texts: Why is chemical accuracy defined as 1 kcal/mol?

texts:
"Chemical accuracy" in computational chemistry, is commonly understood to be $1~\mathrm{kcal\over mol}$, or about $4~\mathrm{kJ\over mol}$. Spectroscopic accuracy is $1~\mathrm{kJ\over mol}$, and that definition has intuitive sense. However, where does the $1~\mathrm{kcal\over mol}$ quantity come from?

From Wikipedia:

  A particularly important objective, called computational thermochemistry, is to calculate thermochemical quantities such as the enthalpy of formation to chemical accuracy. Chemical accuracy is the accuracy required to make realistic chemical predictions and is generally considered to be 1 kcal/mol or 4 kJ/mol.


texts: How can I safely carry out an electrolytic etch on stainless steel without producing relatively harmful by-products?

texts:
I propose to carry out an electrolytic etch on a stainless steel plate like so:

One of electrodes must be the stainless steel plate which is being etched and the surface layer must be removed.

I'm aware such an electrolytic etches can produce harmful by-products such as Chlorine (NaCl electrolyte), Chromium compounds and more.

If it is possible, What electrolytes and electrodes can I use to prevent the production of these substances?

Would it be possible to create safer Chromium compounds?
If I can't, what other non-electrolytic options do I have?


texts: at constant volume why the change of enthalpy doesn't equal the change of heat

texts: At constant pressure $p=\text{const.}$, change of internal energy equals heat subtract work(PV). So, $q=\Delta E - pV$. So is the the change of enthalpy. So we say at constant pressure, the change of enthalpy equals the change of heat. But when the volume is constant $V = \text{const.}$, no work is done. $\Delta E= q$, $\Delta H = \Delta q$. So why not in this situation too?


texts: Is an allene or a conjugated diene formed?

texts:
If we dehydrate the following molecule, which hydrogen ($\ce{H1}$ or $\ce{H2}$) gets removed?

The conclusion that I have drawn from the molecule: The carbon to which $\ce{H1}$ is attached is $\ce{sp2}$ hybridized which makes $\ce{H1}$ slightly more acidic than $\ce{H2}$.


texts: Why is periodicity seen in these certain properties?

texts:
I missed my lesson on periodicity so had to teach myself, and have always forgotten to ask my teacher to explain to me why these trends are seen, which, unfortunately, the textbooks don't.

Density: the density of an element tends to increase across a period up to group 3, and then starts to decrease and become very low at group 5 or so. Why is this?

Melting and boiling point: they tend to rise up to about group 3 or 4, before falling rapidly after that. I would suggest that this is because group 4 elements tend to have giant covalent structures, so also a higher boiling point, whereas on the right hand side of a period they are simple molecular structures, so have a low boiling point. Am I correct?

Atomic size: atomic size always decreases along a period from left to right. My suggestion is that this is because there are more electrons and more protons as the group increases, so there becomes a stronger attraction between them, pulling the electrons closer to the nucleus. Am I right?

So the only one I have no idea about really is density, and the other two I just need clarification on.


texts: Orthogonality of wavefunctions for different normal modes

texts:
Vibrational wavefunctions corresponding to different vibrational levels of the same normal mode are orthogonal because they are eigenfunctions of the harmonic oscillator Hamiltonian, which is hermitian.
Displacement vectors corresponding to different normal modes are orthogonal because they are eigenvectors of the Hessian matrix, which is symmetric.

QUESTION: given the above, how can one show that vibrational wavefunctions corresponding to different normal modes are orthogonal?


texts: Usually textbooks on CI takes the SCF Hartree-Fock orbitals as a starting point. Can one use the configuration interaction method starting directly from the single-particle Slater determinants avoiding the iterative procedure. This question concerns mainly small molecules like the hydrogen molecule. Do I get a high inaccuracy in this case? If yes, why? Could this inaccuracy be decreased taking into account more configurations?


texts: What is a barrier-less reaction in Quantum Chemistry?

texts:
After finding a reaction "Transitional State" by GAMESS, and finding Hessian Eigenvalues, my project instructor said:

  seems your imaginary frequency (negative eigenvalue) is not that big (it is around -13.01), which means your reaction is barrier-less.

As I am a beginner in Quantum Chemistry, I could not figure out what is the relation between a small imaginary frequency and being barrier-less.

As I remember from the Arrhenius equation, being barrier-less has something to do with higher temperature leading to a slower reaction, but I could not understand its relation to imaginary frequencies.


texts: Are common names of substituents accepted by IUPAC?

texts:
Are names of substituents like isopropyl and sec-butyl accepted by IUPAC?

Or do we need to name them according to standard IUPAC conventions?
(Ex- 1-methylethyl for isopropyl)

My book uses common names for substituents at a lot of places but I am doubtful about this.


texts: Isopropyl alcohol to clean Nylon plastic

texts:
I have a hardwood wooden frame, possibly lacquered, containing some very dirty nylon plastic pieces, a bit like the teeth of a comb, where the frame goes along top and bottom.  I know it's nylon because the manufacturers say so, ditto they mention lacquer.
I would normally just scrub the nylon section with soapy water, but the wooden frame MUST NOT warp!
I have some isopropyl alcohol, 99 or 97%, i can't remember, and propose to wipe the nylon clean.  It's 120cm long and has lots of slots in it, so this may take quite a lot of propanol.
My question is:  Is solid nylon 'plastic' affected by isopropyl alcohol of this %?
If I am better off diluting it a bit, would it then warp the wood?  I know it will take the lacquer off - it's not good with furniture finishes generally!
I do know to do this job outside :-)
Thank you


texts: How to find the concentrations of the acid-base equilibrium between sulfuric acid and sulfur dioxide for a known pH using Octave?

texts:
The system is an aqueous solution of sulfuric acid and sulfur dioxide. I know how much sulfur there is and I know the pH.  The system is in equilibrium.  I would like to use Octave to solve the system.

I set up the following equations, ignoring $\ce{SO3^2-}$ because the pH is around 1.5.

By definition:
$$ \mathrm{pH} = -\log [\ce{H+}]$$

Conservation of mass:
$$[\ce{H2SO4}] + [\ce{H2SO3}] + [\ce{HSO4-}] + [\ce{SO4^2-}] + [\ce{HSO3-}] = M $$

Henderson-Hasselbalch equations for the system:
\begin{align}
\mathrm{pH} &= \mathrm{p}K_\mathrm{a}(\ce{HSO3-}) + \log \frac{[\ce{HSO3-}]}{[\ce{H2SO3}]}\\
\mathrm{pH} &= \mathrm{p}K_\mathrm{a}(\ce{SO4^2-}) + \log  \frac{[\ce{SO4^2-}]}{[\ce{HSO4-}]}\\
\mathrm{pH} &= \mathrm{p}K_\mathrm{a}(\ce{HSO4-}) + \log \frac{[\ce{HSO4-}]}{[\ce{H2SO4}]}\\
\end{align}

I then defined the solution vector to have the following order:
$$ x = [ [\ce{H+}], [\ce{HSO4-}], [\ce{SO4^2-}], [\ce{HSO3-}], [\ce{H2SO4}], [\ce{H2SO3}] ]$$

and my code for Octave is attached.  For some reason I always get negative values for some of the results.

function y = phCalc(x)
   pH = 1.87;
   pKa1 = -5;   % this is a guess to drive H2SO4 to ionization in this system
   pKa2 = 1.987;% from a textbook
   pKa3 = 1.857;% from a text book
   M = 0.0012 / 32 * 1000 ; % total sulfur moles per volume
   y(1) = 10^(-pH) - x(1);
   y(2) = x(5) * 10^(pH-pKa1) - x(2);
   y(3) = x(2) * 10^(pH-pKa2) - x(3);
   y(4) = x(1) - x(2) - x(3) - x(4);
   y(5) = x(2) + x(3) + x(4) + x(5) + x(6) - M;
   y(6) = x(4) / 10^(pH-pKa3) - x(6);
endfunction


texts: Why do shampoo ingredient labels feature the term "Aqua"?

texts:
I keep seeing the term "Aqua" in the ingredient labels on several shampoo varieties, but I really don't see why it should be there in the first place.

I mean, if the manufacturers just wanted to say it contains water, couldn't they've printed out "Water" instead?

Or could it be that "Aqua" is slang for purified water (or water that's been treated in some godforsaken way) in the shampoo industry? Well, I guess there could always be the possibility that the manufacturers think "Aqua" sounds a lot fancier than plain ol' "Water".

So why's the term "Aqua" mentioned there?


texts: Inactivation of enzyme: Why inactivation constants do not follow the Arrhenius equation?

texts: The Arrhenius equation may not account for the temperature effect on thermal inactivation rate constants. Why can the thermal inactivation kinetics not be expected to follow Arrhenius? The reason that the inactivation constants do not follow Arrhenius is it because of other chemical processes occuring like diffusion?


texts: What determines 3D printing material compatibility?

texts:
3D printing, specifically the type common for consumers FDM or FFF, involves laying down thin (typically 0.1 to 0.2mm) layers of molten plastic. Modern consumer printers can use various filaments: PLA, ABS, Nylon, polycarbonate, PETG, ASA, etc.

PLA printed on top of PLA will make a decently strong bond, PETG on top of PETG will make a noticeably stronger bond. PETG on top of PLA will effectively not bond at all and can be easily pulled apart.

What's going on here? What determines layer adhesion? Can polymers be "forced" to bond to one another (overheating? pressure?)? Ideally I'd like to put together a compatibility matrix for mixing 3D printing filaments, but I don't even know enough to know what to search for.


texts: What form of zinc's found naturally in vegetables & meat?

texts: What kind of zinc naturally occurs in plants? Zinc oxide, zinc sulphide, or something else?


texts: Iron nomenclature differences between Iron(III) and Ferric

texts: As I was doing my Ap Chem homework, sometimes the question would use Iron(III) and sometimes it would use Ferric.  What's the difference in usage?  Also, what's the difference between Iron(II) and Ferrous?


texts: When MnO2 acts as a catalyst to speed up the decomposition of H2O2 what does it actually do?

texts: Everywhere I look it just states that $\ce{MnO2}$ acts as a catalyst but I have yet to find a simple explanation for what it actually does. What is the mechanism involved in simple terms?


texts: Why is it that the least reactive metals are the best electrical conductors?

texts: Silver, Gold and Platinum are amongst the best conductors of electricity, but also the amongst the most unreactive. Since electrical conductivity depends on the number of delocalized electrons (along with resistivity), if an element gives up its electrons readily (making it highly reactive), then shouldn't that mean it will be a great electrical conductor? Why isn't Cesium the best conductor?


texts: How is Pi antibonding orbital more polar than Pi bonding orbital?

texts:
While reading about the solvent effect on electronic transition in ESR spectroscopy, I found it written somewhere that the pi anti-bonding orbitals are more polar compared to pi bonding orbitals.
Can somebody explain how and why is it so?


texts: Is there a name, or any specific jargon for a precipitation equilibrium involving a solid reactant?

texts:
Let's say you have some ions in solution, for example Na+(aq) and OH-(aq), and some partially dissolved solid, MgCO3(s), Mg+2(aq) and CO3-2(aq), which precipitates Mg(OH)2(s) until equilibrium.

So you have two solubility equilibriums interacting with each other:

$$\ce{ MgCO_3(s) <=> Mg^{+2}(aq) + CO_3^{-2}(aq) }$$

and

$$\ce{ Mg^{+2}(aq) + 2OH^-(aq) <=> Mg(OH)_2(s) }$$

overall (with all spectator ions removed):

$$\ce{ MgCO_3(s) + 2OH^-(aq) <=> Mg(OH)_2(s) + CO_3^{-2}(aq) }$$

Is there a name for this type of reaction, and what method would I use to calculate the equilibrium point, with what physical properties?

