texts: Determining the mechanism followed when alcohols undergo a reaction with sodium bromide and sulphuric acid

texts:
$$\ce{R-OH + NaBr + H2SO4 -> R-Br + NaHSO4 + H2O}$$
Due to sulphuric acid, the $\ce{-OH}$ group will get protonated and convert into $\ce{-H2O+}$ which is a great leaving group in comparison to the hydroxyl group. Therefore I assumed it would readily form a carbocation and then $\ce{Br-}$ could attack to form the alkyl bromide.
That is, it would follow the SN1 pathway (since the reaction is happening in 2 steps, first the formation of carbocation and then the attack of $\ce{Br-}$) but I also read somewhere that we might need to have a look on the substrate, if it is primary then it would follow SN2.
I am a bit confused after so many conditions and situations being introduced so I was hoping if someone could give me a brief and crisp explanation about this, and is there any particular factor that needs to be focused on before judging this mechanism?


texts: Why are isotopes an issue in reading mass spectra?

texts:
It is my understanding that the isotope distribution for carbon and hydrogen, for example, are skewed heavily toward one species, i.e., one isotope accounts for ~99% of the abundance of the element in nature. If this is true (I question my ignorance on this point and others), then, the other isotope peaks should be negligible in the mass spectra or at least fall below the threshold for processing and remain unprocessed peaks.

I am asking this question within the realm of biological compound mass spectra. I read a post here that states that $\ce{Br}$ has near 1:1 abundance for two isotopes. It would explain the need to consider isotopes for those biological compounds with elements such as $\ce{Cl}$ which has ~3:1 ratio for its two most abundant isotopes. So, in light of the fact that $\ce{C, H, N,}$ and $\ce{O}$ make up 96.5% of a biological organism's weight, are isotopes an issue only when elements such as $\ce{Cl}$ or $\ce{Br}$ are constituents of the compound?


texts: Molarity of solids and liquids in equilibrium constant expression

texts: Why  is the molarity of pure liquids , solids and excess solvent taken 1 in the equilibrium constant expression?


texts: How are intermolecular forces between non-metallic substances affected when the substance is heated to its melting point?

texts:
I have 3 main questions that I am unsure of:

Are intermolecular forces acting simultaneously causing attraction between particles in a sample of a substance?
Example: Hydrogen bonding and dipole-dipole attraction present in a substance both influencing the attraction between particles.

If there are multiple intermolecular forces present, would they be overcome in an order?

What actually happens to the intermolecular forces between particles as a non-metallic molecule is heated?


texts: Less electronegative atom is the central atom. $\ce{N}$ is more electronegative than $\ce{Cl}$ as $\ce{Cl}$ has larger atomic radius. So why in $\ce{NCl3}$, $\ce{N}$ is the central atom?


texts: How to obtain the Raman spectrum along every coordinate of a scan in Gaussian?

texts:
I am doing a scan calculation using Gaussian09 and adding the Freq=Raman keyword to my input file. My objective is to obtain the Raman spectrum of each conformation in my compound. However, only the Raman spectrum of the last conformation in the scan is calculated. How can I solve this problem?

I understand that I will get negative frequencies, but these will be in a certain frequency range, so I can observe the variation in the signals.
I need to do these calculations, because I want to see the type of conformation that my compound adopts under heating.


texts: LeChatelier's Principle - Phosphofructokinase in Glycolysis

texts:
In glycolysis, PFK is allosterically regulated by ATP, F6P, etc.

When the concentration of F6P increases, the concentration of ATP increases too. I understand that high levels of ATP shift the eq towards the T-state, and this decreases the affinity of PFK for F6P.  But is there a principle in Le Chatelier's which explains how the increase in conc of one reactant affects the conc of another reactant?

The reaction regulated by PFK is: $F6P$ + $ATP$ <-> $F1,6BP$ + $ADP$

Thanks!


texts: Derivation of relationship between equilibrium constant and Gibbs free energy change

texts:
Why is $\Delta G=\Delta G^o+RT\ln Q?$

It feels like all online sources were written for introductory Chemistry students! Where do I find a rigorous proof of this identity? Greatly appreciate it!


texts: On reaction of diazomethane with ethene a carbene is formed as a intermediate . This carbene then attacks on the double bond and form cyclopropane . However I read that both singlet and triplet carbene can react in this reaction but according to me since the carbon of carbene is overlapping with two different orbitals hence each electron of carbene must be in different orbital hence must be triplet. I can't find a reference to this on the internet, perhaps you all could help me .


texts: Does computational chemistry include neutrons in ground state calculations?

texts: I was under the impression that most particles in computational chemistry were treated as point charges. If this is true, wouldn't there be no need to include neutrons as a separate entity in ground state calculations? Or are particles not treated as point charges?


texts: Quenching rates in nucleation MD simulations

texts:
I am trying to perform nucleation simulations with molecular dynamics. To prepare the metastable fluid, I am equilibrating at temperatures about 30 K above the melting temperature, and then "quenching" down to a sub cooled liquid state. For those familiar with lammps, the method I am using to perform the quench is

fix 1 all nve
fix 2 all viscous 0.01

This just adds a drag force proportional to the velocity to suck heat out of the system.

In the nucleation simulation literature, I can't think of a time I have come across a paper where the author mentions an actual quench rate, or discusses whether the quench rate can have implications for the final results. Is anyone familiar with what an appropriate quench rate to prepare a metastable liquid, or whether I can produce spurious physical artifacts depending not quench rate? Currently for my water simulation, I am quenching from 300 K to 190 K in 50 steps with a 2 fs time step.


texts: Exactly how the subscripted numbers are given to the different types of boron sheets (borophenes)?

texts:
I was going to start a project on Borophene, and hence I was going through a review journal, 2D Boron: Boraphene, Borophene, Boronene, where they have said many types of borophenes had been proposed. They have been given different greek letters like α, β, γ (β12), δ and χ(chi) to classify different types and they also classified those types into different sub-types by using subscripted numbers like α1, α2, α3 or β1, β2, β3, β12 etc.
At first, I thought it was coming from the hexagonal hole density (η) term which is defined by -
η = (a number of hexagonal holes/a number of atoms in the original triangular sheet). But later I found that it's not the case (considering all the types).
My question is - how exactly these subscripted numbers are given to sub-classify the different types of borophene?
Different types of Borophene(name) and their properties

P.S. - All the numbers next to the greek letters will be in subscript.


texts: Why are isomers of parathion less active acetylcholinesterase inhibitors than paraoxon?

texts:
Parathion itself has been found to be a very weak inhibitor of acetylcholinesterase. It normally requires metabolic activation and the conversion into paraoxon in the body to actually start exhibiting anticholinesterase activity. However, the study cited below found that active isomers of parathion, O,S-Diethyl O-4-nitrophenyl thiophosphate and O,O-diethyl S-4-Nitrophenyl thiophosphate (Compounds II and III in the cited paper, respectively), are less active inhibitors of AChE than paraoxon. I would have thought that the isomers of parathion would be more active than paraoxon due to thioethyl and 4-nitrothiophenyl being better leaving groups than 4-nitrophenyl, and thus the two active isomers of parathion would more readily form an adduct with the enzyme. I would presume that they also wouldn't need metabolic activation due to already having an oxygen atom double-bonded to the phosphorus. However, my prediction does not seem to hold true. So, why exactly are the active isomers of parathion (Reference numbers 7 and 8 in the table in the cited study) less active AChE inhibitors than paraoxon (Reference number 9 in the table in the cited study)?
Reference
Diggle, W. M., & Gage, J. C. (1951). Cholinesterase inhibitionin vitrobyOO-diethylO-p-nitrophenyl thiophosphate (Parathion, E 605). Biochemical Journal, 49(4), 491–494. doi:10.1042/bj0490491


texts: Is there any connection between "static correlation" and the Born-Oppenheimer approximation?

texts:
Beware: High probability for that I am mixing two concepts that should not be mixed, just because the same term is used when explaining the two concepts!

For some reason I get really confused when I think about static, or nondynamical, electron correlation. I somehow want to make a connection to the Born-Oppenheimer (BO) approximation.

As we know, the BO approximation is no longer accurate when two electronic states come close in energy, due to the increase in the nonadiabatic coupling terms. These terms couple the electronic motion to the nuclear motion, and arise because the electronic and nuclear motion is not fully separable in the Schrödinger equation.

Static correlation, sometimes called a "near-degeneracy effect", describes the correlated movement of electrons belonging in different electronic configurations. Certain systems are not described properly by just a single-determinant wave function. One example is the H-H molecule at long bond distances, for which the bonding and anti-bonding $\sigma$-orbitals become degenerate. (this was probably a bad explanation, as I struggle with this concept!)

So, as we have just seen, the BO approximation breaks down when two electronic states come close in energy (near-degeneracy), and the static correlation becomes extremely important in molecules with near-degenerate electronic states. Is there a connection here?

Imagine we are in the ground state at a point on some potential energy surface, and the first excited state is very close in energy. At this point, there should be a high coupling between the electronic and nuclear positions (which means what, exactly??). Also, at this nuclear geometry, the electronic wave function should be described as a linear combination of these two near-degenerate electronic states.

It is the BO approximation that introduces the idea of a potential energy surface (PES). The PES itself can be thought of as an approximation, as the nuclei should ideally be fully described by quantum mechanics. The nuclear positions should be described probabilistically by a wave function, and the very idea of a molecular geometry then becomes fuzzy.

What is the connection, if there is any?


texts: Reaction mechanism of tin(II) chloride to reduce nitrobenzene to aniline

texts:
Does anyone know the reaction mechanism for $\ce{SnCl2}$ to reduce nitrobenzene to aniline? I can only find $\ce{Sn/HCl}$ reaction mechanism but can't seem to find any information on $\ce{SnCl2}.$

Figure 1. Proposed mechanism for tin/HCl reduction of nitro compounds.

Source: https://chemistry.sites.clemson.edu/organic/Labs/2280Docs/ReductionNitroacetophenone.pdf


texts: Competition of H2O and NH3 leaving groups in nucleophilic acyl substitutions

texts:
I've learned in several textbooks, that in the nucleophilic acyl substitution $\ce{H2O}$ is a better leaving group than $\ce{NH3}$. This can be explained by the "thumb rule" of the $\mathrm{p}K_\mathrm{a}$. $\ce{NH3}$ is more basic $(\mathrm{p}K_\mathrm{b}(\ce{NH3})= 4.3)$ than $\ce{H2O}$ ($\mathrm{p}K_\mathrm{b}(\ce{H2O})=15.4)$ and therefore a worser leaving group.

But what is the reason for the fact, that the following common reaction happen (and the worser leaving group has left the molecule)?

My idea: Is it more a kind of "equilibrium discussion"? The reaction can happen but the equilibrium lies not really on the "product side"? Compared to another nucleophilic acyl substitution (e.g. water with a acyl chloride) this equilibrium lies far more on the educt side. But nevertheless, this reaction happens and can be exploited for example in the Strecker Synthesis through several methods (Le Chatelier, etc.)?

Additional idea: The excess of water can push the equillibrium to the product.


texts: Is this a feasible synthetic route for 1-(phenylethynyl)cyclopentan-1-ol?

texts: From my notes $\ce{NaNH_2}$ is a good base for the deprotonation of alkynes. After the deprotonation I thought the alkyne would attack the carbon on the cyclopentanone because of the $\delta^+$ charge on the carbonyl carbon due to the EWG effects of the oxygen. Should the protonation of the $\ce{O^-}$ be carried out with conditions specified or can I just leave it as the addition of $\ce{H^+}$?


texts: What chemical that when cured chemically cross-links to already vulcanized rubber

texts:
I'm looking into ways to repair rubber materials and I was wondering if there are any chemicals that when cured will chemically bond to the already vulcanized rubber material.

