texts: I am looking for a source for the radius of gyration of dexamethasone in aqueous solution. Does anyone know where I could get it from? Even better would be an estimation of the Stokes radius, but the radius of gyration will do.


texts:
I came across this about fullerenes-

All carbon atoms are equal and the undergo sp2 hybridisation. Each carbon atom forms three sigma bonds with three other carbon atoms. The remaining electron at each carbon is delocalized in molecular orbitals which in turn give aromatic character to the molecule. This ball-shaped molecule has 60 vertices and each one occupied by one carbon atom and it also contains both single and double bonds with C-C distances of 143.5 pm and 138.5 pm respectively.

It speaks of fullerenes being aromatic, which would imply that the bond lengths in fullerene must be equal. I am aware of the fact that resonance won't mean that bond lengths be equal in all cases, for example, I found this about naphthalene-

The molecule is planar, like benzene. Unlike benzene, the carbon–carbon bonds in naphthalene are not of the same length. The bonds C1−C2, C3−C4, C5−C6, and C7−C8 are about 1.37 Å (137 pm) in length, whereas the other carbon–carbon bonds are about 1.42 Å (142 pm) long.

I know that such a case in naphthalene is due to dissimilar conjugation as it behaves as a benzene ring joined to a diene. Speaking of graphite, as far as I know, all bond lengths are equal in a layer due to conjugation that is quite comparable to benzene and even better than naphthalene (resonance energy per atom). But I would like to know exactly what happens in a fullerene molecule.


texts: Differentiating between Titration, Buffer, diluted buffer, Deionized H₂O

texts:
I had a chemistry lab where we had to titrate three solutions with $\ce{HCl}$: a buffer, a diluted buffer and deionized water. My partner and I didn't label the charts we made, so now I have to figure out which one is which.

The way I see is that from the Henderson-Hasselbalch equation:
 $\mathrm{p}\ce{H} = \mathrm{p}K_a + \log\left(\ce{[A^{-}]/[HA]}\right)$,
 the diluted buffer should have a larger slope at the beginning then the original buffer solution.

My question is, is my logic correct, and how do I differentiate between the original buffer and the deionized water?


texts:
I was solving a question where I had to determine a way to convert benzene into n-propyl benzene.
I figured out a way by first performing Friedel-Craft acylation with propanoyl chloride and then performing Clemmensen reduction to form the desired compound.
On checking the solution,  there were 2 alternative ways portrayed:
One was the same method I had used.
The other involved reaction of benzene with n-chloropropane in the presence of $\ce{FeBr3}$.
However wouldn't there be carbocationic rearrangements taking place that convert the carbocation to isopropyl carbocation?
Please tell me what prevents the rearrangements from happening in the second case.


texts: What do positive, negative and zero overlap of atomic orbitals mean?

texts:
I am confused about positive, negative and zero overlaps.

Do they represent the extent of overlap or are they related to the bonding and anti-bonding orbitals as described in Molecular Orbital Theory?


texts: In a paramgnetic material the induced dipole moment of atoms or (molecules) of the material aligns with the external field. I can understand this by Zeeman splitting. A term symbol splits into states with different energy. According to Boltzmann distribution the lower energy states should have more population. These states would correspond to dipole moments aligned with the external field therefore the field inside the material should be enhanced. Why then the nuclei in NMR "feel" a lower magnetic field? I read that it was according to Lenz law. Is that because we take into account only the field in the region near to the nucleus? I mean if we had a paramagnetic material then the field should be greater.


texts:
I know that the signs '+' and '-' are written in case of lobes of p and d atomic orbitals, which denote the sign of the wave function of that orbital. But s-orbital is also a wave. So, it should also have negative regions. However, most books show the s-orbital with a '+' sign only. What is the significance of this?
Again, the 2s, 3s, 4s, ... etc orbitals have some nodes. So does these nodes indicate the seperation of '+' phase and '-' phase? The 1s orbital does not have any node.So where is the '-' part of the 1s orbital ?


texts: Doubt in a question related to electronic transitions in Bohr's orbits

texts:
Question
In Bohr series of lines of hydrogen spectrum, the third line from the red end corresponds to which one of the following inner-orbit jumps of the electron for Bohr orbits in an atom of hydrogen?
(A) $3\to2$
(B) $5\to2$
(C) $4\to1$
(D) $2\to5$
Only one option is correct.

My approach
I just drew the electron transition diagram like this:

Then, I counted the third line from the red end, i.e., from the left side starting from the first line of the particular series. I then counter checked with the given options. Surprisingly two options matched, i.e., option B as well as C. I don't know further how to decide which is the correct answer out of B and C, since only one answer is correct. There is no other details mentioned in the question and thus I am confused.
Please clarify my doubt.


texts: What is the mechanism of the Clemmensen reduction?

texts:
I have learned that we can reduce a ketone to an alkane using the Clemmensen reduction, where we treat the ketone with amalgamated zinc in the presence of $\ce{HCl}$.

My book didn't mention the mechanisms for this type of reaction and I couldn't find an answer by searching Google.

How does this reaction actually take place? Are there carbocation rearrangements in this reaction?


texts: How to define a new solvent in Gaussian09 to run SCRF?

texts:
I want to run computation of my system in sulphuric acid with Gaussian 09; however sulphuric acid is not among the built-in solvents in G09. I know I have to give some parameters for the new solvent I define (including static and dynamic dielectric constants). Here's an example of my input files where I try to redefine a solvent water2.

#p b3lyp/6-31G(2df,p) int(grid=ultrafine)  SCRF(Solvent=Water2,Read)

Comment

0 1

...

stoichiometry=H2O1
solventname=Water2
eps=78.3553
epsinf=1.77556

G09 keeps telling me that "SCRF(Solvent=Water2,Read)" is not correct. I want to know what the correct input will be.


texts: How to find the amount of moles given mass percentage data

texts:
A hydrated aluminium sulphate, $\ce{Al2(SO4)3.xH2O}$, contains 8.10% of aluminium by mass. Find the value of x.

My attempt: (Assuming 100g sample)

Calculate the amount of aluminium using the formula $\mathrm{amount = \frac{mass}{molar~mass}}$, yielding $\mathrm{0.300~mol}~\ce{Al}$ having a mass of $\mathrm{8.10~g}$.

Determine the amount of sulphate ($\ce{SO4^2-}$) by recognising a ratio between the aluminium and sulphate. 2 moles of aluminium to 3 moles of sulphate, 2:3.

Using the ratio, I determined the amount to be $\mathrm{0.450~mol}~\ce{SO4^2-}$, which has a mass of $\mathrm{43.2~g}$.

I can now calculate the mass of the anhydrous compound, aluminium sulphate ($\ce{Al2(SO4)3}$), to be $\mathrm{51.3~g}$, leaving $\mathrm{48.7~g}$ of anhydrous substance, or $\ce{H2O}$.

