texts: What is the difference between the mean radial distance and the most probable radial distance of an orbital?

texts:
I was reading JD Lee's Concise Inorganic Chemistry and it has given some values of mean radial distance which is increasing from s to p to d orbital. I had earlier read that the most probable radial distance of an orbital has the order s>p>d>f. This makes me wonder what is the difference between the mean radial distance and most probable radial distance. Also, why is the order of mean distance reverse from that of most probable radial distance?
Also can you please explain why is the energy of an orbital proportional to mean radial distance as given in the book?

Image Source: Concise Inorganic Chemistry by JD Lee


texts: Does the solubility of iron (iii) oxide increase when the pH of the water it is in decreases?

texts:
I did an experiment and I got these results:

pH 4: 3.46
pH 3: 3.77
pH 2: 2.18
pH 1: 3.69
The numbers on the right is the amount of iron oxide remaining that was not filtered.

Do these numbers make sense? (The measurements are in grams.) The original amount of iron oxide in each solution (4 different solutions as there are 4 different pH's) was 3.81 grams

I basically put iron (iii) oxide in different pH's, left them, and filtered out the water after. I measured how much iron (iii) oxide remained. I am not sure if my numbers make sense though because I thought that if the pH drops it increases in solubility. However, my pH 2 was the highest in solubility. Do these numbers make sense chemically?


texts: Does an onion completely remove "fresh" paint VOCs and other chemicals emitted?

texts:
I have read that paint contains VOCs(Volatile Organic Compounds), and solvents generally, and I could wait for them to dissipate, but i've read there are ways to remove the smell of paint such as half an onion in a bucket of water, such as slices of lemon on a plate, such as small bowls of distilled white vinegar.

Do these techniques actually remove all the nasty elements from the paint fumes, or just some of the nasty elements from them?  Do they remove all the paint fumes?

I wouldn't want to remove the smell but leave the VOC or other bad elements there.  If that's the case i'd rather just leave a window open in the room, closing it periodically, seeing if there's finally a time when the paint smell doesn't build up when the window is closed, then i'll know the paint isn't emitting any more fumes.


texts: Is it appropriate to call this material a hybrid composite?

texts:
The material I've synthesised is made up of two primary parts at a 1:1 ratio:

Part 1: agar, glycerol, water.
Part 2: polyurethane resin.

The agar mixture on its own was too soft, so I added the resin to harden the material. Would this material be classified as a hybrid composite? If not, why?


texts: Retrosynthesis of spirocyclic compounds?

texts:
I have been trying to complete this retrosynthesis problem for a few days but can’t figure out how to get from Ester starting compound to a spirocyclic compound. I have tried removing the Ester but can’t figure out what best to replace it with.
I have access to any reagents and starting materials as long as the nominated substance is used.


texts:
I am told that chromic acid is exceedingly unstable and that it cannot be purchased as a pure reagent.

Is that so?

I don't find any mentions of stability or lack thereof on Wikipedia, and hey, if I wanted to, I could purchase it here:

http://www.grainger.com/product/LABCHEM-Chromic-Acid-8FV43

So what's the deal with having to make chromic acid in situ? Does this have to do with chromic acid's stability? Or something else?

EDIT: oops I realized that the linked reagent for purchase is just chromic trioxide, which can be used to make chromic acid.


texts: Is there a way to "electroplate" wood with copper?

texts: Maybe wood can be coated with copper (II) sulphate first, or roasted in order to form a conductive charcoal (carbon) layer.


texts: Why do fluoride molecules seem to have abnormally low boiling points?

texts:
As far as I know, to non-polar molecules like CF4 and C2H6,
boiling point is mainly affected by the London dispersion force.
As a result, molecules with more protons and electrons normally have higher boiling points.
However, CF4 (34 electrons) has a boilng point of -128°C, while C2H6 (18 electrons) has -89°C.
Also, I find it puzzling that fluorides tend to have abnormally low boiling points.
 For example (the below are all boiling points of  compounds with a benzene ring)
C6H6 80.1 °C
C6F6 80.2 °C
C6Cl6 322 °C
C6Br6 418 °C
C6I6 531 °C
 It seems to me that fluorides are the abnormal ones. Despite having a lot more electrons than benzene, the boiling point is almost the same.
Is there something I'm missing?


texts: What side reactions are suppressed by the use of TMSCl in the acyloin condensation?

texts:
I was reading about the acyloin condensation and came across a statemant according to which, the use of TMSCl obviates competing reactions. My question is what kind of competing reaction would happen if it was not used and how? I've read about the possiblity of some sort of Claisen condensation but I fail to see how would that be possible.
https://en.wikipedia.org/wiki/Acyloin_condensation


texts: Why do the peaks in a radial distribution function graph have a probability >1

texts:
Why do RDF plots have the probability at a particular distance >1. How can probability be more than one?
I am asking this because I want to understand what do the peaks of different length but at the same position on the x axis mean
The below is an example of a RDF plot:


texts:
Whilst attempting to create salicylic acid/2-hydroxybenzioc acid, one of our experiments produced a compound with a melting point of over $300^\circ\mathrm{C}$ ( as high as the machine would go) and the IR absorption spectra attached. Can anyone help us identify the compound we have produced?

We used:

$4 \,\mathrm{g}$ of oil of wintergreen
$100 \,\mathrm{mL}$ of $2 \,\mathrm{M}$ aqueous sodium hydroxide solution
Sulfuric acid

The experiment was left for two weeks at which point the crystal pictured had formed.


texts:
Ethanol is a clean fuel and added as an additive to petrol.

Why can't ethanol itself be used as fuel?


texts: Safety/health hazards: working with 2-aminobenzimidazole, iminoesters, and 1,3,5-triazine

texts: How dangerous is it working with 2-aminobenzimidazole, iminoesters and 1,3,5-triazine? Has there been any cases of health problems recorded concerning those three compounds?


texts: Determine the oxidation number of sulfur in SF6

texts:
I've just started learning about redox chemistry and oxidation numbers. I can work out most of the oxidation number questions, but I don't know how to determine the oxidation number of sulfur in $\ce{SF6}$. This is not an ionic compound, and doesn't contain $\ce{H}$ or $\ce{O}$, so it seems as if I have no starting point.

If you could, please answer the question and provide a simple explanation.


texts: Field Effect and it's effect on basicity on amines

texts:
What is the order of basicity between $\ce{Me2NH}$, $\ce{Me3N}$, $\ce{MeNH2}$ in a protic solvent.

It has something to do with field effect which I could not understand and could not find anywhere.

Can someone please explain?


texts: Why is Sodium Transported Across the Cation Exchange Membrane in the Chlor Alkali Process?

texts:
In the Chlor Alkali Process, a sodium ion is transported across a cation exchange membrane to create NaOH in the Anode Chamber:

The Half reactions are:
2Cl− → Cl2 + 2e−
and
2H2O + 2e− → H2 + 2OH−
and the full reaction is:
2NaCl + 2H2O → Cl2 + H2 + 2NaOH
Why does the sodium ion get transported across the membrane? Sodium isn't involved in the anode/cathode reactions, so there's no concentration gradient driving it. I understand that the Anode reaction produces OH-, and that there is now a charge imbalance so that the sodium ion crosses in order to maintain electroneutrality. But how can this be described mathematically? I don't see how the standard mass conservation/ Nerset-Plank equations can describe this motion.


texts: Which ethanol derivatives display the gauche effect?

texts:
How many of the following ethanol derivatives of the form $\ce{GCH2CH2OH}$ have a more stable gauche conformer compared to their anti conformer?

  $G =  \ce{F}, \ce{Cl}, \ce{OH}, \ce{NH2}, \ce{OMe}, \ce{NHMe}, \ce{NMe2}, \ce{NO2}$

I was sure that $\ce{F}$, $\ce{OH}$, $\ce{NH2}$ and $\ce{NO2}$ display the gauche effect. I'm not so sure regarding all the other groups: all of them seem bulky and won't form hydrogen bonds with the $\ce{OH}$ group on $\ce{C}_1$. How many of the other substituents are capable of displaying this effect? Also, is there a quantitative way to determine if the gauche conformer would be more stable than the anti conformer?


texts: What is the conjugate acid of NaOH using the Brønsted-Lowry definition of acids?

texts:
To the best of my knowledge, a conjugate acid of a base is the base after it has accepted a proton, or a $\ce{H+}$ ion. In this case:

$$\ce{NaOH + H+ -> Na+ + H2O}$$

Is the conjugate acid of $\ce{NaOH}$ the sodium ion, or the water? Common sense tells me it can't be the $\ce{Na+}$ ion, because it has no protons to donate, so how could it ever be an acid? So I am thinking that the conjugate acid is $\ce{H2O}$. However, wouldn't that mean that the conjugate acid of any base of the form

$$\ce{(something)OH + H+ -> (something)+ + H2O}$$
would be water, and that seems unsettling to me. I also believe that since $\ce{NaOH}$ undergoes the following reaction:

$$\ce{NaOH -> Na+ + OH-}$$

the $\ce{Na+}$ is something of a 'spectator ion' (not sure if that's the correct term), this seems to imply that $\ce{H2O}$ should be the conjugate acid. Basically, I'm really confused, and could use a little help sorting all this out.


texts:
$$\ce{HCl(aq) + NaOH(aq) ->  NaCl(aq) + H2O(l)}$$
Would this reaction be considered homogenous even though there is a liquid in the products?


texts: Confusion in solution for this Question regarding mole concept

texts:
$\pu{48g}$ of graphite and $\pu{16g}$ of $\ce{O2}$ is given. The question is to count the no of molecules of $\ce{CO2}$ produced?
Now, the solution in book is this
No of $\ce{C}$ atoms = $\frac{\pu{48g}}{\pu{12g}}$ = $\pu{4mol}$. No of $\ce{O}$ atoms = $\frac{16}{16}$ =$\pu{1 mol}$ , and no of $\ce{O2}$ atoms = $\pu{0.5 mol}$.
The reaction given is
$\ce{C + 2O ->CO2}$.
$\ce{CO2}$ produced is $\pu{0.5 mol}$ here.
My question is why not to use the reaction $\ce{C + O2 ->CO2}$?
What would the difference be in the answer ?


texts:
Does reduction by carbon itself occur when filtration is performed using activated carbon? Is it part of the central mechanisms involved in activated carbon filtration?
One of the specificities of all activated carbon, per my understanding, is it's large surface area, which allows it to be treated in a way or another and maximize the surface area on which the respective reaction occurs. Now, just as all activated carbon has a high surface area (with some variations), can it be said that all activated carbon acts as a highly potent reducer on some ions?


texts: Will cyanide substitute bromine in bromobenzene?

texts: I've considered synthesizing benzoic acid from bromobenzene using CN-, and subsequently treating the nitrile with acid and heat. But, is this possible?


texts: Mechanism for cyclic enamine formation after N-Boc deprotection

texts:
In this reaction taken from Snyder's total syntheses of Coccinellid alkaloids,1 how does the Boc deprotection lead to ring closure? I understand that the $\ce{PBr3}$ step simply converts the alcohol to a bromide.