I know this might involve having to break the strong carbon-carbon or carbon-sulfur bonds to have it re-bond to the chemical, so said chemical itself might have to be volatile.

So, is there a chemical like that?


texts:
Im not sure if this is the right place to ask, but what are some good chemistry experiments or projects that could be conducted in grade 12?

Here's what I have found so far:

Preparation of aspirin
Synthesis of dyes
Analysing the percentage of metals present in coins

In my opinion, these projects are not something that grade 12 students should be doing, I'm looking for something more complex, more in touch with research being conducted in universities.

Edit: Please refrain from suggesting topics that involve spectroscopy or crystallography or any other equipment unlikely to be found in a high school lab.


texts: Why only molecules with three or more atoms undergo unimolecular reaction?

texts:
Only molecules with three or more atoms undergo unimolecular reactions. A diatomic molecule cannot dissociate in this way because it has a single mode of vibrational freedom. If this mode is excited by an amount equal to dissociation energy, the molecule dissociates in $10^{-12}$ seconds.

What is the connection between the dissociation of diatomic molecules and vibrational degrees of freedom ?

I think this is a false statement because molecular hydrogen dissociates into hydrogen atoms, even its dissociation energy is given alongside other diatomic molecules. Am I missing something ?


texts:
In my lab, my teacher asked me to not cover the beaker or crucible during the crystallization process of different solutions (e.g, FeSO4, NaCl etc). But on the internet, on Youtube, I've come across videos where they suggested that the glassware containing the solution should be covered but loosely.

I accidentally covered my solution with a watchglass and later found crystals formed all around the crucible, inner and outer both surfaces.

So, what's the reason behind it? I think we need to let the water to evaporate and leave the crucible, but why?


texts:
Law of equivalence states that

  One equivalent of an element combines with one equivalent of the other.

Equivalent of $\ce{Na}$ is $22.99$ and that of $\ce{O}$ is $8$. By the law of equivalence, $1$ equivalent of $\ce{Na}$ combines with $1$ equivalent of $\ce{O}$. But in $\ce{Na2O2}$, $$ 23 \times 2 ~\text{parts by weight of sodium combines with } 16 \times 2~\text{parts by weight of oxygen} \\\implies 23~\text{parts by weight of sodium combines with } 16~\text{parts by weight of oxygen}$$ which means one equivalent of sodium combines with two equivalents of oxygen which is contradiction to law of equivalence. So why does this compound not follow the law of equivalence?


texts: Calculation of partial charges and protonation/deprotonation states depending on pH

texts:
What is the best method for calculating partial charges and protonation/deprotonation states of a small molecule such as phenol or caffeine, depending on the pH? For instance, it is well known that above pH=10 or so phenol is deprotonated, but there is data about its protonation around pH=2. For more complex molecules such as caffeine, similar things happen. So I am more interested in calculating partial charges of protonated and deprotonated forms than on pKas (sometimes, experimental data is available).

I head about Gaussian and the like, but I also wonder about software or methods that are easy to use.


texts: Is there an established procedure for titanium tetrachloride titration?

texts:
I’m attempting to do an aldol reaction with $\ce{TiCl4}$ as the catalyst. It worked well in the large scale ($100~\mathrm{mg}$) test system but not, so far, in my $5~\mathrm{mg}$ scale actual system. Our bottle of $\ce{TiCl4}$ is not the youngest, the seal has $\ce{TiO2}$ precipitates on the inner side, and when you finally manage to stick a needle from the argon line in, you almost get a geyser of hydrochloric acid steam — need I mention that the liquid is cloudy from precipitated $\ce{TiO2}$?

My supervisor said distillation is not an option due to unremovable residues of $\ce{TiO2}$ getting stuck in the distillation apparatus. But I would love to know what purity the $\ce{TiCl4}$ still has and thus how much I should upscale it when adding it to the reaction.

Are there any rather simple titration methods for $\ce{TiCl4}$ known or established like they are for n-butyllithium?


texts: Finding concentrations in a voltaic cell

texts:
A voltaic cell with $\ce{Ni/Ni^2+}$ and $\ce{Co/Co^2+}$ half cells has the initial concentrations of $\ce{Ni^2+}$ $\pu{0.80 M}$ and $\ce{Co^2+}$ $\pu{0.20 M}$.
  (a) Find initial cell potential;
  (b) Find concentration of $\ce{Ni^2+}$ when $E_\mathrm{cell}$ reaches $\pu{0.03 V}$

In part (a), I correctly found the initial $E_\mathrm{cell}$ to be $\pu{0.05 V}$.

In part (b), the book doesn't have any other examples that are explained showing how to get one of the concentrations, it's supposed to be $\ce{0.50 M}$, but I'm not sure how they get to that. From my tables, I found $E$ half cell for $\ce{Ni}$ to be $\pu{-0.25 V}$ and $E$ half cell for $\ce{Co}$ to be $\pu{-0.28 V}$, and the overall then to be $\pu{0.03 V}$.

Tried plugging in everything I have into the Nernst equation, but that still leaves me coming up short.


texts: Can the solvent fraction of a sol-gel process containing tetraethyl orthosilicate (TEOS) be analyzed by GCMS? I am worried that the easy polymerization of TEOS to form silica (SiO2) will ruin the GCMS system.


texts: Selective transfer of least/most stable anion from organometallic reagents

texts:
When heterocuprate reagents participate in conjugate addition, the least stable anion is transferred from copper to the electrophile:

On the other hand, palladium-catalysed cross-coupling reactions show a different trend, e.g. in the Stille coupling, the most stable anion is transferred:

How is this dichotomy explained?


texts: for a polydisperse polymer, why is its weight average molecular weight always bigger than its number average molecular weight?

texts:
The statement comes from my lecture slides on polymers. I hope someone can show me the maths proof for the inequality.
I will try come up with the proof, too. It is actually a maths question:D Here is the basic definition for the two average weights: https://en.wikipedia.org/wiki/Molar_mass_distribution


texts: How well can triglycerides be resolved using TLC?

texts: The only part of triglycerides that significantly interacts with a TLC plate are the ester moieties which are present in all triglycerides. Other than that, they do not differ much, except in mass (dependent of the chain lenght of FAs) and shape (saturation degree of FAs). How much do these differences alter the interactions causing the resolution?


texts: Role of the counter/auxiliary electrode in cyclic voltammetry

texts:
I am doing a school project on cyclic voltammetry and am currently studying the topic. I have learnt that the reaction mostly takes place around the working electrode where the current is measured together with the counter/auxiliary electrode. My question is, how does the counter/auxiliary electrode pass current without oxidising or reducing the analyte?

For example, I were to increase the potential in a solution of $\ce{Fe^3+}$ ions. The working electrode would be the cathode and would reduce the ions, giving them electrons and forming $\ce{Fe^2+}$ ions. In this case, what would happen around the counter electrode? How would the electrode be able to pass current to balance it? Would it oxidise the newly formed $\ce{Fe^2+}$ ions? Wouldn't this result in a never ending process? If someone has already asked this question, I apologize. Please link the page, thank you.


texts:
Most kinds of cheese melt but cottage cheese does not at usual cooking temperatures.

During the preparation of various kinds of cheese, I have heard of a coagulant named ‘rennett’ being added along with the acidifying agent. For cottage cheese it is just lemon juice mostly (acidifying agent). Does this have anything to do with the difference in properties?


texts: If ionic compounds are strongly bonded, why are acids with a more polar central atom the stronger types of acids?

texts: If the central atom is more polar, it pulls electron density away from the H+, making it more detachable. But why, then, are ionic compounds (which are even MORE polar than acidic covalent compounds) held tightly together?


texts:
Assuming a perfect diamond with no impurities. Would this diamond considered to be a single large molecule?
Browsing the interweb I found several opinions about this but did not find a clear Yes or No.

From what if gathered so far I'm pretty sure a diamond is a monocrystalline solid. Since all its parts are connected with covalent bonds I would assume that it should be considered a molecule even though it has no fixed number of atoms in its molecule formula.


texts: Why does brown sugar have a strong smell but white sugar doesn't?

texts:
I noticed something while cooking and was wondering what the chemical explanation is for this. White sugar has a smell, but it's different, and much fainter than that of brown sugar.

Brown sugar is unrefined, so does this have something to do with why odorous chemicals are present?

What are these chemicals and why are they present in one, but not the other?


texts: I am not a chemist, but I am interested in Science in a general sense. Can anybody explain why the periodic table is periodic in nature? I would appreciate links for further reading.


texts: Electron density definition of single, double, triple bonds?

texts:
I was reading this question and the answer by user EricBrown to it, and this got me thinking about covalent chemical bonds.

The way I was always taught is that a single bond contains 2 paired electrons, a double bond 4 etc (The Lewis dots drawings always show this nicely). In his answer Eric mentions that the whole definition of single, double etc bonds is ambiguous because there haven't been measurements of the electron density. This notion strikes me as odd, because a simple googling gives me articles like this: How similar is a molecule to another? An electron density measure of similarity between two molecular structures Int. J. Quantum Chem. 1980, 17 (6), 1185–1189. But it did make me think about the way the different types of bonds are defined.

I read up a bit on the Theory of atoms in molecules and indeed this theory only specifies 1 bond type: the line with maximum electron density between two nuclei. According to the theory this line is unique for a given pair of nuclei in a given molecule. I could imagine that a molecule which has a triple bond (6 bonding electrons in the 'classical' theoretical sense) would have a relatively high electron density along this maximum line as compared to e.g. a single bond.

My question is: if we would be able to measure the electron density in a molecule (are we?) couldn't we use this to define a relation between the value of the maximum electron density and the notion of a single, double or triple bond? Or perhaps use the spread in electron density between the nuclei for this?


texts: Advanced Level Chemistry Book Recommendation

texts: I have a test comming up on Chemistry in Advanced Level and I sincerly ask for a book recommendation for chemistry. I already got the book chemistry by Ramond Chang. And I am pretty near to the exam. What I really want is a book with Lesson and Questions related to that specific lesson book.


texts: How is group theory (and matrices) used in symmetry operations?

texts:
I am a high school IB student. For my 2-year math course, there is an internal assessment called "exploration" which should be max. 12 pages long. The goal of this assignment is for students to explore areas or uses of mathematics beyond the course.

Now onto the important stuff. After doing some research on topics to investigate in linear algebra, number theory, graph theory or group theory, I came across a potential subject: "Investigating the use of group theory (and of matrices) in symmetry operations in chemistry."
I know my question very broad but I am here looking for material to learn from. Please post any useful links or names of topics to look at please!


texts: How do I combine z-matrices of multiple molecules into one input stack?

texts:
I'd like to run a calculation in Gaussian which requires me to provide cartesian coordinates for reactants and products respectively. My question is how do I combine the cartesian coordinates for two reactants (that I would obtain from a database)? For instance, CH3 + N?

Is there a specific program/procedure that I need to use?