Using the figure of $\mathrm{48.7~g}$, I can calculate the amount of $\ce{H2O}$ using the formula $\mathrm{amount = \frac{mass}{molar~mass}}$ which produced a figure of $\mathrm{2.71~mol}~\ce{H2O}$.

By using the principle of relative amounts, I find that x=9.

The answer is incorrect. Where did I go wrong?


texts: Why does the alkyl group anti to the hydroxyl migrate in Beckmann rearrangement?

texts:
Background: Many organic reactions involve the migration of an alkyl group from one position to the adjacent one. The migration of the alkyl group is decided by its migratory aptitute i.e. electron-richness. It generally follows the priority order of hydride > phenyl > higher alkyl > methyl.

Main question: The Beckmann rearrangement also involves an alkyl migration. However, this migration is not governed by migratory aptitude. In fact, the $\ce{-R}$ which is in anti-position to the hydroxyl group in the oxime migrates, irrespective of its migratory aptitude! My question is why is this so? And are there other organic reactions which have such a rule for alkyl migration?

MasterOrganicChemistry  and Wikipedia don't even mention the word "trans" or "anti" anywhere. My textbook obviously doesn't mention anything either, hence I am driven to ask this question.


texts: Why is the principal energy of an electron lower for excited electrons in a higher energy state?

texts:
Several places state the 'principal energy of an electron' can be calculated as such:

$$E = \frac{2π^2mZ^2e^4}{n^2h^2}$$

Another equation I found was:

$$E = -\frac{E_0}{n^2},$$

where $$E_0 = \pu{13.6 eV}~(\pu{1 eV} = \pu{1.602e-19 J})$$

As seen in these equations, the greater the principal number ($n$) of the electron, the lower the principal energy $E$ of this electron.

However, the principal number $n$ is associated with higher energy states. The farther from the electron, the higher the energy state of this electron.

I seem to be fumbling the concept of 'principal energy of an electron.' What is the difference between the 'energy state' associated with the principal number, and the 'principal energy' of an electron? What exactly do the 'principal energy' equations mean? I read somewhere that it would be the energy it would take to "unbind" or ionize the electron, which would make sense, but I have not seen 'principal energy' explained as the ionization energy of an electron anywhere else.


texts: Units to use in Morse potential Equation

texts:
I am to graph the Energy potential curve (in $\text{cm}^{-1}$) for a molecule (HI),in the fundamental electronic state, according to the Morse oscillator. I believe I am to use this equation
$$E(R)=D_e\left[1-e^{-a(R-R_e)}\right]^2$$
However when I look at the units they don't seem to make sense to me. Parameters $a$ and $D_e$ should be $\text{cm}^{-1}$, so that the energy can be In $\text{cm}^{-1}$ as well. But that doesn't coincide with the formula given for the parameter $a$:
$$a=\left(\frac{\mu}{2D_e}\right)^{\frac{1}{2}}2\pi\nu_e$$
I know $\mu$ has atomic mass units, and $D_e$ supposedly has $\text{cm}^{-1}$. $\nu_e$ should be Hertz. So the units really don't add up between equations, and I don't know where I am going wrong.


texts: Changing of UV-Vis peak absorption after heating Ni(en)2(NO2)2

texts:
(c) The trans-isomer of $\ce{Ni(en)2(NO2)2}$ D is red $(λ_\mathrm{max} = \pu{500 nm}).$ It can be heated to give a new trans-isomer E, which is violet $(λ_\mathrm{max} = \pu{560 nm}).$ Assume that, within each of D and E, the two $\ce{NO2-}$ ligands exhibit identical coordination modes.
(i) Rationalize the colours of D and E, explaining the difference in d-orbital splitting. [6]
(ii) Sketch structures for D and E. [2]

I've been stuck on this for some time to the stage that I'm probably just melting brain cells. Any help is appreciated.
My initial thoughts were that it was due to one end of the en ligands dissociating to form a 4-coordinate species in sq planar (owing to $\ce{Ni^2+} = \mathrm{d^8});$ however this would mean that it goes low-spin and then the splitting of d-orbitals becomes even greater, hence would expect a smaller UV-vis peak wavelength as a higher $E$ jump between occupied/unoccupied d-orbitals. (Δ(Sp) > Δ(Oct))
I'm probably going about it the wrong way so yes, any help appreciated! Would an MO approach be more useful here rather than CFT?


texts: Priority order of attack of grignard reagents on functional groups

texts: Recently I was solving carbonyl compounds and I came across this. Is there some priority order, or logic behind why alcohol reacts first with Grignard reagent and then ketone. Whereas ester could've reacted with 2 moles of RMgX but didn't.


texts: Why are there different chemical structures for epinephrine (adrenaline)?

texts:
The Wikipedia structure is:

Note the empty bond at far-right.

"Journals on the Web" has:

CH3 added at far-right.

And rxlist.com shows:

There's an extra H going into the page! Is one of these incorrect, or are they all consistent but w/ some implied bonds or something?


texts: Frontier orbital analysis of zinc-catalysed carbonyl-ene reaction

texts:
Q1. Is the $\sigma_\ce{C-H}$ bond a donor in this reaction? If not, then can we take the alternate combination (HOMO of alkene, LUMO of the $\ce{C-H}$ bond and, HOMO of the carbonyl)?
Q2. We can also draw the LUMO of the carbonyl group in the other possible manner(simply flip the shaded lobe on each atom, hence keeping the node). The reaction would then have to go through an antarafacial manner.
Why do we draw the LUMO in this manner?


texts: Application of the Woodward-Hoffman rules to a [14+2] cycloaddition

texts:
I am just doing some pericyclic practice problems and I am just trying to understand the Woodward Hoffman rules.

The attached picture is a problem I attempted that was checked against the answers but I am confused how the symmetry is allowed.

When I add the (4n + 2) and 4n together I get 4. Doesn't n have to be an integer and the sum an odd number for the symmetry to be allowed?

EDIT: I copied the answer below with incorrect stereochemistry. Please refer to the second image for the correct stereochemistry

EDIT: Correct stereochemistry below


texts:
I believe this is a conceptual question and might sound silly, but please help me with it:

I can understand when ions like $\text{Co}^{3+},\text{Mg}^{2+}$ are called electron deficient, because they have no valence electrons, but how do I call a compound like $\text{AlCl}_3$ electron deficient? What's the basis for calling such a compound electron deficient?


texts: I keep trying to figure out how current is conducted through an electrolyte but all I can find are BS half answers. They say the ions conduct, but the specifics are poorly explained or absent. I understand that if you, for example, put sodium chloride in water it will disassociate into positive sodium ions and negative chlorine ions, and that an electric field would cause the ions to move, allowing a current to flow. But what happens once the charges get to the electrodes? Obviously, they can't just stay there in elemental form stably. I would expect the sodium, once given an electron, to be looking for a way to give that electron back. Would it cause the water to split into hydrogen gas and hydroxide ions? On the chlorine side, would the chlorine atoms simply turn into chlorine gas. If this is all correct, it seems one would end up with sodium and hydroxide ions. Does it still conduct then? If so, how so? And don't you have a solution of sodium hydroxide? It seems this process necessitates that the water be split. Is there any salt or other compound which would act similarly but not result in electrolysis (just conducting)?


