have a greater dipole because the $\ce{C-H}$ dipole is weaker than $\ce{C-Cl}$ dipole thereby making the overall net dipole greater in chloroform, as opposed to trichlorofluoromethane where the $\ce{C-F}$ bond dipole being more similar to the $\ce{C-Cl}$ dipole makes the molecule more stable with a smaller net dipole?


texts: pH of an aqueous solution of Mg2+ kept rising above that of clean water. What's going on?

texts:
In a recent inorganic chemistry lab session, we tested the pH of various ions in water. The water turned out to be on the acidic side (5.5 with $\mathrm{pH}$-paper, 5.59 with $\mathrm{pH}$-meter). A solution of $\ce{Mg^{2+}}$ gave some strange results. The $\mathrm{pH}$ kept rising when using a $\mathrm{pH}$-meter, going from around 4.2 to 5.83 (higher than that of the pure water). We stopped at this point, thinking something must be wrong. A classmate experienced the exact same thing, and stopped at 6.5 or something.
I expected $\ce{Mg^{2+}}$ to act as a very weak cation acid, making the solution at least somewhat more acidic than the water. In my limited knowledge, I would think that the only thing $\ce{Mg^{2+}}$ can do in this scenario is to slightly polarize the water ligands, thus making them deprotonate.
Was this a fault in the equipment, or was there some other reaction going on?
I'm having a hard time finding expected $\mathrm{pH}$ of $\ce{Mg^{2+}}$ in aqueous solution, so any data on that would also be welcome.


texts: Does same amount of heat absorbed cause the same changes of temperature in the same amount of different liquids? Explain.


texts:
So I'm cleaning up a lot of my stuff to have more space and I have 2 jugs of grocery bought white vinegar jugs (5% acetic acid). Naturally to make it more compact, I'm trying to concentrate it. I was wondering if leaving the vinegar out in a warm place to let the water evaporate will be effective.

I know that acetic acid solutions form azeotropes at wide ranges, so I might actually be evaporating the acetic acid along with it.

So would it work?


texts: Can I use gasoline as a non-polar solvent?

texts: I was wondering if I can use gasoline for a non-polar extraction of organic substances instead of prescribed diethyl ether, which is a bit hard to get in my country. If not, are there any products that can be found at hardware stores for example and can be used as a non-polar solvent?


texts: Dissolving CNE (cresol novolac epoxy) resin covered computer chips

texts:
I intend to destroy (dissolving would be optimal) a few computer chips (NAND memory chips used eg. on SSDs to be precise).
Why? See foot note.
I am not a chemist, so of course I tried to research the topic a bit before actually attempting anything. I got to know that they are covered in a resin called CNE and that there is surprisingly little entry-level info on liquefying your electronics apart from "Get gold from scrap electronics" youtube videos - so I decided to start there.
Most common scenario described there is to use sulfuric acid heated to 90 degrees celcius which should remove the epoxy coating, then applying the nitric acid mixed with water or nitric acid mixed with hydrochloric acid (like here - link)
However: I do not intend to extract anything from these chips - I just want to have them destroyed, so that data recovery is impossible. Is there a substance (possibly available to me - just a common guy with basic protection, not a specialized lab) that could liquify the whole chip (that is CNE resin on top, and at least some of it's metal contents)? If there is such a substance - can it melt the electronic without the need of having the heat supplied from the outside?
Please do not suggest thermite or "spill gasoline all over it and light it". I am looking for a serious answer - preferably one without igniting or putting something on a heat source. I am wondering if "spill and forget" or "put it in acid bath and forget" is possible at all.

Explanation of my use case: me and my buddy work in computer security field, apart from work it is also our hobby :) The topic of removing data from hard drives is often brought in our discussions and has been widely discussed on stackexchange sites (eg. this question or this one - there's even FAQ entry on data removal). There are DoD and NIST documents mentioning melting of drives. However: while there are often mentions of melting the hard drive - nobody  is actually providing useful details.  My mistake, the documents mention melting which is of course not the same as dissolving (thanks @Mithoron).


texts: Why can a diamond be broken using a hammer if it's the hardest natural substance known?

texts:
I've heard that diamond is the hardest natural known material but, on Google search, I found that it can easily be broken by a hammer as it's not tough.

So, what is difference between hardness and toughness? According to me, both should be the same, and if both are different than what is the toughest known substance?


texts: Do external electronic shells influence internal ones?

texts:
There is a well-known electron shielding effect: negatively-charged internal electronic shell screens external shells from positive nuclei, thus increasing their radii.

Thus, 2S orbital radius of Li atom (ground state) should be greater than radius of excited Li2+ cation with single 2S electron.

But is there a reverse influence: from external electronic shells to internal ones? For example, are radii of 1S orbital in Li and Li+ equal, or not?

I am sure there is not a big difference anyway, but this is theoretically interesting. Probably it can be proved by comparision of internal shell ionisation energies of Li and Li+ but I am not sure where to look for appropriate experimental data.

I have some intuitive considerations, while they did not lead me to certain answer:

Concept of Faraday cage looks to be irrelevant, because electron
shells are not literally material conductive shells, but they are
filled space regions.
Shells interpenetrate, thus external shell
can a bit force out internal shell from nucleus by increasing
electron density in space  adjacent to nucleus.
Classically,
internal one of two concentric  elastic charged spheres should
shrink. If we imagine big spheres, their small areas should interact
repulsively as parallel plates. But considered spheres are actually
not "big".


texts: Composites of Immiscible Solids - Aluminum and Lead Example

texts:
The $\ce{Al}$-$\ce{Pb}$ (aluminium-lead) phase diagram clearly depicts that when cooled from the liquid state, aluminium and lead are not miscible in the solid state, i.e. the crystal structure of only one of the components prevails while the other remains a liquid or does not interact in any way with the other in its own solidification process.

What does this have to do - if anything - with the fact that a solid combination of $\ce{Al}$ and $\ce{Pb}$ is not classified as a composite?


texts: Is it possible to make deuterated organic compounds?

texts: Organic compounds always have a $\ce{C-H}$ bond. But can we make compounds having $\ce{C-D}$ bonds where  D is the deuterium part like $\ce{CD4}$, $\ce{C2D5CHO}$, $\ce{C6D6}$  and other complex organic compounds? Overall, can we make organic compounds containing deuterium? Also, can we consider those compounds organic? Are the compounds stable? Give some example of preparatory reaction of those compounds.


texts: Why is the melting point of p-dichlorobenzene higher than those of o-dichlorobenzene and m-dichlorobenzene?

texts:
I was going through alkyl and aryl halides and noted the following statement in my textbook:

  p-dichlorobenzene has higher melting point and solubility than those of o-dichlorobenzene and m-dichlorobenzene.

I thought over it but could not come to a conclusion. Why is the above assertion true?


texts:
It's a general trend that basicity of oxides decreases down the group.

But recently I came across a statement "the basicity of second group oxide decreases down the group and decrease in basic nature of oxide from Be to Ba is due to decrease in polarizing power with increase in ionic size"

I'm not able to understand the relationship between ionic nature and basicity.

Also I feel that more the ionic nature, more the basicity, (as oxygen easily dissociates )

This is question is related to  this , but generalised explaination is given, I'm looking for specific explaination to this this particular case


texts: Does concentration of salt increase or decrease rate of rusting?

texts:
I want to know whether increasing the concentration of salt, specifically $\ce{NaCl}$, increases or decreases the rate of rusting. There are conflicting theories that explain opposite outcomes:

Increasing concentration of salt decreases the amount of dissolved oxygen and thus    decreases the rate of rusting
Increasing concentration increases electron mobility and thus increases rate of rusting

I haven't been able to how rusting works in full detail nor have I been able to understand why there are two contradicting theories present. It seems that people write it more out of opinion than with factual basis.

Can someone please clarify?


texts: How to theoretically predict thermodynamic stability?

texts:
Let's say we have $\ce{CH3-NH2}$ undergoing Hoffman's exhaustive methylation with $\ce{CH3-Cl}$. In which case side reactions such as $\ce{CH3-NH2 + CH3-NH2 -> CH3NHCH3 + NH3}$ would also occur.

How do we theoretically determine the relative difference in thermodynamic stability between the products of the side reaction ($\ce{CH3NHCH3 + NH3}$) and the main reaction?


texts: How do bonds rotate in pericyclic reactions?

texts:
In Pericyclic reactions, it is shown that the terminal bonds rotate (conrotation or disrotation) to allow for allignment of the FMO's, thereby forming the sigma bond

However, a detail that most of my textbooks and references miss out on is how is the double bond rotating about it's axis? As far as I know, pi bonds are restricted in their rotation which is what gives rise to cis-trans isomerism. If this is the case, how are the bonds rotating about their axis to align the orbitals?
One possibility I can think of is that the double bond is broken before/during rotation, but I haven't seen this explicitly mentioned anywhere. Any insights are appreciated.


texts:
I'm having problems when trying to know the outcome of this reaction.