To be more specific, say I would like to combine the z-matrix of $\ce{CH3}$

0 3
C
X 1 1.0
H 1 r 2 90.0
H 1 r 2 90.0 3 120.0
H 1 r 2 90.0 3 -120.0

r 1.0828

with a z-matrix of $\ce{N}$

0 3
N

And I would like to combine the z-matrix of $\ce{HCN}$

0 1
C
X 1 1.0
H 1 rh 2 90.0
N 1 rn 2 90.0 3 180.0

rh 1.0587
rn 1.1326

with that of $\ce{H2}$

0 1
H
H 1 r

r 0.741

In other words, I want to combine these z-matrices (or geometries) of the two reactant/ product species into a single coordinate, so that I can use them for my QST2 calculation. What do I do?


texts: How can I perform calculations including the relativistic approximation SC-ZORA and solvent approximation COSMO in Gaussian 09?

texts:
I am working on transition metal centered oganometallic complexes.

How can I apply or run the relativistic and non relativistic zero-order regular approximation (SC-ZORA) using Gaussian 09 in a DFT calculation?

I would also like to know about the process of performing COSMO analysis in Gaussian.

I have only available Gaussian 09 package for this purpose.


texts: What is the preferred IUPAC name of hexamethyldisilazane?

texts:
Hexamethyldisilazane (HMDS, $\ce{(SiMe3)2NH}$) and its conjugate base hexamethyldisilazide (as the Li/Na/K salt) find wide use in organic chemistry.

In my quest to only use preferred IUPAC names in my thesis1 I have come across a problem with this compound. According to P-21.2.3.1 of the Blue Book the name disilazane for the parent hydride $\ce{H3Si-NH-SiH3}$ is no longer preferred because

  When nitrogen atoms are present, amine names (see P-62) are preferred because of the higher functionality of amines. This concept does not extend to other elements.

and the name given is N-silylsilanamine.2 Just going off this, I would guess that the PIN of the hexamethyl compound is something along the lines of "trimethyl-N-(trimethylsilyl)silanamine".

However, I'm also not sure whether the addition of the methyl groups makes the choice of parent hydride different, as per P-21.2.3.2 (for example). The frequently used name bis(trimethylsilyl)amine is also a possibility, although I've personally not seen a rule suggesting that it could be a PIN.

What is the PIN of this amine?

I'm just kidding; writing "4-methylbenzene-1-sulfonyl" multiple times is quite silly. But I’m still curious about this PIN.
The original publication has this written as N-silylsilan-1-amine but this has since been corrected in the errata, which are published online.


texts:
I'm trying to get as pure citric acid as possible from a mandarin. It's not because I desperately need citric acid, but because I want to achieve this.

I started by grating the mandarine and filtering the juice. After filtering overnight, I was left with slightly yellow liquid. I heated it while avoiding boiling and I reduced the volume to 50%. When volume was reduced, the solution started to become saturated and crystals appeared. At this point, I stopped.

Now, I'm looking for a way to remove sugar from the solution, as this is the most annoying part. It's sticky.

When crystals appeared while I was boiling the solution, I came to think, that perhaps that could allow to separate sugar. Citric acid has solubility in water 1477.6 g/L (20 °C), while sugar has 2000 g/L (25 °C). Wikipedia unfortunately doesn't provide values for the same temperature.

From the above it seems that I can have more sugar dissolved than citric acid. I think that means that citric acid will crystallise first. Does it work like this? Are the crystals I've produced the citric acid crystals?

Is there another way to separate the compounds? Does something react with sugar to produce precipitate that can be filtered?


texts: What is the product of the reaction of carbon with sulfuric acid?

texts:
I don't know if $\ce{C}$ or $\ce{CuO}$ react with $\ce{H2SO4}$. Some sources say that:
 $$\ce{C + H2SO4 -> CO2 ^ + 2SO2 ^ + 2 H2O}$$
(It seems to be similar to $\ce{Cu}$ reactions with $\ce{H2SO4}$).
Is the reaction possible? If the answer is yes, in what conditions does the reaction take place?

And I was pretty sure that $\ce{CuO + H2SO4 -> CuSO4 v + H2O}$

But my chemistry book says that none of the reactions is possible.
I'm little bit confused, some help would be apreciated.


texts: How should elements be colored? And how many bonds does an atom have?

texts:
I'm working on my own 3D molecule viewer for my AP Chem class. So far everything's going together nicely. There's a couple of things I'm not sure about though...

Is there a certain rule of thumb or standard for what colors each element inside a molecule should be? For example, Jmol renders oxygen red and hydrogen white:

For my app they are currently grey:

Also, how can I check if there are single bonds, double bonds, etc.? As you can see here, I haven't programmed that yet into my app. Tylenol:

I look up coordinates for each molecule in an NCI/CADD group server online database. This database gives me the number of elements, and the X, Y, and Z coordinates for where I should put each element. For example, water:

3
H2O
O   -0.0000   -0.0589   -0.0000
H   -0.8110    0.4677    0.0000
H    0.8110    0.4677    0.0000

It doesn't tell me anything about where bonds go. More info about .xyz file format here.


texts: Why doesn't diborane act as an oxidising agent

texts:
I read that diborane has 3 center's sharing 2 electrons.

Shouldn't it be easier for diborane to accept one more electron and act as an oxidising agent than a reducing agent .

Could someone tell me what's wrong my reasoning?


texts: Why are transition metal hydroxides insoluble?

texts: From what I understand, adding $\ce{NaOH}$ to a solution containing transition metal ions gives transition metal hydroxide precipitates. Why is $\ce{NaOH}$ soluble but transition metal hydroxides insoluble? I have a feeling it has something to do with ligands and complexes formed, which I am familiar with.


texts: How can I bring down the pH of corrosive substance leaving its physical properties intact

texts: I am developing geopolymers with with kaolinite clay, calcium hydroxide activated with sodium carbonate solution. The alkalinity of the mix is too high to handle.. what can i do to bring it down


texts: Difference between "isoaspartyl" and "isoaspartate" in antibody deamidation

texts:
I'm translating a text where antibody deamidation is mentioned.
One sentence goes like this:

We used reversed-phase HPLC to analyze the aspartyl forms of the monoclonal antibody. (Russian original text: "изоаспартильные формы")

However, in scientific papers the word is "isoaspartate", not "isoaspartyl".  (also here)
On the other hand, Wikipedia's page "Isoaspartate" changes the term mid-flight to "isoaspartyl":

Isoaspartyl formation reactions have been conjectured to be one of the factors that limit the useful lifetime of proteins.
Isoaspartyl formation proceeds much more quickly if the asparagine is followed by a small, flexible residue (such as Gly) that leaves the peptide group open for attack. These reactions also proceed much more quickly at elevated pH (>10) and temperatures.

I'm perplexed. Are the forms of an aged antibody "isoaspartate forms" or "isoaspartyl forms"?  What is the exact difference between "isoaspartate" and "isoaspartyl", and why the Wiki page makes no mention of the difference?


texts: Which phase is more efficient for temperature changes?

texts:
In the case of attempting to heat and cool down an object of different states, if you in some case managed to achieve the same temperature of a solid, liquid and gas what state would scientifically heat or cool the object faster?

On my view point I suggested a gas to be more efficient simply due to how the particles move. However I was soon objected by someone else stating that a liquid would be far more efficient.

I was not given a reason , therefore I am asking which would be correct to assume and why.


texts: determination of glucose syrup in sugar product

texts:
I work with a sugar product that contains saccharose (approx. 70 %), glucose syrup (approx. 15 %), glycerine (approx. 3 %) and some other ingedrients, e.g. water. Glucose syrup consists of 5 % glucose (Dx), 50 % maltose (Dp2), 25 % higher connected sugars (Dp3), 20 % water. I'd like to determine the amount of glucose syrup in the sample.

Fehling is time-consuming and well-known as an empirical method. Because the concentration of glucose, saccharose and maltose ist unknown (three variables and two equations: mass of cupperoxide before inversion and mass of cupperoxide after inversion) I think it's not possible to calculate accurate enough the amount of glucose syrup. The error should be lower than 5 % of the real value.

To measure the Brix-value in order to determine the glucose syrupe concentration is too inaccurate.

An alternative would be to use enzymatic test-kits which are selective for maltose. Unfortunately this test is too expensive and when opened it must be used within a few days or weeks.

My idea is to label a protecting group with an fluorescent group and to put it on the maltose molecule. The protecting group should only bind to the molecule, if the distance between two hydroxy-groups is given.

(Unfortunately I don't know the distance between the two hydrox groups).

Which protecting group could be the solution of this problem?

Or do you know an even easier procedure to determine the glucose syrup amount?


texts: Is the QST2 method suitable to find the transition state of an enatiomeric R-S interconversion?

texts: I am trying to calculate the energy barrier between the two possible enantiomeric components of a polymer with Gaussian. I wonder if I am able to locate a transition state between two of those structures with the keyword opt=QST2?


texts: If the gaseous molecules didn't have any kinetic energy would the surface of a filled balloon still be firm?

texts: The most of the ideal gas law equation is based on the fact that the gaseous molecules are moving around and cause collisions and thus have some pressure. If these molecules were to not have any kinetic energy, and thus consequently would not suffer any collisions would the surface of let's say a balloon, a filled balloon, which is firm only due to the pressure offered by the gas inside, still be firm? would the volume of the gad contribute to its firmness and give it shape? won't the volume be affected too


texts: Are there any UV absorbent paints or coatings that can be applied to plastic suitable for the optics of a UV-Vis instrument?  It would need to not fluoresce under a range of about 300 nm to 800ish nm ideally.  I have seen krylon matte black can be used by some groups but I am unsure if it is the best commercially available option that doesn't require a special process by a 3rd party.


texts: Does exchange energy affect completely filled orbitals?

texts: In my textbook, it's written that exchange energy stabilises half filled and completely filled orbitals. But my teacher said electrons can't be exchanged in full filled orbitals because of pairing up of electrons. So which explanation is correct? My textbook has an explanation for half filled electron orbitals, by it had no explanation given for completely filled orbitals.


texts: Why is nitrosobenzene electrophilic on O in organocatalytic oxygenations?

texts:
In 2003 Zhong1 and MacMillan2 reported the use of nitrosobenzene, PhNO, in the organocatalytic asymmetric α-oxygenation of carbonyl compounds:

which is all nice, except for the slightly counterintuitive fact that PhNO is acting as an electrophile on oxygen rather than on nitrogen.

Logically PhNO should be electrophilic on nitrogen (less electronegative than oxygen), and indeed, a 1994 review on the reactivity of PhNO lists numerous examples where this is the case.3 On top of that, if the enamine were to ad to nitrogen instead of oxygen, the phenyl group could be placed equatorial in the transition state:

Is there an explanation for the regioselectivity here?