texts: Where can I find the released combustion energy in NASA CEA rocket problem?

texts:
I am using NASA CEA program for a study project.
I have read the CEA Nasa user's manual over and over, yet I haven't found an answer to my question which is :
where can I found in the output of NASA CEA the energy released during a combustion in a rocket problem ?
For instance, using CEA I have simulated the following problem :

Rocket problem with infinite area-combustor and assuming equilibrium in the combustion chamber
pressure chamber at 1 bar
combustion of H2 with O2

And in the output I have these data, but I am not sure where or how I can find the energy released by the combustion of H2 and O2 : Is it the yellow-highlighted one ? Or is it the red-circled one ? Or it's not given, I have to calculate using the output data ?
Thank you


texts: How does activated carbon catalyse oxidation?

texts:
Context: I am doing an experiment on the quantitative analysis of ascorbic acid in a blackcurrent syrup using fluorescence spectroscopy. In order to do so, ascorbic acid was first oxidised into dehydroascorbic acid. Emission reading was then recorded.
An aliqout of the sample was taken and boric acid was added to form a complex that would be fluorescent inactive to account for other impurities that are fluorescent active and would interfere with the results. The loss in emission between the original sample and the sample with boric acid was used to deduce the amount of ascorbic acid present.

The reagents used were: acetic acid and sodium acetate as buffer, metaphosphoric acid, and activated carbon. In this scenario, how does activated carbon aid in the oxidation of ascorbic acid?

Also, I've done some searching online and found that the purpose of metaphosphoric acid was to prevent the atmospheric oxidation of ascorbic acid. Why would we want to prevent the atmospheric oxidation of ascorbic acid if what we wanted to achieve was to oxidise it anyway?


texts: Autocatalysis / Electroless plating of mercury

texts: As a project I am trying to plate mercury onto a powdered metal amalgam of $\ce{Cu}$ & $\ce{Ag}$. I am using solution of $\ce{HgCl2}$ in normal $\ce{HCl}$ (a reducing agent), Any thoughts for increasing the efficiency of plating process on the metal alloy powder? How can we improve the $\ce{Hg}$ plating on the metal powder? Can the concept of autocatalysis / electroless plating be helpful in this case?


texts: How can iodine oxidise hydrogen peroxide?

texts:
The following is mentioned in NCERT (government textbook in India used in all schools) under chemical properties of $\ce{H2O2}:$

(iv) Reducing action in basic medium
$$\ce{I2 + H2O2 + 2 OH- -> 2 I- + 2 H2O + O2}$$

I feel the reaction is not correct. Since $\ce{H2O2}$ is a moderate/strong oxidizing agent, I don't think it can be oxidized by iodine and the reverse reaction should be true since $\ce{O2}$ is a strong oxidising agent and $\ce{I-}$ is a reducing agent. Can someone please verify it?


texts:
So, I am having difficulty with the following explanation/question.

  (Based on your MO diagram and pi bonding theory) explain why $\ce{CN-}$ is a soft base and prefers to bind to soft acids.

Now, I know that the HOMO is the 5 σ MO and that the electron pair in the 5 σ MO is, to a large extent, more concentrated around the carbon.  So, is $\ce{CN-}$ a soft base because it has a low energy HOMO but large magnitude HOMO coefficient?  Does polarizability have anything to do with it?

When $\ce{CN-}$ reacts with a soft acid what physical changes in the cyanide molecule would such a reaction lead to?

Not really sure about this one.  Would it have to do with the donation of the electron pair in the HOMO and therefore change the HOMO?


texts: How were the absolute masses of atoms calculated before the mass spectrometers?

texts:
I understand that true (non-relative) masses of atoms are calculated with a mass spectrometer. using this relationship: Centripetal Force = Force due to magnetic field(B)

But I was wondering how masses of atoms were calculated before the mass spectrometers were invented.

(Please don't get this mixed up with relative atomic mass. That's not what I'm talking about.)


texts: Does the amount of solvent interaction energy depend on the absolute gas phase energy?

texts:
I've been performing Gaussian 16 DFT optimization and single-point energy calculations on different conformers of a rather large organic molecule. My first series of calculations was without solvent model, the second one was with dichloromethane solvent effects included via SMD model. When I analyzed the results, I saw that the absolute energy of the conformers became lower in solvent (as expected due to solvent interactions) but also the energy differences between the conformers became smaller. The order of conformers according to energy however did not change a lot. This would mean that conformers having a higher energy in gas phase than other conformers would experience more stabilization by the solvent. Is this possible? How could this be caused?
If more information is needed about my problem, feel free to ask.

Thanks in advance


texts: Negative temperature as limiting case for two-level system

texts:
For N particles in a two-energy-level system, with energy levels being 0 and $\Delta$, the internal energy tends to $N \Delta /2$ as temperature tends to infinity. At this point, the occupancy of each energy level is equal, and any further increase in internal energy would lead to a decrease in the entropy of the system.

Temperature is defined as $T = (\frac{\partial U}{\partial S})_V$. Using this definition, for a state with equal occupancies described above, the temperature should be negative. Where is the contradiction?


texts: Finding (∂U/∂V )T = n^2a/V^2 for a van der Waals gas

texts:
$\displaystyle dU = \left(\frac{\partial U}{\partial T}\right)_V dT + \left(\frac{\partial U}{\partial V}\right)_T dV \to dU = C_v dT - C_v\left(\frac{\partial T}{\partial V}\right)_U dV$

Not sure what I do here. Thank you in advance.


texts: Why do higher intermolecular forces lead to a higher change in temperature?

texts:
We performed an experiment in chemistry where tissue paper soaked in various chemicals was wrapped around the end of a temperature probe.

The chemicals with stronger intermolecular forces had a lower drop in temperature (from room temperature to final, after most of the alcohol had evaporated off). For reference, two of the chemicals were ethanol with hydrogen bonding and n-pentane with only London dispersion forces.

My question is why.

Below are just my initial attempts to understand

My initial feeling was that the molecules with stronger intermolecular forces would take more energy to evaporate and would have a larger temperature change than those chemicals with weaker bonds, but we see the opposite in the data.

I was also thinking that maybe that went the other way: The chemicals with stronger forces had fewer molecules evaporate off, so the temperature drop was smaller. Is this more correct?

Thank you!


texts: What conditions to use to crystallise Equine Myoglobin?

texts:
What are the crystallisation conditions for Equine Myoglobin?

I've tried repeating some from the PDB but no success.


texts: How does increasing the Hydrogen Concentration of CuSO4 (electrolyte) affect electroplating of copper

texts:
I'm trying to find an answer as to how lowering the pH of the CuSO4 solution during electroplating of copper affects the amount of copper deposited onto the cathode.