The first step must be a Michael addition of the 1,3-dicarbonyl compound to the  α,β-unsaturated carbonyl compound, followed by a acid hydrolisis and a decarboxylation of the ester.

LDA must deprotone the least hindered hydrogen, that must be the $\alpha$-$\ce{CH3}$ to the non cyclic ketone. But at this point, I don't know how this reaction can continue to give one of the above products.


texts: Remove ethanol from gasoline by mixing it with water?

texts:
I have read on forums that ethanol can be removed from commercial gasoline by mixing it with water, then draining water from the bottom to remove the water-ethanol solution (for example, with a separatory funnel).

Does this really work? I would assume the ethanol is homogenized with the gasoline somehow, so would that interfere with it binding to the water?


texts:
In the book, The theory of atomic structure and spectra, Robert D. Cowan says that the allowed terms of $p^2$ are $^1S$, $^1D$, $^3P$ and so the possible terms of $p^2 + p\quad$ (obtained by using the vector model) are:

$$^2P^\circ,\quad ^2P^\circ D^\circ F^\circ,\quad ^{2,4}S^\circ P^\circ D^\circ
 \tag1$$

I am having trouble in understand the notation in $(1)$. For example  the term $^2P^\circ$ means that $s=1/2,l=1$ and $^\circ$ means odd parity, but for the term $^{2,4}S^\circ P^\circ D^\circ$, I do not know what it means. Can anyone explain me it please?


texts:
Using two equivalents of $\ce{Br2}$ and catalytic $\ce{FeBr3}$, compound A can be converted into B. In the same reaction vessel but in multiple steps, the conversion of B into C ($\ce{C11H12Br3I}$) can be obtained using $\ce{H2SO4, NaNO2}$ and $\ce{NaI}$.
The molecule A is below:

My Attempt
What I am struggling with is determining what double bonds the $\ce{Br2}$ is added on. I am pretty sure that the double that is not on the benzene ring will get brominated, but I am not sure what other double bond will also get brominated.
I know the mechanism for the conversion for B into C, which is basically the sandmeyer reaction followed by substitution of iodine. However what further confuses me is that the end product only has 3 bromine atoms, not 4 bromine which is what I expected (since bromination occurs twice).


texts: Why is liquid mercury conductive if you do not have the lattice periodicity to describe the collective behavior of conducting electrons?

texts: We have electric conductivity in metal because the regularity and interaction in a crystal allow for the creation of conduction bands. We should not find these bands in mercury so how could liquid mercury be an conductor?  How can we describe the electrical conductivty of mercury.


texts: What are the properties of various solutions at pH <2 that may cause injuries?

texts: For example, why do some solutions not cause any injuries at pH 2 while HCl does?


texts: What are the limitations of a waters of hydration experiment?

texts:
When a hydrated salt such as $\ce{CuSO4.5H2O}$ is subjected to heat, an anhydrous salt ($\ce{CuSO4}$) is produced. However the theoretical molar ratio of $\ce{H2O:CuSO4}$ and experimental molar ratio of $\ce{H2O:CuSO4}$ are not the same. Instead there is a percentage error, why does this occur? And how can we minimise this in this experiment?
The hydrated salt was left on hot plate at 70 degrees celsius for 25 mins.


texts: Which proton in cyclohexene is the most acidic?

texts:
I know that $\mathrm{H^b}$ is most acidic due to conjugation (resonance).

But I am confused as to how to compare $\mathrm{H^a}$ and $\mathrm{H^c}$. I think $\mathrm{H^a}$ should be more acidic than $\mathrm{H^c}$ due to hyperconjugation.


texts: How is $\ce{HSO4-}$ formed? If Hydrogen is 1+ and $\ce{SO4}$ has 2- charge? I don't understand this. Could someone please clarify?


texts:
In this video, a water bottle is shown to be crushed by the surrounding air.

My understanding:

When the person pours cold water over the bottle which has hot water inside it, the hot water produces water vapor which increases the pressure inside in bottle. When the person places the bottle into the cold water bowl, the temperature of the bottle decreases, which causes the water vapor inside the bottle to get condensed, thus lowers the pressure inside the water bottle. When the pressure inside decreases, the pressure outside is greater which crushes the water bottle.

If my explanation of this is wrong in anyway, can someone correct it?


texts: Difference in transition lifetimes for near-resonant v/s non-resonant Raman effect

texts: I have read that a virtual state is created when Raman scattering occurs. Since this state is forbidden, the molecule upon absorbing a photon (not enough to take it to the next electronically excited level) immediately gives off the stokes or anti-stokes shifted photon with delay in the order of femto-seconds. If the photon were to be energetic enough to take it close to the excited state(near-resonant), would there be a change in the lifetime of the transition?


texts: Sodium carbonate titration in presence of phenolphthalein

texts:
Why phenolphthalein cannot show the endpoint for the complete titration of Na2CO3 with only phenolphthalein?

What's the reason that we consider only half of the moles of sodium carbonate when titrating with phenolphthalein indicator?


texts: Separation of metal particles from fluid in ferrofluid

texts: I purchased commercial Ferrofluid, and when suspended, the water and/or alcohol turns into a brown sludge.  In 95% alcohol, all the metal particles separated from the "tar" Why, and how can I prevent this?


texts: Is it wrong to write a coefficient of 1 in a chemical equation?

texts:
Take $$\ce{2H2 + O2 -> 2H2O}$$
Is it wrong to write $$\ce{2H2 + 1O2 -> 2 H2O}$$
By wrong I mean that it is against a widely accepted guideline (those of the IUPAC?), not just "your teacher said it's wrong, therefore it's wrong". The only information I could find, is that it is assumed there is a coefficient of 1 when there is none written.


texts: Interaction between a pencil and rubber (eraser)

texts:
Is there a interaction between a graphite pencil and and a eraser. For example, if I drew a line on a piece of paper and then erased that, what interaction is occurring?

Is it a Van der Waals interaction with intermolecular forces or is something else?


texts: What are the roles of pyridine and DCM in the acylation of an alcohol?

texts:
What role does pyridine and $\ce{CH2Cl2}$ play in this reaction?

(Prior to this step, the corresponding carboxylic acid was converted to the acyl chloride using DMF, oxalyl chloride, and DCM.)

This reaction is taken from Bear, R. B.; Shea, K. J. Tandem Hetero Diels−Alder Reaction: Synthesis of Oxygenated Macrocycles. Org. Lett. 2001, 3 (5), 723–726. DOI:10.1021/ol007040s..


texts:
How does one determine the C rate of an aged cell?

I would like to find the discharge rate just before any cliff edge of capacity loss. Can the C rate of a cell be estimated by the cells rated heat dissipation and measured internal resistance? Where I could find the current that will use up all the cells heat dissipation capacity.

I have a number of recycled laptop battery 18650 cells.

Are there any negative effects of the cells being below room temperature?


texts: How do we identify left handed and right handed crystals?

texts:
I was going through this article about how Louis Pasteur studied and explained the absence of optical activity in Racemic acid. Here's an extract:

  When Pasteur next examined crystals of the same
  salt of racemic acid, he found that they, too, were chiral
  but that some of the crystals were left-handed and others
  were right-handed. The crystals were related to one
  another as an object and its non-superimposable mirror
  image, and they were present in equal amounts. With a
  magnifying lens and a pair of tweezers, Pasteur carefully
  separated these crystals into two piles: the left-handed
  ones and the right-handed ones.

My guess is that the left/right handedness refers to the molecular spatial alignment. So,

How exactly can you assign the property of individual molecules to an entire crystal?
How can you determine if a crystal is left/right handed just by looking at it?


texts: Do hard drive platters contain toxic chemicals?

texts: So, I'm considering an Artsy Fartsy project with hard drive platters. Being mildly aware of the world around me, I've come to the conclusion that I probably shouldn't grind up modern (or any) electronics and drink it for tea. To that end, is there anything in hard drive platters that is significantly toxic, or are they fine lying around the house? I don't intend in grinding them or anything, I'll be using them whole, so dust inhalation presumably isn't a big issue.


texts: Is there a formula to tell how many conformers of a molecule to generate?

texts:
Let's say we want to generate conformers of molecules (e.g., ligands for docking in a protein pocket).

Is there a formula, like a function of the number of rotatable bonds, to decide how many conformers (maximum) to generate for a given molecule ?


texts:
Why we cannot solve Roothaan equation
$\mathbf{F} \mathbf{C} = \mathbf{S} \mathbf{C} \mathbf{\epsilon}$
by just move S matrix to the left, as
$\mathbf{S}^{-1} \mathbf{F} \mathbf{C} = \mathbf{C} \mathbf{\epsilon}$ as a new matrix $\mathbf{F}'$, and then solve the eigenvalue problem
$\mathbf{F}' \mathbf{C} = \mathbf{C} \mathbf{\epsilon}$
why we cannot do that?


texts: Difference in Periodic Tables in Block Formation (split in d-block)

texts:
I had a question. When I was learning Chemistry and blocks in the periodic table, my professors always broke the table down like the image below

Recently, when I looked up the periodic table (in block form), I noticed that the first group of the d-block was separated off from the rest of the d-block. So, rather than it going very neatly s, f, d, p (as it does in the picture above), it now goes s, one group of d, f, the other 9 groups of d, then p (like the image below).