I would call it something like a "binary solubility equilibrium". And I guess if I know the starting OH concentration and the solubility constants of the two solids, I could work out the equilibrium?

Any clues and key words appreciated. Thanks.


texts: How is it possible to obtain a value of 8/3 as an oxidation state?

texts: Iron's oxidation state in $\ce{Fe3O4}$. I really can't get the logic behind this.


texts:
Vinylic halides do not show nucleophilic substitution at all, because of their stability due to resonance. But elimination to form alkynes is possible. No nucleophile at all can displace the halide ion in a nucleophilic substitution, but a strong base suffices for elimination.

Why is this?


texts:
Following a book of science experiments for children with my daughter, we did the following:

put some water in a shallow dish;
put some ground pepper floating on the water surface;
touch the water surface with the tip of a small stick previously dipped in liquid soap;
then the floating pepper escapes radially from the soap.

But I was at a loss to explain why. I mumbled something about “surface tension”, but didn't convince even myself.

What was going on?

I am pretty sure that the pepper in itself plays no role but showing the surface motion of water. Am I correct?


texts: What are common solvent removal methods?

texts:
In a laboratory setting, the most common solvent removal method is rotary vacuum distillation. This is something I have performed many times, starting in organic chemistry labs. However, I am interested in learning of other solvent removal techniques.

Specifically, I am having a lot of trouble removing trace levels of solvent (chloroform, heptane, toluene, cyclohexane) from nicotine, which is an oil in its pure form. I have been using a rotary vacuum system to remove the solvent, though traces of solvent always remain. Nicotine is heat sensitive and degrades easily in air. Are there any other methods I should consider?


texts:
Heyo, I'm sure you all know of the experiment where you take a mixture of ice and water, plop some salt in there and the temperature of the solution progressively drops. The salt increases the entropy of the liquid state, shifting somewhat the ice/water equilibrium towards water. As ice is converted to liquid water, the endothermicity of this process leads to a decrease in the temperature of the solution.

Now, I was wondering if the reverse would ever be possible, say you were to have a thermos flask which would be sealed. It would contain Hot Tea and have a slot where one could pour in salt grains without releasing steam. By the logic in the previous question, won't some of the water vapor move to the liquid state (exothermic), resulting in the heatin up of your already hot tea. If possible would this change even be measurable or useful in any sort of way?


texts: Are different enclosing mark types in chemical names needed to differentiate between substances?

texts:
What is the significance of enclosing marks in chemical names in determining the uniqueness of a substance (organic and inorganic)?

Can a simple change in the type of enclosing mark used indicate that we are dealing with a different substance or does it just mean that the names were written slightly differently (or incorrectly)? If I decided that I was always going to use parentheses and never use brackets when naming chemicals would it stop me from being able to differentiate between two substances based on their chemical name or would it just be non-standard?

This article makes me think that switching from a parentheses to a bracket has a different meaning but that a brace could be used in place of brackets just because it makes the name look nicer.

To help illustrate what I mean, the following chemical names differ only by the use of curly braces instead of brackets. Are these two different substances or are they the same substance named slightly differently?

  Poly(oxy-1,2-ethanediyl),.alpha.-[4-[(1,8-dihydroxy-3,6-disulfo-2-naphthalenyl)azo]phenyl]-.ome
  Poly(oxy-1,2-ethanediyl),.alpha.-{4-{(1,8-dihydroxy-3,6-disulfo-2-naphthalenyl)azo}phenyl}-.ome

Update: The Naming and Indexing of Chemical Substances for Chemical Abstracts talks a lot about how punctuation is used to distinguish between different types of substances. It talks a lot about brackets and parentheses in these discussions but almost ignores curly braces. The publication backs up my theory that the differentiation between parentheses and brackets can be important but that curly braces are not. If I am correct then the two chemical names that I listed above are two different names for the same substance. If I can get verification on this or even opinions from chemists, that would be helpful as I am far from a chemist.


texts:
$\pu{1060 g}$ of urea aqueous solution is subjected to heating. It starts boiling at $\pu{100.53 °C}.$  It is heated up to $\pu{102.12 °C}.$ Find amount of water vapourised in grams. (Pure water boiling point is $\pu{100 °C},$ $K_\mathrm{b}$ of $\ce{H2O}$ is $\pu{0.53 K kg mol-1}.)$

When water evaporates will the equivalent amount of urea also evaporate i.e. will we calculate final molality with the same amount of solute or a decreased amount?

I first calculated the initial amount of water as (53000/3) g and then taking the same moles of urea calculated the final amount which came out to be (53000/12) g. So the amount of water evaporated should be 13250 g but the given answer is 750 g.


texts: Why does 1,3-dihydroxybenzene have a higher boiling point than 1,2-dihydroxybenzene?

texts: 1,2-dihydroxybenzene (catechol) shows intramolecular H-bonding. So due to strong bonding, it should be difficult to break the bonds in 1,2-dihydroxybenzene and therefore, 1,2-dihydroxybenzene should have a higher boiling point than 1,3-dihydroxybenzene. Why is it not so?


texts: How to calculate the enthalpy of formation of hydrazine from tabulated values?

texts:
I've been given a problem asking:

  Estimate the standard enthalpy of formation of hydrazine, $\ce{N2H4(g)}$, from the following data.
  \begin{align}
\Delta{}H_\mathrm{B}(\ce{H2}) &= 436~\mathrm{kJ/mol}\\
\Delta{}H_\mathrm{B}(\ce{N2}) &= 944~\mathrm{kJ/mol}\\
\Delta{}H_\mathrm{B}(\ce{N–N}) &= 163~\mathrm{kJ/mol}\\
\Delta{}H_\mathrm{B}(\ce{N–H}) &= 388~\mathrm{kJ/mol}\\
\end{align}

While I know that $\Delta{}H_\mathrm{B}(\ce{N–N})$ refers to the energy released from breaking that bond, I'm not sure what $\Delta{}H_\mathrm{B}(\ce{H2})$ or $\Delta{}H_\mathrm{B}(\ce{N2})$ refers to. Could someone please help me understand?


texts: Rate Expression for Reactions Involving 2° Benzylic Alkyl Halides

texts:
My teacher took off marks because he said the reaction was SN1. Before I go confront him, please tell me if my reasoning is correct.

So, basically, I thought: we have two possibilities:
 1. SN1: a 2°benzylic has the same stability of carbocation as a tertiary carbocation so, SN1 could work.
 2. SN2: we have a secondary carbocation and a weak base cyanide: SN2 could work.

So I just randomly put the rate law for SN2 since the problem did not specify SN1 or SN2 and there is no way I can know which mechanism is prominent.


texts: Why does NO have a residence time of 4 days?

texts: If $\ce{NO}$ is unstable, why does it have an atmospheric lifetime of 4 days? I know that it has a lone pair and one unpaired electron making it highly reactive. Therefore, shouldn't it react immediately in the atmosphere?


texts:
I am using an approximation of density matrix in a high order series expansion to predict the total internal energy of chemical systems. During my research,it was found out that the precision of such algorithm is accurate up to 0.00001 Hartree by optimising the independent parameters, which is roughly 0.026kJ/mol's error fluctuation. I wonder in reality, what can 1 kJ/mol do in our daily life, what phenomena can 1 kJ/mol of energy possibly trigger? I'm quite a mathematical person and haven't really studied enough chemistry nor physics. if someone could give me some physical intuitions that would be greatly appreciated!

And I meant to leave it as a broad question. Since we are not picking a specific chemical system to chew on here, any unbiased thoughts are welcomed and shall be considered in this post! A collective answer from the various point of view is probably a better way to get one's head around rather than a single aspect answer.


texts:
I'm trying to prepare a ZnO thin film deposited on a glass substrate. The precursor solution prepared by sol gel process through dissolving 1 M zinc acetate dihydrate $\ce{Zn(CH_3COO)_2.2H_2O}$ in ethanol with ethanolamine as stabilizer in 1:1 mol ratio with $\ce{Zn(CH_3COO)_2.2H_2O}$. I aged the solution for about 1-2 weeks in a closed glass container. But, after I actually deposited and annealed at 600 °C, the film's XRD measurement seems to show ZnO as well as zinc peak, with zinc somewhat showing stronger peak.

However I also have the one with precursor aged for only 1 day but annealed at 800 °C, this one show peak characteristic that of ZnO with no noticeable Zinc peak. Other samples I have are aged for 3-4 days added with 1-5at% Nickel doping and annealed at 600 °C, they also show strong Zinc peak along with ZnO peak.

In the ones with Ni doping, Zn peak relative to ZnO also seems to get stronger as Ni concentration increasing. It seems like nickel (or its derived compound) acts as catalyst in the reduction of ZnO. The ones with 3at% and 5at% nickel concentration also have solution with green-bluish turbid solution with white precipitates (this probably zinc) unlike 0at% and 1at%, which yields clear solution. This might support that nickel act catalyst.

So, I guess there must be more rate of reduction reaction of ZnO during aging process, or maybe some other reaction that produces Zinc. Maybe something happens during annealing as well, but that seems unlikely since ZnO seems to be stable at 800 °C.

The question:

Looking at the precursor solution, what possible reactions that would produce Zinc from ZnO, and how likely they are?
Is it possible that the reaction of producing Zinc happens during annealing? How likely they are? How much is the rate, can they be neglected?
Do Nickel doping contributes to the production of Zn? If yes, what mechanisms that seem most likely to affect the production of Zn?


texts:
I have some unopened Clorox bleach bought over a year ago (at $8.25~\%\ \ce{NaOCl}$) and read on Wikipedia that bleach naturally decomposes according to

$$\ce{3 NaOCl (aq) -> NaClO3 (aq) + 2 NaCl(aq)}$$

Now, while there potentially might be some further decomposition as

$$\ce{2 NaClO3 (aq) -> 2 NaCl (aq) + 3 O2 (g)}$$

Would I be at risk of filling the air with toxic chlorate intermediates after using this bleach to clean up an ultrasonic ("cool mist") humidifier?


texts:
I saw that most neutralization reactions produce water while some do not.
How can I know if water will be a product in a given neutralization reaction?
I initially thought that water is a product only when an acid reacts with an alkali (producing hydroxide ions) but there apparently exist some counterexamples like the reaction between ethanoic acid and copper oxide.


texts:
While revising Thermodynamics and Thermochemistry from revision material published by Arihant publications I encountered the following mentioned statement.

During dissolution, the physical state of the compound changes while during hydration, there is no change in the physical state of the compound.

How does dissolution result in a change in physical state?

Should not hydration (or solvation in general) be the same as dissolution as in both the bonds of solid salt to be dissolved or solvated weaken and a new bond is formed between constituents of salt and the solvent? Could someone please explain what I'm missing?


texts: Is this chemical name wrong? 2-bromobutane vs 1-bromobutane

texts: Well, technically it's already wrong because it should end in "-propane" but my textbook is so crappy let's just ignore that for a second. The naming convention goes that substituent groups should be named so that they have the lowest number possible. Then, in both of the bromopropanes below, shouldn't they both be 1-bromopropane because there are no other substituent groups besides the bromine?


texts: Calculate rate of reaction of a metal and an acid

texts:
At $10~^{\circ}\mathrm{C}$, a small piece of $\ce{Zn}$ reacts with $\mathrm{2.0~M}$ $\ce{HCl}$ to produce $\pu{15.0 mL}$ of $\ce{H2}$ gas in $\pu{25 s}$. What is the rate of the reaction?