Sherwood, T. C.; Trotta, A. H.; Snyder, S. A. A strategy for complex dimer formation when biomimicry fails: total synthesis of ten coccinellid alkaloids. J. Am. Chem. Soc. 2014, 136 (27), 9743–9753. DOI: 10.1021/ja5045852.


texts: I am a little bit confused between charge distribution and HOMO/LUMO site in determining chemical reactivity. In charge distribution, the sites which are deficient and abundant in electrons are localized (e.g. in carbonyl molecules, we would expect that the carbonyl carbon to be partially positive and we would predict that a nucleophile would attack into that deficient carbon) but in HOMO/LUMO orbitals the site for reactivity differs on the orientation and sign of the orbitals. It may be in HOMO this carbon has an orbital for an overlap but in LUMO a node may appear in that site. My question is where would the nucleophile react in a species, by charge distribution or HOMO/LUMO orbital?


texts: Which of the free access molecular modelling program apply the B3LYP/G-31G(d,p) level of theory?

texts:
Please, let me know which an open free molecular modelling program will apply
the B3LYP/G-31G(d,p) density functional level of theory? Thanks.
Helen


texts:
I'm dealing with a free-energy scam on another forum. It is well-known that $\ce{LiAlH4}$ reacts explosively with water. My chemistry days are long behind me, so I thought I'd come here to ask:

$1~\text{mol}$ of $\ce{LiAlH4}$ reacted with $4~\text{mol}$ of water gives how much energy?

I'm not about to do this, mind you. I was just curious about the specific numbers.


texts: I have seen several chemical papers on where carbon nanotubes are made into host-guest molecules, with the researchers inserting molecules or ions inside the tubes. These talk about the properties of this inclusion but not the process or method in synthesizing or introducing these molecules into the carbon nanotubes. Any clues on how this is performed?


texts: Can chemicals be identified by their molar mass?

texts:
Wouldn't it be possible to identify a chemical by measuring its molar mass? How much accuracy does the measured molar mass need to be to guess what chemical it could be?

EDIT:
@ortho makes an important point about isomers, but organic chemistry is much harder ;). Let's just focus on inorganic chemistry (though there are still isomers, usually there aren't).


texts: Peculiar deprotonation of an alkenyl proton

texts: In this synthesis of Punctatin A, there is this peculiar deprotonation step. When subjected to the base $\ce {NaH}$, we would expect deprotonation at the $\alpha$-position, at the side opposite to the double bond. However, what is observed here is, in fact, the deprotonation at the double bond. Not only is the $\ce {C(sp^2)-H}$ bond stronger, there is also no delocalisation of the negative charge in the conjugate base that is produced. Note that the lone pair in the carbanion conjugate base is held in an $\ce {sp^2}$ hybrid orbital that is perpendicular to the $\ce {p}$ orbitals of the enone $\pi$ system. Does anyone have any idea what is going on here?


texts: Comparing the Lattice energy of different compounds

texts:
I am confused about some concepts related to Lattice energy.

First of all,how to compare lattice energy between $2$ compounds belonging to different groups and periods?

1.Between $\ce{AlF3}$ and $\ce{MgO}$ (In $\ce{AlF3}$ product of ionic charge is $3\times1$ and in MgO it is $2\times 2$. So,according to me $\ce{MgO}$ should have higher lattice energy but the opposite is true.

2.Between $\ce{KF}$ and $\ce{LiF}$ (According to Fajan's rule $\ce{KF}$ is more ionic than $\ce{LiF}$ and lattice energy depends directly on ionic character).But, value of lattice energy of $\ce{KF}$ is $\pu{808 kJ mol-1}$ and $\ce{LiF}$ is $\pu{1030 kJ mol-1}$. How is this possible?

So,can you please explain me how to compare lattice energies of different compounds and which factor is more dominating size of cation and anion or charge on ions.


texts: Ground state elevation for phase transition

texts:
I have a question about the illustration from chem.libretexts.org:

the ground states of the liquid and gas are offset from that of the previous state by the heats of fusion and vaporization, respectively.

Why does the change in enthalpy increase the ground state energy?
I would be very grateful if someone can help me with this problem. I have been struggling with it for five days, but Google could not help me.
P.S. My question mark does not work.


texts: Does the distance between an electron and the nucleus change for excitation and relaxation?

texts:
According to the Bohr model, when an electron moves from a ground state to the excited state, it will absorb energy, but what about the distance between electrons and nucleus, will it be changed? Why ? How?

Also, if there is the distance change when from a ground state to the excited state, will there be also any change in distance when electrons move from excited state to ground state ?


texts: How does the cation radius affect the rate of increase of the electrical conductivity of a salt in aqueous solution?

texts:
Potassium chloride has a greater ionic radius than sodium chloride. How does this affect the  fall in rate of increase in conductivity as concentration concentrations? I know the following factors affect the plateauing of the curve:
lesser dissociation, the equilibrium is disturbed as a result of lack of water molecules to fully solvate the ions, ionic pair association and the increased visocity of the solution
In my experiment I found that the decraase of the rate of increase was greater for KCl, which I found weird.


texts: How much energy is needed to break a water molecule?

texts:
How do you calculate how much energy is needed to break a water molecule into its constituent atoms?

note
This is not homework. I just want to know what is required to get hydrogen out of water.


texts: Why does oxygen not condense onto open dewers of liquid nitrogen?

texts:
I had a discussion with my supervisor today after I was a touch careless pumping down a flask with a liquid nitrogen cold trap attached. I checked, and there are reports of explosions after running air through a liquid nitrogen trap.

Given this, why does liquid oxygen not condense when you leave an open dewer of liquid nitrogen out? I mean, the air touching the surface of the nitrogen on top of the trap is the same as the air pumping through it. Is there too much nitrogen evaporating for the air to get close, or is the surface of the nitrogen too warm, or some other reasons?


texts:
How does $\ce{P(C2H5)3}$ acts as a ligand and forms dπ-dπ bonds with transition elements. Why not pπ-dπ bond?

I understand that transition elements have d subshell available to accept electrons. But what about the electrons from phosphorus? From Chemistry Class 12 (NCERT), Part 1, p. 168.:

  Another factor which affects the chemistry of nitrogen is the absence of d orbitals in its valence shell. Besides restricting its covalency to four, nitrogen cannot form dπ-pπ bond as the heavier elements can e.g., $\ce{R3P=O}$ or $\ce{R3P=CH2}$ ($\ce{R}$ = alkyl group). Phosphorous and arsenic can form dπ-dπ bond also with transition metals when their compounds like $\ce{P(C2H5)3}$ and $\ce{As(C6H5)3}$ act as ligands.


texts:
I think it was Nat Geo.. Not sure exactly.. Where I heard, years ago, that a drop of iodine can be used to disinfect water of say, 1 litre.

But isn't chlorine used to kill all bacteria? I mean I don't completely remember that documentary but I'm pretty sure it was  iodine that they used.

Can iodine be used or does my memory fail me?


texts: Chemically, how stains are removed?what is the principal?

texts: How stains are removed? answering to this question will help me much


texts: How does vinegar get rust off these coins

texts:
As experiment I found some really nasty rusty coins on the street. They were green. After looking on a website I found vinegar could eliminate the rust. It worked pretty well.

I know this is a redox reaction. Can you tell which ones? I know these are pesos of various denominations from Dominican Republic from the past 10 or 20 years. So that might help identify the metal.

The vinegar is household apple cidwe vinegar from the supermarket. Low concentration.


texts: Solubilizing ability of dichlorobenzenes

texts:
I am trying to understand why 1,2- and 1,3-dichlorobenzenes are such good solvents, able to solvate many organic compounds known to be hard to get dissolved.

Any precise answer?

It has something to do with dipolar moment and Hansen's diffusion parameter I think.


texts: How much sulphuric acid can be obtained from 5 kg of sulfur

texts:
How much sulfuric acid $(\ce{H2SO4})$ can be obtained from 5 kg of sulfur $\ce{S8}$?
answer: 15.312 kg

To  make 1 molecules of $\ce{H2SO4}$ we need 1 atoms of S.
Now coming to $\ce{S8}$. This gives us 8 atoms of S. so from this we can obtain 8 $\ce{H2SO4}$ molecules if we take 1 atom of $\ce{S8}$ and use it to make $\ce{H2SO4}$ molecules. So,

1 molecule of $\ce{S_8}$ $\ce{->}$ 8 molecules of $\ce{H2SO4}$
0.019 moles of $\ce{S_8}$   $\ce{->}$  $8 \times 0.019=0.15$ moles of $\ce{H2SO4}$

Formula mass of $\ce{H2SO4} = 1(2)+32+16(4) = 98$
we know the formula
for $$\text{Number of moles} = \frac{\text{Mass}}{\text{Formula Mass}}$$
So from this $\text{Mass}_\ce{H2SO4} = \text{Moles} \times \text{Formula Mass} = 0.15 \times 98=14.7$
Now you see that my answer doesn't match to the answer. What did I do wrong?


texts: Measuring pH of pasty solutions/mixtures

texts:
I'm trying to measure the pH of a very viscous paste mixture and have been told to dilute the sample for more accurate results, because the viscosity of the sample may prevent the sensor to detect the real pH of the sample.

Does this sound right to you? Wouldn't diluting the sample alter the pH?

Thank you


texts: A good book for learning paper and thin-layer chromatography

texts: What book would you recommend for learning paper and thin-layer chromatography? I don't have access to fancy equipment (just to these two basic techniques that are relatively cheap), so it would be nice if the book focused on them in addition to being easy to understand etc. It does not matter if advanced techniques are discussed in a chapter or two but if the book is solely about them, it would not offer me much.


texts:
I hope I am right in this section.

I am unsure with error propagation. When calculation the error in a titration, many errors has to be taken into account:

Error in Glassware/ Error in Balance/ Error in Burette etc.

I learned that the absolute and relative error have only 1 significant figure and that the total amount is rounded to the decimal place of the error.

Therefore   5.34532g ± 0.001428g  would be 5.345g ± 0.001g

The relative error 0.001g/5.345g = 0.00018709 = 0.0002

If there is an experiment with a lot of steps and error propagation wouldn't the rounding of all the errors in every single step change the result a lot?
Wouldn't be rounding the error just in the end make more sense?

Many thanks in advance


texts:
Is there any formula that can help determine the order of the reaction?
Cause my teacher told me to plot line chart. So, I am curious about another method that doesn't use line chart (like formula maybe)


texts: Why is the inductive effect of chlorine, bromine, and iodine stronger than that of hydroxy group, even though oxygen is more electronegative?


texts: Cl in HCl has three lone pairs of electrons. So it can donate a lone pair and thus become a lewis base. Right? Just like water is called a lewis base because oxygen has 2 lone pairs and can donate a lone pair.


texts: Interpretation of 1H-NMR spectra for Z-ochtodenol

texts:
I'm struggling to understand the 1H-NMR data for this compound. I managed to find the compound using the data I had, but at the end I can't assign the peaks properly.

My confusions are:

Shouldn't the $1.96~\mathrm{ppm}$ (2H, s) protons couple with the proton from the blue carbon and give a (2H, d, $J~2~\mathrm{Hz}$) by allylic coupling? [Same issue with the protons from the blue carbon.]
What's up with the broad multiplet?
Counting the protons from the data gives us 15 instead of 18; why's that?


texts:
What are the basic differences between inhibitors and poisons which are used in a reaction
Actually both the names confuse me so please help me out.


texts:
Pectin is an example of a food safe polyelectrolyte. It acts as an acid because it is a proton donor and develops negative charges along the polymer.