References

Zhong, G. A Facile and Rapid Route to Highly Enantiopure 1,2-Diols by Novel Catalytic Asymmetric α-Aminoxylation of Aldehydes. Angew. Chem. Int. Ed. 2003, 42 (35), 4247–4250. DOI: 10.1002/anie.200352097.
Brown, S. P.; Brochu, M. P.; Sinz, C. J.; MacMillan, D. W. C.The Direct and Enantioselective Organocatalytic α-Oxidation of Aldehydes. J. Am. Chem. Soc. 2003, 125 (36), 10808–10809. DOI: 10.1021/ja037096s.
Zuman, P.; Shah, B. Addition, Reduction, and Oxidation Reactions of Nitrosobenzene. Chem. Rev. 1994, 94 (6), 1621–1641. DOI: 10.1021/cr00030a007.


texts: How to obtain the linear form of Redlich Peterson isotherm model by algebraic transformation or any other ways?

texts:
The Redlich Peterson isotherm model is known as:
$$
\begin{aligned}
q_e=\frac{AC_e}{1+BC^g_e}
\end{aligned}
$$
Is there any way to obtain the linear form of this equation by algebraic transformation or any ohter ways(like using software origin)?In other words,given that $q_e$ and $C_e$ as variables and A,B,g as parameters,how can I make linear fitting based on this equation?


texts: Froth floatation process - Use of stabilizers in froth floatation method

texts: How exactly do the stabilizers affect the process of Froth floatation method? I mean how do they stabilize the froth in the process?


texts: What is the graphical formula when nitrobenzene is added to HCL and tin?

texts: On the image i want to work out the structure of compound Q. I know that it is a reduction reaction. However why is it that the answer to this question is not C6H5NH2, but is actually (C6H5NH3)+Cl-


texts: Why is SN2 favored greatly over SN2' in this reaction?

texts:
Secondary allylic halides can be produced in high yield with the following Mitsunobu-type reaction:[1]

The yield being $94~\%$.
The last step in the mechanism is:

Why is the $\mathrm{S_N2}$ reaction favored so much over the $\mathrm{S_N2'}$ reaction?

Reference: Magid, R. M.; Fruchey, O. S.; Johnson, W. L.; Allen, T. G. Hexachloroacetone/triphenylphosphine: a mild reagent for the regioselective and stereospecific production of allylic chlorides from the alcohols. J. Org. Chem. 1979, 44 (3), 359–363. DOI: 10.1021/jo01317a011.


texts: Why is neutralization reaction exothermic in nature?

texts: Why is heat liberated in such reaction. Isn't it just a simple rearrangement of ions? Hydrogen ion joining hydroxyl ion.


texts: How do structural differences between neostigmine and TL-599 contribute to differences in toxicity?

texts:
Stevens and Beutel studied the activity of several carbamate anticholinesterases. Among other things, they found that the (4-trimethylammonio)phenyl dimethylcarbamate iodide (The para-analog of neostigmine) is significantly less active than neostigmine (Subcutaneous LD50 in mice of the para-analog was 120 mg/kg compared to 0.45 mg/kg for neostigmine). However, ((4-trimethylammonio)-3-isopropyl)phenyl dimethylcarbamate iodide, also known as TL-599, was more toxic than neostigmine, having an LD50 of 0.075 mg/kg. How exactly do the differences in the structures of TL-599, neostigmine, and the para-analog of neostigmine contribute to their differences in toxicity?
Reference:
Stevens, J. R., & Beutel, R. H. (1941). Physostigmine Substitutes. Journal of the American Chemical Society, 63(1), 308–311. doi:10.1021/ja01846a078


texts:
The Wikipedia article about aqueous solutions claims that:

  An aqueous solution is a solution in which the solvent is water

So basically, is writing $\ce{HCl(aq)}$ equal to: $\ce{HCl(l) + H2O(l)}$?


texts: Van der Waals equation at high temperature and high molar volume

texts:
At high temperatures the Van Der Waals equation has the form
  $$P\approx\frac{RT}{V_\mathrm{M}-b}$$

  What would happen with the equation if in addition to high T, molar volume of the gas ($V_\mathrm{m}$) will get very large too?

The only sense I was able to make out of this was that the pressure would be reduced, but if $V_\mathrm{m}$ stands for the volume occupied by a mole of a substance, than wouldn't a larger $V_\mathrm{M}$ mean less available void space, less volume, and thus a greater pressure?


texts:
According to Graham's law, we can calculate de average speed of gasses by using the formula
$$v^2=\frac{3RT}{M}$$
I tried to use this simulation and got these data by keeping same particles amount and increasing the temperature(average speed(m/s) - temperatura(°C)):

T in C
V  in  m/s

27
454

50
480

90
510

130
530

225
590

350
660

425
710

500
740

But, shouldn't be the speed ($v$) a square function of the temperature? ($T=\frac{Mv^2}{3R}$ ) What am I doing wrong?


texts: Calculating the Molecular Orbitals of a Molecular State

texts:
I am performing ab initio calculations on a heteronuclear diatomic compound using the MRCI method on the MOLPRO quantum chemistry package. I obtained the molecular states of the compound but I was wondering how to find the molecular orbital configuration of each electronic state in addition to their associated compositions. I tried to include the "print, orbitals" before and after the CI, but I didn't get anything!
Your help and support are much appreciated...


texts:
In the 3,4-dihydropyran shown below will the oxygen or the pi electrons of the double bond attack the hydrogen cation during hydrolysis and why?

This is my attempt towards a solution: The oxygen lone pair clearly can attack the hydrogen cation better than the pi electrons being a better a nucleophile, but according to my textbook (T.W.Grahams Solomons) the pi electrons of the double bond attacks, but shouldn't the oxygen atom be a better nucleophile than the pi electrons?


texts: I'm not sure I understand the stoichiometry of this mechanism

texts: I was going through the experimental mechanism of nickelocene synthesis, and I looked through the notes and it said that there would be $\frac12$ $\ce{NiCl2}$.  I'm sort of confused by the $\frac12$.  It may be the fact I'm pretty sleep deprived and missing something.


texts:
Is this an aluminum screw dislocation?
https://youtu.be/zbUPjHHml1E?t=55s

I have heard of zinc pest which looks similar.


texts: How does the process of protein denaturatation work?

texts:
I know it's the proteins that somehow change their properties at some temparature.

But what kind of change, in terms of molecule-level structure?


texts: Identification of a compound C10H12O with 1H and 13C NMR data

texts: I was given this problem to do for Organic Chem II.  I know that it's a benzene (unsat # 5), with 2 para-substituents due to the doublets in the 7 region of the HNMR.  I know that the oxygen is not an OH due to the absence of a D2O shake.  There's probably an alkene in one substituent to finish out the unsaturation number.  However, I can't figure out what the 2 substituents are - but I'm guessing one's either an ether or ketone!  Can anyone help?


texts: Is there a known crown ether analog to fullerenes?

texts:
It is well known that endohedral fullerenes have potential quantum computing applications example 1,example 2, and example 3. But, currently they are too expensive, around $167 million per gram at this time. A huge part of the cost is currently because only about 1/650,000 fullerenes have an atom trapped in it.

But looking at this made me wonder if there was a known way to form a stable polyhedral molecule where each side contains a crown ether, or a single crown ether surrounded by carbon atoms. This way it might be much easier trap an atom inside.


texts: What coefficients can I use in a Reaction-Diffusion Equation?

texts:
I am qualitatively analyzing an abstract chemical reaction

$A + B \rightarrow 2A$

where $A$ and $B$ are some liquid substances that undergo Reaction-Diffusion with a second order reaction (actually my model is much more complicated than that, but this is for simplicity). I have Reaction-Diffusion Equation that models this reaction:

$u = \left(\begin{array}{c}a\\b\end{array}\right), \quad u(0) = u_0, \quad d \in \mathbb{R}_+, k \in \mathbb{R}_+$,

$a_t = d \Delta a + k a b$,

$b_t = d \Delta b - k a b$.

However, I need some specific coefficients $d$ and $k$, and starting densities for $u$ to do my simulations on.

What would be a decent Fermi estimate for diffusion coefficient $d$, reaction rate $k$ and density $u_0$ for reactions present in reality?

In terms of speed, I'm interested in reactions like one of reactions present in the Belousov–Zhabotinsky Reaction-Diffusion model and I just need a very, very rough estimate of values (with physical units) to put in my model so that I keep studying behavior of reactions that might plausibly happen in reality for some specific substances. So far I used $k \approx 1 \frac{dm^3}{kg \cdotp s}$, $d \approx 1 \frac{dm^2}{s}$, and $u_0 \approx 1 \frac{kg}{dm^3}$, but I'm particularly unsure if this ratio of $k$ to $d$ is anywhere near realistic. I know I could just scale time, space, and mass in this equation, but I'm interested in specific value ranges or examples.


texts: How does PEDOT:PSS work (mechanism) in Organic Electrochemical Transistors?

texts:
I have a question about the fairly fundamental theory behind the application of PEDOT:PSS in an organic electrochemical transistor (OECT) device.

As at least I understand it, the polyethylenedioxythiophene (PEDOT) chain is rich with holes and then is doped with polystyrene sulfonate (PSS) which has sulfonate anions that compensate these holes. Now according to the literature I have read, PEDOT:PSS is conductive (p-type) in its initial state (i.e. no gate voltage is applied). This confuses me a bit because I would have thought compensating these holes by adding PSS would have made the PEDOT less conductive.

Then of course when you apply a gate voltage, cations compensate the PSS anions instead which according to literature makes the PEDOT:PSS less conductive, but I would have thought this would make it more conductive as it liberates the holes in the PEDOT backbone.

What do I seem to be missing here?


texts: Calculating volume ethanol in an fermented aqueous solution of sucrose, water, and ethanol

texts:
I've been working on a biology experiment where I calculate the fermentation yield of yeast under various light induced stress responses inhibiting the translation of various fermentation enzymes. My solution initially contained 12.5g of sucrose, and 50g of water, resulting in 20% by mass sucrose.

Initially, I expected to measure this value before and after using a refractometer that measures in brix, which is a measure of percent mass of sucrose in a solution. I figured that the difference between these two values would represent the percent by mass ethanol in the final solution.

I failed to consider though that the yeast produced ethanol as the experiment progressed changing the mass of the solvent and therefore the percent mass of sucrose of the solution.

Primarily, my goal is to calculate the volume of ethanol in the solution. In order to do this though, I would need to be able to calculate the volume of the whole solution based on the change in the percent by mass sucrose in the solution, and the volume of the sucrose in the solution. With these values I could subtract the volume sucrose and the constant volume water from the solution and obtain the volume of ethanol.

Based on some internet searching, I've gathered that this is possible but it involves a knowledge of intermolecular interactions paired with a knowledge of the molarity of particular molecules. This is beyond my scope of knowledge for chemestry. Overall, I'm trying to develop a generalized equation for determining volume ethanol based on change in brix of the solution. This has been baffling me for a while now and I figured there may be other amateur researchers with the same questions I have so I figured I'd pose the question to the community at large. Thanks for the help!


texts: Materials with solid volume greater than liquid volume

texts:
Water has a solid volume greater than its liquid volume.

This question is in two parts.

1) Are there other materials that have solid volumes greater than liquid volumes? 2) What about the structure of a molecule makes its solid volume greater than its liquid volume?


texts: What chemical equation proves that KHCO3 can extinguish a fire?

texts: In a dry powder fire extinguisher, there is a chemical known as $\ce{KHCO3}$ and I was wondering how $\ce{KHCO3}$ works in a chemical equation to extinguish the fire.


texts: How to recycle olive oil manufacturing wastes?

texts:
The fact that only 20% of the olive used to make olive oil becomes olive oil and the other 80% is spread between hard wastes and liquid water wastes  made me want to ask this question. Isn't there a way to recycle the other 80% and use it in an effective way either in other industries (energy, agriculture, or cosmetics)?

I'd like to know if there is a simple and low-cost way people can do so.


texts:
At $25 ^\circ C$, $K=0.090$ for the reaction
  $$\ce{H2O (g) + Cl2O (g) -> 2HOCl (g)}$$
  calculate the concentrations of all species at equilibrium for the case: $\pu{1.0 g} \ce{H2O}$ and $\pu{2.0 g} \ce{Cl2O}$ are mixed in a $\pu{1.0 L}$ flask.