My effort:

I know that the $\mathrm{2.0~M~} \ce{HCl}$ concentration needs to be used and started the following calculation:

$$\mathrm{2.0~M} \times \frac{1}{2} \times \frac{1}{\mathrm{25~s \times 0.015~ mL}} = \mathrm{0.00060~mol}~ \ce{H2}$$

$\mathrm{mol ~\ce{H2}} = \mathrm{mol~Zn} = \mathrm{0.0006~mol}$

However, the given answer is 0.060 mol of Zn.


texts: Why might two different chemical structures smell the same?

texts: From what I understand, it is the functional group attached to a structure that determines the odor it will give off, for the most part. Which explains why two similar molecules, except for their functional groups, would smell different. So, would that make it so that two different molecules with the same functional groups would smell the same?


texts: Why is silicon oxide giant covalent structure? Why it doesn't bond like carbon dioxide?


texts: Is there a scale for stickiness of glue?

texts:
Non-specialist question stemming from standing in front of a dizzying aisle of consumer adhesives... These differentiate themselves via meaningless superlatives like "serious", "extra" and "ultra". I just wanted to know suitability-for-different-materials and some quantitative measure of "stickiness" :)

Update: Could there be a consumer rating system for glue - based on existing professional testing standards?
(Note a rating system doesn't have to be a single numeric measurement in scientific units so can include any scaling/grouping function and include material classfications etc)


texts: Why isn't Indigo soluble in water? I mean, it has 2 H-N groups, shouldn't it then be able to hydrogen bond with water?


texts: How many electrons are around the platinum in an ethenetriplatinate complex?

texts:
In $\ce{[Pt3(C2H4)]-}$, how many electrons are there around platinum?

While solving this problem I thought three $\ce{Pt}$ formed a triangle with ethylene above. But I was confused about how the $\ce{C2H4}$ gave electron pairs to $\ce{Pt}$. In addition, the answer gives $16$, but I only see the initial $10$ electrons around a $\ce{Pt}$ and $2$ given by another two $\ce{Pt}$.
What is the exact structure of this coordination compound, and how can it be deduced?


texts: What are the dimensions of a and b in van der Waal's real gas formula?

texts:
In the van der Waal's formula for real gases $\left( p+\frac{a}{V^2}\right)(V-b)=nRT$, what are the dimensions of $a$ and $b$?

I learnt that $a$ is related to the average force of attraction between the molecules and $b$ is related to the total volume of the molecules, but I fail to understand their dimensions.


texts: What form is the ionic equalibrium equation? I have problem asking for it, but I'be done so many different equalibrium equations that I'm starting to get mixed up on which one is called what... Which one is it?


texts: Why is the thermal expansion coefficient zero along the line of maximum density in liquids? Why is $(∂^{2}V/∂T^{2})_{P} > 0$ along the same line?


texts:
I have synthesized (1S, 2S)-1,2-diphenylethene-1,2-diol, and I'm wondering why the $\ce{OH}$-peaks in the IR-spectrum looks the way it does. I would expect a broad signal (because the solution wasn't diluted, and because free $\ce{OH}$-stretch happens at $\pu{3580-3700 cm^{-1}}$). So why these two separate, distinct, signals at $\pu{3394}$ and $\pu{ 3499 cm^{-1}}$?

(the IR-spectrum)


texts: Why is fluorine the best oxidising agent, but also the most basic?

texts:
(Please note that all comparisons I have made below are with respect to halide ions only.)

According to what I have learnt, the fluoride ion is the most basic ion, because it has the smallest size and thus the highest electron density. This implies that it has the highest tendency of sharing/giving away its electron density.

Why isn't the same logic applicable when reducing strength is compared? Fluorine should have the highest tendency to lose electrons, and hence should be the best reducing agent.


texts: Can the reaction intermediate be lower in energy than the reactants or products?

texts:
It makes sense to me that reaction intermediates exist transiently if they are of higher energy than the reactants and the products, my organic chemistry textbook seems to give me information that doesn’t seem to match up.

My knowledge is that the overall activation energy of the reaction is the energy change between reactants and the highest-energy transition state and the overall energy change is he energy difference between the reactants and the final products. If intermediates could be of lower energy levels than either the reactants or products, would this definition change?

I am confused because the solutions manual to one of the problems gives me an energy diagram with an intermediate that is of lower energy than both the reactants (but not the products), and labels the overall activation energy as the energy change between the intermediate state and the highest-energy transition state. The textbook also gives me an energy diagram of a catalyzed reaction that has several intermediates of lower energy than the reactants, but not the products.

(The textbook I’m referring to is Organic Chemistry. 8th edition by John McMurry)

Would it make sense for intermediates to only be lower in energy than the reactants but not the products since the products would still be more favorable and stable than any of the intermediates? Would this only happen if there is a catalyst?


texts:
I have been thinking of the rate of reaction of aryl bromide and aryl chloride with  $\ce{Mg}$ to form Grignard.

When considering the electronegativities the carbon in aryl chloride is more positively polarized. But when considering the bond energies carbon chlorine bond is stronger.

I want to know which factor is more significant when we consider the reaction rates of aryl chloride and aryl bromide with $\ce{Mg}$ to form Grignard.


texts: I seem to have a drain pipe in my flat blocked by what seems to be a latex/rubber glove. I am unable to pull it out — is there a chemical that can reliably dissolve the glove and at the same time not damage the PVC pipe itself?


texts: Can stimulated Raman processes be strong enough to drive out of equilibrium?

texts:
In the (spontaneous) Raman process, incident light $\hbar \omega_1$ scatters and transfers some energy $\hbar \omega$ to a vibrational excitation of molecule or solid.

Typically this is a very rare process, and only happens to one of every $10^9$ photons or so. So even if a sample is irradiated with a ultrafast pump laser of high intensity, Raman processes tend to not be significant enough to move the system out of equilibrium. This is in comparison to something like direct absorption processes which easily bring the system out of equilibrium and often dominate the response.

But the discussion above is for spontaneous Raman processes and makes me wonder, what about stimulated Raman processes? In the case of stimulated Raman, two photons come in with $\omega_1-\omega_2=\omega$, causing vibrational excitations to be much more efficiently created.

So my questions are

In practical cases, what is the efficiency of Stimulated Raman processes? In other words, for a given number of pump photon $n_1$ and Stokes photon $n_2$, what are some ballpark numbers for the number of vibrational excitations created?
Can stimulated Raman processes be so strong as to move a system out of equilibrium in a pump-probe setup?


texts: Omission of locants for functional groups in IUPAC names

texts:
I'm having a bit of conflict while naming molecules as per IUPAC the nomenclature rules. If we take the following compound for example,

IUPAC would say that that correct name is 2-phenylacetaldehyde. But then for this molecule,

IUPAC designate it the name is chloroacetaldehyde.

Why does the aldehyde with a benzene ring as a functional group receive a '2' while the aldehyde with a halide as a functional group does not? I figured the molecules mentioned above wouldn't require a number to designate their functional groups given they're both substituents to an ethane parent chain.

Also, would it be acceptable to drop 'aldehyde'  and replace it with 'ethanal'. I've always been taught to add '-al' with a '-CHO' functional group?


texts: I have looked at other questions, videos and articles but  I kept reading disorganization, messiness or energy distribution (probability) or a thermodynamical equilibrium and stuff. What do we mean by disorganization? And some say that it is a wrong definition. Also, there is this spontaneity and what is its relation to entropy? I am very confused and I would be very pleased if anyone explained it.


texts: Synthesis of methylenecyclohexane from cyclohexylmethanol

texts:
I want to form methylenecyclohexane from cyclohexylmethanol

I'm thinking about an $\mathrm{E1cB}$ mechanism since the β-hydrogens will be quite acidic (similar electronegativity to fluorine). So I can use a strong and hindered base (to reduce $\mathrm{S_N2}$) to form methylenecyclohexane.

Another possibility is a weak hindered base for an $\mathrm{E1}$ Hofmann elimination (since the carbocation will rearrange). But not only will this lead to a some amount of Zaitsev product, $\mathrm{S_N1}$ will dominate because of better thermodynamics (net 1 σ formed vs net 1 π formed that is not very stabilized either).

I feel like $\mathrm{E1cB}$ would be a better idea.

Are there any better methods?


texts: Expressions for constant volume and constant pressure heat capacities

texts:
My lecture handout says:

$$C_V = \frac{\mathrm{d}q_V}{\mathrm{d}T} = \left(\frac{\partial U}{\partial T}\right)_{\!V}$$

I understand that $C_V = \mathrm{d}q_V/\mathrm{d}T$ and that $\mathrm{d}U = \mathrm{d}q_V$, but what's the need for the partial derivative? Why can't you just substitute and get:

$$C_V = \frac{\mathrm{d}U}{\mathrm{d}T}$$

Likewise for the constant pressure heat capacity:

$$C_p = \frac{\mathrm{d}q_p}{\mathrm{d}T} = \left(\frac{\partial H}{\partial T}\right)_{\!p}$$


texts:
For my AP Chemistry class we were told to make a molecular diagram that was "better than excellent" and the rest is up to us (we could choose the molecule and how we wanted to represent it).

My group chose benzoylmethylecgonine, or $\ce{C17H21NO4}$, also known as cocaine.

This is proving to be a difficult task as I now realize that cocaine is a pretty complicated molecule and I couldn't find much on the 3D molecular structure.  If anyone could explain its chemical structure, it would be very appreciated.


texts: Calculations for making a buffer from a weak base and strong acid

texts:
How many moles of $\ce{HCl}$ must be added to $\pu{100 ml}$ of a $\pu{0.100 M}$ solution of methylamine ($\mathrm pK_\mathrm b = 3.36$) to give a buffer having a $\mathrm{pH}$ of $10.00$?

(The answer is supposed to be $\pu{8.1 mmol}$.)

My thought process:

First, I found the $\mathrm pK_\mathrm a$ of methylammonium ion:

$$\begin{align}
\mathrm pK_\mathrm a(\ce{CH3NH3+}) &= 14 - \mathrm pK_\mathrm b(\ce{CH3NH2}) \\
&= 10.64
\end{align}$$

Substituting this into the Henderson–Hasselbalch equation

$$\begin{align}
\mathrm{pH} &= \mathrm pK_\mathrm a + \log\left(\frac{[\ce{CH3NH2}]}{[\ce{CH3NH3+}]}\right) \\
10.00 &= 10.64 + \log\left(\frac{\pu{10 mmol}}{x}\right)
\end{align}$$

where $x$ is the amount of $\ce{HCl}$ that must be added. However, when I solve for $x$ I find $x = \pu{43.7 mmol}$, nowhere near the correct answer. What am I missing?


texts: If we use Magnesium instead of the sodium with alkyl halide in dry ether then will a reaction similar to Wurtz reaction will occur

texts: I know that a grignard reagent will formed will be formed but if you look at his question then the answer of this question is b. so I just want to know if something like wurtz reaction will take place if there is some another explanation for this answer.


texts: Why does the equilibrium constant change on scaling the stoichiometric coefficients of a reaction?

texts:
I read in my textbook that if we multiply a chemical reaction by some factor(let's say $b$) its new equilibrium constant becomes $K^b$.But I don't understand why this happens..
What is the difference between the reaction $\ce{A} + \ce{B} = \ce{C}$ and $b \ce{A} + b \ce{B} = b \ce{C}$ ?
Aren't the two reactions same? So why does the equilibrium constant change?


texts:
For an elementary chemistry class percent error is calculated as:
 [actual-experimental]/actual x 100%  edit:bracket represents absolute value

So my question is if the experimental is close enough to the actual that the subtraction would give zero significant figures, would then the percent error then be zero?
EX: measured density of 0.997g/ml and actual density of 0.997171g/ml then,
0.997171-0.997=0.000171 which would be rounded to 0.000 due to sig. figs. -> there are no significant figures so this would mean the calculated 0.0171% error would be zero correct.  If I remember my analytical correctly we will do away with sig. figs. and work with the propagation of error within each measurement but I have not thought about how this would work in a problem like this.