Can you think of any examples of food safe polyelectrolytes that act as bases and develop positive charges along the polymer?


texts:
I have come to know that nitrogen can undergo both $\mathrm{sp}^3$ and $\mathrm{sp}^2$ hybridization.
Does a different hybridization lead to a different atomic radius?


texts: Alkenes v/s Alkynes in two different reactions

texts:
Alkynes are less reactive towards electrophylic addition than alkenes. However, in case of catalytic hydrogenation, alkynes are said to be more reactive. Why? Also, if I want to add H+ as an electrophile, then will alkenes be still more reactive than alkynes?

Does the reason lie in the mechanism of both the reactions (that was obvious, I guess)? If so, please explain, I cannot seem to justify for the later one.


texts: Biphenyl symmetry group dependence on torsional angle

texts: What is the symmetry group of the biphenyl when the torsional angle between the phenyls is 20 degrees? What about when it is 90 degrees?


texts:
When a heavy nucleus  undergoes nuclear fission , it splits to two smaller, more stable nuclei and produces heat, similarly, when two light nuclei fuse, to make a heavier, more stable nucleus and produces energy.

The produced energy, is due to the mass defect between the reactants and the products, which is transformed to energy, according the mass-energy equivalence.

  But if the products of each process(fission, and fusion) are more stable, that means that they have  more binding energy, thus, shouldn't the mass defect be transformed to nucleus binding energy, rather than emitted as heat or another sort of energy ?


texts: How does the activity of Sn chemical potential vary as a function of composition at 900 C?

texts: This is referring to the Cu-Sn phase diagram in which composition varies along a horizontal line at a certain temperature. I understand that as you move along that line different intermetallic or liquid phases form, but from a activity point of view does the activity go up because of different crystallographic arrangements that are present at different compositions?


texts: Why are reactions with higher activation energy more sensitive to temperature?

texts:
In the above picture it is stated clearly, with an example, that the more the Ea of a rxn the more it's sensitive to temperature, and hence even a small change in temperature in a reaction with high Ea, would have a drastic effect on the rate of rxn, as compared to a rxn with low Ea (about the probability factor and collision frequency, it's stated in the book as - "it must be understood that we are justified in doing this only when the reaction being compared are so closely related that differences in collision frequency and probability factor are comparatively insignificant" ).

My doubt is - If the energy-barrier (Ea) is high, doesn't it mean, (kind of) that, it's difficult to reach the intermediate stage, and hence a little change in temperature doesn't do good to the reaction as the barrier has still not been overcome and the reactants have a long way to go; and hence making the reaction more "temperature resistant" ? And on the other hand, if the energy-barrier is low, doesn't it mean that even a small change in temperature would be enough to overcome it and hence would increase the rate of reaction ?

After reading a bit more, I found that the statement is repeated again as - "the larger the activation energy of a reaction the larger the increase in the rate brought about by a given rise in temperature".    WHY ?

My appeal to the answerers is that - Can you plz answer in what-is-actually-happening-on-the-backstage way and without ,if necessary, equations ?

Thank you very much and sorry for poor English.


texts: Observability of Orbitals and Orbital Energies

texts:
This question comes from some thoughts I had after reading this question.

First of all, is an orbital an observable? I know the answer to this question is no because there is no "single-orbital operator" or whatever you'd like to call this. I brig this up because exactly what this means should be a part of a thorough answer. Plus an orbital is a state and we don't observe the eigenvectors but the eigenvalues.

Second, is the energy of an orbital an observable? It's more tempting to think that the answer to this is yes, but if it's true that there is no "single-orbital operator" then there must be no corresponding eigenvalue which represents the energy of this orbital. As I understand it, if one runs a HF calculation and sums the energies calculated for the individual orbitals, this is the total electronic energy. In the answer linked above, however, it is said that there is an infinite number of unitary transformations for a given set of orbitals to another set. Is there any correspondence between the energies of these transformed orbitals and the original set of orbitals? By that I mean, the orbitals themselves change, but would the optimized energies of each orbital change and it is the only the wavefunction and total energy which stay constant?

Finally, how do the answers to the above questions connect with Koopmans' theorem and photoelectron spectroscopy? That is to say, Koopmans' theorem says that the energy of the HOMO as calculated from Hartree-Fock corresponds to the first ionization energy of the system. Additionally, in photoelectron spectroscopy, it sure seems like people are observing the energies of individual orbitals, but I don't really know anything about this technique in detail so that may just be a misunderstanding.

Additionally, is Koopmans' theorem still true once we perform a unitary transformation on the Hartree-Fock wavefunction?

The reason I lump all these questions together is because I think in order to sufficiently answer the question of whether or not an orbital energy is observable, all of these points should be addressed, so I just asked them all at once. I hope it's not overkill.


texts: How can I be safe and protect myself using trimethyl tin chloride?

texts:
I will be using trimethyl tin chloride (1M in THF) in a few days for the first time. Looking at the MSDS, it looks like it is very toxic and has noxious vapors. Are there any more standard precautions for working with it other than the usual?

E.g.,

Check for proper airflow in the hood
Wear lab coat, safety glasses, and double gloves


texts: Why does two nails of the same material not produce electricity when placed in saltwater?

texts: If I put two the same nails in a saltwater why could it not produce electricity when I put the metal aluminum and copper it produces electricity?


texts: What is involved in this firey demonstration?

texts:
In this rather shaky Facebook video (sorry I can't provide a better link), a science teacher takes a burning beaker of something and spills it out onto the floor.  It then proceeds to shoot fire out in all directions, and we can see embers burning themselves out, leaving black ash of some sort.

I've seen teachers do similar stunts with alcohol fires, but those burn blue.  This one is much more explosive and stays yellow.

Is there any way to tell what the teacher is using here?


texts: Can anybody help me out with this chain conversion?

texts: I can understand that grignard reagent will attack the oxygen breaking the double bond of the oxygen forming a diol but that is unstable so it should form a Ketone but after that I can't really understand.


texts: Finding equation of line of the P-T graph for a gas dissociation reaction

texts:
Gas A (1 mol) dissociates in a closed rigid container of volume 0.16 lit as per following reaction.

  $$\ce{2A (g) -> 3B (g) + 2C (g)}$$

  If degree of dissociation of $\ce{A}$ is 0.4 and remains constant in entire range of temperature, then correct P Vs T graph is

  Slope 0.75 and passing through origin
  Slope 0.8 and passing through origin
  slope 1.1 and passing through origin
  slope 0.4 and passing through origin

\begin{align}
\ce{2A &&-> 3B& + &2C}\\
1-2x&&3x&&2x\\
\end{align}

where $2x$ is dissociation constant. Substituting value of $x$ we get moles of A, B and C to be 0.4, 0.6 and 0.4 respectively.

I am confused about how to proceed after this. How to proceed?


texts: How is bond angle of a molecule measured?

texts:
Simply, how are (average?) bond angles for simple (or complex) molecules such as methane or ethene measured (determined)?
I'm guessing that X Ray crystallography can be used to determine bond angles for, well, materials that have a regular crystalline form. However, is there some other technique for determining bond angles in non crystalline  molecules?
I have researched on Chemistry SE and on the wider web and I can't find this question addressed - which I find strange as it seems to me an elementary question. Apologies if this question has already been addressed in Chem SE - I just wasn't able to find it using my search terms. I can find many resources about predicting bond angle and none on measuring them.


texts:
While reading my chemistry textbook I came across the phrase:

  forward reaction is favoured by decrease in temperature in exothermic reactions.

I was tripped off by the term 'forward reaction', can someone explain in layman terms what is meant by this?


texts: Why doesn’t AlCl3 form the dative bond within the same molecule?

texts:
AlCl3 is said to be an electron deficient molecule as Al only has 6 electrons in its valence shell. Why doesn’t it just form a dative bond with one of the chlorine’s? I know this gives the more electronegative chlorine a positive formal charge, but then the diner Al2Cl6 shouldn’t exist either.
How does forming a dative bond with a chlorine from a different molecule instead of its own  make the situation more stable?


texts: Addition of anodes and cathodes in electrolysis

texts: I am doing a research on the production of hypochlorite through an electrochemical cell using a brine feed. I know that using using an undivided cell would allow for the chlorine atoms that was oxidised at the anode to react with the $\ce{OH-}$ ions in the solution. However, I was just wondering what the addition of more anodes and electrodes would do to the product?


texts: I'm looking for a substance that can be used as an adhesive, but that will burn without producing any ash

texts:
I need to 'adhese' paper to plastic, but I need the adhesive to be flammable and quick burning, but without producing any ash or too many toxic fumes.

I know this is an absurd question, but does anything like this exist?

Thanks so much


texts:
I have tried for several hours to answer this question with no luck. I believe I may be missing a couple of steps or I am not utilizing the given information properly. Nonetheless, some guidance will be greatly appreciated.

The concentration of $\ce{N2}$ in the ocean at 25C is 445 $\ce{\mu}$M. The Henry's Law constant for $\ce{N2}$ is 0.61 x $\ce 10^{-3}$ mol $\ce L^{-1}$ atm $\ce L^{-1}$.

Part A:

Calculate the mass of $\ce{N2}$ in a liter of ocean water.

4.45 x $\ce 10^{-4}$ mol/kg = molality

$\ce{N2}$ in moles = 28.014 g/mol

Using Molality Equation

Molality = $\frac{amount of solute (mols)}{mass of solvent(kg)}$

I want kilograms, thus:

4.45 x $\ce 10^{-4}$ $\frac{mol}{kg}$ = $\frac{28.014 g}{mol}$

Where do I go from here?

Part B:

Calculate the partial pressure of $\ce{N2}$ in the atmosphere

Use C = K x $P_(gas)$

4.45 x $\ce 10^{-4}$ = (0.61 x $\ce 10^{-3}$ mol $\ce L^{-1}$ atm $\ce L^{-1}$)x

x = 0.73 atm


texts:
Is there a way to detect whether sugar is completely dissolved in a cup of water other than looking at the bottom of the cup?

I was wondering if there is a test or something that can be carried out to determine whether sugar is fully dissolved.


texts: Is a Methoxy group meta directing in this problem?

texts:
The following question was given in chemistry today , August 2020 edition , page 47 , problem 9. The answer to this problem is (a).

My Attempt

In the third step , the carbon electrophile can attack at ortho position to carbon substituent to give a 6 membered ring.
But , the O-Methyl group is ortho para directing. The resonance structures are as follows.

The given answer is , a , is possible only if we consider O-Methyl group on Benzene as meta directing group.
My Question:
Is methoxy group on ANISOLE Meta directing ?


texts: Molar ratio of two oxides of the same metal

texts:
A certain "metal oxide" is made of the oxides $A$ and $B$ of the same metal. In the oxide $A$, the metal is divalent, and in B, the metal is tetravalent. By reduction with hydrogen of a quantity $a$ of the "metal oxide", $B$ is transformed into metal, and $A$ remains unchanged, and $a$ drops by $0.15 g$. By treating the same mass $a$ of the "metal oxide" with dilute sulfuric acid, only $A$ reacts and becomes an insoluble sulfate and the mass $a$ increases by $0.75 g$.
  What is the molar ratio between $A$ and $B$?

So far, I have come up with this solution:

Let $Me$ be the metal.
The reduction reaction of $B$ goes like this: $$\ce{MeO2 + 2H2 -> Me + 2H2O}$$
The mass drop of $0.15 g$ must be given by the loss of oxygen that goes into water.
When reacted with dilute sulfuric acid (for $A$): $$\ce{MeO + H2SO4 -> MeSO4 + H2O}$$
The mass increase must be given by the addition of $0.75 g$ $\ce{SO4^2-}$.