Can someone please explain this to me? I am not a chemistry major or even good at chemistry, just curious. I thought it may have something to do with electron configurations (1s2 2s2 2p6... etc) but when I tried it out, I couldn't understand. If you could explain it in layman terms, I would greatly appreciate it.

Thank you


texts:
I am asked to indicate what is the product of this reaction, and the mechanism by which it is formed:
3-Bromo-3-ethylpentane + sodium hydroxide in methanol, 50 ºC
I identify it as an elimination reaction. I would say that it is a bimolecular elimination, E2, because a tertiary alkyl halide and a strong base (NaOH) are used. However, my teacher told me that it was unimolecular, E1, and I don't understand why.


texts: What is "activated red phosphorus"? What made it so long to be discovered?

texts:
[WP = white phosphorus ; RP = red phosphorus ; ARP = activated red phosphorus]

Tom from Extraction & Ire did a video two years ago(2018) on converting WP to RP by keeping the former in sunlight for several days. He chose chloroform solvent to dissolve WP in a glass vial. The solution started to go deep orange to red on slight heating and then keeping in sunlight for 5 days. After 5 days, he tested the solution with sodium hydroxide solution to confirm that it is RP (RP doesn't react with $\ce{NaOH}$, WP does). On dumping it to the $\ce{NaOH}$ solution, it immediately started reacting (phosphine was evolving which had a dreadful smell). After 15 minutes on adding, the orange-red color vanished, that means all of the phosphorus has reacted. Some white crystals formed in the solution which is presumed to be sodium formate ($\ce{HCOONa}$) due to the chloroform (isn't it soluble in water?).
$$\ce{P4_{(?)} + 3NaOH + 3H2O -> PH3 ^ + 3NaH2PO2}$$
$$\ce{2NaH2PO2 -> PH3 ^ + Na2HPO4}$$
$$\ce{CHCl3 + 4NaOH -> HCOONa (\downarrow ?) + 3NaCl + 2H2O}$$
So, the conversion failed. He apparently named the species "ARP". He made the following conclusion:
\begin{array}{c|c|c|c}
\mathbf{~} & \mathbf{WP} & \mathbf{RP} & \mathbf{ARP}  \\\hline
\text{color} & \text{white} & \text{red} & \text{red}\\
\text{soluble in CHCl3} & \text{Yes} & \text{No} & \text{No}\\
\text{Reactive towards NaOH} & \text{Yes} & \text{No} & \text{Yes}\end{array}
So, apparently WP converted to an unknown species(allotrope?) which he assumed to be ARP. He doesn't know its composition nor did he find convincing literature. Google didn't give any relevant hits except two papers. First one says it is polymerized organophosphorus chains and the second one says it is series of polyphosphides*.
Questions:

What is the actual composition of ARP?
Is it an allotrope? If so, other allotropes were discovered centuries ago, why was it unknown until recently? What made it so long to be discovered?

References

Sukhov, Boris & Malysheva, S. & Kuimov, Vladimir & Smetannikov, Yu & Tarasova, N. & Lupanov, A. & Gusarova, N. & Trofimov, BA. (2004). Reaction of Activated Red Phosphorus with Allyl Bromide under Phase-Transfer Catalysis. Russian Journal of General Chemistry - RUSS J GEN CHEM. 74. 1128-1129. 10.1023/B:RUGC.0000045878.42411.31.
Nucleophilic Activation of Red Phosphorus for Controlled Synthesis of Polyphosphides, Minyoung Jo, Alina Dragulescu-Andrasi, L. Zane Miller, Chongin Pak, and Michael Shatruk,Inorganic Chemistry 2020 59 (8), 5483-5489
DOI: 10.1021/acs.inorgchem.0c00108

The 2020 paper says "RP is readily activated by refluxing it with different potassium alkoxide to give soluble polyphosphide ions". Now, polyphosphides is known and has been studied a lot (first paper I could find dates way back in 1967). So, what does "readily activation of red phosphorus" mean in this context? Could it mean ARP?


texts: Polarisability of alkynes, alkenes and alkanes

texts:
I have noted a little trend in the boiling points of alkynes, alkenes and alkanes. Upon searching for the explanation, I have chanced upon an answer written by M.A.R. (Alkane, Alkene, Alkyne boiling point). In his answer, he explains the boiling point trend which goes in the order alkyne > alkane > alkene by invoking the concept of polarisability of the electron cloud. This makes perfect sense as polarisability is linked to the strength of intermolecular forces and the strength of such forces determines the boiling points of the substances in the liquid state.

However, my point of contention is his explanation of how alkynes are more polarisable due to their more electron-dense triple bond and how alkanes are more polarisable than alkenes because they have two more electrons.

This leads me to wonder what is meant by polarisability. Evidently, I have learnt it in school and I know perfectly well what is meant by it (Refer to https://en.wikipedia.org/wiki/Fajans%27_rules). However, it seems to me that M.A.R.'s "polarisability" is completely different from what I perceive it to be.

M.A.R. says that the more electron-dense triple bond is more polarisable. However, there are so many electrons packed in that small space. That is analogous to a small anion and evidently, small anions are very much not very polarisable.

M.A.R. then seems to contradict himself by not subscribing to the same logic in his explanation of the case of the boiling points of alkanes vs. alkenes. By his previous logic used in the case of alkynes, the double bond being more electron-dense than the single bond would mean that the polarisability of alkenes is more than that of alkanes. Instead, he uses another reasoning that the alkenes have 2 less electrons than the alkanes.

Thus, this leads me to question: Is M.A.R.'s use of "polarisability" correct in a chemistry sense?

On a side note, I would have rationalised this boiling trend using electronegativity and bond dipoles because atoms with sp-hybridised orbitals are more electronegative than sp2 and subsequently sp3. However, this is also flawed because I would not be able to explain why alkane > alkene.


texts: Is Polymorphism accompanied with an energy change?

texts:
Differential Scanning Colorimetry (DSC) is a technique used to identify Polymorphism by revealing two melting points of a pure crystalline structure.

DSC shows a peak associated with the formation of the crystals. Hot Stage Microscopy (HSM) shows that only one of the polymorphs forms at the crystallisation temperature, the second polymorph forms between the crystallisation temperature and the melting temperatures.

Is the formation of the second polymorph not accompanied with a change in energy? If not, then why would the two structures have a different melting point seeing as no energy has entered or exited the system?


texts: Difference in collision cross-section obtained by measurement method

texts:
I have a simple question of Physical Chemistry, but I don't know the answer.
We can find collision cross-section(σ) through experiments in three ways.
first, diffusion flux experiment. diffusion coefficient D = (1/3)x(vλ) = (1/3)x(8RT/πM)x(RT/PNσ). So, σ can be found by measuring the diffusion flux.
Second, Thermal conduction experiment. κ = (1/3)x(C/N)x(8RT/πM)x(RT/PNσ). So, σ can be found by measuring the thermal conductivity.
Third, viscosity experiment. μ = (1/3)x(m)x(8RT/πM)x(RT/PNσ). So, σ can be found by measuring the viscosity.
This is the question. I do not know why the sigma obtained through each experiment is different. The sigma obtained by measuring the diffusion flux is different from the sigma obtained by measuring the viscosity. The same is true of thermal conductivity. Why is this happening?


texts:
I am doing a project that involves activating carbon. The method my team is using is simply to heat it within the range of 400-500°C, and then testing for activity by using a dye.

Why does simply heating it (without any additional reactants like zinc chloride and so on) activate it?


texts:
How are gases all so similar unlike any other state of matter?

For ex:

1) 1 mole of any gas will occupy 22.4 litres at atmospheric pressure. (Cannot be said of all solids/ liquids)

2) partial pressure of any gas is directly proportional only to mole fraction. ( even weight of atoms is irrelevant.)

I guessed it would be due to negligible intermolecular attractions but I'm not too clear. Could someone explain.


texts:
One of the often-touted uses of WD-40 is that it "dissolves rust". The official website states that WD-40 "breaks down the bonds between metal and rust".

I can't understand how this would work, since there seem to be no rust-dissolving ingredients in WD-40 and it seems the product is more basic than acidic.

A (possibly not exhaustive) list of ingredients:

Mineral oil, I guess for lubrication and rust protection layer (but not a rust solvent?)
Decane, freeze-resisting
Nonane, water-displacing
Tetradecane, freeze-resisting and water-repelling
Undecane, freeze-resisting and water-repelling
Dimethyl Naphthalene (C12H12), likely used as a solvent
Cyclohexane, solvent
Carbon dioxide, likely used as a propellant

I can imagine that the low viscosity of WD-40 allows it to get in all nooks, making it easier to grind rust particles away because it acts as a short-term lubricant. Is that actually how it works, or am I missing something?


texts:
Ice floats in its liquid state, water, because it is less dense, and I know fat also floats in water BUT will a piece of fat dropped into a pot of melted fat also float? or will it sink and what is it about its molecular structure that allows this?