My very basic understanding is that if the concentration of hydrogen is too high, then there is greater competition and hydrogen will be reduced instead of the copper. (But why?)

Also the reason why CuSO4 is acidified is to prevent copper from hydrolysing from the solution as it prevents the oxidised Cu2+ from reacting with the OH- ions to form Cu(OH)2 precipitate.

However, I was wondering if this could be related to electrode potentials. That the increase of H+ concentration in the electrolyte affects the electrode potential, which is why increasing H+ increases the competition and makes it more likely for H+ to be reduced.

Im trying to explain why there is an optimal pH for the electroplating of copper and I need background information as to why too low pH or too high pH decreases the amount of copper deposition on the cathode.


texts: Chile 2017, One of the Largest Fires in South America: Wood Ash Derivates for Industrial Applications

texts:
Hi: We're a group of people who wants to help people, domestic animals and wildlife recovering from this fire.

Summary:

We're having in Chile one of the largest fires in South American history.
More than 1,235,527 wood acres have already been burned
The fires aren't stopped but rather increased
People, domestic animals and wild fauna are suffering badly
We're a group that wants to help in the recovery of the lands that have been burned
There're several products with industrial applications that can be extracted from Wood Ashes. For instance, Potassium Peroxide
Our idea is to do the following onsite:

Build over a truck(s) a mobile laboratory
Go to the places where there's too much ashes (making the soil extremely alkaline and hard to recover)
Get some of the ashes, and extract a product with industrial application  that can be sold for a price that produce profitability
The profits would be used for supporting the people who lost everything, helping the wildlife to recover faster and financing the project

The Question:

Are there Wood Ash sub products that you think are suitable to be extracted on site and allow the mentioned objectives mentioned above?
Do you know a technology to be used to do the extraction onsite?
Do you know a chemist who could be interested to participate in the project?


texts: Role of intermediate in determining the exothermic or endothermic nature of reaction

texts:
I was given a question to answer:

Which of the following reactions is “not” exothermic?

$\ce{CH3-Cl + CH3-CH3 -> CH4 + CH3-CH2-Cl}$
$\ce{CH3-Cl + (CH3)3-CH -> CH4 + (CH3)3C-Cl}$
$\ce{CH3-Cl + CH2=CH-CH3 -> CH4 + CH2=CH-CH2-Cl}$
$\ce{CH3-Cl + CH2=CH2 -> CH4 + CH2=CH-Cl}$

Now, what my teacher told was that; the 4th reaction proceeds through a very unstable free radical as compared to the other three reactions. Therefore the 4th reaction must not be exothermic.
But I have a doubt that stability of an intermediate in any reaction can only give us an idea of the activation energy required to reach the intermediate from the reactant via a transition state. Whereas the stability of product (with respect to the reactant) determines whether a reaction is endothermic or exothermic.
So how do we check here product stability to determine exothermic or endothermic nature of the reactions?
Or if something is wrong in what I think then please correct it.


texts: Identifying the gas given ratio of its specific heats

texts:
The ratio of the heat capacities $\frac{C_\mathrm p}{C_\mathrm v}$ for one mole of a gas is $1.67$. The gas is:

  a) $\ce{He}$
  b) $\ce{H2}$
  c) $\ce{CO2}$
  d) $\ce{CH4}$

I know how to answer this by analysing the degrees of freedom of the gas molecule. Is there any other way to derive the ratio?


texts: What are the biochemical ramifications of ingesting of distilled water?

texts:
Are there any distinct biochemical reactions that are affected by the ingestion of distilled water?

The water is "distilled" in its literal sense.


texts:
The picture shows the correct answer.

At Eq., I have:

3 Mol of A
1 Mol of B
12 Mol of C

I was looking at each answer in terms of ratio of reactants to products, but its clearly not correct since I got 0.4/2.0. How should I think when approaching this problem?


texts: What is the effect of temperature changes on rate of chemisorption?

texts:
In chemisorption, if temperature increases, then after some time why does its rate decrease? I tried to explain it by Le Chatelier's principle but I don't believe it's valid as chemisorption is irreversible, so there won't be any equilibrium.

I also wonder what effect would the decrease of the temperature have on chemisorption. Going by the above pattern I believe it should be the reverse but I am not sure.


texts:
I once saw a problem, iron ions(II) titrated with potassium dichromate to produce Fe(II) and Cr(III). If I am to write the net ionic equation of this reaction, I got to make potassium dichromate on the right into dichromate ion since potassium is a spectator.
I got very confused over here. Why should you see potassium as a spectator if K(II) will be balanced as 2K on the right.


texts: Mechanism of reaction of benzenediazonium chloride with ethanol to form benzene and acetaldehyde

texts:
In my textbook, all that was told was that ethanol is a mild reducing agent and hence reduces BDC while oxidising itself. Is there any mechanism or am I just supposed to remember this like a redox reaction?
I did search for a mechanism but did not find anything. I have no idea as to how this reaction works. Can someone please point me in the right direction?


texts:
In a container with volume 4 litres we have 2 moles $\ce{COCl2}$ and 4 moles $\ce{Cl2}$. Equilibrium is achieved when 60 % of the reactant $\ce{COCl2}$ is wasted 60 %. What is the equilibrium constant $\ce{CO + Cl2 <=> COCl2}$?
In my book it is explained the solution. I understand it when it says that $\ce{PCl5}$ is the substance that is wasted, but after finding the concentration of each substance to find the constant it uses the formula: $k=I$ understand that we get the concentration of $\ce{Cl2}$, $\ce{COCl2}$, but then when he finds the constant it divides $[\ce{CO}]\cdot[\ce{Cl2}]$ with $[\ce{COCl2}]$.

But I think that they should divide $[\ce{COCl2}]$ with $[\ce{CO}]\cdot[\ce{Cl2}]$.


texts: What would the phosphorus-NMR of trifluorodiphenylphosphorane look like?

texts:
I'm fairly new to NMR especially $\ce{^{19}F}$ and $\ce{^{31}P}$ NMR, we've not been formally taught NMR yet but we're expected to know $\ce{^{19}F}/\ce{^{31}P}$ NMR for our exam for basic molecules.