Am I right up to this point? What should I do next? How do I use this information?


texts: Amount of substance produced in chemical reaction

texts:
If $15.0\ \mathrm{mol}$ of nitrogen are reacted with $30.0\ \mathrm{mol}$ of hydrogen, how much ammonia will be produced?

$$\ce{N2 + 3H2 -> 2NH3}$$

What I’ve tried is the following:

$$\dfrac{n(\ce{N2})}{n(\ce{H2})}=\dfrac{1}{3}=\dfrac{15.0\ \mathrm{mol}}{x}$$

$$\dfrac{n(\ce{N2})}{n(\ce{H2})}=\dfrac{1}{3}=\dfrac{x}{30\ \mathrm{mol}}$$

I’m not sure how to proceed from here. Any help would be appreciated.


texts: Are the $+\leftrightarrow+$ and $-\leftrightarrow-$ methanol rotational transitions dipole-allowed?

texts:
I am quite confused about the origin and justification of the rotational selection rules of methanol, and I would appreciate any help or references. As far as I understand, there are three irreducible representations of the symmetry group of methanol ($A_1$, $A_2$,and $E$) and the two $A$-type are linked by dipole-allowed radiative transitions. Now, I think the literature also calls these ($A_1$ and $A_2$) $A^+$ and $A^-$ representations, I suppose because the parity of the eigenfunctions which generate the $A_1$ and $A_2$ are $+1$ and $-1$, respectively. Is this correct?

From what I have studied, because the electric dipole generates the $A_2$ representation, usually the allowed transitions follow the selection rule $A_1\leftrightarrow A_2$ (because $A_2\times A_2=A_1$), and I have seen this in many references. However, a lot of strong $A$-type methanol rotational lines are $++$ or $--$. I have noticed that all of these are associated with transitions with $|\Delta J|=1$ and all of the $+-$ and $-+$ transitions are associated with $\Delta J=0$. In fact, I have seen this statement as a selection rule in some papers (in this reference, they say that the $+-$ refers to K-type doubling ... ?), but it is not at all clear to me where does these rules come from.

I assume that the symmetry group of methanol is $C_{3v}$ (in books sometimes they call it $G_6$), and the representations above are usually the three which appear in the character tables. I think the group $C_{3v}$ represent permutations and permutation-inversions involving the protons of only the methyl group, because the other proton is too far and cannot be easily swapped with the others. The $J$ above represent the total rotational angular momentum of the molecule. Apparently, the usual approach is to express the wavefunctions as linear combinations of the product of symmetric top rotor wavefunctions and the wavefunctions  associated with the (hindered or not) rotation of the methyl group around the CO axis. I am interested in transitions at the torsional ground state ($\nu_t=0$) so I guess we can assume that the rotational potential is large. The $K$ I mention briefly above is the projection of the angular momentum in the main principal axis of the molecule, which is roughly aligned with the CO bond. Since methanol is asymmetric, there are two energy levels with the same $J$ and $K$ in the rotational spectrum, which is what I think they call the $K$ doubling.
I am in no way an expert on this, so if you want to point out inaccuracies in what I have just wrote I would be thankful.


texts: Reversed trends in stability of transition metal ions with respect to oxidation state

texts:
Why is titanium more stable with a lower oxidation state, but vanadium more stable with a larger oxidation state?

More specifically, why is $\ce{Ti^{+}}$ more stable than $\ce{Ti^{3+}}$, but $\ce{V^{2+}}$ is less stable than $\ce{V^{4+}}$ in aqueous solution?

Both $\ce{Ti^{+}}$ ($\mathrm{3d^{2}4s^{1}}$) and $\ce{V^{2+}}$ ($\mathrm{3d^{3}4s^{0}}$) have a half filled $t^3_{\mathrm{2g}}$ orbital configuration which imparts stability during the formation of aqua complexes, assuming the $\mathrm{4s}$ electron of $\ce{Ti^{+}}$ can go to the $\mathrm{3d}$ sub-shell.

Is this discrepancy related to the charge/size ratio, which is larger in $\ce{Ti^{3+}}$ than in $\ce{Ti^+}$?


texts: Why are noble metals more electronegative then most metals?

texts:
I was researching about electronegativity when I looked up what a graph of electronegativity within the periodic table is. And, this appeared. I scanned it, matching up everything I knew about the elements up to that table. Yep, Group 1 is all light colored; yea, the nonmetals are all really dark blue culminating in fluorine; and yes, the noble gases are mostly zero (with the exception of the traitors xenon and krypton, which coincidentally are also the only electronegative noble gases!)

But while I was scanning the page from Wikipedia on noble gas compounds, I suddenly realized that there was a compound called xenon hexafluoroplatinate, meaning that xenon could bond with...platinum? Checking the table, I was astonished to find that the entire noble metal group was actually more electronegative then the metals surrounding them! Why?! Aren't they extremely non-reactive? How then can they crave electrons even more then regular metals?


texts: Propose a synthesis of indane from benzene

texts: The question is to propose a synthesis of indane from benzene. I started by the following. The black box is what I am not sure about. I know that the stable carbocation should be the middle one, this is why I am not sure. I need help here.


texts:
I am interested in disaccarides of D-glucose linked 1-4 style. Anomerization is the interconversion of alpha-D-glucose into beta-D-glucose. I realize that this could only be possible on one of the glucose sub-units: The other glucose is obviously unable to inter-convert due to the glycosidic bond preventing ring-opening.

I do not see what would prevent it:


texts: How to run a B2PLYP-D3 calculation in Gaussian 09?

texts:
Can anyone help me to run a geometry optimization and frequency calculation using B2PLYP-D3 functional including the DFT-D3 dispersion correction? I went through Gaussian manual, however, it was not very clear to me.

%NProcshared=4
%Mem=4gb
%chk=fohsdft3
# B3PLYP/aug-cc-pVDZ opt freq scf=tight

Input file taken from fohsdft

0 1
 O                  -3.46278   2.54045   0.
 H                  -2.50278   2.54045   0.
 H                  -3.78324   3.44539   0.

We have the Gaussian 09 Revision C.01 version.


texts: What is the difference between Fukui FMO approach and Woodward-Hoffmann rules?

texts:
If I understand correctly Frontier MO-theory is based on the perturbation theory of reactivity and the Woodward-Hoffmann rules consider conservation of orbital symmetry.

Does FMO use symmetry considerations?

Do the Woodward-Hoffman rules consider differences in HOMO/LUMO energies?


texts: Why is a bridgehead atom bearing a negative or a positive charge unstable? Is it something with the structure of bridge bonds? I am unable to understand why.


texts: What are the products of the reaction of methoxypropane with HBr?

texts:
The products of the reaction of methoxypropane ($\ce{CH3CH2CH2OCH3}$) with $\ce{HBr}$ are?

In my opinion, the products should be: bromopropane ($\ce{CH3CH2CH2Br}$) + methanol ($\ce{CH3OH}$). The first step is the cleavage of the ether. This can happen via the formation of a propyl carbonation or a methyl carbocation. Since the propyl carbocation is more stable, bromine will react with the same to form bromopropane (the other product thus formed is methanol)

But the products given in the solution were propanol ($\ce{CH3CH2CH2OH}$) + bromomethane ($\ce{CH3Br}$). So, what is wrong in my reasoning? And what is the correct reasoning?

Source: NCERT (India) 12th


texts:
In statistical thermodynamics, the quantity omega potential is defined and is different for fermions, photons, phonons and other particles .
I have been understanding the derivations of omega potential for varied particles but I feel I am not really able to physically interpret what it actually is.
Is it similar to Gibbs energy? Since there are many energy parameters like internal energy, Gibbs free energy, energy of states - I am unable to understand what exactly omega potential signifies.
I tried to search over internet but I mostly found literature which was hard to decipher and get a quick answer.
Below is the omega potential for a fermion. What exactly does this equation provide us with?
\begin{align}
\Omega^* &= \sum_i\Omega_i^* \\
&= -KT\sum_i \ln\left[1+ \exp(\frac{\mu -\epsilon_i}{\mu T})\right]
\end{align}


texts: Calculating ideal chemical work using extent of reaction and chemical potential

texts:
I have a electrochemical reactor assumed isothermal and isobaric with 4 reactions and I am trying to calculate the "ideal chemical work' exerted by each reaction using the extent of reactions for each reaction (which I have already calculated).

I am calculating the 'chemical work' $w$ by multiplying the extent of reaction by the Gibbs energy of the respective reaction $k$:

$$w_k = \mathrm{d}G_k = \Delta_\mathrm{r} G_k \cdot \mathrm{d}\xi _k $$

I'm calculating the reaction Gibbs energy $\Delta_\mathrm{r}G$ as basically the stoichiometric sum of the chemical potentials

$$\Delta_\mathrm{r} G = \sum_i(\nu_i \cdot \mu_i)$$

However, I am not sure which conditions to use for the calculation for the reaction Gibbs energy as the reactions are reversible and for 2 of the reactions I have taken the forward reaction as the opposite of the expected (i.e. the forward reaction is the fuel cell reaction but I am operating in electrolyser mode so the extent of reaction for these reactions is negative).
Do I use the conditions at the reactor outlet? Average of the inlet and outlet or am I going about this completely wrong?


texts: Rotational degrees of freedom (3N-5 and 3N-6)

texts:
In spectroscopy we described the electric energy with the approximative separability of internal motions as:

\begin{equation}
E=E_e+E_v+E_r+E_{ns}
\end{equation}

(energies: electronic, vibratory, rotatory; nuclear spin (neclected))

With the Born Oppenheimer approximation of nuclei and electrons you get a formula which describes the degrees of freedoms for vibration motions:

3N-5 for linear molecules
3N-6 for non-linear molecules

This formula can be understood by:

the coordinates of 3N atoms.
3 degrees of motions for the three translation of the centre-of-mass motion
2 (for linear) respective 3 (for non-linear) degrees of freedoms reduced for the rotation of the whole molecule

I guess trans buta-1,3-diene is here described as a linear molecule. [added: in the rigid rotor approximation]

First I was thinking why we are so much interested on the number of freedoms for vibrations. We consider only the rotation of the whole molecule but not around bonds.

Why do we not consider rotation about a bond axis, e.g. for pentane a rotation of an ethyle around the propyle group? (rotation about the C(2)-C(3) axis)

May be because it's much another energy range as rotational energy of about 1-100 cm-1 (typical period of 0.1-10 ps).


texts:
I am reading wikipedia page on Molybdenum bronze and they mention this:

  Blue bronzes, with limiting composition $\ce{A_{0.3}MoO3}$ that is,
  $\ce{A_3Mo10O30}$.

I used to see these fractional numbers (e.g. 0.3) and always wondered whether technically speaking they are correct or not. I understand that, as the wikipedia page says, they are equivalent to the 'full' numbers (e.g. 3) but still I am not sure whether in literature one of them is preferred or more common than the other?


texts: 13C NMR of bromobenzene ipso carbon shielding

texts:
I've got a $\ce{^{13}C}$ NMR spectrum for bromobenzene. The ipso carbon is significantly more shielded (appearing upfield) than the two ortho carbons. Why is this? Wouldn't the electron-withdrawing effects of the halogen be enough to deshield the ipso carbon?