I've searched google for about three hours and all I can find are articles on fat floating in water, so any help is greatly appreciated!


texts: How did Planck reach the conclusion that energy comes in packets based on black body curves?

texts: I understand that if wavelength continues to decrease energy emitted by an atom would get to infinite, but how does the max wavelength at a particular temperature translate to discrete energy packets. Please explain.


texts: If a chemical reaction is repeated multiple times, will it produce the same result?

texts:
If a chemical reaction is repeated multiple(infinity) times, will it produce the same result?
For example, I put two $\ce{H}$ and one $\ce{O}$ together, and repeat it many (infinity) times within an exact same environment, will it produce $\ce{H2O}$ every time?
My chemistry teacher tells me it will. But I still wonder if it's true. Hope you will help me. Thanks.


texts: Focusing on HOMO when discussing thermal electrocyclic reactions

texts: When taking into consideration the outcome of a thermal electrocyclic reaction, why do we focus specifically on the HOMO of the conjugated polyene? Why does it seemingly have the highest contribution on the product?


texts: Hydrochloric acids inability to chlorinate cinnamyl alcohol on 2 sites

texts: According to a reference (J.  Am.  Chem.  SOC.  1985,  107,  2033-2046), cinnamyl chloride can be prepared in quantitative yield by the reaction of cinnamyl alcohol with hydrochloric acid. Looking at the structure, I can see that the hydroxy group will be chlorinated, but I do not understand why the delicate double bond will be left untouched?


texts: What does it actually mean by stability of an atom

texts: There are several rules related to stability of an atom, like octet rule, half filled or fully filled d orbital etc. But none of them (at my best knowledge) does not explain why an atom is stable when it obeys those rules. So, is there any reason at all or are they just based on experimental results?


texts:
As we know that the first step of E1cB step is second of E1 and vice versa. So can we say that by reversing E1cB reaction we will get E1 reaction.

In this the main problem which I am getting is in E1cB reaction carbanion is formed while in E1 carbocation. By reversing we will convert carbanion into neutral not into carbocation. So is this possible?


texts: I can't rationalize why S- is a worse nucleophile than N-. I thought nucelophilicity was related to electronegativity, the more electronegative an atom is, the less of a nucleophile it is. Sulfur is less electronegative than Nitrogen. What concept am I not considering or misunderstanding?


texts: Why are Methyl vibr. modes called r modes and methylene vibr. modes called d modes

texts:
I am coming from a chemical background and currently work in the field of vibrational spectroscopy. When I talk to fellow physicists or chemists I always encounter the same question. "Why are the vibrational modes of methyl- and methylenegroups are called r and d modes".
Does this have a group theory background? Can someone elaborate on that?


texts:
Reasons which explain why the efficiency of a reaction increases as the average rate decreases? in other words, why does a slow chemical reaction is more effective than quick ones?
I done an experiment and the reletionship I found was that. I added a catalyst to vary the average rate (speed) of my reaction and the slower it took to react, the most product was got. Cant find a possible reason for that. any help??


texts: Does acetone eat through Thermoplastic polyurethane and Polycarbonate

texts: I used nail polish remover on an expensive phone case to remove sticker residue (and it worked, no longer sticky). I didn't know it didn't mix well with plastic materials. Did the acetone damage it?


texts: Why doesn't fast-scan cyclic voltammetry work with metal electrodes?

texts:
Every paper I've seen discussing it uses it with carbon nanofiber or some other carbon material like a diamond. If the physical principles by which it works are based on sweeping through voltages, I don't understand why it can't be used with metal electrodes.

I've tried to search through the literature but I haven't come across any clear answers.


texts: The mechanism of demethylation of a quaternary ammonium

texts:
The problem is such:

I know that the t-Bu locks the ring in equatorial position as I have drawn out:

Could someone please point me in the right direction as how I can get rid of a Me in the NMe3+ group?

Is it possible that tBuO- is acting as a nucleophile in this case?


texts: Classical reason for good heat conductance in diamond?

texts:
My teacher in my physics course attributed this effect to phonons, more here, but I am skeptical about this argument, it feels like he is overlooking the whole question -- what about with Silica that has similar structure to diamond with covalent bonds?

My friend attributed this to the small mass of atoms and large Young constant, considering the system to be made of springs -- $v_{sound}=\sqrt{\frac{Y}{\rho}}$. He suggested to think of heat as sound to use the formula.

Silica has less strong bonds to diamond so perhaps this is a reason why diamondis a good conductor of hear and silica is not. Air is good insulator so does it mean that carbon atoms are so closely packed and silicon atoms not? Is this the reason for the difference in conductance?


texts: Does the weird 4s and 3d rule apply for much of the p-block from Ga-Rn?

texts:
In the transition metals, $4s$ has a higher energy level than $3d$, because in ionization, the electrons from the $4s$ energy level are lost first.

I was thinking that this might be the same for much of the p-block from elements Ga-Rn because:

Ga has a electron configuration of: $1s^22s^22p^63s^22p^63s^23p^63d^{10}4s^24p^1$

Ga$^{3+}$ has an electron configuration of: $1s^22s^22p^63s^23p^63d^{10}$


texts: Protonated forms of EDTA and their constants of formation with metal ions

texts:
It is widely known that the fully deprotonated form of EDTA (usually written as Y4-) is the only form that is significantly involved in complexation reactions. From what I have read, this accounts for the fact that the fully deprotonated form has the highest number of complexation sites (the other protonated forms obstruct oxygen atoms from interacting with the metal since those atoms bear protons). Hence, this form has the largest constant of formation, Kf, given the thermodynamical implications of the chelation effect. Also, correct me if I am wrong, but this is exactly the reason why complexometric titrations that use EDTA as a titrant are carried out for a specific metal ion at a fixed pH - at that pH value, the fully deprotonated form has the maximum concentration it could have while also avoiding the precipitation of the metal ion as a hydroxide.

Out of sheer curiosity I looked for any experimental or theoretical evidence to find out whether or not the other protonated forms were involved as well in this complexation equilibria. Even though their influence is neglected (because their formation constants are orders of magnitude smaller than our main Kf), I am still interested to hear to what degree do they participate in complexation with the metal.
To my disappointment, I have found no explicit answer to my question. The two analytical chemistry textbooks I have been studying from (Gary D. Christian, Purnendu K. Dasgupta, Kevin A. Schug - Analytical Chemistry-John Wiley & Sons (2013) and Douglas A. Skoog, Donald M. West, F. James Holler, Stanley R. Crouch - Fundamentals of Analytical Chemistry-Cengage Learning (2013)) covered this topic briefly, but failed at offering any insightful information.
 To sum up, are the other partially protonated forms of EDTA involved in complexation equlibria with metallic ions? If yes, to what extent, what are their formation constants? Also, feel free to correct every scientific detail that I have mentioned you might disagree with.


texts: Will these K-alum crystals combine into a "cohesive/well-glued" mass?

texts:
The attempt to make a single solid mass of K-alum, using over 125 grams of McCormick K-alum powder, has resulted, in less than 2 hours, in:

So besides the growth around the loop of the seed "crystal", there are 3 other regions where crystals are forming.
Context: I am seeking a solid mass of K-alum to use as an astringent and antiseptic after shave (starting at 30 seconds into this video).
Questions: (1) Assuming that the over 125 grams of powder is large enough, will the bottom two or three masses combine into a big "cohesive/well-glued" mass? (2) Or should I dismantle the setup -- keep the seed-block, but heat the water to dissolve the other three masses to become very slightly under-saturated and put the seed back in?
Update: It has been under 3 hours, and the bottom three masses have combined into a single mass. I do not know how "cohesive/well-glued" that single mass will be when it is eventually removed and dried with a paper-towel.
The comment by @tstone-1 suggests this simpler approach for creating a single mass of K-alum: Heat about 200 ml of water to about 88C; saturate this with K-alum powder (about 100 grams); filter this solution into a paper coffee cup; cover cup and wait till most of the water evaporates; tear off paper cup to get solid mass. Question: how cohesive/well-glued will this mass be?
Update 2: Did end up with two consolidated masses, one from the starter near the rim and the other from the bottom three chunks;  both are suitable for use after-shave as an astringent and antiseptic:


texts: Why gives NaBH4 more Felkin-Anh product than LiAlH4 gives?

texts:
In lecture we discussed the nature of the nucleophile for the attack of the carbonyl.

LiAlH4 acts as a better nucleophile (hydride) than NaBH4. I know there is no hydroboration! So I would have expected that LiAlH4 gives more Felkin Anh product as the NaBH4 gives.