I don't know where I go wrong in my calculations:

We have $\pu{0.0555 M}$ $\ce{H2O}$ and $\pu{0.023 M}$ $\ce{Cl2O}$. So at equilibrium,
\begin{align}
  \ce{[H2O]} &= 0.0555 - x,\\
  \ce{[Cl2O]} &= 0.023 - x\\
  \ce{[HOCl]} &= 2x\\
\therefore K &= \frac{[\ce{HOCl}]^2}{[\ce{H2O}][\ce{Cl2O}]}
\end{align}

After some moving about I get to
$$-3.91x^2 - 7.1\times10^{-3}x + 1.15\times10^{-4} = 0$$
Where I end up getting $x = -8.74\times10^{-3}$ or $x=8.4\times10^{-3}$.

And this is where it all goes wrong, doing some quick calculations, I see that it does not match what the book says the answer is. So I'm doing something wrong, but I don't know what it is or where it's at.


texts: Reaction of getting jarosite from pyrite

texts:
I am doing a PhD about archaeometry in order to study the contaminations and alterations that occur to the ceramics which are buried in a marine environment.
In my research, I have found pyrite in the cracks of my ceramics. Now, I am trying to find jarosite.
Well, I have found bibliography about pyrite's oxidation reaction to give jarosite (Secco et al. [1]). Now, trying to understand the redox reaction of pyrite to jarosite, I am getting blocked. The image of the reaction is the next:

The presence of jarosite and absence of pyrite in the outermost part of the margin in the Olbia potsherds is due to the oxidation of pyrite and reaction with dissolved alkali (Faure 1991), according to the following reactions (Faure 1991):
$$
\begin{align}
\ce{FeS2(s) + 7/2 O2 + H2O &-> Fe^2+ + 2 SO4^2- + 2 H+};\tag{18}\\
\ce{Fe^2+ + 1/4 O2 + H+ &-> Fe^3+ + 1/2 H2O};\tag{19}\\
\ce{Fe^3+(aq) + 3 H2O &-> Fe(OH)3(s) + 3 H+};\tag{20}\\
\ce{(K+{,}Na+) + 3 Fe(OH)3 + 2 SO4^2- + 3 H+ &-> (K{,}Na)Fe3(SO4)2(OH)6 + 3 H2O}.\tag{21}
\end{align}
$$

I would like to understand the half redox reactions (oxidation and reduction). I have tried to solve this, but I have not been able to. I identify the reducing agent (the S, which oxidizes from S(1-) to S(6+)), and the oxidizing agent (the oxygen, which reduces from O(0) to O(2-). However, I think I am unable to write the half reactions properly, because I do not obtain the same as the equation (18) of the bibliography:

What I obtain is that the second half reaction also seems an oxidation. I can't solve it like a reduction.
I will appreciate a lot your help, maybe you can shed a little bit of light on this.
References

Secco, M.; Maritan, L.; Mazzoli, C.; Lampronti, G. I.; Zorzi, F.; Nodari, L.; Russo, U.; Mattioli, S. P. Alteration Processes of Pottery in Lagoon-like Environments. Archaeometry 2011, 53 (4), 809–829. https://doi.org/10/cp6gkh.


texts: Why does the emission wavelength of sodium appear to be an exception despite the trend for ionisation enthalpies among alkali metals?

texts:
The wavelengths for emissions in the visible region for Group 1 elements is as follows:

$$
\begin{array}{lc}
\hline
\text{Element} & λ/\pu{nm} \\
\hline
\ce{Li} & 670.8 \\
\ce{Na} & 589.2 \\
\ce{K} & 766.5 \\
\ce{Rb} & 780.0 \\
\ce{Cs} & 455.5 \\
\hline
\end{array}
$$

Now, considering that the ionisation enthalpies (I.E.s) decrease going down the group, it should be relatively easier to remove an electron, which should reflect in the energy band gaps and ultimately in the wavelengths. Thus, there should be increase in this trend. However, $\ce{Na}$ is an exception. Why so?

I think the $\mathrm{d}$-electrons play a role in the increased band gap for $\ce{Cs}$, which shows in the trend. But I am missing something for $\ce{Na}$. Is its I.E. decreases because size outweighs nuclear charge along with fair amount of screening? But $\ce{Na}$ has a unique balance wherein size and screening are not enough to tip over.


texts: Clarifying the concept of the dative covalent bond

texts:
Part 1: I was just reviewing concept of the dative covalent bond in some simple molecules. One of which was carbon monoxide.

Some structures I saw featured the use of formal charges, in which the carbon atom had a negative formal charge while the oxygen atom had positive formal charge. These did not show that a dative bond was involved.

Some I saw claimed the molecule remained neutral and showed a dative bond between the two atoms.

I understand that the formal charge is a theoretical construct and does not refer to actual charges on atoms. Rather, they indicate to the chemists where are the regions of electron-richness and electron-deficiency.

So these two structures do not contradict each other and each are limited in some way.

However, dative bonding in complex metal ions always show dative bonding which is the latter structure, never the former structure, with formal charges. Why is this so?

Part 2: Secondly, what are the differences between a dative covalent bond, where one species donating both electrons, and a typical covalent bond, where each species donates one electron. Other than the process of bond making, is every other characteristic of the two bonds the same?

If you think about it, a lot of covalent bonds are actually "dative". Consider all the bonds between nucleophiles and electrophiles. Isn't it always the case where the nucleophile donates a pair of electrons?

In my opinion, the only difference appears to only be the difference in the bond making process and all else is exactly the same.


texts: Safety concerns - Heating PMMA (acrylic glass) and fluorinated polymers

texts:
I have some plastic optical fiber, which consists of a thin core of PMMA (polymethyl methacrylate), covered by a fluorinated polymer.

I would like to heat a bundle of these fibers to ~130 degrees, in order to form a simple image guide.

However, I won't start until I know this is safe. Can you help me find out what types of gases I may encounter by heating these materials? Anything known dangerous? What other safety precautions should I take?


texts: Adhesion of polymerized fats to cast iron

texts:
I'm trying to make an informed decision as to which oil is best to use for cast iron seasoning. I've read all kinds of conflicting information online and the only consistency seems to be that seasoning involves polymerization of fatty chains.

This explains the formation of the coating itself, but I'm interesting in choosing the oil that is least likely to separate from the cast iron surface. So my question is this:

What is the chemical (or physical) reaction (or process) which is responsible for the adhesion between the polymerized oil and the surface of a cast iron pan? Is it different from that of unpolymerized oil?


texts: Reaction of 1 equivalent of Mg in ether with 1,4-dibromobut-2-yne

texts:
What will be the product formed the if the reaction of Mg in ether with 1,4-dibromobut-2-yne occurs? At first, I thought the answer would be cyclobutyne, but the correct answer is buta-1,2,3-triene.

Can anyone please explain how?


texts: Hamiltonian 2nd positional derivative analogous to acceleration?

texts:
In Quantum Mechanics, we learn that the Hamiltonian operator for an electron confined to a 1-D space is:

We learn in QM that many operators have analogous interpretations familiar to us from classical mechanics. My question is then: is there a classical mechanics interpretation for the second positional derivative? Is its physical significance at all related to the second positional derivative in classical mechanics (i.e. acceleration)?


texts: What open-source software can produce 3D PDF representation of molecules?

texts:
Most of the existing software I know (like VMD or Pymol) say that they can be used to create PDF files with 3D representations of molecules: actual 3D models, which you can rotate inside the Adobe Acrobat viewer. However, they all require the use of “Adobe Acrobat Pro 9 Extended” for its 3D capture feature. From what I can read, this feature does not exist any more in Acrobat X and was transferred to a separate product, Tetra4D, which doesn't work on Mac OS.

So, how can I produce PDF files including 3D molecular models using free (or better, open source) tools?


texts: DIY Brass Etching methods (safer etchants, waste, and disposal of)

texts:
I want to etch brass for making name plates etc. (Also for copper PCBs but brass is probably more complicated given the other metals).

Several etchants commonly used, and I'm sure many more are possible; I'm not fussed what is used. Even vinegar, although something a bit faster would be great.

I want a method easy for someone with minimal chemistry knowledge and equipment to safely perform, and dispose of byproducts etc as household waste, or down a drain.

(Since AFAIK for example copper compounds for example are hazardous to the environment, and etchants can be dangerous/toxic/corrosive), and in the UK for example, getting it disposed of professionally is prohibitively expensive for responsible DIYers on low budgets)

What would be a good choice of etchant? And what would the process be for using and disposing of the waste / bi-products? In general, the less hazardous the better.

PCB resists and techniques would be used, so need an etchant compatible with any of those.


texts:
I have calculated all the roots for a specific symmetry and I need to calculate the CASPT2 energy for all the roots. For example: here I have 4 roots and I need to calculate the CASPT2 energy for all 4 roots. However If I only use the CASPT2 keyword, only the energy for first root wil be calculated. How can I calculate the energy for all of the roots?

Natural orbitals and occupation numbers for root  1
    sym 1:   0.999414   2.000000
    sym 2:   2.000000
    sym 3:   2.000000
    sym 4:   1.000587   2.000000
    Natural orbitals and occupation numbers for root  2
    sym 1:   1.501037   1.504109
    sym 2:   2.000000
    sym 3:   2.000000
    sym 4:   1.496113   1.498741
    Natural orbitals and occupation numbers for root  3
    sym 1:   2.000000   1.999999
    sym 2:   0.999213
    sym 3:   1.000789
    sym 4:   2.000000   1.999999
    Natural orbitals and occupation numbers for root  4
    sym 1:   2.000000   1.011097
    sym 2:   1.999999
    sym 3:   2.000000
    sym 4:   2.000000   0.988905


texts: What is the mechanism for the double bond migration in 4-methylcyclopent-2-en-1-one?

texts:
The problem I was asked to answer:

Please explain using only enolisation and protonation steps:

My work so far:

Seems completely wrong... can someone please correct me?
EDIT I just proposed a new mechanism:


texts: Why does the E1cb mechanism proceed in the specific way it does?

texts:
We have been learning the E1cB mechanism in organic chemistry, but we have not been delving into the motivation as to why this mechanism occurs instead of others. Consider the following mechanism:

I am confused as to why we push the electrons to the left, creating an anion on the oxygen, instead of simply performing an E2 reaction on the right hand side. What is the functional reason for drawing this intermediate? Why does it arise?


texts: I am looking for a database or printed document providing the RH0 (relative humidity above which deliquescence will occur) for inorganic salts. I've looked everywhere on the internet can find nothing.


texts:
Water ($\ce{H2O}$) is a dipole. The reason why is simply because it is not symmetrical, there are more electrons on the oxygen side than on the hydrogen side, and the electronegativity of oxygen.

But why isn't $\ce{H2O}$ symmetrical like $\ce{CO2}$? Why isn't $\ce{H2O}$ non-polar like $\ce{CO2}$? Does it have anything to do with the orbitals?


texts:
Yes it's a white ppt. which is soluble in dil. $\ce{HCl}$, but I'm not sure which of the following happens:
$$\ce{BaSO3 +$dil.$HCl->Ba(HSO)3 +Cl-}\tag1$$
$$\ce{BaSO3 +2H+->Ba^2+ +SO2 ^ +H2O}\tag2$$
Questions:

Which of the above actually happens? I have these two from different sources.
Does it becomes $\ce{BaSO4}$ on standing? Is it afterwards soluble in dil. $\ce{HCl}$, does this change require an oxidising agent, if yes then which one is more suitable - bromine water or $\ce{HNO3}$?


texts: What happened to this 10 year old unopened plastic bottle?

texts:
A colleague of mine found this unopened Aquarius bottle (non-carbonated drink) that was 10 years past its expiration date.