Does it have to do with the fact the $\ce{Br}$ is a deactivating group? I see that on an NMR database site, the ipso carbon for the $\ce{^{13}C}$ spectrum of fluorobenzene is deshielded. Does it have to do with the size difference between fluorine and bromine?


texts: Tungsten-Rhenium alloy connections to Copper. Methods?

texts:
I want to use some fine WRe wire (50 micron diameter, 80/20) in a particular environment where it has to conduct a few millamps of current while supporting 100g of mass. The problem being the contact between the wire and its copper/bronze supports has to be extremely consistent. We are looking for changes in current in the nanoamps, so just clamping it in place will not work given oxide layers, surface electronic effects etc. not to mention mechanical tension.
We have done this before with a Platinum alloy which we could solder.

So, first question - can this be soldered or spot welded in place?

Second, if not can we perhaps alloy the surface with Gold by heating the wire to (say) 2500degC when coated in a Auric salt or Gold foil? And would this help us to find a solder that would "stick" to the surface?


texts: Non-zero dipole moment of parahydroxy phenol

texts: How can we explain the non-zero dipole moment of parahydroxy phenol? I know that it cannot be explained by inductive effect, and has something to do with resonance, but still how can we say it is non-zero? I mean, since it's symmetrical, even the resonance effect should cancel out, right?


texts: How will Back-Bonding affect molecular geometry?

texts:
While going through a textbook, I came across the following line:

  $\ce{R3C-}$ is pyramidal while $\ce{(CN)3C-}$ is planar due to lack of back bonding from the lone pair of carbon atom into the $\pi^*$ orbital of the $\ce{CN}$ group.

I am having trouble understanding how exactly back-bonding occurs in the first species and how it causes the structure to be pyramidal while the latter is planar.


texts: Why oxides with the element in higher oxidation state are more acidic

texts:
We see this trend of acidic-basic property of oxides in most cases:
$\ce{Mn2O7}$ is acidic, $\ce{MnO}$ is basic, the intermediate oxides are progressively less acidic and more basic, as the oxidation state of $\ce{Mn}$ decreases.

What is the reason of this general trend in almost all cases?

I have seen many explanations of this, most of them involving the proton releasing capacity of $\ce{E-O-H}$ bond, in the hydrolysed oxide. But most oxides of transition metals do not hydrolyze in water. So, I am seeking an alternative explanation without having to involve the hydrolysis of oxide. Also, most explanations on the internet lack any reference, so I prefer a reference.


texts: What about the aromaticity of cyclopropenylidene?

texts:
Here's a compound which we have to tell whether it's aromatic or not.

Drawing pi-orbital for the 3-membered ring, I think there are only 2 pi electrons delocalised all over the ring. The orbital having non-bonding electrons on the carbon having sp2 hybridization(carbon no. 1) is not having the correct orientation with the pi-orbital of the ring so these electrons are not delocalised over the ring. 2 being a Huckel's number, I think that this compound should be aromatic.

But the answer key says that it is ANTI-AROMATIC! Where am I going wrong? Perhaps the ring is not planar?

EDIT: The carbon no. 1 doesn't have a negative charge so it is not an anion. It is neutral.


texts: How does electrolyte impurities affect the voltage in a voltaic cell?

texts: I'm currently doing my FYP assignment on electrochemistry (predominantly on voltaic cells). As I was conducting my research I managed to come off with this topic as stated in the title, however, I am not too keen with the term electrolyte impurities. So, my question is what are electrolyte impurities? Can anyone give a brief explanation with an example? And how does the presence of this impurities affect the voltage in a voltaic cell?


texts: Saturated vs unsaturated fats - Structure in relation to room temperature state?

texts:
I'm sure most of us have heard that saturated fats are solid at room temperature, and unsaturated fats are liquid at room temperature. I'm wondering how this relates to their chemical structure -- saturated fats contain only single bonds between carbons, yet to qualify as an unsaturated fat a C=C double bond must exist.

Since a double bond is stronger than a single bond, and the length of the C=C double bond is shorter than that of the single bond, why is it that the fat containing a double bond is a liquid and saturated fats are solids at room temperature? Seems like the double bond would inhibit movement and the resulting substance would be less like olive oil and more like butter.


texts: What to do about a un-dissolved substance?

texts:
To exterminate a coackroach infestation, I bought solid boric acid (in powder form). Rather than awaiting the cockroaches' encounter with the boric acid, I thought about spraying boric acid onto affected areas or cockroaches. I only took high school chemistry, but remembered solubility so checked its solubility in water. I then compared it with the solubility of other compounds, to see if this were an effective idea:

Boric acid: At 100 Celsius, 27.53 g/100 g of water.
Sodium chloride: At 100 Celsius, 38.99 g/100 g of water.

This looks fine, so I poured boiling water into a bottle with the boric acid powder. I shook it and saw the boric acid dissolve. Yet two weeks later, the boric acid seems to have reversed dissolution. Now, it's separated from the water and sits at the bottom of the water.
Can substances do this? What should I do now? I'd need a pot to boil the mixture over the stove. But then, in the interest of health and safety, I couldn't use this pot anymore, so don't want to sacrifice one.
Update: With thanks to and in view of the instructive answers, would it help to refill the bottle, to benefit from the low solubility of boric acid at room temperature? There's only around 10% of water left, with the boric acid sitting at the bottom.


texts: Stability of transition metals in aqueous solution

texts:
Which is more stable in aqueous solution: $\ce{Cr^3+}$ or $\ce{Mn^3+}$? Why?

My approach: $\ce{Cr^{3+}}$ should be more stable as the $\ce{3d}$ electrons will enter the $\mathrm{t_{2g}}$ orbitals. Due to CFSE (Crystal Field Stabilization Energy) of half filled $\mathrm{t_{2g}}$ orbitals $\ce{Cr^{3+}}$ should be most stable.


texts:
Given a source with no gamma rays at 511 keV, what are two reasons for a peak at this location in a gamma spectrum (on HPGe detector)?

I know the annihilation peak from pair production appears at 511 keV and if a gamma ray had an energy of 1533 keV then the double escape peak (1533- 1022 = 511) would also appear at this energy.

Is there another reason that a peak could appear at this location, or are these the only reasons?


texts: What is the composition, function, and classification of “6-Thio-2-Deoxyguanosine” and “13-mer thio-phosphoramidate”? How do I learn more about them?

texts:
I am assigned the task of explaining a biomedical research paper, it is about telomere and telomerase , and it talks a lot about the molecule Thio-2-Deoxyguanosine , 13-mer thio-phosphoramidate and " 6-thio-2-deoxyguanosine 5′-triphosphate".
I have a good understanding of what the paper is saying , but I would really like to know as much as I can about those molecules, their chemical classification and biological function and chemical composition, any ideas?
Thanks in advance
(Please do not mark this as off-topic , as I asked this in biochemistry stack exchange, and they wanted me to put it here )


texts: In almost every butyl rubber product (stopper, gloves, masks) a thin white, powdery spots appear over time. I have tried scraping it, cleaning it with detergent, etc. But it comes back a day or maybe three after cleaning it. What is causing this? Is debris sticking to the rubber? Is the butyl rubber reacting in some way?


texts: Which way is major in this interesting intramolecular SN2 reaction to form different five memeber ring?

texts: Which direction of the intramolecular reactions is major and why? Could someone could depict the mechanism step by step and it is better to draw out the transitional state configurations


texts: Is there a cheap and effective way to make PdZn-Ag foam?

texts: I am trying to design a machine that can convert carbon dioxide into methanol and/or hydrocarbons. My design requires PdZn-Ag foam (nanoparticles), which is made by depositing palladium-zinc vapor onto a silver base, but this seems to be very costly. So is there is a cheap and effective way of producing a measurable amount of PdZn-Ag foam?


texts: Creating an IR Spectrum using Gaussian ADMP Calculation

texts:
I have a Gaussian 16 trajectory for a small cluster of water molecules carried out with ADMP technique. I was wondering if anyone knows how to compute the IR spectrum from the information in the trajectory.
Thank you


texts:
The equilibrium for this reaction is on the left side.

Why is this? I thought since the sulphur in molecule X has bigger p-orbitals than the oxygen in molecule Z, resonance would be a less important factor for stabilization, meaning Z is more stable, and the equilibrium should go to the right.
What part of the concept am I misunderstanding?


texts: How can I prevent the effervescence of a solvent during evaporation?

texts: How can I prevent the effervescence of a solvent like petroleum ether when I evaporate it on a water bath?


texts:
If you leave something outside, its colors seem to inevitably fade or bleach due to exposure. Is this due to UV absorption? What sort of mechanism causes this - is it that man-made dyes deform on a molecular level? Are there notable materials that are exceptions?

I have a full undergraduate background in physics but not so much training in chemistry. A technical explanation would be cool, though.

To turn this string of questions into a focused query, let me refer back to the title:

Why does sunlight cause colors to fade?


texts:
Case -1

In a free expansion of an ideal gas in a region or container, we cannot trace a pressure-volume path since the pressure, temperature and volume of the gas fluctuate unpredictably when the gas fills the region (container).

But since entropy is a state property, the difference in entropy must depend only on initial and final state. So we can replace the irreversible free expansion with a reversible process with same initial and final condition.

Consider an insulated container along with a thermal reservoir attached to it whose temperature can be varied by a knob. It's current temperature is T. A piston is also attached to it. Above the piston is kept a small container containing iron balls (to balance the pressure due to atoms below it). The initial state is the same as the initial state of a free expansion.

Removing the iron balls one by one, we increase the volume with an infinitesimally amount and also by keeping the temperature constant. Since it follows an isothermal path, the heat absorbed by gas from reservoir is equal to the work done by the system (positive).

W=Q

After the final condition by the reversible isothermal process is achieved,

Change in entropy = Q/T
And so, Entropy increases

To sum it up:- we can write :-

To find the entropy change for an reversible process occuring in a closed system, we replace that process with any reversible process that connects the same initial and final states.

Case - 2

Since the process is reversible we can proceed in a reversible manner, i.e we can add more and more iron balls to decrease the volume and consequently the energy must be extracted from the gas and be given to the thermal reservoir, i.e the heat Q is negative. Thus entropy must decrease.

But this does not happen since the thermal reservoir's entropy increases and the system consisting of the gas and reservoir, the total entropy change is 0.

Note - By taking the gas as the system, we do not meet the requirement of the entropy's definition of having a Closed System.

To sum up this :-

If a process occurs in a closed system, the entropy of the system increases for irreversible processes and remains constant for reversible process. It never decreases.

I have explained here in short about what has been given in my textbook for entropy.

My Question - In case 2, we take the system to be the gas as well as the reservoir and so the total entropy change is 0 while in case 1, we take the system to be only the gas. If I take the system, in case 1, to be gas and reservoir, the entropy should be zero. Since heat is being removed from the reservoir thus Heat Q in the entropy formula for reservoir should be negative. And thus the total change should be zero in case 1 as well.

Why doesn't this happen?


texts: Covalent bond nature in electronegativity gap

texts:
Does a large difference in electronegativity mean the covalent bond is weaker?

In a covalent bond between two atoms of different electronegativities, the bonding electrons are pulled towards the more electronegative electron. This makes the bond polar (eg. $HCl$).