However LiAlH4 gives a Felkin Anh : Anti Felkin Anh ratio of 3:1 and
NaBH4 gives a ratio of 5:1.

detailed reaction
Source: Carreira, E.M.; Classics in Stereoselective Synthesis

Is there any good rational?


texts: Sand grains and kinetic two-body processes in the gas phase

texts:
This question stems from a search for an answer to this other one regarding which molecules are most abundant in the universe (specifically which multielemental compound).

I found an article on the subject of interstellar water chemistry, which states in the introduction that

  Molecules such as water form in localized regions of cold and dense gas and dust between the stars (see Figure 1). Typical densities in such interstellar clouds are $10^4$ hydrogen molecules per $cm^3$ and temperatures can be as low as 8 K (pressure∼10−14mbar). The clouds also contain small 0.001–0.1 μm sized solid dust particles or ‘grains’, consisting of amorphous silicates and carbonaceous material.  Grains are important because they absorb and scatter the ultraviolet(UV) radiation produced by stars and thereby protect molecules from dissociating photons. Reactions on the surfaces of the dust particles promote the formation of molecules, especially of H2 and other hydrogen-rich species like H2O. [emphasis mine]

But in the paragraph immediately following this statement it says that

  Interstellar space is a gigantic ultrahigh vacuum laboratory with densities low enough that molecules can form only through kinetic two-body processes in the gas phase.

The process described in the first paragraph does not seem to comply with the statement in the second one. In particular, involvement of the surface of a sand particle would appear to define (at least) a "three-body process" and while exposure to the gas phase is important to bring reagents together, it would still not seem sufficient to call this a "gas-phase" reaction. Am I wrong? How to reconcile this apparent contradiction?

Reference

Interstellar water chemistry: from laboratory to observations. Ewine F. van Dishoeck,Eric Herbst, and David A. Neufeld. Chem. Rev. (2013), 113 (12), 9043-9085, https://doi.org/10.1021/cr4003177.


texts: According to this source hydrophobic behaviour occurs when a molecule does not have a charge or is neutral and therefore cannot be attracted to the negative nor positive parts of water. Casein has an isoelectric point of 4.6 and milk has a pH of about 6.7. As a result, the casein proteins would have a negative charge, hence wouldn't the casein be attracted to the positive part of water?


texts: Why are there multiple lines in the hydrogen line spectrum?

texts: Hydrogen has only one electron, yet it exhibits multiple lines in a spectral series, why is this?


texts: Maximum density of heavy water at 11.6 degree Celsius?

texts: I came across a question asking me the temperature at which $\ce{D2O}$ will have maximum density. I didn't really know, so I checked the answer, and I found that the answer is $\pu{11.6^oC}$. But why ? Why is the density of $\ce{D2O}$ maximum at $\pu{11.6^oC}$? I can't find the reason anywhere...


texts:
Why are the bond angles in the diborane $\ce{B2H6}$ ring much less than $\ce{109.5^o}$? Below is the structure:

This source says that the boron atoms are approximately $\ce{sp^3}$ hybridized, so I thought that the bond angles of the ring would be approximately $\ce{109.5^o}$. However, the diagram indicates that the angles of the ring are $\ce{97^o}$ and $\ce{83^o}$. Why is this so?


texts: How did the first amino acids appear on Earth?

texts: Is there proof or a theory that shows that the first amino acid syntheses on Earth were influenced by a change in heat, gravity, radiation, or something similar?


texts: How can one tell from the MO diagram of the cyanide ion that the HOMO is carbon-centred?

texts:
The cyanide ion, when acting as a nucleophile, typically attacks via carbon as its HOMO has a greater contribution from carbon. But how can we deduce this from the MO diagram?

To me it appears that the nitrogen $\mathrm{2p}$ orbitals are energetically closest to the $3\sigma$ HOMO, so its coefficient should be larger in the HOMO. What is wrong with this line of reasoning?

.


texts: Effect of noble gas configuration on polarising power

texts:
I don't understand this statement written in my textbook about the polarising power of cations:

If two cations have the same size and charge, then the one with pseudo noble gas configuration ( with 18 electrons in the outermost shell) has greater polarising power than the other with noble gas configuration (with 8 electrons in the outermost shell). This explains why $\ce{CuCl}$ is more covalent than $\ce{NaCl}$.

Why does this happen?


texts: Why does NOCl dissociate as +NO and Cl-?

texts:
$\ce{N}$ is more electronegative than $\ce{Cl}$ (albeit by a very small difference) but it should ideally dissociate as $\ce{Cl+}$ and $\ce{-NO}$ (similar to the dissociation of $\ce{Cl}$ in $\ce{HOCl}$). Moreover, due to the stronger bonding between $\ce{N}$ and $\ce{O, N}$ should also be pulling electrons even more tightly to itself due to the very electronegative $\ce{ O}$  by its side.

I was doing a problem on the electrophilic addition of $\ce{NOCl}$ on alkene and ended by getting the wrong product (according to the book) because I took $\ce{Cl+}$ and $\ce{-NO}$ in the mechanism at the very beginning.
Could someone explain?

I've attached pictures of what I have done and what the book has done too. Please correct me if I am wrong.

What I did:

What the book did:


texts: Is Delta H = Delta U for bomb calorimeter or Delta H = Delta U + Delta n(g)RT?

texts: As we know volume change in bomb calorimeter is zero. So if we use $\Delta H = \Delta U + p\Delta V$ then we get $\Delta H = \Delta U$. But in some reaction there is change in number of moles like $$\ce{NH2CN(g) + 3/2O2(g) -> N2(g) + CO2(g)+ H2O(l)}$$ so here $\Delta H = \Delta U + (-0.5)RT$.


texts: I was wondering, how do I determine what metal (element) has the highest density by using the periodic table? Is it possible?


texts: Why does potassium react more violently with water than lithium?

texts:
Recently, I was telling my friends about the violent reaction that takes place when you throw potassium into water. Soon after, a friend of mine claimed that lithium would react more violently than potassium.

I disagreed with him, because potassium is more electropositive than lithium and thus more reactive.

My friend claimed lithium to be more reactive than potassium due to its position in the reactivity series of metals:

$$\ce{Li > Cs > Rb > K > Ba > Sr > Ca > Na > Mg}$$

Then we found out that potassium reacts indeed more violently in water.
But what about his argument? Why isn't he right?


texts: Reaction between chlorobenzene and sodium methoxide to produce anisole

texts:
$$\ce{C6H5Cl + NaOCH3 -> C6H5OCH3 + NaCl}$$

So this reaction undergoes $\ce{S_N2}$ mechanism, but $\ce{C6H5Cl}$ is not likely to undergo such mechanism, so I doubt if anisole would be formed or not?


texts:
Ok, so the following question is given in my text book.

  Of the molar conductance value of $\ce{Ca^2+}$ and $\ce{Cl^-}$ at infinite dilution are respectively $118.88\times10^{-4}$ and $77.33\times10^{-4}$ then that of $\ce{CaCl2}$ is  (all have same unit)

So what I did was I added the molar conductivity of $\ce{Ca^2+}$ and added $2\times$ molar conductivity of  $\ce{Cl^-}$. I got the answer. It was one of the options. So I basically wanted to know: Did I do it correctly and is my process correct? And if I did it wrong then what is the correct process?


texts: How come electrons in the d-subshell are considered valence electrons in transition metals?

texts:
Similarly, why are f-subshell electrons considered valence electrons in the lanthanides and actinides?

I was under the impression that the outermost electrons, and therefore the electrons with the highest principal quantum number, made up the valence electrons.

Also, if the d-subshell electrons are considered valence electrons in transition metals, how come they're not considered valence electrons for elements in Groups 13-18?

I understand that the highest d-subshell is of higher energy than the highest s-subshell but I fail to see the logic in how it would be considered a valence electron.


texts: How to measure the electrical conductivity of a substance?

texts:
Suppose you are given these substances:

$\ce{NaOH(aq)}$

$\ce{HCl(aq)  }$

$\ce{C6H12O6(aq)  }$

$\ce{NH3(l)}$

Are there rules to figure out how conductive each compound is? Is it based on intermolecular forces or polarity?


texts: Ring expansion and carbocation formation

texts: If in a reaction the carbocation is formed outside the ring then why does the ring expansion does not happen as follows:


texts:
I am embarrassed to ask but I don't get something really basic.

When molecular oxygen and hydrogen react to produce water, we say the oxygen has been reduced and the hydrogen has been oxidised. Reduction, I understand, is the gain of electrons.

So I look at the oxygen atoms prior to the reaction and it seems to me each has six of its own plus two more that are shared.

And I look at the oxygen in the water molecule and it has... six of its own and two that are shared.

So in what sense has it gained electrons?

Of course, before posting this question I have searched and read for several hours. All I can find is talk of half-reactions. The clue here seems to be that the oxygen is ionised to $\ce{O_2-}$ prior to reacting with $\ce{2H+}$. But this just confuses me. Maybe this intermediate step does involve reduced oxygen but the end point is still the same number of electrons as we started with, so if it does get reduced it must be oxidised again immediately afterwards, for no net effect.