Thank you in advance.


texts: Rock salt structure: chloride lattice or sodium lattice?

texts:
Source

From this diagram of the rock salt structure ($\ce{NaCl}$) we see that both the chloride and sodium ions have the same environment. That is to say, they each have the same number of neighbours at every distance, except that the charges are opposite.

However, I've always been taught to consider the chloride ions as forming a face-centred cubic (fcc) [or cubic close packed (ccp)] lattice, with sodium ions filling octahedral holes.

Is there any reason why we can't think of it the other way round, with sodium ions forming the fcc lattice and chloride ions filling octahedral holes?

Is it perhaps because sodium ions are smaller than chloride ions, or something else?


texts:
I know iron can react with many solutions, but when I tried to mix iron powder together with permanganate or dilute sulphuric acid, the iron powder would not react and instead, it just float on the surface of the solution. I tried to stir it for several minutes but it seems doesn't work.

It is pure iron powder, can be attracted by magnet

How can I dissolve iron powder and let it become $\ce{Fe^2+}$ or $\ce{Fe^3+}$ ? (Just dissolve it is ok)


texts: ORCA: How to plot an adiabatic potential in dihydrogen H2 molecule?

texts:
I stared to study ORCA, and I try to obtain classical results for dihydrogen as for example. I need to get a starting point to understand what needs to be done.
So, How to plot an adiabatic potential in dihydrogen H2 molecule with ORCA calculation?
! RHF OPT def2-QZVPP
%geom Scan
B 0 1 = 1.0, 3.0, 12
end
end

* xyz 0 1
   H        0.000000       0.00000        0.00000
   H        0.800000       0.00000        0.00000
*


texts: Synthesis of trans alkene with organoborane

texts:
Trans alkenes can be synthesized with organoboranes. The following sequence is represented in Smith's Organic Synthesis

How does the mechanism look like after the first step (hydroboration)?


texts:
Disclaimer: This question comes from a physics student.

I was studying electrostatics and I was wondering how to charge a conductor at home without any fancy furs etc. So an idea came to me: take a battery, touch for example the negative terminal with the conductor and then remove it. Since the negative battery terminal is at a negative potential and the conductor was previously grounded ($V = 0$) then as their potentials must become equal, it means that electrons will flow from the battery terminal to the conductor for a short period of time. Afterwards, I disconnect the conductor and the electrons remain 'trapped' in it hence the conductor is now negatively charged.

At least that was the idea. Now suppose that the battery is a galvanic cell ($Zn, Cu$). The question is whether there are free electrons floating inside the $Zn$ anode when it is not connected to the cathode?

The whole system (battery, wires) is electroneutral while the current is flowing e.g. Zinc atoms at anode dissolve and electrons stay at the anode while the $Zn^{2+}$ ions go to the solution, but in the same instant other electrons leave the anode.

When the electrodes are not connected, I'm not sure would the redox reactions happen. In my understanding, $Zn$ oxidizes because $Cu$ on the other side has greater electron affinity, but $Zn$ would have to be able to 'sense' $Cu$ on the other side somehow, otherwise the oxidation reaction happens anyways for a short time until it reaches some equilibrium point. This is what I think actually happens and that's why the anode would actually be negative until connected to the cathode.

So am I on the right track with this and ultimately, will my attempt to charge the conductor a bit succeed?


texts: Finding 1/V from absorbance in Lineweaver-burk plot

texts:
I’ve got six test-tubes with $0.5\ \mathrm{ml}+0.5\ \mathrm{ml}$ of 0.005 %, 0.0025 %, 0.00125 %, 0.000625 %, 0.0003125 % and 0.0003125 % starch and 4.2 pH phosphate buffer solution (2, 4, 8, 16, and 32-fold dilution of 1 % starch solution).
0.5 ml of beta-amylase was added to each test-tube, and heated (without sixth test-tube). Then the absorbance of each specimen was measured (sixth test-tube used as reference) in 530 nm wavelength.

I have to find the $K_\text{M}$ of β-amylase from Lineweaver–Burk graph.
There is no problem with plotting $x$ points on graph (it’s just a reciprocal of substrate concentration).
But how can I use absorbance data to find $V$ that I need to plot on $y$-axis?


texts:
The rates of diffusion of two gases $\ce{A}$ and $\ce{B}$ are in the ratio $1:4$. If the ratio of their masses present in the mixture is $2:3$, the ratio of their mole fraction is?

My tries:

$\frac{r_1}{r_2}=\frac{1}{4}=\sqrt{\frac{M_2}{M_1}}\to\frac{1}{16}=\frac{M_2}{M_1}$, $M_i$ is molar mass of $i$.

Also given $\frac{w_1}{w_2}=\frac{2}{3}$, multiplying this by above one gives $\frac{M_2\cdot w_1}{M_1\cdot w_2}=\frac{2}{3\cdot 16}\to\frac{n_1}{n_2}=\frac{1}{24}$, where $n_i$ represents number of moles of $i$.

But this is not a correct answer please help.


texts: Closed shell structure & intrinsic molecular (electric) dipole moment

texts:
Does the closed shell structure of a molecule imply that it has an intrinsic (electric) molecular dipole moment? If so, why is that?

I came across this in paper [1], which seems to suggest that this is the case on page 6 (top left-hand corner):

  While both inorganic thin ﬁlms and organic monolayers alter the charge rearrangements between the two contacting bulks, organic molecules add their own, “intrinsic” dipole caused by the closed shell nature of molecules. Thus, electron-withdrawing (e.g., halogens, $\ce{CN}$, and $\ce{NO2}$) or -donating groups (e.g., $\ce{OMe}$ and $\ce{NH2}$) can induce huge electric ﬁelds within a
  single molecule. Adsorbing molecules so that they will be at solid interfaces can in principle aﬀect, and thus modify, any of the interfacial mechanisms: interface traps ..., molecular dipoles ..., and charge rearrangement ...

Bibiliography

Vilan, A.; Cahen, D. Chemical Reviews 2017, 117 (5), 4624–4666.
DOI 10.1021/acs.chemrev.6b00746.


texts: When is it necessary to include solvent effects?

texts:
When modelling a process like keto-enol tautomerization or SN2 ring opening reaction, I am unsure as to what factors need to be considered when deciding whether solvent effects need to be accounted for. Because if they are important, a solvation approach, implicit or explicit is chosen to model the process.
For example, in a keto-enol tautomerization, solvent effects are important as the equilibrium is maintained by the solvent.

What I was thinking is that using the explicit water model, as few as  1 to 2 water molecules can be used to model the tautomerization. But many studies are showing that continuum solvent models (implicit) are the benchmark for keto-enol tautomerizations. I don't understand why and what factors determine this?


texts: How can randomly oriented molecules in a liquid solution create a certain polarization pattern (d or l)?

texts:
How can a large number of moving, randomly-oriented chiral molecules in a watery solution twist light only to the left or only to the right?

Wouldn't a levorotary molecule become dextrorotary if I turned it around?


texts: Where to find data for Gibbs energy, enthalpy, and entropy?

texts: Where can you find the enthalpy and Gibbs free energy of formation and entropy of compounds either as a data file or web API? Technically, I only need two since I can figure out the other one from two of them.


texts: What is the molarity of a solution made by dissolving 25.63 grams of naphthalene (MM = 128.17g) in 250.0 grams of benzene?

texts: I don't really understand how to find the amount of liters with benzene in order to find the molarity.


texts: Freezing Point Depression and Temperature Decrease

texts:
I don't have a problem understanding the chemical mechanisms underlying freezing point depression or colligative properties in general, but what I cannot seem to grasp is how if you add salt to ice you end up with a salt-ice-water solution that is actually colder than the ice you started with.

Two other places on this site go into detail about this matter but I feel like it is either not totally correct or just not fully explained. I assume I must not fully understand in the first place, also. The two links are posted immediately below pertaining to the subject.

Where does the energy come from to lower the temperature of a brine solution?

Why does ice water get colder when salt is added?

How can the ice be cooling as it melts, as these links seem to claim?  I understand that it would be cooling its surroundings by needing to absorb heat to melt, but it's a phase transition so the temperature of the ice should remain constant. Furthermore, if the temperature remains constant, and the ice continues to absorb heat from the water surrounding it in order to melt since it's above its depressed freezing point, wouldn't you have the impossible feat of heat flowing from cold to hot as the water gets continuously colder, as alleged?

Energy is being used in the phase change from solid ice to liquid water. Heat is being absorbed by the ice. Yes, the ice freezes at a much lower temperature and so it will be liquid at a certain range of higher temperatures than it otherwise would be without salt. As it melts it tries to approach its new
ice-water-salt equilibrium which will be at a depressed freezing point. Why does the temperature fall? Especially if phase changes occur at constant temperature?

The energy must be coming from somewhere and going to somewhere, but where? And how can a hot-to-cold temperature difference for heat transfer actually be maintained if the salt solution is getting colder but the phase change (melting ice) is constant temperature?

I'd really appreciate some sort of insight to this.


texts: Does this reaction require catalyst/solvent?

texts: Planning on synthesising 2-formylphenyl benzoate by reacting benzoyl chloride with salicylaldehyde. Since both Benzoyl chloride and salicylaldehyde is liquid, will it require a catalyst/ solvent? Or do I just add them both in a conical flask and let a magnetic stirrer do the job?


texts:
Determine the concentrations of the three ionic forms of glycine present if 1.0 mol of glycine is used to make 1.00 L of aqueous solution. $\mathrm{p}K_1 = 2.34, \mathrm{p}K_2 = 9.60$. Do you need to make any other assumptions to simplify the calculation?

Source: David Ball's Physical Chemistry.

I tried to solve this problem but I think it's quite flaw and naive. So I want to put it here if anybody have an improvement.

The question asked us to determine the concentrations of 3 ionic forms of glycine in aqueous solution. Let me call

$\ce{Gly}$ = $\ce{NH2-CH2-COO^-}$ at high alkalinity
$\ce{GlyH}$ = $\ce{NH3^+-CH2-COO^-}$ at neutral
$\ce{GlyH2}$ = $\ce{NH3^+-CH2-COOH}$ at high acidity

I can calculate the isoelectric point $\mathrm{pI} = (\mathrm{p}K_1 + \mathrm{p}K_2)/2 = 5.97$

If I assume "used to make $\pu{1.00L}$ of aqueous solution" means putting glycine into water, $T = \pu{25^\circ C}$, thus $\mathrm{pH}$ must be 7.00. However, the isoelectric point is 5.97. That means the solution cannot contain completely GlyH but also an $x$ amount of Gly.