In a diatomic molecule, the electronegativity is the same so the electrons are equally attracted to either atom. Does this make diatomic covalent bonds stronger than the former? And if so, as the difference in electronegativity increases, does the strength of the covalent bond decrease?


texts: How to compute 2-electron integral for Hartree-Fock code?

texts:
I'm working on writing my own code for $\ce{H2}$ in an STO-3G basis set using Hartree-Fock (HF), and I am currently stuck on how to construct the two-electron integral matrix.  I know how to evaluate the primitive two-electron integrals, but I can't figure out how to transform that into the $4\times4$ matrix of possible values for this system.

For my previous integrals, I determined the sum of the primitives by constructing a $6\times6$ matrix of the primitive integrals, and did a transformation using a $6\times2$ matrix of the coefficient values from the fit to the Slater function, for example:
\begin{align}
\mathbf{D} &=
  \begin{bmatrix}
     d_{11} & 0 \\
     d_{12} & 0 \\
     d_{13} & 0 \\
     0 & d_{21} \\
     0 & d_{22} \\
     0 & d_{23}
  \end{bmatrix}\\
\mathbf{S} &=
  \mathbf{D}' * \mathbf{S}_{prim} * \mathbf{D}
\end{align}

I tried doing a similar technique for the two-electron integrals but with a $12\times12$ matrix, but the values didn't come out right.  It seems that I need to make a $4$-dimensional array of all the primitive integrals, but I don't know how to evaluate that in order to determine the sum and hence the final
$4\times4$ matrix.

I've been using Szabo and Ostlund's Modern Quantum Chemistry book as my main reference.


texts: Is turning graphite carbon into diamond industrially doable?

texts:
I've read somewhere on the Internet that heating graphite at 4200°K at a sufficiently high pressure would turn it into diamond.

This chart seems to support this idea:

Is that doable industrially?


texts: Relationship between dipole moment of a molecule and electronegativities of constituent atoms

texts:
I want to know if I can calculate the dipole moment of a molecule given the electronegativity values for the atoms comprising it.

I think that dipole moments determine the polarity of molecules, so if one molecule has a larger dipole moment than another, the one with the larger dipole moment is more polar than the other. Is this correct?

Can the magnitude of how polar a molecule is be calculated from the difference in electronegativities among the elements comprising the molecule?


texts:
I'm a bit confused when asked to specify the chiral carbons on this sketch of Propranolol as I'm not sure how the $\ce{H3C}$ and $\ce{CH3}$ play in if they are reversed in the name like that...Does that even matter?

I'm pretty sure the only chiral carbon is the one in the middle of those and the $\ce{NH}$. I've heard that you need 4 different groups/atoms surrounding the carbon for it to be chiral but how much truth is there in that, as I've found several with only 3?


texts: Why HBr has stronger attraction between molecules than CH3NH2?

texts:
Which of the following compounds exhibits dipole-dipole forces as its strongest attraction between molecules?
a) $\ce{CO2}$
b) $\ce{CH3NH2}$
c) $\ce{Kr}$
d) $\ce{H2}$
e) $\ce{HBr}$

From what I understand, $\ce{CH3NH2}$ has an H-bond and it's the strongest form of dipole-dipole. So I thought that would be the answer.
I also knew that $\ce{HBr}$ shows the greatest electronegativity difference between $\ce{H}$ and $\ce{Br}$ atom, it would be a polar covalent bond (?!).
In that case, $\ce{HBr}$ may have stronger attraction between molecules than $\ce{CH3NH2},$ but it is not dipole-dipole. Isn't that correct? Then shouldn't the answer be $\ce{CH3NH2}$ instead of $\ce{HBr}?$
I must have some concept issues here.


texts: How exactly does copper react with hydrogen peroxide, salt and citric acid?

texts:
Context
I have no knowledge in chemistry. I am looking for information about etching circuit boards with citric acid instead of hydrochloric acid because it seems it could be a safer, easier way as citric acid is way safer to handle and not that toxic and harmful.
I am struggling to find much information online about the process since it is not as popular as other etchants.
The process
It seems to work really well if I mix 100ml of 3% hydrogen peroxide solution in water with quite a lot of citric acid powder(4-6 teaspoons) and a bit of salt(around 1 teaspoon), heat everything in a microwave oven to a warmer temperature(not boiling, around 70-80° C) so everything dissolves and then while it's still warm I put the copper clad in it and this seems to work just as good as hydrochloric acid and hydrogen peroxide in room temperature - etches 10x15cm PCB in 15-20 minutes.
Concerns/questions
I have done it a few times in well ventilated room, but I have no knowledge about what exactly happens in the reaction and if it is dangerous in any way, so I would like some insight into what exactly might be happening, what materials are produced and how safe/toxic they are.


texts: Can anyone explain the reaction mechanisms of these synthesis?

texts:
Can anyone explain the reaction mechanism of the following synthesis?

$\ce{2NH4Cl + Ca(OH)2 -> 2NH3 + 2H2O + CaCl2}$

$\ce{(NH4)2SO4 + 2NaOH -> 2NH3 + 2H2O + Na2SO4}$


texts: What is the maximum distance over which van der Waals forces act?

texts:
The VDW radius places a lower limit on the distance between atoms mutually attracted to one another. I am looking for the upper limit:  what is the name of the concept or theory that describes the maximum distance over which the various attractive forces (Keesom, Debye, London...) become operable / take effect?

This question is similar to the following Q, which didn't get fully answered:

Range of distance for Van der Waals force


texts: Computational Chemistry Modelling Redox Potentials

texts: How could I accurately determine the Fe3+/Fe2+ redox potential in an aqueous solution? What would be a good computational model(s) for this?


texts: Determining which hydrate of calcium chloride I have?

texts:
I have calcium chloride in the form of small (1-2 mm) round white pellets, originally bought at a home-brew shop. The packaging gives no indication what hydrate it is. Since each water molecule adds ~16% of the weight of anhydrous CaCl2 this introduces a big error when using it to treat water to a specified amount (in ppm).

Naturally I figured I could throw it in the toaster-oven for a while at 350°F and weigh it every 15 minutes, to figure out how much water was driven off. Results:

0 min.  -  1.15 g.
15 min. -  0.92 g.
30 min. -  0.90 g.
45 min. -  0.90 g.

I originally assumed this would be anhydrous, but after reading that calcium chloride dihydrate decomposes at 347°F, and calcium chloride monohydrate decomposes at 500°F, I'm not so sure.

I couldn't find any other information on figuring out the hydrate online  or indicating what state calcium chloride is typically in (at least that I could understand). Am I correct in thinking I'm left with the monohydrate? Or is it actually anhydrous?


texts: How to derive composite acidity constant for H2CO3*?

texts:
I see the equation (19) and (20) on Stumm and Morgan's Aquatic Chemistry book (Fig. 1 here). They said "a combination of equations 19 and 20" gives Equation 21. But I don't know how the Equation (21) is generated? Because if I make summation of (19) and (20), it will be:

$$\ce{2H2CO3 <=> H2O + CO2(aq) + H+ + HCO3-}$$


texts: How to dissolve composite In2O3 with SnO2 without affecting stainless steel?

texts: I found this article, but it was not helpful. The $\ce{In2O3}$ is probably amorphous. $\ce{HNO3}$ and $\ce{HCl}$ do not work. Any ideas?


texts: Why is only monochromatic light used in polarimeter?

texts: While using the polarimeter to determine optical rotation, why can't we use polychromatic light? What would change?


texts: Would his be a valid synthesis? I'm just unsure about the oxidative clevage step. I know that there is a benzylic hydrogen. So should oxidative clevage work here? What happens to the fragment that is lopped off? Is it also oxidized?


texts: If for a chemical reaction the standard gibbs free energy is negative then :

texts:
If the standard gibbs free energy for a reaction is negative then the forward reaction will take place and the reaction will not be reversible. Is it true ? I have a problem understanding what is gibbs free energy and its significance in a chemical reaction.

Thanks in advance !


texts: How did hypophosphoric acid get its name?

texts:
Why does hypophosphoric acid has a strange name? My knowledge of inorganic nomenclature tells me that the prefix "per-" should be used with "-ic" acids and the prefix "hypo-" goes with "-ous" acids, which isn't the case here. Why is this so?

Just as part of an additional observation, two other things which I find strange about $\ce{H4P2O6}$ are:

I think this is the only oxy-acid of phosphorus having a $\ce{P-P}$ bond.
It has phosphorus in $+4$ oxidation state.


texts: Interpreting data on molecular orbitals in GaussView 6.0

texts:
Introduction
I have been trying to use computational software to gain more insight into how molecular orbitals are formed, as well as their shapes and sizes in accordance with Molecular Orbital Theory.
What I know so far
The molecule I examined was allyl bromide.
What I knew theoretically was that, contrary to VBT, all of the orbitals interact with each other, generating more complex hybrid orbitals. This makes sense, given the fact that GaussView generated 60 molecular orbitals.
Here is a snapshot of the LUMO for this molecule:

Questions
My question is what accounts for the shape of these orbitals?
According to my textbook (which offers a simplified representation for this orbital), the LUMO should behave like an arithmetic combination between the π* orbital of the C-C bond and the σ* orbital of the C-Br bond. But this approach seems localized, as if the influence of other orbitals would be negligible. Since MOT states that all of the orbitals interact to some extent, isn't this approach wrong?

So, how is this LUMO actually supposed to look like? What is the mathematical mechanism behind orbital structure and energy? To what extent is it wrong to just add orbitals together to try and predict their behaviour?
References
Jonathan Clayden, Nick Greeves, Stuart Warren, Peter Wothers - Organic Chemistry-Oxford University Press, USA (2000)


texts: what does "overlapping" of orbitals mean and why does it effect bond strength(VBT)?

texts:
according to valence bond theory, bonds are formed due to the pairing of unpaired valence electrons due to the overlap of half-filled orbitals, and the strength of the bond depends on the extent of overlap.
the concept of "overlapping" sounds visually intuitive and a good qualitative explanation, but the dependence of the strength of the bond on the extent of overlap implies there is a quantitative framework behind this.
Orbitals, as far as I understand, are just physical representations of the 3d probability distribution of finding an electron in a given region given by modulus-squared of its wavefunction. So what does it actually mean when atomic orbitals "overlap"? Secondly, what exactly is the extent of overlap and why does it affect bond strength?


texts: How to distinguish first excited state and second excited state?

texts:
I am learning excited state calculation. In this paper, the author use "$D_0$","$D_1$" represent excited state of nitrate radical.