Where am I going wrong?


texts: When to permute two times to find optical configuration

texts:
I'm learning about S and R configuration, and I know that in case where the 4th substituant is not behind we should permute it with the one which is behind. then we find the new configuration and use the opposit, if we find it R then the original configuration is S.

My question concerns the case when should I make 2 permutations ? Is that even possible ? because this will give back the original configuration but I dont know what are the cases which I use only one permutation and what are the cases where I apply more than one permutation, this seems very confusing.


texts: What do the different grades of chemicals mean?

texts:
When purchasing chemicals from Sigma, Fisher, or wherever, there are often -grade's attached to their description like reagent-grade, technical-grade, analytical-grade, or more niche-sounding biotech-grade, HPLC-grade, DNA grade (DNase free perhaps?)

Is there some sort of standard for what these actually mean or are they arbitrary, differing from supplier to supplier or even chemical to chemical?  Beyond the 'niche' grades, is there a common order of purity between the others or do they depend on the types of impurities?


texts: Does increasing the entropy of a system cause it to absorb heat?

texts:
This is my first time posting here, so bear with me. It was stated (in this video: https://youtu.be/7jT5rbE69ho?t=325) (Watch about the next fifteen seconds, until 5:40) that an increase in entropy leads to a decrease in heat (or temperature or absorbs energy - unsure of the correct terminology). (If I'm understanding correctly.) Now, I've never taken a thermodynamics class or anything past high school chemistry, but this is a little confusing to me and I'm hoping to get an explanation. What follows below is my best attempt at understanding why. It is most likely mis-guided, so feel free to correct at will.

I understand that entropy can be partially understood as disorder. When the Helium-3 enters the Helium-4, that constitutes an increase in entropy.
The change in entropy is defined as Heat/Temperature (see below)

  Rudolf Clausius invented the idea of entropy in such a way that the change in entropy is the ratio of the heat exchanged in any process and the absolute temperature at which that heat is exchanged. That is, he defined the change in entropy DS of an object which either absorbs or gives off heat Q at some temperature T as simply the ratio Q/T.

I then figured that maybe the Q-T ratio (entropy) increased by the total energy (of the helium system) increasing, requiring it to pull heat from somewhere

Miscellaneous thought: My above reasoning confused me because I thought it required energy to decrease entropy locally (add order to a system), so it seems strange that a system increasing in entropy
(like my helium example) would absorb energy.


texts: Why heating up things before H2C2O4 &KMnO4 titration?

texts: In my school, there is a redox titration between H2C2O4 being titrand and KMnO4 being titrant. After adding H2SO4 to the acid to give an acidic medium for redox, the whole mixture inside the conical flask is heated up to 80 degree Celsius before titration starts, what is the need of heating?


texts: How does (E)CA glue ("super glue", "crazy glue", etc.) cure?

texts:
I use CA glue† very frequently in my shop, but I'm not entirely sure how it works. I've noticed three main modes of curing, I've emphasized the key observations:

When dispensed, it will remain fluid until even a small amount of pressure is applied. With pressure, it will set and cure in 5 - 45 seconds. Often, depending on the materials, it remains completely clear after curing.
If a drop of it is left out undisturbed (also applies to glue that may have been squeezed out of the joint), it will cure after a relatively long time, on the order of 20 - 60 minutes. If it cures in this way, it will develop a white crystalline substance (ranging from on-the-surface-only to the entire drop). This structure is hard and brittle.
It will cure in the bottle after a very long time, on the order of months or years (depending on whether or not the bottle has been opened). When it cures this way, it remains clear. It also becomes hard and brittle, but seems to have a higher strength than the white crystalline form.

So; here's what I know about it and some other factoids I found in research:

The active chemical in most consumer-grade CA glues† is ethyl 2‑cyanoacrylate (CAS 7085‑85‑0).
Generally, it's present in the glue at a concentration of 60% to 100% by weight.
It emits very strong, irritating, noxious fumes as it cures, but is odorless after cure.
I know that curing is some type of polymerization and is a reaction with water.
† It seems "CA" has either become a misused colloquialism, or is used to refer to the entire class of cyanoacrylate glues (e.g. "ECA" appears to be the technically correct abbreviation for ethyl 2‑cyanoacrylate). I actually didn't even know there were different types until right this moment (hence the awkwardly placed †'s, heh).

So my question is, basically: What is going on here? In other words: How, exactly does it cure? Why does pressure seem to be involved? What is the white crystalline substance and why does it only form in certain situations? What are the fumes? What is the reaction here? All the details.
I'm looking for a detailed answer, as much as possible -- for example, I already know from the Wikipedia page that it polymerizes in presence of water. What I'd like to know is some more advanced information about how and why that reaction takes place, energies involved, intermediates, crystal structure, what causes my observations, etc. I'm not a chemist but hit me with all the jargon, I could stand to learn a few new words.
I'm actually not particularly interested in how it reacts with the materials it is applied to or how it achieves adhesion, I'm much more interested in the curing process itself.


texts:
I believe that a compound which is planar and having parallel p orbital with $4n\,\pi$ electrons is antiaromatic, but azirene has a lone pair in a $\text{sp}^3$ hybrid orbital.

Shouldn't it be non-aromatic rather than antiaromatic?


texts: Difference between reversible and irreversible thermodynamic process

texts:
I have been reading up (on this website) about the difference between reversible and irreversible thermodynamic process and it defines them saying that reversible processes are ideal processes while irreversible processes are the natural processes. Are these definitions correct?

If not how are they defined?


texts: Why do t-butyl bromide and silver(I) nitrite form the nitroalkane, not the nitrite ester?

texts:
We know that reaction of $\ce{AgNO2}$ with alkyl halides is SN1 type reaction and follows HSAB principle. So in the reaction of $\ce{(CH3)3C Br}$ we would expect $\ce{AgBr}$ to form and also a carbocation $\ce{(CH3)3C+}$.

According to HSAB, since the electrophile is hard, we expect the hard nucleophile to attack. So attack is expected from oxygen, and expected product is $\ce{(CH3)3C-ONO}$

But my book states that reaction product is  $\ce{(CH3)3C-NO2}$. Why is this product formed?


texts: What constitutes something being designated as big, bulky in terms of SN2 vs E2

texts: When deciding between $\mathrm{S_N2}$ and $\mathrm{E2}$ for primary and secondary alkyl halides, is there a particular method or molecular size or any other threshold, which allows us to designate something as big and bulky?


texts: Final temperature after caustic dilution: Interpreting the graph

texts:
I found the below graph in the Occidental Handbook on Caustic.

I'm confused, what may be the parameter noted on the four curves? 80-100-120-140 F?

The final Temperature is on the y-axis & initial water T is fixed as 70 F.


texts: Which orbitals are filled? Is it diamagnetic? According to CFT, $\ce{CO}$ is a strong field ligand, so will it pair the electrons and be diamagnetic?


texts:
Why is EDTA ($\ce{C10H16N2O8}$) poorly soluble in water?
I am interested in analyzing the hardness of water in a sample due to the presence of $\ce{Ca^2+}$ cations. I attempted to do this by titrating with ethylene diamine tetraacetic acid ($\ce{C10H16N2O8}$) however these attempts have proven to be futile.


texts: How do we determine molecule chirality in these examples?

texts:
I understand that in the first example, the molecule is chiral as there is no symmetry. For the second and third example, I see no symmetry in the 3d conformation after twisting the right hand side. In the third example, I do see symmetry if we twist the right hand side so that the carbon molecules are in one plane. What am I missing?

Edit: typo corrected. Also I was not clear in that the picture I attached is the answers the professor provided. I see why the first one is right as there is no symmetry. But I did not see why the second and third ones were considered chiral and achiral, as I saw symmetry in the third example and not in the second. From the answers though, I am understanding that we consider if the molecule is super imposable with it's mirror image?


texts: What are the steps of Hartree-Fock Theory?

texts:
Outline the steps involved in the Hartree–Fock method for the calculation of molecular electronic structure.

I understand the basics of HF, in that it does not account for electron correlation (neither non-dynamical or dynamical) but I do not understand what the question means by steps.

Are the steps of the HF method just those of the self-consistent procedure or is this something difference?