Therefore, I use the Henderson-Hasselbalch equation to determine the amount of Gly and GlyH in the solution

$$
\begin{align}
\mathrm{pH} &= \mathrm{p}K_2 + \log\frac{[\text{Gly}]}{[\text{GlyH}]}\\
7 &= 9.6 + \log \frac{x}{1-x}\\
x &= 0.0025 M = [\text{Gly}] (\text{rounded})\\
[\ce{GlyH}] &= \pu{0.9975 M}\\
\text{Obviously } [\ce{GlyH2}] &= \mathrm{0 M}
\end{align}
$$

I think the wrong with my solution is to assume a fixed value of water pH. In common sense I think when glycine is put into water, it would drag the pH of the solution down a little bit, but not over pI, it means $\mathrm{p}K_1 < \mathrm{pI} < \mathrm{pH} < 7 < \mathrm{p}K_2$. But I really don't know how to find the value. Please guide me because I tried my best but really don't know how to solve this.


texts: Isomer Identification Using Condensed Structural Formulae

texts:
Which of the following pairs are isomers?
a) $\ce{C5H10}$ and $\ce{C10H20}$
b) $\ce{CH3(CH2)4CH3}$ and $\ce{CH3(CH2)3CH3}$
c) $\ce{CH3CH(CH3)(CH2)2CH3}$ and $\ce{CH3(CH2)2CH(CH3)2}$
d) $\ce{(CH3)3CH}$ and $\ce{CH3CH2CH2CH3}$

My textbook says the answer is C). I beg to differ. I think it is D). C) is just a different way of writing 2-methylpentane.


texts: What metals aren't dissolved in/attacked by aqua regia?

texts:
Aqua regia (Latin: Royal Water) is one of the strongest acids known in Chemistry, and is capable of dissolving gold and platinum.

My copy of the Oxford science dictionary goes on to say (under the entry: Aqua regia) that metallic silver does not dissolve in aqua regia. Morever it does not  mention any other examples of aqua regia-resistant metals. Further down, it mentions that silver's invulnerability to aqua regia is due to the formation of a protective silver chloride coating on the metal, which serves to protect the metal from further decomposition.

However, this Wikipedia article claims:

  ...aqua regia does not dissolve or corrode silver...

This, I find contradictory to the dictionary's "formation of silver chloride" claim.

So,

What metals (elemental, forget alloys) are neither attacked by nor dissolved in (freshly prepared) aqua regia?
What makes those metals that don't dissolve or corrode in aqua regia so impervious to the acid?
Does silver metal actually develop a silver chloride layer on exposure to aqua regia? If so, would that mean the Wikipedia article is incorrect?


texts: Is it possible to synthesize amino acids from hydrocarbons?

texts: I recently heard that during some period of time Purina pet food was being produced from crude oil via a set of complex chemical transformations. Which, I think, is mostly bluff and marketing. So is it possible, and have somebody had any real positive practical experience of getting amino acids from hydrocarbons?


texts: Sugar solutions have a neutral pH in themselves, but it makes your body acidic. Why?

texts:
I'm not an expert, but as far as I understood a sugar solution is completely neutral since sugar can't take hydrogen ions out of the water or donate them in. Sugar is a non ionic compound, so it does not release H and OH ions in the water so it will not make the solution acidic or alkaline.
I keep on reading and seeing charts of how sugars make your body acidic, like this one:

What process makes a neutral pH solution into an acidic one?
I'm not into chemistry at all and therefore the simpler the answer the better.


texts: Why doesn't fluoride ion have highest nucleophilic power (nucleophilicity)?

texts:
As you can see from the image above,

'$\ce{R3C}$' anion has 1 lone pair
'$\ce{R2N}$' anion has 2 lone pairs
$\ce{RO}$ anion has 3 lone pairs
$\ce{F}$ anion has 4 lone pairs

According to VSEPR theory,

  lone pair-lone pair repulsion >  bond pair-lone pair repulsion >  bond pair-bond pair repulsion

As fluoride ion has the greatest number of lone pairs (= 4), it should suffer from highest number of lone pair-lone pair repulsions.

In order to reduce its  lone pair-lone pair repulsions and thus its unstability, shouldn't it donate its lone pair more readily than other anions? Thereby, shouldn't fluoride ion have more nucleophilic tendency than the other (mentioned) anions?


texts: acid strength: Periodic trends vs delocalisation, which one is more important

texts:
In 1st year chemistry questions, the concept of acid strength is often introduced to students including the 3 factors that provide a heuristic explanation for most of the common acids and conjugate bases: Electronegativity of the atom directly attached to the protic hydrogen, resonance stabilisation and inductive effects. It is also often taught that resonance stabilisation dominate inductive effects.

Now it seems there is the following curious case: $\ce{HNO3}$ and $\ce{HCl}$. Both are considered as strong acids with negative pKa and experimental measurements showed that the pKa of $\ce{HCl}$ (and all halide acids except HF) are lower than $\ce{HNO3}$ and hence $\ce{HCl}$ is stronger.

The common explanation is often given as because $\ce{Cl}$ is more electronegative than $\ce{N}$. However such explanation is quite unsatisfactory as it ignores the fact that the $\ce{NO_3^-}$ is not only larger in size than $\ce{Cl^-}$, but has its negative charge being more delocalised among the oxygens than $\ce{Cl^-}$ (argued from its 3 resonance contributors where each oxygen has a formal charge of -2/3 and also that in MO theory, none of the antibonding orbitals of $\ce{NO_3^-}$ are occupied. Thus based on these heuristic, it seems there is every reason that the electron delocalisation of $\ce{NO_3^-}$ could have dominate the electronegativity of $\ce{Cl^-}$ as their values are only -0.12 apart (meanwhile $\ce{O}$ is roughly 0.24 apart from $\ce{Cl^-}$)

It is also hinted in this comment, that $\ce{Cl^-}$ is more solvated than $\ce{NO_3^-}$ and hence may play a role in the easier dissociation of $\ce{HCl}$. However, such concepts will not be covered in great detail for first years, and hence such a complication can be potentially confusing to students.

  How can we check whether delocalisation or electronegativity effect dominates in the stability of a conjugate base, and how should we rationalise to students that electronegativity often beats delocalisation?


texts: Two electron integral evaluation over primitive Gaussians without recurrence relations

texts: I want to evaluate two-electron integrals over s, p, and d primitive Gaussian functions. The procedure is presented for s-type ones in "Modern Quantum Chemistry" by Szabo and Ostlund, but I need to evaluate these integrals for p and d ones. However, most books, such as "Molecular Electronic-Structure Theory" by Helgaker which I read, evaluate these integrals using recurrence relations. Is there any other method which can evaluate two-electron integrals, without using recurrence relations?


texts:
While solving a few questions a came across a problem which asked me what would happen when sec-butyl ethanoate was heated.
I had never read about this reaction before and took to researching through a few of my textbooks, but could not find an explanation as to what would happen.
I also thought along the lines free radical formations and tried to make an attempt.
However according to the answer the reaction was a syn elimination and it would give a Hoffmann product. But I couldn't get any more information out of it.
But now I was stumped. So please help me out of you know anything about this.

Edit:
After googling for sometime I came across a paper which said that this particular compound would decompose to give cis butene.
However I could not understand the reason for this. Here is where I saw it:
https://pubs.acs.org/doi/pdf/10.1021/i360047a014


texts: How can I prepare two phosphate buffer of different concentrations but give same pH?

texts:
How is it that buffers of different compositions can have the same pH? For example, it is possible to prepare 0.01 M phosphate buffer of pH 7.0 and 0.1 M phosphate buffer of pH 7.0? How?

I used Henderson-Hasselbalch equation, but still failed. No way is working. Is it something related to volume? Can it be shown mathematically? Can anyone show it mathematically that it is possible?


texts: Comparing pKa of Alpha and Beta Amino Acids

texts:
The $\mathrm{p}K_{\mathrm{a}}$ of the functional groups in L-glutamic acid (shown below on the right) from left to right are $4.1$, $9.5$, and $2.1$. Predict the $\mathrm{p}K_{\mathrm{a}}$ values of B-glutamic acid (below on the left).

I am not sure on the answer and I am just guessing here.
The $\mathrm{p}K_{\mathrm{a}}$ value for the $\ce{COOH}$ group on the right will increase at it won't be stabilised by the amino group any more. The $\mathrm{p}K_{\mathrm{a}}$ of the $\ce{COOH}$ on the left won't really change.I am guessing that the $\mathrm{p}K_{\mathrm{a}}$ of the amino group will decrease. That is a complete guess.
Can anyone please explain how exactly the amino group effects the stability of the $\ce{COO-}$ group and also how the $\ce{COOH}$ group effects the stability of the $\ce{NH3+}$ group.


texts: How to report a triplet of septets in NMR tabulation?

texts:
Does anyone know the proper format to report an iso-butyl group, eg. $\ce{R-CH2-C\color{red}{H}(CH3)2}$, in $\ce{^1H}$ NMR tabulation? The proton in red should be a triplet of septets, so I've written:

δ 2.72 (d, J = 5.5 Hz, 2H), 1.80 (tsep, J = 5.5, 5.3 Hz, 1H), 1.02 (d, J = 5.3 Hz, 6 H).

Is the use of "tsep" acceptable here?


texts: How to determine relative size of polyatomic ions?

texts:
How would you determine the size of a polyatomic ion?

For example when determining which ion is bigger, $\ce{NH2-}$ or $\ce{I-}$, what would you use to determine the size difference?

I know that $\ce{I-}$ would be much smaller than $\ce{I2-}$ (since the $\ce{e-}$ are not held as tightly in the $\ce{I2-}$ causing the repulsion to increase)

But what basis do we use to determine size of a nonelemental atom like the polyatomic ion or a more complex molecule for that matter?


texts: How can a Zn-Cu galvanic cell have a voltage of 1v in stead of 1.1v

texts:
Let s say a galvanic cell based on the reaction of zinc and copper half-cells. How is it possible to get the voltage at 1V in stead of 1,1V?

My guess: maybe by modifying the salt bridge in some way as this influences the charges in some way, but I am really not sure.


texts: Why are the axial bonds of PF5 longer than those of the equatorial bonds? (Hybridization)

texts:
The axial bonds of $\ce{PF5}$ are longer than those of the equatorial positions.

One explanation is that because the axial bonds are experiencing more repulsion
than those of the equatorial and this leads to longer bonds.

Another explanation is that the axial bonds of p/d hybrids, whereas the equatorial bonds are s/p hybrids.

I am able to comprehend and appreciate the first explanation. However, I am unable to understand how there are differences in the hybrids. I had always considered d hybrids a dubious argument at best, and I believed the hybridization would lead to degenerate orbitals.

However,  the explanation provided would suggest otherwise, that there are different hybridized orbitals of different energies at different portions of a single hybridized atom (excluding lone pairs. I understand those being non-hybridized in a hybridized atom).

Thus, my question is how the hybrid argument that was presented works and how would one be able  to realize the different hybridized states of an atom in a molecule (as an approximation).


texts: Thermal Decomposition of Sulfur Hexafluoride

texts:
What is the thermal decomposition temperature for $\ce{SF6}?$ I've heard it decomposes into $\ce{F2}$ and $\ce{SF4}$ only to decompose further into $\ce{S2}$ and $\ce{F2},$ but I haven't found much on the topic.
I became curious since I was considering using it to flush out oxygen for some reactions I was doing, due to its density and stability (plus we have a bunch lying around), but was concerned about it decomposing into more toxic compounds if the reaction or apparatus were to get too hot or if a spark were to occur.