The bottle was collapsed inward which would suggest that the pressure in the bottle was lower then outside the bottle.

Can someone explain what happened here? Also, what happened to the air inside the bottle?


texts:
While studying about Cannizzaro reaction, it came to my mind as a wild thought what if this HCH(ONa)(ONa) molecule could pop out in some step of this reaction (not giving much details about how I thought it as it would be irrelevant). Then I thought this molecule might have some problem with stability. The $\mathrm{sp^3}$ hybridized carbon might have some have problem with spacing two -ONa groups close together.

So, is this molecule stable or not? If not why?


texts: Explain the function of this Galvanic Cell in detail

texts:
So I failed my test because of this question. It was titled Galvanic Cell although it looks more like an electrolytic cell with the external voltage and everything.

What was asked: explain the function of this cell in detail.
some keywords were also presented (not mentioning them all) but there were Gibbs, Faraday, K, and -nFE

I got too confused with the left side while Ni2+ + 2e- -> Ni (s) on the right side looks like a normal reduction in the cathode. What is going on in here?

Standard Reduction Potentials at 25 degrees Celcius:

**Cr2O7- (aq) + 14 H+ (aq) + 6 e- -> 2 Cr3+ (aq) + 7 H20 (l)  +1.33 V
                              Ni2+ (aq) + 2e- --> Ni (s)  -0.25 V**


texts:
My prof noted that if the two components of any ionic compound undergo a large extent reaction with each other, then the substance CANNOT exist as a pure substance.

For example, consider ammonium hydroxide. This is simply ammonia (at least in the solution phase). Can we have a solid, crystalline ammonium hydroxide lattice?

I think this is thermodynamically valid. What about kinetically? Isn't it theoretically possible to have two substances that would otherwise undergo a large extent reaction with each other but don't due to an activation energy barrier?

Are there any such examples?

Also what do you think of the below question?


texts:
Why is a C-Br bond considered polar? From electronegativity considerations, both carbon and bromine have very similar electronegativities - 2.5 and 2.8 - respectively.

Nonetheless, I am told that such a bond would be polar. We generally classify bond between atoms with EN differences < 0.5 as non-polar; why would C-Br be an exception?


texts: What is the ideal temperature and pressure to crack water?

texts:
Using sun mirrors and solar cells for electricity. What temperature, pressure and voltage ideal for cracking water.

Source: NPR

Source

Would it take more or less electricity to crack water under pressure or in a liquid or vapor state?


texts: Can there still exist equilibrium with a very high equilibrium constant?

texts:
Problem

Consider the reaction translated by:
$$\ce{2 CO(g) + O2(g) <=> 2 CO2(g)} \quad  K_c = 2 \times 10^{22}~\text{at } \pu{1000 K}$$
The order of magnitude of the equilibrium constant, $K_c$, at the temperature considered, indicates that
(A) the reaction has a very high yield;
(B) both reagents were completely consumed.

Answer

 (B)

My thoughts
In my point of view, the higher the equilibrium constant, the more extensive the direct reaction is. Thus the conversion of reagents into products of the reaction is "bigger", so the yield of the direct reaction has to be very high. With that, my answer was (A).

Can we assume both reagents were completely consumed just by analysing the magnitude of the equilibrium constant or can still exist equilibrium even though the magnitude of the constant is so elevated?
Having in mind your chemistry knowledge, what answer do you think it's the "most correct"?


texts: Why are vinylic and arylic carbocations highly unstable?

texts:
I have checked the internet and read quite a few books, but I still am not able to understand why vinylic and arylic carbocations are highly unstable.

What I found while surfing the internet is: For arylic carbocation, the carbon bearing postive charge cannot participate in resonance with adjacent carbons because it's p orbital is perpendicular to the other orbitals. But, I didn't really understand what this means.


texts:
Can someone explain (and preferably draw) the intermediates of this reaction?

I understand that it is a Claisen Reaction, and likely a condensation due to the heat, but I am not sure why there isn't an ester in the final product.


texts:
How would one prepare a one molar sodium hydroxide solution?

I see a few issues with this:

$\ce{NaOH}$ absorbs carbon dioxide. So old NaOH samples might have a significant portion of $\ce{NaHCO3}$ or sodium bicarbonate. How would get get rid of the sodium bicarbonate?
I am told that $\ce{NaOH}$ is hygroscopic. So it absorbs water, apparently. What is the mechanism for this? I can see the hydroxide attacking carbon dioxide in the above bullet point, that's easy, but I can't really see $\ce{NaOH}$ attacking water. Also couldn't we circumvent the water absorption problem by cooking the $\ce{NaOH}$?


texts: Why do higher-mass isotopes have higher melting and boiling points than lower-mass isotopes?

texts:
Different isotopes of the same element have the same number of electrons, so the nature of bonding between different isotopes of the same element should be the same, yet their melting points and boiling points vary. This would suggest that the interparticle forces and distances are different for different isotopes of the same element. Why is this exactly?

My best guess is that is has something to do with the kinetic energy (KE) formula

$$E_k = mv^2/2$$

If two samples of different isotopes of the same element were kept under the same pressure and temperature (so the KE of the particles in the different samples would the same), the particles of the heavier isotope would have a lower velocity than the particles of the lighter isotope, as a greater mass means a lower velocity (where KE is equal). Does it have something to do with the fact particles of a heavier isotope move more slowly when KE is equal?


texts: Do all the precipitates undergo an equilibrium with its respective ions, why can't they dissociate fully?

texts:
I’m really confused about this. If we consider $\ce{Ca3(PO4)2}$, it can be seen it undergoes an equilibrium. But why it’s an equilibrium?

This is the equilibrium it undergoes $$\ce{Ca3(PO4)2_{(s)}<=> 3Ca^2+_{(aq)} + 2 PO4_{(aq)}^3-}$$

By the way I’m having a doubt of why some are using backward arrow for a dissociation of a particular precipitate while some are using a solid forward arrow for the same reaction. For an example let’s take $\ce{AgCl(s)}$

Now this is a place where a backward arrow is used,
$$\ce{AgCl_{(s)}<=> Ag+_{(aq)} + Cl_{(aq)}-}$$

But I have seen in some books where there is a solid forward arrow instead of back-ward arrow for the dissociation of $\ce{AgCl(s)}$.


texts: Is the VSEPR theory correct in determining the bond angle of sulfur dioxide?

texts:
Recently when we were doing the VSEPR Theory in class and discussing the bond angles in various compounds. That's when I thought of sulfur dioxide whose structure can be like this:

According to the Internet, the bond angle between the two oxygen atoms = 120°. But mathematics shows a little off. I was taught that the VSEPR Theory states that

  Lone Pair-Lone Pair Repulsion > Bond Pair-LonePair Repulsion > Bond Pair-Bond Pair Repulsion

According to this, the angle between the two oxygens should be less than 120º and I can prove it.

Imagine that instead of the lone pair there was a double bond of oxygen with sulfur. This would imply that the bond angle between the oxygens would be exactly 120° on the same plane because each one of them would repel each other with the same repulsion force. But now instead of a bond pair, we have a lone pair which means (according to the VSEPR Theory) that it would repel the two oxygens much more than the imaginary bond pair was repelling. Therefore the angle between the lone pair and the bond pairs with oxygen would be more than 120°. This would result in a smaller than 120º angle between the two oxygen atoms. Then how does the net say that the bond angle is close to 120°? If what the web says is right, it implies that the repulsion of a lone pair and 2 bonds is exactly equal to the repulsion between 2 double bonds. Is it correct?


texts:
I've learnt that pressure is an intensive measure,
but I have also learnt that pressure can be added (partial pressures), which doesn't make sense since intensive variables are non-additive.
Where is the flaw in my understanding?


texts: Molar ratios not leading to complete reaction in Schweizer's reagent production

texts:
In my home lab, I've reacted $\ce{Cu(OH)2}$ with aqueous ammonia to produce Schweizer's reagent.  However, I'm surprised by the amount of ammonia required to react with this amount of $\ce{Cu(OH)2}$. Have I mistaken some calculation or formula?

Background/procedures:

8.89 g of copper (II) hydroxide was prepared by combining 24.98 g of $\ce{CuSO4 (aq)}$  with excess aqueous ammonia, to which was added 8.01 g $\ce{NaOH (aq)}$, precipitating a blue-green solid, which was filtered and allowed to dry, producing a blue-green powder with no visible hint of black copper oxide. This is believed to be reasonably pure copper (II) hydroxide.

This 8.89 g of copper (II) hydroxide was combined with aqueous ammonia (assayed at "28% to 30%"), gradually, in amounts of 30 mL, 30 mL, 70 mL, and 70 mL, a total of 200 mL. Also, 80 mL of distilled water was added, but I assume this is merely diluting the reagent and not affecting the reaction.

At each addition of aqueous ammonia, more of the copper hydroxide reacted to form a clear, deep blue liquid, consistent with the expected appearance of Schweizer's reagent. However, a sizable amount of green-blue solid remains:

Assumptions and calculations:

8.89 g $\ce{Cu(OH)2}$, with a molar mass of 97.56 g/mol, equals 0.0911 mol $\ce{Cu(OH)2}$.
200 mL of "28-30%" aqueous ammonia, at roughly 14 mol/L, equals 2.8 mol $\ce{NH3}$.
Balanced equation for this reaction is $\ce{Cu(OH)2 + 4 NH3 -> [Cu(NH3)4](OH)2}$ ; this indicates a ratio of 1:4 for copper hydroxide to ammonia.
However, my ratio so far is closer to 1:28, and it's still not enough.

Question:

If my calculations are correct, I've added about 7 times the amount of ammonia needed to fully react with this amount of copper hydroxide, but it appears not all of it has reacted. Where have I miscalculated?


texts: Hybridisation and the Schrödinger equation

texts:
I am slightly confused about hybridisation and how it relates to molecular and atomic orbitals, despite having pored through many sources online. I was hoping someone could verify whether my current understanding is correct, in particular regarding what hybridisation actually is/does because I have not read this explicitly, but am assuming it is the case from what I have read so far:

The Schrödinger equation can be solved to give the atomic orbitals (at least, some simplification involving the effective nuclear charge can be used to find the outer (and inner?) atomic orbitals.
In hybridisation, we first consider the shape of a molecule and then we consider each atom seperately and how we could combine the atomic orbitals so that the geometry about each atom is correct. Now what I am particularly unsure about is: Are the hybridised orbitals entirely a conceptual construct, or are they mathematical solutions to the Schrödinger equation? I was thinking that maybe the hybrid atomic orbitals that are created are a linear combination of the atomic orbitals, and thus this linear combination also solved the Schrödinger equation and can exist but would have a different energy to the individual atomic orbitals? I am finding it difficult to think how a linear combination of the atomic orbitals could produce something with a completely different shape though (although I suppose the orbitals are orientated and essentially vectorial, so I think it could work). Perhaps  the hybrid atomic orbital form could also be, say, the product of the atomic orbital forms? Although then I do not think this would solve the Schrödinger equation anymore. But I am not sure. And anyway, all of these ideas assume that hybridisation has a mathematical basis in the Schrödinger equation, which I am not sure about at all!
Then molecular orbital theory takes the orbitals of each atom (I think theoretically it takes every orbital in every atom?) in the molecule and combines them to form a molecular orbital for the whole molecule - no longer simply an overlap between two atoms. This certainly also solves the Schrödinger equation. From what I understand, theoretically the calculation to form MOs should involve only the AOs of each atom, but to simplify the situation sometimes hybrid atomic orbitals are used in MO construction? If so, surely the hybrid atomic orbitals must be a linear combination of the atomic orbitals that solve the Schrödinger equation, so that this can be used in molecular obrital theory which is based in the solution to the Schrödinger equation? Also, where in the calulcation are the coefficients for each atomic orbital arising? Is it from the boundary conditions including things like molecule geometry, or perhaps that we know the energy of a molecule and when we put this particular energy in to the Schrödinger equation it gives us the coefficients?