In addition, does Hartree-Fock account for the antisymmetry requirement or not? I have notes that say it does, because it uses a Slater determinant, but I also have notes that say DFT accounts for the antisymmetry neglected by HF.


texts: I'm trying to prepare protected urea and I'd like to protect it with some alkali stable PG. Is it possible to protect urea with t-Boc? Or is there another way to get boc-protected urea?


texts: Why are all the $\ce{C-O}$ bonds in $\ce{CO_3^2-}$ equal but not those in $\ce{H2CO3}$?


texts: Balancing a redox reaction with only one product

texts:
Consider the following comproportionation reaction:
$$\ce{NH4NO3 -> N2}$$
How would I go about balancing this using the half reaction/ion-electron method?


texts: Can we determine apriori the volume of solvent in an electrolyte

texts:
Suppose I would like to create a one molar solution of NaCl in water. The molar concentration is defined as

$c_i=\frac{n_i}{V} $

$n_i=1$ in this case. I need to take 58.5 grams of NaCl (atomic weight of Na=23 & Cl=35.5) and dissolve it in water until the total solvent volume is 1 litre. The total volume of the water added is less than 1 litre. But what exactly is that amount of water and how can I determine it apriori from thermodynamics?


texts: Compound having highest standard reduction potential

texts:
Which compound has highest SRP (standard reduction potential) value, e.g. the strongest oxidising agent? In most tables $\ce{F2}$ is at top with $E^\circ = \pu{2.87 V}$, but I've found a table listing $\ce{H4XeO6}$ at top with $E^\circ = \pu{3.0 V}$.

Is there a more strongest oxidising agent on basis of $E^\circ$ value and is $E^\circ$ value defined for every compound? If yes, what is $E^\circ$ value for $\ce{ClF3}$?


texts: Can orbitals in a molecule be occupied via excitation like they can in atomic orbitals?

texts:
I am facing a conundrum in the way I am viewing molecule orbitals due to the existence of excited states. What I wanted to know is, since atomic orbitals can exist in excited states (i.e. you get hydrogen accessing states outside the 1s orbital and such when a high-enough energy photon is used), is this the case with molecular orbitals, where 'technically' many more states exist than shown on a molecular orbital diagram? I mean, they tend to only show the valence and core electrons, but not past that, hence the question. For example, could methane, that only whose MO diagram only shows molecular orbitals composed of 1s, 2s, and 2p orbitals, have an electronic transition that occupies a 3s orbital? And if so, how would that occur? Would it occupy one particular atom or be 'spread out' like most electrons in MO theory?
Sorry, long question, but something that is bugging me for some strange reason.


texts: Conversion between anisotropic temperature factors and geometric ellipsoids

texts:
I am using the ANISOU of the PDB standard to represent ellipsoid shaped colloids.  I am writing a Monte Carlo simulation to transform the position and orientation of the ellipsoids and want to use a PDB file to represent the result.

I am not sure how to convert between a geometric representation of an ellipsoid to the anisotropic temperature factor tensor, $\mathbf{U}$.  I am able to define an ellipsoid aligned to the coordinate axes using the diagonal elements of $\mathbf{U}$: $\mathbf{U}(1,1)$, $\mathbf{U}(2,2)$, $\mathbf{U}(3,3)$, but I am not sure how to represent a rotated ellipsoid, i.e., I am not sure how to set $\mathbf{U}(1,2)$, $\mathbf{U}(1,3)$, and $\mathbf{U}(2,3)$.  I came across this resource which introduces the topic.  This second link mentions the similarity between tensor elements and geometric definitions and says the conversion is "rather complicated" but does not provide a link for further study.

Any guidance or direction to a good resource would be appreciated.


texts: Understanding colour changes of systems in dynamic equilbrium

texts:
Consider an aqueous reversible reaction of two chemicals $\ce{A <-> B}$, where $\ce{A}$ is red and $\ce{B}$ is yellow. The reaction is in equilibrium when there is $\pu{1 dm^3}$ of A with concentration $\pu{1 M}$ and  $\pu{0.5 dm^3}$ of $\ce{B}$ with concentration $\pu{1 M}$, such that $K_C = 0.5$ and the solution is orange (due to the equal parts of red and yellow).

If I were to add $\pu{1 mol}$ of $\ce{A}$ to the system without increasing the total volume of the solution, Le Châtelier's principle predicts that the equilibrium position would move to the right, hence there would be more of $\ce{B}$ than $\ce{A}$ and the solution would become more yellow, however this does not seem to agree with my understanding:

$K_C = 0.5$, and is constant when the concentrations of chemicals are changed, so some of $\ce{A}$ must be converted to $\ce{B}$ by the forwards reaction to keep $K_C$ as $0.5$. This will make the concentration of $\ce{A}$ $\pu{\frac{5}{3} M}$ and the concentration of $\ce{B}$ $\pu{ \frac{5}{6} M}$ at equilibrium. The chemicals are still in the same ratio, so shouldn't the colour remain the same instead of becoming more yellow as Le Châtelier suggests?

This is a simplified problem, and I am wondering if the logic applies to more complicated cases (if it's correct in the first place of course!) Essentially, in my understanding, if you increase the concentration of a chemical in a dynamic equilibrium, when equilibrium is re-established, some but not all of the added chemical would be converted into the products on the opposite side of the reaction. This means the amounts of chemical on both sides of the reaction have increased, so it doesn't make any sense to say that the equilibrium position moves to one side of the other - both sides have increased in concentration, and in terms of coloured chemicals, the colour would remain the same.

Please use this more complicated reaction for demonstrative purposes:

$$\ce{Fe^{3+}_{(aq)} + 3\,SCN^-_{(aq)} <--> Fe(SCN)3_{(aq)} }$$

where $\ce{Fe^{3+}}$ is yellow, $\ce{SCN^-}$ is colourless and $\ce{Fe(SCN)3}$ is red. How would the reaction behave if the concentration of $\ce{Fe^{3+}}$ ions is increased (e.g. add iron III nitrate).

Apologies in advance if this question is a little convoluted, I'm not a professional chemist (I'm studying A-level chemistry), and I'm quite confused, so I'm struggling to form a coherent question.

Addition (edit):
In the case of the more complicated reaction, my understanding is as follows:

If I add $\ce{Fe^{3+}}$, the forwards reaction will convert some of the added $\ce{Fe^{3+}}$ and some $\ce{SCN^-}$ (already present) into $\ce{Fe(SCN)3}$.
Not all of the added $\ce{Fe^{3+}}$ will be converted (the equilibrium cannot completely counteract the change, as this would involve converting all the $\ce{Fe^{3+}}$ into $\ce{Fe(SCN)3}$, and this would be an increase in the amount of $\ce{Fe(SCN)3}$ which the reaction would have to counteract).
Therefore the concentration of reactants and products increases, because the added $\ce{Fe^{3+}}$ is split between some which is converted into $\ce{Fe(SCN)3}$, and some that stays as $\ce{Fe^{3+}}$.
Since this gives an overall increase in the concentrations of both chemicals, neither has increased relative to the other, and the equilibrium position hasn't moved, so the colour doesn't change.


texts: Do auto-catalytic aromatic compounds capable of forming self-replicating molecules exist?

texts:
I want to know are there any aromatic compounds able to catalyze their own synthesis? Do aromatic compounds with molecules capable of self-replication exist?

P.S.I'm looking specifically for heterocyclic aromatic compounds (preferably containing nitrogen in the ring) capable of self-replication which could self-assemble into sheets of planar structures capable of self-replication. Is such thing possible and are such structures known in modern organic chemistry and/or nanotechnology?


texts: How do I interpret the results of this chromatogram and does it tell me about the compounds' polarities?

texts:
I am reading this journal article which discusses using high-performance liquid chromatography (HPLC) to separate dyes from wine. Here are the relevant facts about the experimental setup:

Two mobile phases are used, a solvent A and a solvent B. Solvent A is is 40% methanol and solvent B is 70% methanol. Both solvents also have 25% 0.02M tetrabutyl-ammoniumhydroxide phosphate solution as well.
The stationary phase is a LiChrospher 100 RP-18e column.

Below are the chromatograms and the retention time tables that this experiment produced:

From the chromatogram, we see that amaranth has the fastest elution time of 6.60 minutes. My questions relate to what inferences can we draw from elution times:

Does the elution time correlate with the polarity of the compound itself? Here, it states that similarities in polarity correlates positively with elution time. The stationary phase used in this experiment (the LiChrospher) is a nonpolar silica column. Thus, with amaranth coming out the fastest, would it make it the most polar compound?
Further, how does the use of two solvents (A and B) affect making an inference like the one above? In the chromatogram above (specifically chromatogram "a") and the associated table, the elution time for the three compounds ranged from 6.60 minutes to 9.76 minutes. Since a solvent A and a solvent B were used, how do I know which compounds were eluted by which solvent? (If my interpretation of how the solvents A and B work is wrong, please correct me). Also, how does the use of two solvents affect understanding the relative polarity of the compounds?


texts: Number of stereoisomers of 3-ethylpent-1-ene-1,4-diol

texts: I am trying to figure out how many stereoisomers this compound has. I know that there are two chiral carbon atoms, which allow $2\times2 = 4$ possible isomers. There is also a double bond which, as far as I know, doubles the number of stereoisomers, since there are now four possibilities for the cis-isomer, and four for the trans-isomer. So I thought the total number of stereoisomers was eight, but my teacher told me the answer was six. I have thought about it for a while, but I can't figure out why it should be six. What did I do wrong?