I do not plan to actually do this. It was a silly idea I had, and I realized soon after posting this that $\ce{SF6}$ is a bad idea for these purposes since it is a greenhouse gas.


texts: Is the inductive effect always measured relative to hydrogen?

texts:
Wikipedia has defined the Inductive effect thus:

  "In Chemistry and Physics, the inductive effect is an experimentally observable effect of the transmission of charge through a chain of atoms in a molecule, resulting in a permanent dipole in a bond."

Recently, I learned from a teacher that the inductive effect of any atom/group is always measured with respect to hydrogen.

Under this definition, we would ideally attach the atom/group with an atom of hydrogen and observe the direction of the dipole moment caused by the difference in electronegativity between hydrogen and the atom/group in question. If the electrons-initially positioned at the middle of the bond-are pushed toward hydrogen, the atom/group is termed as a "$+I$", electron-donating group. On the other hand, if the electrons are pulled toward the atom/group, it is termed as a "$-I$", electron-withdrawing group. Thereafter, this atom/group will always exhibit this type of inductive effect. Even if a situation does arise, in which it appears as though an atom/group that exhibits the $-I$ effect with hydrogen is exhibiting the $+I$ effect with another atom/group, this must be the cause of other dominating effects such as the mesomeric effect and in those cases also, it is said that the atom exhibits the $-I$ and not the $+I$ effect.

To illustrate the clear distinction between the definition put forward by the teacher and the one on Wikipedia, let us consider a molecule of $\ce{Cl2}$.

Under the definition on Wikipedia, it is clear that $\ce{Cl2}$ is a non-polar molecule (i.e. No permanent dipole moment has been experimentally observed in this molecule). Hence, no inductive effect is in play and neither of the two $\ce{Cl}$ atoms show either the $+I$ or $-I$ effect.

On the other hand, if we work with the definition put forward by the teacher, we observe that an atom of $\ce{Cl}$ exhibits the $-I$ effect when attached to an atom of hydrogen, being more electronegative than it. Therefore, in the $\ce{Cl2}$ molecule, no permanent dipole exists as a result of the $-I$ effect of both chlorine atoms cancelling away from opposite directions.

It appears that only one of these two definitions is definitely correct and I am confused as to which one that is.


texts: How is this Cope Reaction forming Ethene as major product?

texts:
I have been asked to find the major product of the reaction:

As this a case of pyrolysis of $3^{\circ}$ Amine Oxide (or, in other words, Cope Reaction), I figured there are two possible products hexene and hex-2-ene. Therefore, hex-2-ene should be the major product as it is the more substituted alkene.
But the solution to the question states that the major product is Ethene ($\ce{H_2C=CH_2}$). I have no idea how that is even possible.
Here is how I came to the conclusion that hex-2-ene will be the major product (which is basically the standard Cope reaction mechanism):

Please provide clarification on this.


texts: Most contributing resonance structure of phosphoric acid

texts:
I am uncertain about the structure of $\ce {H_3PO_4}$ because different sources show different ones.

The structure shown here is:

while Wikipedia gives this one:

Arguments in favour of the 2nd structure:

Structure having filled octet for second row elements (C, N, O, F) are stable.
Structure having minimum number of formal charges and maximum number of bonds.
Structure in which there is minimal charge separation while keeping the formal charges closer together.

Arguments supporting the first structure:

Structure in which negative charge appears on the most electronegative atom should be chosen.
I feel that this could be more contributing because in the first structure sulphur has an expanded octet while $d$ orbitals are of higher energy so it's more favourable to form bonds without using them.
Structure having filled octet a for second row elements ($\ce {C, N, O, F}$) are stable. (followed by both structures)

$\ce {H_3PO_4}$ is different from phosphate ion.None of the answers in the linked question directly state what would be the more contributing structure. They focus on the hybridisation of P in phosphate.


texts: What is the possible side product when mixing citric acid, NaCl, Cu, Al, H2O2, and an unknown photoresist?

texts:
When etching circuit boards, a somewhat commonly used substitute for (expensive and messy) ferric chloride is a mixture of an acid, a source of chloride ions, and hydrogen peroxide. If I understand the chemistry correctly, the acidic environment allows the copper to react with the chlorine ions to make $\ce{CuCl2}$, which will more slowly react with the copper again to make $\ce{2 CuCl}$. Adding oxygen to the solution (from the peroxide or just by aerating it) makes $\ce{CuO}$ and $\ce{CuCl2}$ again, allowing the process to repeat.

I meant to mix $\ce{H2O2}$, acetic acid and table salt, but accidentally used citric acid instead of acetic acid. After realizing my mistake, I added scraps of aluminum foil to the mixture to displace the copper, and render the mixture safer to dispose of. I went to filter out the copper and dispose of the rest, when I found that there was a layer of some kind of gelatinous substance coating the exposed surfaces in my container. Does anyone have any idea of what it could be, and how I might safely dispose it?


texts:
Is radiation time the same thing as half life period?

Also, if I'm talking about excited species in a gas, how would the gas interaction affect the radiation time, are there some formulas/approaches?


texts:
I am currently studying Diode Lasers and Photonic Integrated Circuits, second edition, by Coldren, Corzine, and Mashanovitch. In chapter 1.2 ENERGY LEVELS AND BANDS IN SOLIDS, the authors say the following:

On the other hand, in a covalently bonded solid like the semiconductor materials we use to make diode lasers, the uppermost energy levels of individual constituent atoms each broaden into bands of levels as the bonds are formed to make the solid. This phenomenon is illustrated in Fig. 1.4. The reason for the splitting can be realized most easily by first considering a single covalent bond. When two atoms are in close proximity, the outer valence electron of one atom can arrange itself into a low-energy bonding (symmetric) charge distribution concentrated between the two nuclei, or into a high-energy antibonding (antisymmetric) distribution devoid of charge between the two nuclei. In other words, the isolated energy level of the electron is now split into two levels due to the two ways the electron can arrange itself around the two atoms.$^1$ In a covalent bond, the electrons of the two atoms both occupy the lower energy bonding level (provided they have opposite spin), whereas the higher energy antibonding level remains empty.
$^1$The energy level splitting is often incorrectly attributed to the Pauli exclusion principle, which forbids electrons from occupying the same energy state (and thus forces the split, as the argument goes). In actuality, the splitting is a fundamental phenomenon associated with solutions to the wave equation involving two coupled systems and applies equally to probability, electromagnetic, or any other kind of waves. It has nothing to do with the Pauli exclusion principle.

If another atom is brought in line with the first two, a new charge distribution becomes possible that is neither completely bonding nor antibonding. Hence, a third energy level is formed between the two extremes. When $N$ atoms are covalently bonded into a linear chain, $N$ energy levels distributed between the lowest-energy bonding state and the highest-energy antibonding state appear, forming a band of energies. In our linear chain of atoms, spin degeneracy allows all $N$ electrons to fall into the lower half of the energy band, leaving the upper half of the band empty.

What does "spin degeneracy" mean in this context?


texts: Did both temperature of nernst equation same

texts:
I saw the nernst equation
I have a doubt.Did the temparature at which Standard potential is measured is also the temparature at which electrode potential is measured.
I mean Did the temperature (T) in the equation should always taken as the standard temperature at which Standard potential is measured.
See the below link
https://photos.app.goo.gl/EPxTHcPZ4Tynwvqc6
https://photos.app.goo.gl/cAbVFVHexCPgPXE88
In the above given Links it was written
V(metal)-V(solution)=kT/ze×ln{C(reference)/C(metal)} +kT/ze×ln{C(solution)/C(reference)}
Here kT/ze×ln{Preference/C solution}=V electrode


texts: What type of bond(s) are present in the borohydride ion?

texts:
In the $\ce{BH4-}$ ion, what bonds are present between boron and hydrogen?

Are there three covalent bonds between boron and three hydrogen atoms (using the boron 2s, 2px, and 2py orbitals), with the fourth hydrogen being a hydride ion $\ce{H-}$ which forms a coordinate or dative bond to the boron 2pz orbital?


texts: Determining overtones bands of degenerate modes

texts:
I have a question of a more mathematical nature on the mathSE (Symmetric Direct Product Distributive?) that received a good answer, but I think an answer more oriented to chemists would be a useful resource here.

I'm trying to determine the symmetry of the second overtone band of the degenerate $\Pi_u$ bend of $\ce{CO2}$. I'm told I need to use the formula$$\chi_v(\hat{R})=\frac{1}{2}[\chi(\hat{R})\chi_{v-1}(\hat{R})+\chi(\hat{R}^v)]$$
where $v$ is the number of quanta in the mode, $\hat{R}$ is an operation and $\chi_{v}$ is the character of that operation for the $(v-1)^{\text{th}}$ overtone. I arrive at the correct answer, which is that the second overtone has symmetry $\Pi_u\oplus\Phi_u$.

But this formula seemed complicated so I wanted to see if I could get the result just from taking the symmetric direct product of the state three times like so:
$$\Pi_u\otimes\Pi_u\otimes\Pi_u=(\Sigma^+_g\oplus\Delta_g)\otimes\Pi_u=2\Pi_u\oplus\Phi_u$$

Following the direct product tables I seem to get this, which has an extra $\Pi_u$.

I know this is wrong because the representation should only be quadruply degenerate, corresponding to the 4 different ways of distributing the quanta between the original degenerate modes: $(3,0) (2,1) (1,2) (0,3)$.

Why does this approach fail? Does the symmetric direct product not distribute over the direct sums?


texts: What criteria based on expressing standard rate of reaction?

texts:
When given the reaction: $\ce{NO2}$ reacts with $\ce{O2}$ to produce $\ce{N2O5}$, how do I calculate the rate of consumption of $\ce{NO2}$ when the rate of the reaction= 0.02 M/s?

I am confused  about which of these  expressions of reaction rate  can be used to calculate the rate of consumption of $\ce{NO2}$.

a )   r = 0.02 = (1/4) ×  rate of consumption of $\ce{NO2}$

Or :

b)    r = 0.02 = (1/2) ×  rate of consumption of $\ce{NO2}$

Does the rate of the reaction changed when we multiply balanced reaction equation by integer? Why?


texts: I don't understand why nitrogen dioxide $\ce{NO2}$ is coloured brown when nitrate $\ce{NO2-}$ and dinitrogen tetroxide $\ce{N2O4}$ are not. I understand it is due to absorption of light when its frequency matches the energy of an electronic transition. But what makes $\ce{NO2}$ special, i.e. what electronic transition gives rise to the brown color in $\ce{NO2}$, and why do $\ce{NO2-}$ and $\ce{N2O4}$ lack these transitions? Is there are way to explain this difference using molecular orbital theory?


texts: Calculating the ionization energy for hydrogen

texts:
What energy would be needed to remove the electron from the $n = 4$ level of the hydrogen atom?

  $\pu{−3.49 * 10^{−17} J}$
  $\pu{−1.36 * 10^{−19} J}$
  $\pu{+2.18 * 10^{−18} J}$
  $\pu{+1.36 * 10^{−19} J}$

I assume that the way to do this is to start from the Rydberg formula,

$$
E = \mathcal{R}Z^2 \left( \frac{1}{n_i^2}-\frac{1}{n_f^2} \right),
$$

set the initial level of the electron as $n_i = 4$, and the final level corresponding to removing the electron (ionization) as $n_f = \infty \implies \frac{1}{\infty^2} = 0$, leading to

$$
E = \pu{13.6*\frac{1}{4^2} eV = 0.85 eV = 1.36*10^{-19} J}.
$$


texts: Basis sets that can be used for macrocyclic complexes

texts:
What could be the possible basis set that can be used for a metal base macrocyclic complex in gaussian09?