I know $\ce{PPh2F3}$ will have a trigonal bipyramidal geometry, I know in $\ce{PPh2F3}$ the phenyl groups will be equatorial due to the torsional angle and sterics. This leaves two fluorines axial and one fluorine equatorial, but  what I don't understand is why this gives a doublet of triplets signal (for $\ce{^{31}P}$). Any explanation to why you get this pattern would be helpful, taking into account my fundamental understanding of $\ce{^{31}P}$ NMR is not so great.

also what would the $\ce{^{19}F}$ NMR be for the same molecule?


texts: Selectivity in Thermodynamically-Driven Silyl Enol Ether Formation, and Optimistic Avoidance of Protecting Group Chemistry

texts:
I am aware of the regioselectivity of silyl enol ether formation at an unsymmetrical ketone under 'thermodynamic conditions'.
Does this selectivity extend to systems containing more than one ketone group?
In other words, if some starting material were to contain two ketone groups, under 'thermodynamic conditions' with one equivalent of TMSCl, would the overall most substituted double bond product be formed in majority?
Context:
I am particularly curious about the specific example below as it would form part of a solution to a synthesis problem I've been working on. I fear that here, assuming the answer to the above is yes, the somewhat conjugation-supported product might be formed between both carbonyls instead? If this is the case I would protect the lower ketone as a ketal which wouldn't be unhelpful as my next intended step is a Mukaiyama-Michael, which might pose another selectivity issue due to possible competition with Mukaiyama-Aldol (?). Naturally, I just want to avoid using protecting groups.
I apologise for the crude appearance of my ChemDraw-ings.


texts: Can the idea of entropy be extended to orbitals?

texts:
The forward reaction for: $\ce{HF<->H^+ +F^-}$ is entropically favourable; but energetically unfavorable: as there is too much electron density for $\ce{F^-}$ ion to cope up. That's a reason why $\ce{HF}$ is a weaker than $\ce{HI, HCl}$ etc.

But, can there be another explanation for weak acidity of $\ce{HF}$?

How about we introduce the idea of entropy to orbitals. Let me explain, in $\ce{HF}$ the elctron is in a molecular orbital of greater region than in $\ce{F^-}$. So, the valence electron pair is in an entropically more favorable state in $\ce{HF}$ than in $\ce{F^-}$: where it is contained in little space. That's why, $\ce{HF}$ is more favorable than   separated $\ce{H^+}$ and $\ce{F^+}$.

Maybe, for other hydracids of same kind eg. $\ce{HI, HCl}$ this effect isn't so important. That's why they are stronger acids.

Share your thoughts.


texts: Which type of orbital, 4s or 3d, is closer to the nucleus of an atom?

texts:
In my textbook it is explained that 4s electrons show greater penetration than that of 3d electrons, and, thus, the energy of the 4s orbital is lower than that of the orbitals in a 3d energy sublevel. Here is what my textbook (General Chemistry Principles and Modern Applications, Tenth Edition) says exactly:

  "For example, because of the extra penetration of a 4s electron over that of a 3d electron, the 4s energy level is below the 3d level despite its higher principal quantum number n..."

I took this to mean that 4s electrons are closer to the nucleus than that of 3d electrons. Is this true?

Furthermore, after doing research on why electrons are removed from the 4s orbital before the 3d orbital (a topic that still confuses me) I ran into a source that seemingly contradicts what my textbook says:

  "When you talk about ionisation energies for these elements, you talk in terms of the 4s electrons as the outer electrons being shielded from the nucleus by the inner 3d levels."

From: http://www.chemguide.co.uk/atoms/properties/3d4sproblem.html

This sounds like it contradicts my textbook. Perhaps it does not. However, it does raise a few questions (one of which I posed earlier). Does the term "penetration" mean that the 4s electrons are closer to the nucleus than the 3d electrons? If not, what does it really mean? Also, what distinction is there between the aufbau process and ionization regarding differences in energies between 4s and 3d orbitals?


texts: Does the Hydrogen/Chlorine reaction in light proceed instantaneously?

texts: When a mixture of Hydrogen and Chlorine is exposed to short wavelength light it reacts explosively. Does the reaction happen simultaneously through the bulk of the mixture?


texts: The question is asking for the major organic product. This seems like an $S_N1$ reaction to me as there is a weak base in $\ce{CH3OH}$ and heat. If it is, shouldn't there be 2 products. One with the $\ce{OCH3}$ in the equatorial position (shown in the answer key here) and another with the $\ce{OCH3}$ in the axial position. I think there are 2 products because the C attached to Cl is an asymmetric center, thus there will be an $\ce{OCH3}$ that is wedge and an $\ce{OCH3}$ that is dash.


texts: What's the reaction when bleaching hair with lemon juice (citric acid)?

texts: Is the acid working as an oxidizer or reducer with the melanin of the hair breaking down the bonds?


texts: Defining sensitivity of TOF Mass Spec - Does the detector play a role?

texts:
Looking at TOF MS systems, my current understanding is that temporal resolution results in mass resolution - so by controlling the flight time (with distance) and sampling rate, you can start to distinguish smaller and smaller changes in mass. Hopefully, this is correct.

Where I'm confused is when people start talking about sensitivity.
I heard a talk where they mentioned femtogram and attogram sensitivity.

Does this refer to the amount of the sample they are using?
OR is this referring to the minimum amount of the analyte they can detect?
Does that translate to needing a certain number of ions to hit the detector in a single scan to have a signal significantly above the noise?
Finally, what types of detectors are capable of measuring so low and are there any issues with them?

Thanks for your help!
Cheers


texts:
The atomic masses of gold and platinum are 196.96657 u and 195.084 u respectively, meaning that (on average) an individual gold atom is heavier than an individual platinum atom.
At the same time, the van der Waals radius of gold is 166 pm, whereas that of platinum is 175 pm. So an individual gold atom is smaller than an individual platinum atom.
Given these data, how is it possible that platinum metal can actually be denser than gold (21.5 g/cm3 vs 19.3 g/cm3)?


texts: What is the effect of oxygen on soap foam?

texts:
I've been wondering the effect of $\ce{O2}$ on soap foam in a closed, test room. The room contains a candle and soap foam.

That is to say: if the room has lower and decreasing $\ce{O2}$ in its air, does the foam is effected (i.e., the soap produces lower foams)?

PS: I have very basic knowledge in Chemistry, and, excuse me if I didn't formalize the question in a good manner.


texts: What mixing ratio of ethanol and acetone has the lowest freezing point?

texts:
I am in the lab trying to make a sample for 1H NMR. It has to remain liquid at the lowest possible temperature.

I was recommended to use a mixture of ethanol and acetone because when they're mixed in the right proportions, the mixture has a very low freezing point.

I can not find this proportion anywhere. Does anyone know where to look for these things?

Here is a picture of what I'm looking for, but with ethanol and acetone instead of water - solvent:

PD:it's very likely that its methanol instead of ethanol, please let me know... I have access to both, I just want the one that will go to the lowest temp.


texts: Finding change in enthalpy for a reaction with an atom in elemental state using bond energy

texts:
For example, consider $\ce{C(s) + O2(g) -> CO2(g)}$.

If we know the bond energies for $\ce{O=O}$ and $\ce{C=O}$, can we determine $\Delta H$, even though there is carbon in the reaction? Can we ignore it, or is there a certain way to compute the energy?


texts:
Suppose we carry out a reaction in a bomb calorimeter whose starting temperature is $298.15\ \mathrm K$. Here we assume $\Delta V$ is close enough to zero that we consider the process to be at constant volume.