texts: Second Peak in X-Ray Diffraction Pattern of bcc Metal

texts:
By Bragg’s law,
$$2d\sin\theta=n\lambda$$
and
$$d=\frac{a}{\sqrt{h^2+k^2+l^2}}$$

Combining the two gives:
$$\sin\theta=\frac{n\lambda\sqrt{h^2+k^2+l^2}}{2a}$$

By the reflection rule for bcc, there will be destructive interference when $\sqrt{h^2+k^2+l^2}=\sqrt{1}$, on the (100) plane. The first peak will thus occur when $n=1$ and $\sqrt{h^2+k^2+l^2}=\sqrt{2}$, on the (110) plane. However, I’m confused about the second peak. It will be impossible to get $\sqrt3$ while satisfying the reflection rule for bcc, so I’ve moved on to $\sqrt4$, which is equal to 2. However, mathematically there is no difference between having $n=2,\sqrt{h^2+k^2+l^2}=1$ ((100) plane) and $n=1,\sqrt{h^2+k^2+l^2}=2$ ((200) plane). Which one does the second peak represent, then? Does it represent both? Why then is this peak so much smaller than the other peaks in most diffraction patterns that I see? For example, for $\alpha$-iron, the diffraction pattern is

Image Link: http://questions.transtutors.com/Transtutors001/Images/Transtutors001_6804131b-7ca5-47cd-984a-b824a4926c3a.PNG


texts: Can you color a flame and what would the effects be?

texts:
I read this question (Flame temperature for cooking food) and came up with the following questions:

Could companies color their flames so that products would heat quicker?
How would they do this?
Could you use this to make an infrared or ultraviolet flame? If
you could, how hot would they be?


texts: Alcoholic potassium hydroxide and aqueous potassium hydroxide

texts:
I searched much about alcoholic KOH and aqueous KOH, but I was unable to understand it.

I mean, I want to know how ionisation of KOH in alcohol is different from that in water.

I also don't know what actually happens during its ionisation. Why is alcoholic KOH used in dehydrohalogenation of alkyl halides?


texts: How does the Jahn-Teller distortion result in both elongation and compression?

texts:
Recently, I have been reading up on the Jahn-Teller effect and I have read articles and posts on it, such as What is the mathematical basis behind the Jahn-Teller effect?. However, many of these rigorously discuss the quantum mechanical basis of the effect (which is fundamentally what it is about). But I seek to understand it using the simpler more intuitive "chemistry" explanation, which is through invoking an understanding of the nature of the d orbitals. Perhaps, the two explanations, both QM and chemistry, are equivalent and they very likely are... But I would just like to focus on the latter.

The reference I have cited was one of the literature I have come across which discussed the chemistry explanation I have mentioned above:

  When looking for example at the configuration of $\ce {d^{0}_{x^{2}−y^{2}}}$ $\ce {d^1_{z^{2}}}$ ($\ce {d^4}$) and $\ce {d^{1}_{x^{2}−y^{2}}}$ $\ce {d^2_{z^{2}}}$ ($\ce {d^9}$), the ligand(s) along the z axis are much more screened from the charge of the central metal ion than the other four ligands along the x and y axes, because most of the electron density will be concentrated in the $\ce {d_{z^2}}$ orbital between the metal and the two ligands on the z axis. Consequently, there will be greater electrostatic repulsion between the electron(s) in the $\ce {d_{z^2}}$ orbital and the ligands along the z axis than between the electrons in the $\ce {t_{2g}}$ set of orbitals pointing between the axes and the ligands on the x and y axes itself. The ligands on the z axis will thus move further away from the central metal ion and thus lower the symmetry (z-out or elongation Jahn−Teller distortion). This causes the $\ce {d_{z^{2}}}$ orbital to be more stable (lower in energy) than the $\ce {d_{x^{2}−y^{2}}}$ orbital, as is shown in Figure 2.

As can be read, their explanation points to the elongation of the axial bonds. However, they do not explain how does the other scenario (i.e. compression) result in detail and they simply stated what happens in the other scenario. From what I read from the paper, the argument presented can only lead to one conclusion, and that is the axial bonds elongate. Could only help to fill in the other half of the story? In other words, I would like to know how do we explain the Jahn-Teller effect for the compression of axial bonds using a chemistry-orbitals approach.

Reference

Freitag, R., & Conradie, J. (2013). Understanding the Jahn−Teller Effect in Octahedral Transition-Metal Complexes: A Molecular Orbital View of the Mn(β-diketonato)3 Complex. Journal of Chemical Education, 90, 1692-1696. doi:dx.doi.org/10.1021/ed400370p


texts: For those of you that have watched Season 1 of Prison Break (TV Series), in the "Cute Poison" Episode Micheal Scofield combined $\ce{CuSO4}$ (Copper Sulfate) and $\ce{H3PO4}$ (Phosphoric Acid) to weaken the metal. Is it true?


texts: So I'm having trouble understanding the difference between the two. Looking specifically at water and carbon dioxide, CO2 is non-polar, because it is symmetrical and carbon shares two electrons with each oxygen and vice versa. But doesn't oxygen also share 1 electron with each hydrogen and vice versa? I know water isn't symmetrical, but for a molecule which I haven't seen the shape before how would I figure it out?


texts: Avogadro - How can bonds be hidden and only show atoms?

texts:
I am using Avogadro for visualizing some cluster systems. Is there a way to hide the bonds of the system, ie. only showing atoms?

Thanks!


texts: Reacting Grignard reagent with esters to excusively produce a ketone

texts:
Adding 2 moles of grignard reagent to an ester, gives out 2 alcohols. But, if 1 mole of grignard reagent is added, will the reaction exclusively produce a ketone? How to prepare a ketone in a reaction only with esters and grignard reagent as starting materials?
CH2=CH2-C(=O)OCH3 + CH3MgBr -> CH3-CH2-CH=C=O + CH3OH
Is the above reaction possible?


texts: Up to which dilution can one assume that 1 mg/l = 1 ppm?

texts:
For aqueous solutions it is often assumed that 1 milligram per liter equals 1 ppm. Are there any guidelines up to which concentration this shortcut is admissible?
Are there any formulas which calculate the error when using this shortcut?


texts: Does KCN prefer SN2 or nucleophilic addition?

texts:
If we have a 1° halide that also contains a carbonyl group (like 5‐chloropentan‐2‐one), and we add 1 mole of KCN in DMSO to it, what will happen?

Will the SN2 product by substitution of chlorine or nucleophilic addition at the carbonyl carbon be the major product, and why? And does using HCN instead of KCN have a different effect?


texts: Why does chlorine oxidise iron to iron(III), not iron(II)?

texts:
I was asked to predict the product of the reaction between iron metal and chlorine gas:

$$\ce{Fe +Cl2->} ?$$

The product here is supposed to be $\ce{FeCl3}$. But how would we know if the product is $\ce{FeCl2}$ or $\ce{FeCl3}$? Why should it be $\ce{FeCl3}$ and not $\ce{FeCl2}$?


texts:
1,2,3-Trimethylcyclopropane has two stereoisomers. When one of the methyl groups is above the plane and other two are below the plane, then there are two chiral centres as well as a plane of symmetry. By definition this compound should have a meso isomer. However I read that this compound has zero meso isomers since it does not have any optically active stereoisomers.
So what is the exact definition of meso?


texts: Is it possible to separate salt from food, or at least convert it into something that doesn't taste salty?

texts:
A couple months ago, one of my room mates accidentally used a cup of salt to make apple crumble. She asked if there was any way to separate it, probably because I had recently reduced the acidity of a tomato sauce by adding baking soda. I said "probably not", but ever since then I have wondered if there is a way to get the salt out.
At this point, I would settle for a difficult method that requires a lab and ruins the dish, as long as it is still harmless to eat and retains most of it's nutritional value.
Here are some of the ideas I have thought of:
First, scrape off the oat layer, because it is the only hard solid and the salt wasn't mixed with it.
Seperate it by mass:

The apple crumble could be puréed and spun in a centrifuge to separate the salty water, which could be poured off and replaced with sugar water.
It could be atomized and sprayed sideways into a cold vacuum chamber, and then if the salt fell in a consistent radius around the nozzle, we could scrape up the salt, mix the rest back together and eat it.

Alter the the properties of the salt:

Is there a way to encourage the salt to form large crystals, even when it is a relatively minor component of a complicated mixture? If so, those crystals could be filtered out of puréed apple crumble with a coarse filter.

Crazy biochemistry:

Are there proteins or enzymes that could break the salt apart and bind the sodium to something oily that would float up by itself, leaving the chlorine to evaporate? I saw a documentary about bull sharks which mentioned that they have a gland that can absorb salt against the salinity gradient, so that the shark can expel it's salt and move up into fresh water.
Are there bacteria that require lots of salt to survive, and by using it, convert it into something that doesn't taste salty, and wouldn't release tons of sodium in my stomach?