I am using transition metals such as $\ce{Ni}$, $\ce{Co}$, etc.  Also, I have tried using DFT and HF theory for optimization but I am not getting appropriate results.

I am basically looking for binding of metal with the ligand in these coordinate complexes on basis of which i can use them for a particular application.
The basis set that I am using right now for DFT is Opt=(Cartesian,maxcycles=500)  b3lyp/gen  nosymm   pseudo=read SCF=(conver=5,vshift=400,maxcycles=1000)

Edit: Earlier I was using a specific basis set for transition metals and now I am using lanl2 as a single basis set for the DFT calculation. I am also using hf cal in which the sto3g basis set is used but iam getting two consistent errors in optimization which are convergence failure and number of step exceed error processed link 9999.


texts: Why are there only a few types of sigma overlaps?

texts: While studying σ-bonds, I saw that only s–s, s–p and p–p orbital overlaps are being taught. But are there more such cases possible? Because apart from s and p, there are also d and f orbitals.


texts: How can one determine an atomic mass with high accuracy using gravimetric analysis?

texts:
In the Wikipedia article on gravimetric analysis it is said that gravimetric analysis was used to determine the atomic masses of many elements in the periodic table to six figure accuracy. There are, however, no references to that claim.

Could someone please tell me, the molar masses of which elements can be determined using gravimetric analysis and what the exact procedure is?


texts: What does the "3,4" mean in 3,4-methylenedioxymethamphetamine (MDMA)?

texts: I'm curious to know, what exactly does the 3,4 part of 3,4-methylenedioxymethamphetamine represent?


texts: Is there a molecular orbital/Woodward-Hoffmann explanation as to why Diels-Alder reactants don't commonly undergo electrocyclization instead of cycloaddition?


texts: Why does a low concentration of soap in water behave as a strong electrolytes?

texts:
According to my text, "a colloid in which the dispersed phase consists of micelles is called an association colloid." An example would be soap in water. They use the term 'associated colloid' and 'association colloid' interchangeably.

They state that, "associated colloids at low concentrations, behave as normal, strong electrolytes."

I can't provide further context as they haven't provided further information.


texts: What do final zeros to the right of decimal point indicate?

texts: Final zeros to the right of the decimal point are considered significant. What do those zeros indicate and why are they significant? For example, in 2.000 there are four significant figures.


texts: Relation between Temperature and viscosity of Linseed Oil?

texts:
I have been trying to get a relationship formula to determine the viscosity of Linseed oil. I have Absolute viscosity of the oil at 33.1 Cp (Source: http://www.engineeringtoolbox.com/absolute-viscosity-liquids-d_1259.html).

The problem is the system where I am using the fluid has a varying temperature, and I want to be able to know what the varying viscosity is. I am aware that the viscosity reduces with increase in temperature, but wasn't able to find a specific formula to relate the two.

Is there a formula to get the relationship between temperature and viscosity?

Thank you


texts: An example to illustrate the difference between an inversion operation and a twofold rotation

texts:
Reading in Atkin's Inorganic Chemistry book, I cam accross:

  Although an inversion and a twofold rotation may sometimes achieve the
  same effect, that is not the case in general and the two operations
  must be distinguished.

He does not give an example of an occasion where such cases are not the same.

I will appreciate if someone can give an example of when inversion and twofold operation won't give the same result.


texts: Which occurs first: nitration or oxidation of aniline by concentrated nitric acid?

texts: Which of the cases is possible or both or none?


texts:
I have seen many machine learning algorithms for prediction of quantum chemistry properties that use Coulomb matrix as their input. Coulomb matrix is defined as,

$$\boldsymbol{M}_{i j}^{\mathrm{Coulomb}}=\left\{\begin{array}{cc}{0.5 Z_{i}^{2.4}} & {\text { for } i=j} \\ {\frac{Z_{i} Z_{j}}{R_{i j}}} & {\text { for } i \neq j}\end{array}\right.,$$

where the diagonal terms:

  ... can be seen as the interaction of an atom with itself and are
  essentially a polynomial fit of the atomic energies to the nuclear
  charge.

I was trying to read more about these diagonal terms and how exactly this equation is fitted. Essentially, something that says: "... and from there we get $0.5Z^{2.4}$." If these energies can be extended to bonds as well, as the off-diagonal term in Coulomb matrix represents repulsion forces rather than potentials, any references would be appreciated as well.


texts: CF and MO theories: seeing connections between the two approaches

texts:
I wonder if and how when considering MO theory, we are accounting for the electrostatic interaction / repulsion between electrons on the metal and the ligand. It seems like MO assumes pure covalency, so why is this necessarily more accurate than crystal field?

I am primarily looking for a quantum mechanical explanation of what is accounted for when MOs are being constructed, but any suggestion or indication of the right direction would be great. Thank you!


texts: The lone pair of phosphorus and the double bonds in benzene looks to be in conjugation. Do the molecule show resonance? If so, how?


texts: Boundary conditions in a closed system for diffusion (2nd Fick's law) in a porous medium

texts:
I would like to calculate the chloride redistribution in concrete (assumption: porous and homogeneous structure, purely diffusion-controlled mass transfer, closed system). For this I have derived a solution of the differential equation of Fick's 2nd law.

Since the chloride ions cannot leave the system at the borders, I have assumed the following boundary condition:

$$\frac{dc(0,t)}{dx} = \frac{dC(L,t)}{dx} =0, ~~~t>0$$

I have taken this boundary condition from another post on this site (When is diffusion steady-state?)

My solution of the differential equation assuming this boundary condition is correct. I have checked it with the help of an FEM simulation. Now to my question:

Does anyone know of a literature source with which I can prove my chosen boundary condition?
Can one generally assume that the derivative of the concentration at the edges is always zero when the system is closed?

Thanks a lot for your help in advance!


texts: Is precision measured by significant digits in chemistry?

texts:
I was recently asked this question:

An experiment is done 3 times, with a different measuring tool used
for each time. The results of the experiment are 1.39, 0.9, and 1.0
(all centimeters). Which measurement is the most precise, and how do
you know?

On my paper, I put that the answer was 1.39 because it had the most digits past the decimal point and submitted. However, I've read online and found since then that my explanation actually referred to accuracy, not precision. My question is, would saying "1.39 is the most precise because it has the most significant digits" be a correct answer?


texts: Gattermann-Koch Reaction with Phenol Substrates

texts:
The Gattermann-Koch Reaction involves the formation of an aryl aldehyde using carbon monoxide and hydrochloric acid as reactants. The reaction is catalyzed by aluminium trichloride in the presence of trace amounts of cuprous chloride.

What I don't understand about this reaction is that according to Wikipedia along with other online texts I've used, the Gattermann-Koch reaction is inapplicable to phenol substrates. The drawback has been left unexplained by all my resources (online and textbooks) and even my professor was oblivious to it.
I am unable to understand why the reaction doesn't apply to phenol and what exact side reactions might occur.

Additionally, why is the explanation so obscure?

[EDIT] I found the explanation. The Gattermann-Koch Reaction is not applicable to phenol and phenol ethers because they "could not be successfully formylated at atmospheric pressure in benzene as a solvent."
"This failure to react was attributed to the insolubility of the cuprous chloride in the reaction mixture."

Can someone please explain this in simple terms?


texts: By how many pH units does rain vs distilled water change a soil pH test?

texts:
Sources state that the concentration of $\ce{H2CO3}$ in rain is of a few µmol; I don't know if that's per ml. The buffering effect of most soils is >1000 µmol $\ce{H+}$/kg.

Is the difference from low acid rain water versus lab distilled water on a pH test for soil less than 0.1 in pH values?


texts:
When silver acetate reacts with iodine and $\ce{CCl4}$, it gives esters and 2 moles of $\ce{AgI}.$ But when it reacts with iodine  and lead acetate, why does it give alkyl halide, $\ce{AgI}$ and $\ce{CO2}?$
$$
\begin{align}
\ce{2CH3COOAg + I2 &->[CCl4][\phantom{(CH3COO)2Pb}] CH3COOCH3 + 2AgI + CO2}\tag{R1}\\
\ce{CH3COOAg + I2 &->[(CH3COO)2Pb] CH3I + AgI + CO2}\tag{R2}
\end{align}
$$
Why doesn't the alkyl-iodide bond break similar to when $\ce{CCl4}$ was used as solvent? What exactly lead acetate do such that alkyl-iodide bond don't break and we get alkyl iodide as product?
Also, my lecturer told that the alkyl iodide bond wont break since lead will form the complex with acetate which is not so clear. I tried to get the answer on Google but no where it shows the explanation for it.


texts:
The Belousov-Zhabotinsky reaction is a very fascinating one. The Chemistry behind the reaction concerns thermodynamics and equilibrium. I want to perform the experiment, but I'm not able to find detailed instructions about the reaction. Like, proportions of the chemicals, explanation of the reaction, duration of the reaction, sequence of mixing the reagents, etc.

The Belousov-Zhabotinsky reaction is a video I found on YouTube.

But that does not give any details at all. Can anyone give me a detailed reaction procedure?


texts: How would sodium amide react with a non-terminal alkyne?

texts:
The reaction of a terminal alkyne with $\ce{NaNH2}$ leads to the loss of hydrogen ion from the terminal carbon.
But what will happen if the alkyne is a non-terminal one? How would $\ce{NH2-}$ attack then? Would any reaction even happen?
As an example, what would happen in case of this following reaction:
$$\ce{H3C-C#C-CH3 + NaNH2 ->[\text{liq.}~NH3] ?}$$


texts: Reversible and irreversible cyclic processes

texts:
The answer in Arihant's book is given as (b), but wouldn't (c) be correct as well? This is a question of IIT JAM Chemistry.

  A system undergoes two cyclic processes 1 and 2. Process 1 is reversible and Process 2 is irreversible. The correct statement relating to the two processes is
  (a) $\delta S=0$ for Process 1, while $\Delta S\neq0$ for Process 2
  (b) $Q_\text{cyclic}=0$ for Process 1 and $Q_\text{cyclic}\neq0$ for Process 2
  (c) More heat can be converted to work in Process 1 than in Process 2
  (d) More work can be converted to heat in Process 1 than in Process 2


texts: Ascorbic acid and aldehydes: Reaction and Influencing Metals

texts:
I've researched online and I've read that ascorbic acid can both promote oxidation and reduction depending on the conditions (I've read about trace metals but I've never found which metals affect its chemistry and which ones don't).
So if I mix ascorbic acid with a bunch of different aldehydes, will it react with all if them? Some of them? Will it reduce them (into alcohols?) or oxidate them (into carboxylic acids)? Do metals have any influence on what happens? And if so, which metals do?


texts:
Question : Can DIBAL-H (Diisobutylaluminium hydride) reduce carboxylic acid?

According to "March's Advanced Organic Chemistry" (by Jerry March),  acid can be reduced upto aldehyde using DIBAL-H. But on the other hand, "Solomons & Fryhle Organic Chemistry" and "Organic Chemistry by Jonathan Clayden" this isn't possible (though not said explicitly).

I am confused now. Can someone please confirm that whether this reduction is possible or not?


texts: Symmetry forbidden cycloaddition in the Wittig reaction?

texts:
My textbook (Klein) describes the mechanism for the Wittig reaction as a [2+2] cycloaddition, followed by a collapse of the ring.

As far as I'm aware, [2+2] cycloadditions are symmetry forbidden, unless the reaction is light-initiated, which the text does not mention. Is the book wrong? If not, what is going on here?


texts: What bases are fit for human consumption and can be used in foods?

texts:
I know that are several acids that can be found in the kitchen, such as citric acid and vinegar.