Based on $\Delta T$ and the calorimeter constant, we determine the internal energy change for the reaction at constant $T$ and $V$, which I'll call $\Delta U_\mathrm r$. (We can assume constant $T$ because we know how much heat flow would be required to return the calorimeter to its starting temperature.)

A typical pchem textbook will then say you can calculate what $\Delta H$ would be if the reaction were instead carried out at the same temperature, but at a constant external pressure of $1\ \mathrm{bar}$, namely $\Delta H_\mathrm r^⦵$, from the $\Delta U$ we determined in the calorimeter, as follows:

$$\Delta H_\mathrm r^⦵=\Delta U_\mathrm r^⦵+\Delta pV=\Delta U_\mathrm r^⦵+p\,\Delta V\approx\Delta U_\mathrm r^⦵+\Delta n_\text{gas}RT$$

But: we didn't determine $\Delta U$ at standard state ($1\ \mathrm{bar}$).  We determined it at constant volume. Thus, strictly speaking, when we do the following calculation using the $\Delta U$ from the calorimeter

$$\Delta H_\mathrm r^⦵\approx\Delta U_\mathrm r^⦵+\Delta nRT$$

aren't we additionally making the approximation that $\Delta U_\mathrm  r=\Delta U_\mathrm r^⦵$? I.e., aren't we ignoring the volume-dependence of $U$? Typically, this is a very good approximation since, for most substances, $U$ is only weakly dependent upon $V$. But it seems it's an approximation nonetheless. If so, it is one that is not (but should be) explicitly acknowledged in these textbooks.

There are other approximations, of course, such as the one shown above, that $p\Delta V\approx\Delta n_\text{gas}RT$ (ignore volume change in liquids and solids, and use ideal gas law to calculate volume change due to change in number of moles of gas), but I'm specifically wondering about this one.


texts: Confused about parity of atom and chirality

texts:
OK. I'm working in computational chemistry and the problem that bothers me is:

Given a molecule, I know that it has a central asymmetric atom with some parity which is either "Anticlockwise" or "AntiAntiClockwise" (or a really stupid way to say clockwise). I have the molecule drawn on a 2D canvas (they are in one plane).

For this example you could imagine 4 atoms. I have to specify which atoms lie in a different plane (3D perspective) and I can't seem to understand why is the parity important in that case? I'm using the SMILES O[C@@](F)(Cl)Br notation.

I'm really confused about this concept and it seems like the internet doesn't offer me a lot of information about it. So please tell me how is parity related to the plane the atom lies in? How can I map the edges and dashes to the SMILES  of this structure?


texts: Why does copper(II) sulfate react with ammonia?

texts:
We've done preparation of Tetraamminecopper(II) sulphate $\ce{[Cu(NH_3)_4(H_2O)_n]SO_4}$ using copper sulphate and 50% ammonia solution.
Initially, a pale blue color of $\ce{Cu(OH)_2}$ appeared with turbidity then after a dark blue color solution is obtained.
It is a substitution reaction Initially,
why formation of $\ce{Cu(OH)_2}$ is taking place ??

Is initially NH3 acting as a base and ripping off the proton from the complex $\ce{[Cu(H_2O)_6]^2+}$?
Then on the further increment of the concentration of $\ce{NH_3}$, it starts to act as Nucleophile??
My high school teacher taught me that acid-base reactions are always fast, so in this example is everything is about kinetics? What is the role of the thermodynamics? From where can I get a quantitative explanation with proper data?


texts: Does RedP+HI reduce all carbon functional groups to alkane?

texts:
I've seen the related questions 1 and 2, they're not duplicates

So. when introducing Red P+HI reduction, our teacher said that it is the strongest reducing agent, and it can reduce any functional group i.e. all of these: carboxylic acid,  acid anhydride, ether, amide, acid halide, carbonyl, and nitrile

However, today I stumbled upon a question in my book involving a step in the synthesis of ibuprofen, where they did not reduce the carboxylic acid group even after using RedP+HI. I searched a lot on the internet, and finally came across this paper which confirms this:

paper - notice they've only reduced the alcohol in step (ii)

This now makes me wonder if what I was taught is actually correct. Which brings me to the question:

  Does RedP+HI really reduce all carbon functional groups to alkane?


texts: Reversed size dependence in ion solubility

texts: My book says that solubility increases with interionic distance, because the attractive forces between ions gets smaller. However, if one of the ions in a binary ionic system is very large compared to the other, the trend is reversed. For example, CsF has greater solubility than CsCl. Why is this?


texts: Is the Henderson–Hasselbalch equation volume independent?

texts:
Looking at this equation $\mathrm{pH} = \mathrm{p}K_\text{a} +\log\frac{[\ce{CB}]}{[\ce{A}]}$ makes me think that it is concentration independent.

What I mean is, when we look at $\frac{[\ce{CB}]}{[\ce{A}]}$, the volumes cancels out, so we are only left with the molar ratio of the conjugate acid and conjugate base. So does this mean that the pH is only dependent on the molar ratios? Obviously not, because $0.003\ \mathrm{mol/L}$ of acid $\ce{A}$ and $0.003\ \mathrm{mol/L}$ of its conjugate base is going to have a different $\mathrm{pH}$ from $0.3\ \mathrm{mol/L}$ of acid $\ce{A}$ and $0.3\ \mathrm{mol/L}$ of its conjugate base right?

What am I missing here? This is seriously confusing me. Please help, I want to use the Henderson–Hasselbalch equation to calculate the $\mathrm{pH}$ of a weak acid as it’s being titrated with a strong base, but this is making me reluctant about the results.


texts:
I am confused with the last step of clozapine synthesis:

How can the amine group attack the amide group to form the amidine in such acidic environment? Is the intermolecular reaction between an amine and amide group feasible under not too extreme conditions?


texts: Second-step activation energy in SN1 reactions

texts:
In SN1 reactions, it's known that there are generally two steps, with the first being the R.D.S step involving carbocation formation and the next having a lower activation energy.
Why does the second step require activation energy at all? It's going from being a carbocation to a stable molecule, which will be more stable than the former, no matter how stabilized a cation it is.


texts: Is there a chemical which fluoresces only after coming in contact with water?

texts: I require an easily available chemical compound which in its pure form, does not  fluoresce under UV light. However upon coming in contact with water (at room temperature) it fluoresces under UV light.


texts: Are there economical ways of synthesizing nanotubes?

texts: I've heard Nanotubes will replace Li-ion batteries in the future and it is much more relevant. I just wanted to know could it really replace Li-ion batteries? Is synthesizing nanotubes economic?


texts: Why isn't auto ionisation of water considered when we find the pH during salt hydrolysis?