I apologise for the long post and I realise there seem to be many questions within here, however they are all linked and about the mathematical underpinnings of hybridisation/valence bond theory and molecular orbitals, so I thought they belonged in one post.


texts:
Azobenzenes trap heat when exposed to sunlight due to the principle of photo-isomerism. But this occurs in nanoseconds.

I was wondering if we can store this heat for hours and utilize this later on. Is there any way to do that?


texts: How can off-diagonal Hamiltonian matrix elements be nonzero when the overlap matrix is diagonal?

texts:
While studying about Hückel theory, I got accustomed to the approximation of making the overlap matrix an identity matrix; that is making the off-diagonal elements zero as $S_{AB}= S_{BA}= 0\;;$ this implies the use of orthogonal base states of AOs. The off-diagonal elements of the Hamiltonian matrix are still taken as constants that may be non-zero: $H_{AB}= H_{BA}= \beta_{AB}$, where $\beta_{AB}$ is a negative quantity.

Then I wondered why it isn't the case that $H_{AB}= H_{BA}= 0$ strictly, as it represents the expectation value - the average energy contribution of the overlapping region of AOs $A$ and $B$.  But, it would seem that overlapping is not actually possible, as is evident from the fact that $S_{AB}$ is zero.

In this question, when I asked about this, ifilot replied:

  Indeed, this seems rather counterintuitive, but it is not. Another way of looking at $S_{ij}=δ_{ij}$ is saying that all atomic orbitals are orthonormal to each other. So if you would evaluate the overlap integral of two different orbitals, it would result in zero. This does not necessarily mean that evaluating the Hamiltonian integral $\langle ϕ_i|\hat H|ϕ_j\rangle$ results in zero, because first applying the Hamiltonian operator on the wave function and then integrating might result in a non-zero outcome.

I know he is right in this point; but I'm still having trouble seeing how this is possible.

As Peter Atkins in his book Elements of Physical Chemistry wrote:

  [...] The integral $H_{AB}$ depends on both $\psi_A$ and $\psi_B$, and we can interpret it as the contribution to the energy due to the accumulation of electron density where the two atomic orbitals overlap, including, for instance, the Coulombic attraction between the extra accumulation of electron density and both nuclei.

Evidently, this phrase makes clear that $H_{AB}$ is non-zero iff there is overlap between the AOs.

So, how can $H_{AB}\ne 0$ and $S_{AB}= 0$ both be true at the same time? And, what are the physical implications? While the former means there is overlap, the latter means the opposite; it seems really contradictory.


texts: Why is 4-hydroxypyridine more acidic than benzoic acid?

texts:
4-hydroxypyridine (or 4-pyridone) has a $\mathrm{p}K_\mathrm{a}$ in the ballpark of $3$ to $3.33\:^1$ (in the pdf linked below, the $\mathrm{p}K_\mathrm{a}$ of 1-methyl-4-pyridone has been given to be $3.33$, however I suppose removing a methyl would only cause a slight decrease in the $\mathrm{p}K_\mathrm{a}$ value). This seems an unexpectedly low value to me. 4-pyridone seems more acidic than I expected it to be, since the $\mathrm{p}K_\mathrm{a}$ of other common acids are:$\:^2$
\begin{array}{lr}
\hline
\mathrm{Acid} & \mathrm{p}K_\mathrm{a} \\
\hline
\text{Benzoic acid} & 4.20 \\
\text{Formic acid} & 3.75 \\
\text{Acetic acid} & 4.75\\
\text{Phenol} & 10.0 \\
\text{Carbonic acid} & 6.37\rlap{\:^1} \\ \hline
\end{array}
Now I had expected 4-hydroxypyridine to be more acidic than phenol, because of the negative charge in the former's conjugate base being delocalised onto the electronegative nitrogen, yielding a more stable resonating structure than the latter's corresponding resonating structure. I thought that 4-pyridone's $\mathrm{p}K_\mathrm{a}$ might be somewhere around $\ce{H2CO3}$'s $\mathrm{p}K_\mathrm{a}$, but I was wrong. Also, I wasn't quite sure that it would be acidic enough to have a $\mathrm{p}K_\mathrm{a}$ value any close to other carboxylic acids. But it seems to me that it is more acidic than benzoic acid, formic acid and acetic acid.
Why is this so? I can't see any excetional characteristic in its structure which might impart it such a low $\mathrm{p}K_\mathrm{a}$. This does seem more of an exception to me, as of now, but it would be very helpful if someone clarified and explained such a trend.
References:
$[1]:$ http://gissmo.nmrfam.wisc.edu/static/pKa_compilation_R_Williams.pdf
$[2]:$ https://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/acidity2.htm


texts:
When I was milling NaOH for some purpose, I noticed that the powder is incredibly hygroscopic. Because I have problems with drying certain chemicals safely (without extensive heating), I thought this might be a safer solution:

But I'm not so sure about that safety. Can NaOH exit into the air and pollute the compound in the second beaker? If it can, which compounds are safe and strongly hygroscopic?

Could I use this technique to increase sulfuric acid concentration? What about acetic acid?


texts: How to use Sodium Thiosulfate for fixing dicopper (I) tetraiodomercurate (II)?

texts:
DISCLAIMER
DO NOT TRY TO DEMERCURATE USING DESCRIBED PROCEDURE. CONSULT YOUR EMERGENCY SERVICE.

I found a discrepancy between a government-approved procedure of living quarters demercuration and the patent RU 2081198 C1 the procedure is based on.
The last phase of cleaning involves fixing remaining mercury salts $\ce{HgI2}$, $\ce{Hg2I2}$, $\ce{Cu2Hg2I2}$ (I didn't find any mentions of $\ce{Cu2Hg2I2}$ in literature), and $\ce{Cu2[HgI4]}$ using $\ce{Na2S2O3}$. According to the patent one should use acidified $\ce{Na2S2O3}$:
$$\ce{Na2S2O3} + 2\ce{H+} \rightarrow \ce{H2SO3} + \ce{S} + 2\ce{Na+}$$
$$\ce{mercury salts + S -> \ce{HgS} + other products}$$
However, the government-approved procedure suggests using not acidified $\ce{Na2S2O3}$ or $\ce{HOOC-COOH}$. I am wondering if it is a mistake. I found that $\ce{HgI2}$ is soluble in $\ce{Na2S2O3}$ in the Russian book on analytical mercury chemistry. So using $\ce{Na2S2O3}$ for $\ce{HgI2}$ removal makes sense.
My question
Is $\ce{Cu2[HgI4]}$ soluble in presence of $\ce{Na2S2O3}$ or $\ce{HOOC-COOH}$? Or are there other reactions that make it less dangerous or make $\ce{Cu2[HgI4]}$ easy to remove?
Reactions involved in demercuration according to the patent RU 2081198 C1
$$2\ce{CuSO4} + 4\ce{KI} \rightarrow \ce{Cu2I2} + \ce{I2} + 2\ce{K2SO4}$$
$$\ce{Hg} + \ce{I2} \rightarrow \ce{HgI2}$$
$$\ce{Hg} + 2\ce{KI} + \ce{I2} \rightarrow \ce{K2[HgI4]}$$
$$\ce{Hg} + \ce{Cu2I2} + \ce{I2} \rightarrow \ce{Cu2[HgI4]}$$
$$\ce{HgI2} + 2\ce{KI} \rightarrow \ce{K2[HgI4]}$$
$$\ce{K2[HgI4]} + \ce{Cu2I2} \rightarrow \ce{Cu2[HgI4]} + 2 \ce{KI}$$
Binding mercury wapors???
$$\ce{Hg} + \ce{Cu2I2} \rightarrow \ce{Cu2HgI2}$$
The method of demercuration from the patent RU 2081198 C1
Materials

$\ce{CuSO4} \bullet \ce{H2O}$ $10\%$ aqueous solution
$\ce{KI}$ $10\%$ aqueous solution
$\ce{Na2S2O3}$ $25\%$ aqueous solution
$\ce{HOOC-COOH}$ $5\%$ aqueous solution
sawdust (if a floor in demercurated room is made of material with many cracks, e.g. parquet)

Procedure

Remove visible mercury droplets
Spray copper sulfate until the floor is moistened
Spray double volume of potassium iodide over the floor
Wait for 10 days. Mercury droplets are located as red spots on the white layer of salts
Remove located mercury and salts from the floor
If the floor is made of material with many cracks, the floor is covered by a layer of sawdust impregnated by the mixture of $\ce{CuSO4}$ and $\ce{KI}$ and exposed for another 10 days. There may be several repeats of sawdust mercury absorption.
Fix remaining salts of mercury by the spraying of $\ce{Na2SO3}$ and then spraying of $\ce{HOOC-COOH}$.
Wait for 1 day
Wet cleaning.

The method of demercuration according to government-approved procedure
Materials

$\ce{CuSO4} \bullet \ce{H2O}$ $10\%$ aqueous solution
$\ce{KI}$ $10\%$ aqueous solution
$\ce{Na2S2O3}$ $25\%$ aqueous solution or $\ce{HOOC-COOH}$ $3-5\%$ aqueous solution

Procedure

Remove visible mercury droplets
Spray copper sulfate $0.1 - 0.15 L/m^2$
Wait for 2-3 minutes
Spray potassium iodide $0.2 - 0.3 L/m^2$
Wait for 1-3 days exposition for spilled mercury or 5-10 days if mercury is removed from the air
Remove mercury and salts
In rooms with the floor made of material that is not penetrable for mercury one turn of $\ce{CuSO4}$ and $\ce{KI}$ cleaning is enough
If the floor is made of parquet mercury droplets are removed from cracks using a flat knife
In living quarters, schools, and kindergartens remaining mercury salts are fixed using $\ce{Na2S2O3}$ or $\ce{HOOC-COOH}$ $0.15 - 0.2 L/m^2$.
Wait for 1 day
Wet cleaning

My question
Is $\ce{Cu2[HgI4]}$ soluble in presence of $\ce{Na2S2O3}$ or $\ce{HOOC-COOH}$? Or are there other reactions that make it less dangerous or make $\ce{Cu2[HgI4]}$ easy to remove?
Related questions:

about chemical properties of $\ce{Cu2[HgI4]}$,
about toxicity of $\ce{HgI}$ and $\ce{Cu2[HgI4]}$.


texts:
I had to identify whether a few compounds are ambident substrates or not.
However, as I did not know the term, I took to googling it, but I could not find any explanation for this group anywhere.
I know about ambident nucleophiles and electrophiles, yet I had never heard of ambident substrates.
Please explain what they are.


texts: Work done in an isothermal irreversible process

texts: In calculating the work done in an isothermal irreversible process, why do we consider the external pressure only (using formula: $W_{\text{ext}} = P_{\text{ext}} \mathrm{d}V)$ but not the internal pressure? When the system expands, the internal pressure does the positive work, but even in this scenario, we use the equation as mentioned above. Why is this happening?


texts: Na2HPO4 is amphoteric: write the two reactions

texts:
$\ce{Na_2HPO_4}$ is amphoteric, which means it can act as a base or as a acid depending on which substance they react with.