I know the symbol such as "$D_1$","$T_2$" means first excited doublet state, second excited triplet state. Can I get specific electron configuration of a molecule with these symbol,like ${}^2\!A_2$ symbol in this answer? Or first and second excited state are different in a range of energy? In other word, Can I write a electron configuration use symbols like "${}^1\!A_2$" for $D_1$ state of nitrate molecule?


texts: Fermentation in the presence of UV light

texts: Does the presence of UV light, or any radiation for that matter, affect the process of fermentation? I'm not sure, but I seem to recall somebody telling me before that yeast will not function properly, but I can't seem to find it anywhere. Thanks for any help.


texts: How do I find the expiration time of drug in the following example?

texts:
An optically active drug has one chiral center and only dextrorotatory isomer is effective. Moreover, it becomes ineffective when original activity is reduced to 35 % of original. The rate constant is  $1 \cdot 10^{-8}\ \mathrm s^{-1}$. Find the expiration time of drug in years.
I considered the reaction as $$\ce{A -> B}$$ $$a-x \rightarrow x $$
so the, $\left(a-2x\right)r = 0.35$ and then I got $x$ and then I used
$$ t=\frac{2.303}{k}\log\frac{a}{a-x} $$ I got answer 3.65 years. But the answer given is 1.37 years.


texts: Can you get potassium by reducing KCl with lithium?

texts:
I would have said that the answer was no, because lithium is less reactive than potassium is, so you would expect the reaction to go the other way: with potassium and lithium chloride reacting to produce lithium metal and potassium chloride.
However, this Youtube video from Cody's Lab appears to show that the answer is yes. See https://www.youtube.com/watch?v=fmaZdEq-Xzs (the actual reaction is at around 17 minutes in to the clip).
Can anyone explain this result, which contradicts what I thought I had learned in high school chemistry?


texts:
As far as I know the chemistry of $\ce{Ag}$ and $\ce{Au}$ are almost the same; because $\ce{Ag}$ belongs to the 4d series and $\ce{Au}$ belongs to the 5d series, we know the size of 4d and 5d are similar, so their chemistry remains similar.

Thermal study and mechanism of $\ce{Ag2S}$ oxidation in air

In this paper, it is given that $\ce{Ag2S}$ can be oxidised thermally in the presence of $\ce{O2}$ to give $\ce{Ag}$ and $\ce{SO2}$ over 510 °C. I am not able to find any references where a similar experiment is done for $\ce{Au2S}$. Can somebody please help me ?


texts: why do we denature proteins before mass spectroscopy?

texts: I'm learning about mass spectroscopy in particular the use of it in analyzing protein structure. they said we have to use trypsinolysis to cut the protein to segments, but why does the protein have to be denatured first before trypsinolysis?


texts: Why is the end of a roll of cling film worse at sticking to itself?

texts: I've noticed, with various brands of cling film, that as you get close to the end of the roll it does a much worse job of clinging to itself. Is there a chemical reason for this? Maybe something to do with the manufacturing process?


texts: Calculating enthalpy change for a real gas

texts:
I know this question would be closed citing it to be a homework question. I posted it earlier also. But believe me I have tried it for myself before and that too many times but then couldn't arrive at a solution maybe due to lack of my conceptual understanding. Any help would greatly be appreciated.

  Calculate $∆H$ for $1$ mole of real gas undergoing change of state from $\pu{10^5 Pa}$, $\pu{300 K}$ to $\pu{2e5 Pa}$, $\pu{600 K}$. The values of real gas constants are $a = 0$ and $b = \pu{50 mL/mol}$.

Besides, we have been given $C_p = 20$ (in SI unit) and the relation

$$ \frac{∂H}{∂P} = T\frac{∂V}{∂P} + V$$

(the partial derivative has been taken keeping the temperature constant on both sides of equality.)

My approach has been like this:

First, I wrote the real gas equation. Then I partially differentiated this whole equation w.r.t. $P$ keeping temperature constant so as to find $∂V/∂P$ and substituted the value of $∂V/∂P$ in the equation given in the question. My actual aim was to use the formula

$$\mathrm{d}H = nC_p\mathrm{d}t + \left(\frac{∂H}{∂p}\right)\mathrm{d}p.$$

Next, I substituted $(∂H/∂p)$ from the given equation in the the given formula, but now I am stuck here.


texts: Can an organic molecule have a triplet ground state?

texts:
Can the ground state of an organic molecule be a triplet. This would imply something like a "HOMO" formed by 2 degenerate levels and less than 4 electrons to fill them.
If yes, what are the conditions?


texts: Can we create human muscles artificially?

texts: Can chemical processes create sarcomeres? Not the entire cell with mitochondria, just what basically makes the muscle contract, myosin and actin, in the goal of reproducing our muscles. The source of energy and the activation of troponin could then be controlled externally.


texts: What is the oxidation state of bromine in BrO3?

texts:
I came across this compound $\ce{BrO3}$ in my textbook, and was trying to find the oxidation state of bromine.

This is how I proceeded:

Since this is not a superoxide or a peroxide, or any other case where the oxidation state of oxygen is not −2 according to this, so the oxidation state of oxygen should be −2.
For oxidation state of Br as $x$, I can have $x + 3(-2) = 0$, which gives $x = +6$.

But, according to Wikipedia, the +6 oxidation state of Br is not listed.

I was confused because my book (NCERT Part I for class XII) says that "The bromine oxides Br2O, BrO2, BrO3 are the least stable halogen oxides (middle row anomaly) and exist only at low temperatures."

Please tell me where I am going wrong.

P. S. This is not an ion $(\ce{BrO3-})$ but a neutral compound.


texts:
I need to calculate the kinetics energy of a photon and I'm trying to deduce a correct expression for calculating it.

So we have that

$K= \frac{1}{2} m_fv_f^2$

So $v_f= c$

For De Broglie equation we have that $m_f = \frac{h}{\lambda c}$

And then

$K = \frac{hc}{2 \lambda}$

But apparently the correct expression is:

$K = \frac{hc}{\lambda}$

Can someone help me figure out what I'm doing wrong?
Thanks!


texts: How to separate KCl from NaCl and MgCl₂?

texts: Having mixed powder of $\ce{KCl}$, $\ce{NaCl}$, and $\ce{MgCl2}$ (and, perhaps, some crap), how can the components be separated?


texts:
I stored water in a bucket (of aluminium probably), and some random fractal-like patterns are formed on the water:

See here for some more pictures.

Why this happened?

I'm unable to reproduce it. How can I reproduce it ?


texts: Dissociation percentages of N2O4 at different pressures using Gibbs' free energy

texts:
\begin{align}
\ce{N2O4(g)&<=>2NO2(g)} &
\Delta_\mathrm{r}G^\circ &= \pu{4.7 kJ mol^-1}
\end{align}

  Knowing that the standard values for pressure and temperature are $\pu{1 bar}$ and $\pu{298 K}$ respectively, find:

  a) the dissociation grade (noted as $\alpha$) of $\ce{N2O4}$ at equilibrium, in standard conditions

  b) the dissociation grade of $\ce{N2O4}$ at equilibrium and at $\pu{298 K}$ / $\pu{10 bar}$

First, we find $K$ from $\Delta G$

Then we write the partial pressures as the molar fraction of the compound times the total pressure of the system (at equilibrium)

After that, we write the relation for $K_p$ using partial pressures

and I'm stuck...

\begin{align}
  \Delta_\mathrm{r}G^\circ &= -RT \ln K &
  \Rightarrow K&=0.15 \mathrm{~(unitless)}
  \\
  P_{\ce{N2O4}} &= \frac{1-\alpha}{1+\alpha}\cdot P &
  P_{\ce{NO2}}  &= \frac{2\alpha}{1+\alpha}\cdot P &
  K_p = \frac{(P_{\ce{NO2}})^2}{P_{\ce{N2O4}}}
  \\
  \Rightarrow K_p &= \frac{4\alpha^2}{1-\alpha^2}\cdot P
\\
\end{align}

My question is: how can I convert between $K$ (which is unitless) and $K_p$ (which is not) so that I can find the dissociation grade at $\pu{1 bar}$ and $\pu{10 bar}$?


texts:
Before I begin, I think it's worth mentioning that I know little about chemistry and even less about knives.

My question is this, having seen many people talk about how patinas work and the best ways of applying them and which ones are best etc., It seemed to me like people just assumed that they work, presumably because they heard someone else do it, and them from someone else and so forth but that doesn't always make it true. If anyone has any idea If there is any reasoning behind this and if there any flaws behind the logic in it that would be greatly appreciated.

I don't exactly want to ruin or change my new knife for no reason. I assume people might think that this works similar to the thin oxide coating on aluminium, but my guess is that the corrosion acts like it would on any metal and slowly "eat away" at it.

So, simply, does it work?


texts: Is this a phase change in a gas under Thermodynamic Equilibrium?

texts:
The above graph shows the molar density (i.e. n/V from PV=nRT) of a gas plotted against pressure. There are two regions with good fit to a linear relationship which I have coloured green and blue (though these are all from a single set of measurements. The visual distinction is just to highlight where the linear fit applies)

My rusty physical chemistry knowledge suggests that the regions where there is a linear fit are in Thermodynamic Equilibrium as the Ideal Gas law would appear to be holding. Given that we have two linear regions I would also conclude that there is a phase change and that the whole is actually in Thermodynamic Equilibrium when we account for the phase change (i.e. n is different between the two regions)

Is this naïve analysis based on a foggy recollection of Phys Chem lectures from 20 years ago correct or is there another explanation for this data (and if so what is the explanation)

Update

To clarify on the hypothesized phase change. The suggestion is that this phase change is a X + X <=> X2 phase change where X and X2 are both gaseous but the X2 form is only thermodynamically stable at lower temperatures (which correspond to the lower pressures). i.e. not the more common gas-liquid phase change


texts: How do I measure out these salts using the proper method?

texts:
I'm planning on preparing a water solution using the following salts of reagent grade with approximately these concentrations:
\begin{array}{lr}
  \ce{CaCl2}  & \pu{10 mg/L}\\
  \ce{Na2SO4} & \pu{1 mg/L}\\
  \ce{NaHCO3} & \pu{20 mg/L}\\
  \ce{KHCO3}  & \pu{5 mg/L}\\
  \ce{NaF}    & \pu{0.25 mg/L}\\
  \ce{NaNO3}  & \pu{1 mg/L}\\
\end{array}
I suspect some of these salts are hygroscopic. Do any of them need to be oven dried prior to weighing? What is an appropriate procedure for this (i.e. what temperature, for how long, etc.). Are there any other requirements in order to correctly produce a solution of the above composition?
It's for an experiment where I'm needing to replicate a natural water source so I'm needing to be as accurate as possible.


texts: Trouble understanding interplanar spacing using miller indices

texts:
We know that two parallel planes have the same Miller indices, this implies that we can have an infinite number of parallel planes close to one another all of which have the same Miller indices.
But it's claimed that

the interplanar distance between two adjacent planes is given as $$d_{hkl} = \frac{a}{\sqrt{h^2+k^2+l^2}}$$.

I can't understand what adjacent means here?
to me the next parallel plane to any plane is infinitely close to it, hence the $$d_{h k l }=0$$
Can someone please explain what exactly is interplanar spacing?
Thank you.


texts: why heavier transition metals can stabilise higher oxidations states

texts:
I believe similar questions have been asked but this is different and the answers I have looked at don't answer this question. I have read that oxidation states of heavier transition elements (Ru, Os etc) are more stable than first row transition metals.
I understand how they can get to the oxidation state (which is the usual answer to this question) but im asking why they are more stable then the oxidation state is reached. And although an element like Os is bigger meaning the ionisation energy should be small for the first few electrons doesn't the lanthanide contraction mean the valence electrons have a stronger effective nuclear attraction.
By more stable I mean why is RuO4 explosive but OsO4 on the other hand is stable and FeO4 doesn't exist.


texts:
If we add a weak acid such as carbonic acid in water it weakly dissociates to form bicarbonate and hydrogen ions . Now water already has some hydrogen ions, having a ph=7.

So now indirectly we added hydrogen ions and base (bicarbonate ) ions to water which already has a hydrogen ion concentration.  The resulting solution is acidic . This means that in the addition of equimolar hydrogen ions and bicarbonate ions( base) hydrogen ions dominate.