texts:
$\ce{H+}$ concentration from the auto-ionisation of water is $10^{-7}$
If we have $\ce{HA}$ as weak acid and $\ce{BOH}$ as weak base having $\mathrm pK_\mathrm{a} = 3.2$ and $\mathrm pK_\mathrm{b} =3.4$ respectively, we are get a salt $\ce{AB}$.
When we find $\ce{H+}$ concentration for this salt using the formula,
$$\ce{H+} = \sqrt{\frac{K_\mathrm wK_\mathrm a}{K_\mathrm b}}$$
We get $\ce{H+}$ concentration in the solution to be $10^{-8}$.
In such a scenario, why don't we add $\ce{H+}$ concentration from the auto-ionisation of water to the $\ce{H+}$ concentration?


texts:
How can one electrodeposit Nickel on a substrate using a liquid crystal template?

substrate is Indium Tin Oxide coated plate and the template is cetyl trimethylammonium bromide(CTAB)+WATER+ETHANOL


texts: Generating hybrid atomic orbitals for Boron

texts:
My professor was showing us how to form hybrid atomic orbitals for Boron by taking a linear combination of rotated 2p orbitals and 2s orbitals (of Boron). This was done in a particular manner such that the geometry of BH3 is correct. We were given BH3:

He proposed 3 new hybrid atomic orbitals:

2Py(rot,1): a 2Py orbital rotated 30 degrees clockwise

-2Py(rot,2): take the negative of 2Py, which is then rotated 30 degrees counterclockwise

Can someone provide a visual (picture) showing the "mixing" of the atomic orbitals to create the three hybrid orbitals (while maintaining the same orientation of BH3 as in my first image)?

EDIT: Feodoran helped me clear my confusion regarding the first hybrid wavefunction. If possible, I would still be interested if someone could display the formation of the hybrid wavefunctions with some visuals.


texts: Why does oxygen in OH have an oxidation state of 2-?

texts:
I am watching videos on Khan Academy in order to go over redox reactions (a really weak area for me.) In Sal's video, "Oxidation state trends in periodic table" at 7:10, he says:

  If you had to pretend this was an ionic bond, then maybe this hydrogen
  would fully lose an electron, so it would get an oxidation state of
  plus 1. It would be oxidized by the oxygen.

  And the oxygen actually has fully gained one electron. And if we're
  forced to think about this is an ionic bond, we'd say it fully gains
  two electrons. So we'd have an oxidation state of negative 2.

I'm having a hard time understanding how he is able to deduce that oxygen has an oxidation state of 2- given the above reasoning. He does add that the states add up to the overall charge which is helpful, but I think I need a little more clarity than that. My reasoning for oxygen being 2- is that "it usually is because my textbook says it usually is," which is probably an even worse explanation.

Could anyone clarify this for me?


texts: Junction Potential at Each End of a Salt Bridge

texts:
I am having trouble with the concept of a junction potential as it relates to the salt bridge of an electrochemical cell. I understand that a junction potential occurs between two solutions of differing concentrations and that it depends on the mobilities of the ions in solution.

For example, between a solution of sodium chloride and deionized water, a junction potential will develop when the ions of the sodium chloride solution are allowed to diffuse into the deionized water. The junction potential occurs because the chloride anions will diffuse more quickly into the deionized water (due to its greater mobility) than the sodium cations. This leaves the sodium chloride side of the junction between the two solutions more positive and the deionized water side more negative, creating a junction potential.

However, what I do not understand is how a junction potential develops in an electrochemical cell. A junction potential develops at both ends of the salt bridge. Are the junction potentials at either end different? If so, why? If not, how would a junction potential occur between two solutions that don't directly interact (the two solutions in this case being the solutions of the respective half cells)?


texts: What is the purpose of halogen in oxidation of thiols?

texts: Why do you need molecules like $\ce{Br2, I2}$ as one of the reagents in oxidation of thiols? I am saying this because when you look at the mechanism of reaction, it seems that you can have same product of disulfide by simply joining two protonated thiols (by strong base like $\ce{OH^{-}}$) together. Thanks.


texts:
Most of the books dive into formation of micelles by soaps. They go on talking about alkyl sulphate and carboxylates, but never do they mention anything about cations. My textbook says that at critical micelle concentration, molecules of colloid aggregate to form micelles.

Can things like $\ce{RNH4+}$ or $\ce{R4N+}$ form micelles, why/why not?


texts: What would happen if equal parts of hydrochloric acid, mercury and methylene chloride were mixed?

texts:
I was going through the archive of Real Life Comics (first time reader, enjoying it so far), and in one of the comics, the main character of the comic reveals he has ordered hydrochloric acid, methylene chloride and mercury from an online chemist, and then says he ordered them to "pour them together and see what he gets".

I assume mixing these chemicals is probably not a good idea, but what would happen when mixing them? Like, I don't expect anyone to try this out (though if you can or have done this, your experience is definitely valued), but based on the properties of these chemicals, what would be the likely outcome?


texts: How can we write the wave function in quantum mechanics?

texts: In quantum mechanics, while writing the wave functions we can take a product of the spatial and the spin parts.But what does it means? What is the meaning of the spatial wave function and the spin wave function?


texts: OpenBabel: how to get correct SMILES from Gaussian output?

texts:
I would like to get the molecular structure as SMILES from Gaussian output files. OpenBabel seems to be the tool made for such tasks.
However, the structure is not always correct.

One example:

OpenBabel conversion Gaussian09 to SMILES (left):

N1(c2ccccc2)[C]2C=CC=CC2=[N]=C1c1ccccc1

SMILES generated by some drawing program (right):

C12=CC=CC=C1N(C3=CC=CC=C3)C(C4=CC=CC=C4)=N2

Is there a way (maybe a special option in OpenBabel which I missed) to directly get a correct output or to do some "postprocessing" to correct the SMILES afterward for example with RDKit or others?

Update:

One way to increase the yield of correct output seems to be the following.
If you convert the Gaussian output to InChI first, for the above example you'll get:

InChI=1S/C19H14N2/c1-3-9-15(10-4-1)19-20-17-13-7-8-14-18(17)21(19)16-11-5-2-6-12-16/h1-14H

Then, if you convert this InChI to SMILES, you'll get:

c1ccc(cc1)c1nc2ccccc2n1c1ccccc1

Which results in the right picture above.
However, even with this workaround some compounds, e.g. with ...C#N... triple bonds are sometimes still incorrect.

I placed a bug report on GitHub. Let's see...

Any strategies, tips, and tricks to reliably and directly get a correct SMILES output are appreciated.


texts: What is the chemical composition of petrol? What are the molecular available in petrol? Some time which is marked with 95% octane. So what is the remain element occupied 5%?


texts: How can electron move between two metals without the presence of electric field?

texts: Electron can move from one location to another if it feels a force that is if there is a presence of electric field. Now suppose I have a $\ce{Zn}$ rod immersed in $\ce{CuSO4}$ solution. Electrons are transferred from $\ce{Zn}$ to $\ce{Cu}$. What results in this motion of electrons from $\ce{Zn}$ to $\ce{Cu}$. How can electron move without a field?


texts: Is it possible to make Spider-Man like web fluid?

texts: Is it possible to make a substance which has similar properties to that of the web fluid e.g. High tensile strength, sticky (can attach to most of the surfaces), evaporates within few hours etc. If so then how?


texts: I want to electrolyze water as a personal project, but I have found conflicting power recommendations on google. Some sources recommended a higher voltage, claiming that higher amps will just destroy the electrodes, while others insist a higher amperage is required, and extra voltage will be wasted heating up the water. Unable to find one absolute result, I'm turning here- assuming not a crazy amount of amps or volts, what is a good ratio to get the best results? (an explanation of the answer would be appreciated.)


texts: Why is the eclipsed conformer more stable than the bisected conformer in 1-butene?

texts:
I have just started learning conformational analysis, and a major doubt came into my mind.