This is the reaction in which disodium phosphate appears to be an acid:

$$\ce{Na_2HPO_4 + H_2O \rightarrow H3O+ + Na_2PO_4-}$$

This is when it acts as a base:

$$\ce{Na_2HPO_4 + H_2O \rightarrow OH- + Na_2H_2PO_4+}$$

Did I write those two reactions currently? If not, what's wrong with my reasoning?


texts: This may sound weird but could one 'zap' some liquid like milk with electricity of a certain voltage for a 'few' seconds hoping to kill any bacteria in it? I know some people suggested some type of radiation on meat ( I think) but could a small charge of electricity on liquid products kill any bacteria in them?


texts: How to calculate saturation point of a solution?

texts:
Is there a way to calculate theoretical saturation point between 2 materials?

For example, let's say I want to determine solubility of vitamin A in water, or vitamin B in olive oil, or vitamin D in milk. In these examples, if I know the molecular structure of the vitamins and the various liquids, can I figure out at what point saturation will be reached?

To be clear: If there's a way, I want to learn how to calculate these theoretical saturation values. I don't want to just get them from a table somewhere.


texts: Ab initio molecular properties which can be experimentally measured and don't require derivatives/gradients

texts: I'm attempting to teach myself HF and DFT by implementing various algorithms, but I've run into a snag: many molecular properties which are experimentally measurable appear to require taking gradients, which is considerable extra work (from a coding perspective). Are there any properties where I can start with a known optimized geometry, run my HF or DFT implementation, and then compare the results to experimental values? Pedagogically, I'd like to be able to motivate DFT by showing it clearly outperforms HF SCF in some experimental regime.


texts:
I know that the Gibbs function for pure substances is given by

$$\mathrm dG = V\,\mathrm dp - S\,\mathrm dT.\tag{1}$$

However, I also saw the same equation in the form

$$ΔG = VΔp - SΔT,\tag{2}$$

however I am doubtful if the second equation is correct as now $Δ$ represents finite changes which is different from the infinitesimal changes in the first equation. Is the second equation correct?


texts: What are radicals and how do they act in radical chain reactions?

texts: What really is a radical? For example, when $\ce{Cl2}$ receives enough energy to dissociate the bond and turn into $\ce{ 2Cl.}$, the two chlorine atoms each carry one of the electrons that form the bond. What is the difference between the $\ce{Cl}$ radical and the original $\ce{Cl}$? They have exactly the same number of electrons. And how do they act as a chain carrier?


texts: Identifying lone pairs when looking for formal charges

texts: Why are there no formal charges on the 1st compound? I am specifically referring to the nitrogen atom, which I would think should exhibit a +2 formal charge? However, in David Klein's organic chemistry textbook it is said that the 1st compound shows no formal charge anywhere. The second compound, of course, exhibits a +1 formal charge on the nitrogen atom and -1 formal charge on the oxygen atom. This would make more sense if I were to take into account the lone pair for Nitrogen in compound 1 (and the 2 lone pairs for oxygen), but then why would they hide the lone pairs in compound 1 and exhibit them in compound 2? Please, correct my incorrect thinking.


texts:
Its known that the only method to determine mercury in atomic absorbtion spectroscopy is the cold vapor method.

What is the reason that mercury can't be determined with other methods, such as flame, electrothermal AAS or even emission spectroscopy ?


texts:
For instance, if an atom loses an electron and becomes a cation, such as sodium, how does that make the sodium atom positively charged? The sodium's atomic radii decreases due to less electron-electron repulsions which in effect makes the sodium atom more electron dense.

The common response I get from TA's is that positive and negative charges cancel each other out so essentially one proton isn't getting canceled out which results in a net positive charge. However, protons and electrons don't cancel each other out in an atom (effective nuclear charge), so I know that response is incorrect since the electrons closest to nucleus of an atom feel a greater positive charge than the valance electrons.


texts:
If you look at $\ce{Na}$, it has a very low ionization energy, but the question is, why does it have an ionization energy at all? If it can get to the electronic configuration of $\ce{Ne}$, by losing an electron, which is a very stable configuration, then it should release energy. Consider the analogy to gravitational potential energy, you can consider $\ce{Na}$ to be analogous to standing on a very high ledge. And $\ce{Na^+}$, is the position at the ground. Obviously, getting to the ground is much more stable. And if I jump down from the ledge I convert my potential energy to kinetic energy and ultimately to heat, thus releasing energy. Why does sodium require energy to ionize?

And, consider ferric chloride $\ce{FeCl_3}$.

Why does iron form this bond? I mean, it makes sense from chlorine's point of view to share an electron with iron. All the chlorines have a full outer shell. But what about iron? It had $2$ valence electrons, now it has $5$. It would make much more sense for iron to bond with chlorine to form $\ce{FeCl_6}$, since then it, too would have a full outer shell. Or, $\ce{Fe}$ could give away its $2$ electrons to $2$ chlorines and form ionic bonds. Why does this not happen?


texts: Why is it important to do the nitrosation of aniline to diazonium salts at low temperatures (0-5°C)?

texts: The reaction the formation of diazonium salts starting from aniline (nitrosation of aniline), which should be performed at low temperature.


texts: Proving using ideal gas law that molar volume at NTP is 22.4 litres

texts:
The definition of NTP as given by IUPAC is

NTP – Normal Temperature and Pressure – is defined as air
at $20\ ^\circ\mathrm C$ ($\pu{293.15 K}$, $\pu{68^{\circ}F}$) and $\pu{1 atm}$ ($\pu{101.325 kN/m2}$, $101.325\ \mathrm{kPa}$, $14.7\ \mathrm{psia}$, $0\ \mathrm{psig}$, $29.92\ \mathrm{inHg}$, $407\ \mathrm{in}\ce{H2O}$, $760\ \mathrm{Torr}$).
It is also known that volume occupied by $1$ mole of gas at NTP is
$\pu{22.4 L}$.

My attempt at proving the above statement,
For $1$ mole,  $PV=RT$
Substituting $P=\pu{1 atm}$, $T=\pu{293 K}$,  $R=0.0821\ \mathrm{L\ atm\ K^{-1}\ mol^{-1}}$, we get $V=\pu{24.05 L}$ as the molar volume.
On putting $T=\pu{273 K}$ and $P=\pu{1 bar}$ (conditions of STP), we get $V=\pu{22.2 L}$
Therefore, molar volume at STP is $\pu{22.4L}$.
Why is the above calculation in NTP condition giving wrong results? How else to prove that molar volume at NTP is ${22.4\ \mathrm L}$?


texts:
In the question I've to find out the ionic product of water using the facts that the degree of dissociation of water at $18\ \mathrm{^\circ C}$ is $1.8\times10^{-9}$.

My attempt

Let the concentration of water be $1\ \mathrm M$.

$$\ce{H2O <=> H+ + OH-}$$

Initial:

$$\begin{align}
[\ce{H2O}] &= 1\ \mathrm M\\[6pt]
[\ce{H+}] &= 0\ \mathrm M\\[6pt]
[\ce{OH-}] &= 0\ \mathrm M
\end{align}$$

At equilibrium:

$$\begin{align}
[\ce{H2O}] &= (1 - 1.8×10^{-9})\ \mathrm M\\[6pt]
[\ce{H+}] &= 1.8×10^{-9}\ \mathrm M\\[6pt]
[\ce{OH-}] &= 1.8×10^{-9}\ \mathrm M
\end{align}$$

Therefore,
$$\begin{align}
K_\mathrm w &= \frac{[\ce{H+}] + [\ce{OH-}]}{[\ce{H2O}]}\\[6pt]
&= \left(1.8\times10^{-9}\right) \times \left(1.8\times10^{-9}\right)\\[6pt]
&= 3.24 \times 10^{-18}
\end{align}$$

According to my book answer is $1.0\times10^{-14}$, which I know is correct. I want to know where am I going wrong?


texts:
I am studying the reaction of dissolved dioxygen with manganese(II) hydroxide for the Winkler method:

                   2Mn(OH)2(s)+O2(aq)⟶2MnO2(s)+2H2O(l)

The data I have been given is Mn(OH)2's pKs=12.7, as well as the standard potential for MnO2(s)/Mn(OH)2(s), which is 1.23V, and the one of O2/H2O, which is also 1.23V; nothing more. Using Gibbs free energy  for each half reaction, I have managed to calculate the quilibrium constant for the reaction at 298K, which I found to be 10^-25.4, making it dramatically unfavorable to products.

Does anyone find the same thing for this constant, or have I made a mistake? If it is the right constant, how come the reaction takes place?

I am aware that it is not the commonly used reaction when it comes to the Winkler method, but its the only one I can propose when it comes to having the dioxygen react with manganese hydroxide owing to what few data I have. Also sorry for my shaky English, I'm french.

Thanks in advance for your answers!


texts: What is the precise definition of maximum work in the context of electrochemistry and thermodynamics?

texts:
I'd like clarification of the meaning of $W_\text{max}$ in the following equations (and thus in the combined result in the third equation):
\begin{align}
W_\text{max} &= \Delta G\\
W_\text{max} &= -nF\varepsilon\\
\Delta G &= -nF\varepsilon\\
\end{align}

In the first equation, we somehow come to the conclusion that the maximum useful work available from a process is that process' change in Gibbs Free Energy. I ask now what work that means - does it mean work done on the surroundings by release of energy from the system? Does it mean the maximum work done on the system via a chemical process (this makes more sense because it doesn't make sense that an increase in Gibbs Free Energy of a system would do work on anything but the system)?

Secondly, in the electrochemical definition of $W_\text{max}$, we have the point of view of the system; that is, positive work is done on the system and negative by the system. Therefore, we add the negative sign because when cell potential is positive the work done on the system is negative (it does work on the surroundings).

The only logical conclusion I can come to is that the two $W_\text{max}$ definitions must be both with respect to the system's point of view, which means that $W_\text{max} = \Delta G$ refers to the maximum amount of work done on a system during a chemical process (the intuitive interpretation that I posed). However, it still makes me uncomfortable to define "useful work" as work done on the system. How can we harness work from putting energy into something?


texts: Representation of chemical formulas as strings?

texts:
Is there a standard manner of representing chemical formulas as linear strings?

For example, $H_2O$ can be represented with the string H2O. Isotopes are usually specified with a number before the element. But this must be preceded by a space, or it can be get mixed with the number right before: O4 13CH, which is equivalent to $O_4{^{13}C}H$.

I'm just wondering if there is any set of accepted conventions when representing chemical formulas as linear strings.


texts:
Will cinnamaldehyde undergo self-aldol condensation?

My book says it won't, but since it has an α-hydrogen, I'm confused.


texts: Conductivity of a semiconductor at high temperatures

texts:
I understand that increasing the temperature of a semiconductor excites electrons in the valence band into the conduction band. Hence, the resistivity of a semiconductor decreases with temperature.

Is there a high enough temperature where the conduction band would be saturated from electron with the valence band and the resistance of the semiconductor would start to increase like a regular metal?

Assuming the seminconductor couldn't melt, as temperature got aribtrarily high would the seminconductor's resistance get arbitrarily low?


texts: Is the $\ce{NO-}$ a radical species?  If so, can someone please explain why because $\ce{NO}$ has an odd number of electrons (11), so adding an additional electron would give 12 valence electrons and a formal charge of -1 on the nitrogen. Is my general chemistry failing me or?