The only reason which I can think of is this: lets say there were 1000 hydrogen ions in water, now addition of 100 hydrogen ions and 100 bicarbonate ions will cause a net increase in hydrogen ion concentration because bicarbonate wont be able to counteract the increase in hydrogen ions because bicarbonate, when acting as a base, will be in equilibrium with carbonic acid. I.e. 100 bicarbonate ions won be able to neutralize 100 hydrogen ions present in the solution, and because of their equilibrium they will ionize only say 50 and overall, and there will be an increase of 50 hydrogen ions.

Is my explanation correct?


texts: Why molten lithium burns through the glass but sodium not?

texts:
It's well-known in laboratory practice that one shouldn't melt lithium in a glass equipment and there isn't such rule about other alkali metals.
You may damage the glass with sodium but lithium will make a hole in your flask.

So, why does this rule only hold for lithium?


texts: I know that formic acid will dehydrate upon heating to 100°C (under normal pressure) or adding sulfuric acid. What other catalysts can be used to induce this reaction?


texts: Why does potassium react the most vigorously with water?

texts:
Link to exam

Which metal reacts most vigorously with water?
(A) Ca (B) K (C) Mg (D) Na

The given answer is B and the reasoning is that is is the most electropositive since it the furthest left and down according to periodic trends.
However, isn't $\ce{K}$ the conjugate acid from a strong base -- $\ce{KOH}$? So isn't the conjugate base of a strong acid quite weak? So why would $\ce{K}$ react strongly?


texts: Why do the f-block elements ( inner transition metals) have an oxidation number of +3?

texts: The f-block valence electrons understandably include the outermost two from 6s. But why do the f-block elements have an oxidation number of +3, pulling an electron from an inner shell, not even a d-block electron?


texts: Working principle of Fisher-Price Light Sketcher

texts:
I was just searching around in my store room and I found this Fisher-Price Light Sketcher. I am just amazed how the light from the pen draws on the board without even contact! I searched a lot but couldn't find a working principle of this thing. Probably the light emitted by the pen is black light. Can you tell me how it works? Thanks! The product: https://service.mattel.com/us/productDetail.aspx?prodno=L3244&siteid=27
The text mentions that Light from the child-safe pen reacts with special ink on the product drawing surface. How does this work? And is this type of light safe for human skin?


texts: Why is the acylium ion stable? Doesn't the inductive effect of oxygen destabilize it? Compared to an alkyl cation, is an acylium ion more stable or less stable?


texts: What happens when an electron in a metal is excited?

texts:
For special glasses, crystals, or gases absorb energy from an electrical current or another laser they become "excited." The excited electrons move from a lower-energy orbit to a higher-energy orbit around the atom's nucleus. When they return to their normal or "ground" state, the electrons emit photons.

I think the excited electron is always the valence electron. However In metals the valence electrons are not contained to orbitals, they exist in a sea of electrons that flow freely through the object. Does this mean that valence electrons in metals can not be excited or can not move up orbitals? or perhaps the next electron in line moves up an orbital. If so does it join the sea of electrons? (I'm just throwing out ideas here).

Maybe I'm misunderstanding what it means to be 'excited' because, as it says, energy from current can excite electrons.

Any insight is appreciated.


texts:
I'm working in a project, and for a specific thing, I need to work on a possible recovery of $\ce{HCl}$ in aqueous phase. I found a patent on the net in which they use an amine to make a complex with $\ce{HCl}$.

They say in the summary:

  where a complex between the
  tertiary amine and the methyl chloride is formed, a hydrocarbon
  solvent, such as mineral spirits, is added to the phase containing the
  complex and the complex is then thermally dissociated.

I have never heard about that until yet.

I did some research on Sigma-Aldrich and I found that but I have not too much information, if you have ever heard about that can you please tell me a bit more about? Is that a molecule or a mixture?


texts: What would be the concentration of products in this calcium producing system?

texts:
I wanted to figure out a way to make calcium metal with potassium oxide. $\ce{K2O}$ undergoes disproportionation at $\pu{350-430 °C}:$

$$\ce{2 K2O -> K2O2 + 2 K}$$

Now, if I mixed in $\ce{CaO}$ (1:2 molar ratio with $\ce{K2O})$ it would react with the potassium formed in the first reaction, forming calcium metal and $\ce{K2O}$ that would feed back into the first reaction. Eventually I should be left with mostly $\ce{K2O2}$ and calcium metal, but since these two react together, this can't be as simple.

Reaction of these two would lead to the same mixture as I started with. Is there a way to figure out what the concentration of Ca will be when the reaction reaches equilibrium?


texts: How do you calculate the dipole moment of larger molecules?

texts:
I know that the dipole moment is obtained by:

$$
\vec{\mu} = Q \cdot \vec{d}
$$

with the condition that charges of a pair of atoms are equal and opposite, i.e. $\ce{NaCl}$.

But, in order to obtain the molecular dipole moment of water, how is the $\ce{-OH}$ group handled? What about even larger systems such as $\ce{NH3}$?

For example, the water molecular dipole moment is 1.85 Debye. How was this value was obtained?

I have read 1, 2, 3, and chemistry textbooks.

I am interested in a more mathematical or physical description.


texts: Materials for growing large quality sugar crystals

texts: I am trying to grow large, solid, quality crystals on a course fabric, and I was wondering what other than sugar I would need to put in my solution, as well as how long it may take, and if food coloring/another dye would change the color of the crystals without destroying them. Any tips or advice would be great.


texts: How to identify where a bond will break and where a bond will form (acetals)

texts:
In the following reaction:

The $\ce{H}$ from $\ce{ROH}$  joins the $\ce{O}$ in the carbonyl.

So the Alcohol breaks at the bond between the $\ce{R'O}$ and the $\ce{H}$.

How do I know this occurs, and that the alcohol doesn't break at the $\ce{R'}$ and the $\ce{OH}$ bond (and then the $\ce{OH}$ joining the $\ce{C}$, and the $\ce{R'}$ joining the carbonyl $\ce{O}$)?

Is it because the electronegativity difference between the  $\ce{H}$ and the $\ce{O}$ is greater than the electronegativity difference between the  $\ce{R'}$ and the $\ce{O}$?


texts:
I realize anything NMR-related is essentially physics, but I figured this was a better place to ask this. I have this issue fairly regularly (with one instrument in particular) where my baseline ends up looking like the one in the image below. The (inverted) sine wave-shape is what I'm referring to, if it's not obvious.

Is there something specific that causes this baseline shape?  Is there a way to fix it? Preferably I'd want to use something that fixed the signal/input, but if I have to resort to a processing method, I'd settle for that.


texts: Speed at which methanol dissolve in water?

texts: Suppose that in a container of volume V we pour V1 of methanol and V2 of water (V2>V1), supposing that V2 is big enough that all the methanol will be dissolved, do we have to mix them mechanically or the diffusion will be enough if we want them to mix in seconds?


texts:
I learnt that halogens always form covalent bonds to becoms diatomic molecules. So why is astatine monoatomic?

I mean they have the same properties, why shouldn't they all be diatomic?


texts: Are geminal disubstituted alkenes more stable than their cis/trans isomers?

texts:
I know for a fact that cis alkenes are less stable than trans alkenes due to steric repulsions.

But what bugs me is the fact that why systems such as 2-methylprop-1-ene, where I believe steric repulsions are greater than that in cis-but-2-ene, are more stable than its cis and trans counterparts.

I saw this being given in the stability order of alkenes in Solomons and Frhyle.
I looked up Morrison and Boyd and it said the same thing. Paula Bruice said otherwise stating trans to be more stable.

Which is the correct order, and why?

Paula Bruice

Solomons and Frhyle

For reference, free energies of formation:

$$
\begin{array}{c|c} \text{Compound} & \Delta G^{\circ}_{f}\text{ in kJ mol}^{-1} \\\hline \text{2-methylpropene} & 58.1 \\ E\text{-2-butene} & 63.0 \\ Z\text{-2-butene} & 65.9  \\\hline \end{array}
$$


texts: How would I find R/S configuration in this case?

texts:
I know about the rules to assign R/S configurations when the orientation of each bond to the central Carbon atom is given- the whole, give them a priority order based on their Atomic number/masses, move the group with the least priority as far as possible from the eye, and then draw an arrow joining the other groups in order of their priority. If the arrow goes clockwise, it's an R configuration, otherwise it's an S configuration. But how would I do the same when the orientation of none of the groups are given? The answer key says that compounds I and II have R orientation- but when I simply apply the steps above to the  compound I, I get S. How do I do this?
https://imgur.com/a/K57fCJL is the question


texts: How to calculate bond angle of simple molecules quantitatively?

texts:
Hi I'm new to this forum so spare me if I've made mistakes.

Our high school chemistry teacher explained that bond angles of different molecules varies slightly, e.g. 107 degrees in ammonia and 104.5 degrees in water, which could be predicted by VSEPR theory qualitatively.

I have checked literature either through google or stack-exchange, but none point me to any formula/algorithm/computationally inexpensive methods to  find non-ideal bond angles by calculation.


texts: Difference between actual position of electron and Radial Distribution Probability

texts:
Its known that the radius of maximum probability of 2s orbitals is more than that of 2p orbitals. It means that the maximum probability of finding an electron in an 2s is further away from electron than that of 2p. This means 2p electron are mostly found nearer to atom than the 2s atom. Well! thats totally wrong.

So I want to know the factors due to which 2p orbital lie further to nucleus than the 2s one.


texts: Difference between non-thermal and thermal ionized gases

texts:
Why or when does non-thermal plasma become thermal? How do we know before hand if the ion temperature will differ from the electron temperature, on what parameters does it depend - where is the quantitative gap between the two options?

(Has it to do with the heat release in ion-recombination reactions?)


texts: Aqua regia has the famous property of being able to dissolve noble metals, like gold and silver. I read that this has to do with the generation of nascent chlorine. How does this happen and how does it help to dissolve such metals?


texts: Can there be more than one combination of reactant/product concentration for a specific equilibrium constant?

texts:
For an elementary reaction like $$\ce{A + B -> AB},$$ $$K_{c} = \frac{\ce{[AB]}}{\ce{[A][B]}}$$ and $$\frac{\mathrm{d}\ce{[AB]}}{\mathrm{d}t} = k\ce{[A][B]}.$$ If I let the reaction reach equilibrium, and at this point, without altering temperature, suck away $\ce{A}$ and add $\ce{B}$ at the same rate (so $-\mathrm{d}\ce{[A]}/\mathrm{d}t = \mathrm{d}\ce{[B]}/\mathrm{d}t$) and alter both concentrations slightly, once I am finished, will the system still be in equilibrium or try to shift?

What if the reaction is not an elementary reaction such that $\frac{\mathrm{d}\ce{[AB]}}{\mathrm{d}t} = k\ce{[A]}^n\ce{[B]}^m$?


texts: What is the mechanism of functionalisation of nanoparticle using long chain alcohols

texts:
How can long chain alcohols(not thiols) be functionalised on the surface of silver or gold nanoparticles?

I have read in an article that Polyvinyl alcohol is used as a capping agent for silver nanoparticle synthesis, but what is the mechanism for that?

What type of bonds form between nanoparticle and the long chain alcohol(covalent or ionic)?

Is there any relationship between chain length of alcohols(or thiols) to the functionalisation of nanoparticles?