However, I never heard of a base that can be used in the kitchen to raise the pH levels of any food. I am well aware that this mix would probably make a salt as a result. Something like hydrogen peroxide doesn't sound safe for food. So, my question is:

What are (if any) the bases that can be used on those acids and still be human-consumable?


texts: Why is acidic hydrogen peroxide a potent oxidizer?

texts:
When hydrogen peroxide acts as an oxidizer it itself is reduced. Broadly this means that the peroxide bond is broken and that water is formed.

However, why is there a tendency for hydrogen peroxide to be such a potent oxidizer in acidic media?

  In acidic solutions, H2O2 is one of the most powerful oxidizers known—stronger than chlorine, chlorine dioxide, and potassium permanganate.

Why is it not as potent without added acid, i.e. 3% hydrogen peroxide, the stuff you find in medicine cabinets, isn't a very good oxidizer?

The "duh" answer is that hydrogen peroxide is especially unstable in acidic media. But why can't acidic media stabilize hydrogen peroxide, and specifically the peroxide bond?

Simple electrostatics tells me that having a bunch of positively charged hydronium ions around the positively polarized oxygens in the peroxide bond isn't a "good" situation. Of course there are anions from the dissociation of the strong acid but these anions necessarily have diffuse negative charge, which is probably not enough to stabilize the polarized peroxide bond to significant extent. Is there anything else?


texts: Order of reactivity of alkyl halides in Sn1 reactions

texts:
Problem:: Predict the order of reactivity of the following compounds in SN1 reactions .

i) $\ce{PhCH2Br}$

ii) $\ce{Ph2CHBr}$

iii) $\ce{PhMeCHBr}$

iv) $\ce{Ph2MeCBr}$

Answer::

SN1:iv>ii>iii>i

Reason:: SN1resonance due to phenyl groups.

I didn't understood why it doesn't consider loss of planarity as two or three phenyls groups can't arrange themselves in a plane around one carbon atom because of ortho hydrogen clash with each other which will no allow
Effective resonance

Please provide some examples or explanation to it
Here is an example of loss of planarity in a compound with 3 phenyl groups


texts: Naming alkenes with double bond branches

texts: After reading the IUPAC rules, I found the parent chain to be from the $\ce{CH2}$ numbered 1 to the one numbered 9, and I considered both methyl groups as branches. However, my confusion lies in naming the branch in the middle (depicted in red color) since it contains a double bond:


texts: How to convert benzene to 1-bromo-3-iodobenzene?

texts:
Today, my chemistry teacher gave the following organic conversion as homework: benzene to 1-bromo-3-iodobenzene.

I tried something like:

I am not sure about it, can someone review my conversion (as I have got an exam tomorrow)?


texts:
What is chemical free energy?  How can we practically explain its existence?  How can it be used to do some useful work like in an electrochemical cell?

I couldn't understand clearly about it when I referred a few books


texts:
https://chem.libretexts.org/Textbook_Maps/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Kinetics/Reaction_Rates/Second-Order_Reactions

When you will read this webpage ,then you will find that they have made cases for different types of second order reaction .

In  $situation 2A $ of case 2 in  the article (eq 1.13 and 1.14) ,they have taken change in concentration of A to be dx/dt instead of
d(a-x)/dt .What is the reason for this ?

Also what I am also finding difficulty is how did they combine the reactants to make it $[A]^2$.......  it would mean that individually the concentration of a single reactant A  is following 1st order reaction. So the rate constant in disappearence of A should be first order instead of second so what is the reason for this .I t would have make sense for 2A to follow second order instead of just A


texts: Do bond energies differ for surface and bulk atoms in nanoparticles?

texts:
In nano-particles, surface atoms have fewer neighboring atoms in compare to bulk atoms.
Is there any difference between bond energy of surface atoms and bulk atoms?


texts: What alcohol concentration makes bathroom cleaner "disinfecting"?

texts:
There are many do-it-yourself cleaner solutions out there, using a combination of vinegar, alcohol (in a "cheap vodka" concentration), dish soap, baking soda and essential oils. I like these recipes for two reasons, first for cost and second for health (sometimes my toddler helps me clean his bathtub, and I wouldn't want him to use too harsh stuff).

However, many of these recipes claim to be "disinfecting", and as far as my understanding goes, alcohol has that effect, as has stuff that offsets the pH-level (such as the acidity of vinegar). But given that this stuff is just sprayed onto the surface, can a mixture of 2 parts water 1 part vodka really be concentrated enough to be "disinfecting"? And if you mix baking soda and vinegar, won't that bring you closer to a neutral pH, i.e. offset any "disinfecting powers"?

Is there some sort of guideline as to how much alcohol/other agent should be in the final solution for it to be of good use in cleaning a bathroom?


texts: Fick's second law atomic diffusion question

texts:
I have a question about diffusion and i'm not sure how to tackle it.

A new processing method is being tried for a lithium battery cathode material -LiCoO2. the process leaves the ceramic oxygen deficient, which is causing problems. to counter this problem the LiCoO2 is annealed at low temp (400 K) in oxygen rich atmosphere to encourage oxygen take up. this generates a localised atmosphere of oxygen at the surface of $1.16\times 10^5 \pu{mol/m^3}$.
i. The initial concentration of oxygen in the cathode material is $9.64\times 10^4  \pu{mol/m3}$. The diffusion constant is $4.92\times 10^{-7} \pu{cm^2 s^-1}$ for the oxygen in the cathode material. calculate how long the material must be annealed for it to reach the desired concentration of $1.04\times 10^5 \pu{mol/m^-3}$ across the whole sample (which is 5 mm in depth).
ii. The oxygen is though to primarily diffuse into the material via a grain boundary diffusion mechanism, draw a diagram showing how the oxygen concentration would vary across the material and around the grain boundaries."

For part i. I have tried using $$c(x,t)=\frac{A_0}{\sqrt{\pi Dt}}\exp(-x^2/4Dt)$$ but ended up with negative time which doesn't make any sense, I have also tried solving it using error function table $$c(x,t)=0.5A_0[1-erf(\frac{x}{2 \sqrt{Dt}})]$$ but ended up with negative time too (different value)
Could someone advise me which equation to use


texts:
According to Wikipedia, the term click chemistry was coined by K. Barry Sharpless in 1998.

What does the word 'click' mean here? I guess it means "join" here but I'm not sure.


texts: How can I deduce the linearity of XeF2 from the IR spectrum?

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The vibrational modes of $\ce{XeF2}$ are at $555$, $515$, and $213~\mathrm{cm^{-1}}$ but only two are IR active.
Explain why this is consistent with $\ce{XeF2}$ having a linear structure.

From what I know, since it has $3$ atoms it should have $3n - 5$ vibrational modes, thus $3(3) - 5 = 4$ modes. Yet the problem tells me it only has $3$, which would suggest a non-linear shape. How to explain this?


texts: Why do Grignard reagents act as sources of nucleophilic R− and not Br−?

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In reactions with Grignard reagents, I've always seen the alkyl group being the nucleophilic component, with the R–MgBr bond being broken. This is always rationalised by the fact that the alkyl carbon has a partial negative charge, whereas the electrophile (e.g. a carbonyl group) has a partial positive charge.
However, the halogen atom should also have a partial negative charge. Why doesn't it attack the electrophile instead, breaking the RMg–Br bond?


texts:
Every now and then, when I pop over to my grandparents' house, they make sure to give me a glass (or two) full of fresh milk (or "whole milk" if you will) and then proceed to pamper me for the rest of the day.

Now, it suddenly struck me that the fresh milk I get over there actually has this really faint yellow tinge, as opposed to the skimmed milk I get at the store which is almost pure white.

I did try Googling this up, but I can't seem to find anything on what imparts the yellow tinge to fresh milk.

So,

What substance/pigment is responsible for the yellow tinge associated with fresh milk?


texts: translation of a sentence involving antigen/buffer/solution

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I'm trying to translate a sentence about biochemical testing into English.

So far, I can figure out the following:

Make a 10,000 pg/ml stock solution from[?] antigen into[?] 7.5 % BSA-TSA buffer.

The prepositions are the literal translations of what the foreign language says. However, despite knowing very little about biochemistry, I'm doubtful that either translation is correct in English.

If you were to read this sentence, would you be able to guess how to replace the highlighted words so that the phrase would sound idiomatic in English?


texts: Should I have a pair of shoes that I wear only in the lab?

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I bought some very nice heavy leather boots when I was working in a solid state synthesis lab, mainly with selenium and sulfur compounds, a few years back. I probably did spill small quantities of some very basic/acidic solutions with some selenium/selenate content on them a few times.

I don't work in a synthetic lab anymore, but I wore them again this weekend. It feels strange though, perhaps just from ingrained lab safety habits, to touch my face after putting them on etc. My gut feeling is that a) rain has washed away anything which was on them b) most chemists I knew as a research student wore their normal day shoes in the lab, so it should be fine. But what are the standard safety rules on this? Is it generally okay to wear the same shoes in the lab and in daily life?


texts:
I am learning a bit about Uv-vis spectroscopy filters. As far as I know there are two commonly used: interference and absotion filters.
The first one works with the interference of light principle and the second is a glass with some pigments which absorbs light (of some specific frequency).

Question

Have you got any idea if there is any further classification of absortion filters? Any help will be greatly welcome.


texts: What is the mechanism for the oxidative cleavage of diketones via permanganate under basic/hot conditions?

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The products of the reaction are carboxylates.
What exactly would cause the alkyne to cleave?


texts: Can I perform electroplating with sodium carbonate and copper?

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I want to avoid anything poisonous during electroplating. I can't avoid copper oxide though.

I have dissolved $\ce{Na2CO3}$ in water and I'm trying to electroplate aluminium with copper:

As you can see I'm doing it with no actual chemical equipment. Actually I'm trying to discover ways that can be done at home.

In the water, I can see copper hydroxide ($\ce{Cu(OH)2}$) and copper carbonate ($\ce{CuCO3}$), both formed from the copper anode. But the aluminium heatsink does not seem to have any copper on it. Will it take time or am I just wasting copper here?

If this is not gonna work, what is gonna work? Could I use vinegar?


texts: Is the active mass of every solid and liquid taken to be unity?

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I learnt from my textbook and the question/answer - Why is active mass of a pure solid or liquid always taken as unity? that active mass of a solid or liquid is taken to be unity as:

$$[A]=\frac n V=\frac{m}{M\times V}=\frac{\rho}{M}=k$$

where $[A]$ is the active mass, $n$ is the amount of substance, $V$ is the volume, $m$ is the mass, $M$ is the molar mass, $\rho$ is the density and $k$ is a constant.

This is concisely stated in the linked question by:

  Molar concentration is directly proportional to density. Since density of solid or liquid always remains constant, the active mass is taken as 1 .

The answer to the linked question explains that, in the course of a reaction mass and volume of solid and liquid substances change but their ratio i.e., density remains constant at a fixed temperature.

As far as I understood, the above explanation holds true for all solids and liquids. So, is the active mass of every solid and liquid taken to be unity? Or are there any exceptions to this fact? If so, how do such substances vary from others for which the active mass is taken to be unity?


texts: What is the mechanism of hydroperoxide reduction by bisulfite?

texts: I am using bisulfite to quench allylic hydroperoxide products from a singlet oxygen ene reaction, to the corresponding alcohols. What is known about the mechanism of this reaction, and in particular could it involve an alkyl peroxysulfate ($\ce{R-O-O-SO3H}$)?