In simple alkanes such as ethane, the staggered conformer is much more stable than the eclipsed conformer. This fact may be explained as follows:

In the staggered conformer, the repulsion between the hydrogens is minimized as they are "anti" with respect to each other.
We have a case of favorable overlap between sigma bonding MO of the C-H bond, and sigma anti bonding orbital of the C-H bond of the second Carbon.

I have no issues with this part. Then, I started reading about alkenes. In the simple example of propene, two cases may arise, as shown in the figure.

Note that (2) can be obtained from (1) by rotating the C-C bond by 60 degrees. Unlike in the case of alkanes, the eclipsed form is more stable, not the bisected form. This can be easily accounted for:
In the eclipsed form, the Hydrogen is oriented in the right way to allow for effective Hyperconjugation. This involves delocalization of electrons from C-H sigma bond to the C=C pi antibonding orbital.

My main question is about when it becomes more complicated. Let me take the example of 1-butene. Here, we have twice the number of eclipsed and bisected conformers. I have labelled them as E1, E2, B1 and B2 (E= eclipsed;B=bisected)

The correct order of stability is E2 > E1 > B1 > B2.
I do not understand this order. When I attempted to find the order of stability, I got: E2 > B1 > B2 > E1. I based this mainly on steric effects.

E2 is clearly the most stable as we have Hyperconjugation due to the C-H bond which is oriented in just the right way.
I couldn't get the rest of the order. Why is E1 the second most stable? I understand that it is eclipsed, but shouldn't that lead to greater torsional strain? Is Hyperconjugation the reason for stability, again?
Can Hyperconjugation take place when we have a C-C bond(when there is no alpha Hydrogen with respect to the double bond), or is it restricted to C-H bonds(where we have an alpha Hydrogen)?


texts: Why does old gasoline seem to have more "kick"?

texts:
From my personal experience, old gasoline (leftover in a container from the previous year) has more "kick" (power) when I actually use it. Higher idle RPM, higher throttle sensitivity.

It says here that it's not the gasoline itself that burns, but the vapour. And old gasoline is bad because it has vaporised over time. Thus, old gasoline must be weaker.

However, I read somewhere that gasoline vapour has nothing to do with octane rate, so there's no difference in octane between the gas left out in the open for a while and the gas sealed in a container.

I'm confused. Does old gasoline seem to have more "kick" because it needs more compression to combust? Or what is it?


texts: How does molecular collision excites the electron?

texts:
I have this question for a long time that in LASER when we do the pumping by heating how does molecular collision causes the atoms(molecules) to reach in excited state. E.g. in $\ce{He-Ne}$ laser when the excited $\ce{He}$ atom collides with the $\ce{Ne}$ atom the $\ce{Ne}$ atom gets excited and $\ce{He}$ atom reaches its ground state.

My question are

What happens at the molecular level that causes $\ce{Ne}$'s electron to jump into higher state? Does Ne atom absorb some kind of photon by some mechanism?
Another thing is if we take $\ce{He}$ atom as the frame of reference then the high energy $\ce{Ne}$ atom is striking $\ce{He}$ so the high enrgy $\ce{Ne}$ must give its energy to $\ce{He}$ not the other way round.Where did I go wrong here?


texts: Naturally Occurring Sulfites or Sulphites form

texts:
In the following link, it says that the product

  May contain trace amounts of naturally occurring sulfite residue

I asked the manufacturer about it and the explanation I got was:

  The trace amounts of naturally occurring sulfites are present in hydrolyzed collagen (as are most other proteins as well). The sulfur that holds the bonds between the molecules is broken up from these processes and changes them to sulfite

Does anybody knows the exact chemical form of the sulfite that this product contain?

Is it in the form of an anion or in the form of a compound?


texts:
I am a high school student and I don't know a whole lot about molecular simulation. I wish to view different conformers of cyclohexane and the changes that occur when substituents are attached (for example cis-1,4-di-tertbutylcyclohexane attains a twist boat shape) through molecular simulation.

The only easy-to-use tool I could find was MolView, but I can't see the above molecule getting into a twist boat shape when I ran an energy minimization because it swapped the cis to a trans form (which is in a chair conformation). Couldn't find the molecule through PubChem as well, so that I could import it.

I would also like to try out ortho effect on substituted benzene rings. Basically, I want to see a few simple molecules, (not anything like proteins and other macromolecules) and run an energy minimization on them.

So, is there any easy-to-use, free molecular energy minimization simulation program that can help me achieve this?


texts: What is the difference between molar conductance and molar conductivity?

texts:
I'm learning (or at least trying to learn) about electrochemistry, but a major obstacle to that, is that different books I refer use different terms for the same symbols. So in a last ditch attempt to clear stuff up, I've resorted to Chem.SE.

So here's what I intend to do; I'll list out everything I think I've understood, as well as pose a couple of questions regarding some of them. I'd really appreciate it if someone would take the time to go through what I've listed out, checking them for errors and then clearing those queries which I've got. So here I go

  Symbols used:

  Resistance ($R$) , Resistivity or specific resistance ($\rho$), Conductance ($C$), Conductivity or specific conductance ($\kappa$), Area of cross-section of the electrode ($A$), distance between the electrodes ($L$),

and the REALLY confusing bit, Molar conductance according to some books and Molar conductivity according to others and one book uses both terms, both represented by $\mathrm{Λ_{m}}$

Now,
$$
R = \rho \frac{L}{A}\\
R = \frac1C\\
$$
Therefore
$$\frac1\rho = \frac1R\cdot\frac{L}A = C\cdot\frac{L}A = \kappa$$

Now if I've got this right, then,

Conductance is the degree to which the solution conducts electricity.
Conductivity is the conductance per unit volume of the solution; it may also be considered as the concentration of ions per unit volume of solution.
Molar Conductivity is the conductance of the entire solution having 1 mole of electrolyte dissolved in it.

Q1. So what's Molar Conductance?

Q2. Is there a difference between Molar Conductivity and Molar Conductance?

Also, according to Ostwald's Dilution Law, greater the dilution, greater the dissociation of the electrolyte in solution.

Regarding dilution of an electrolyte solution, this is what I've understood

As dilution increases, Conductivity (ion concentration per unit volume) DECREASES.
As dilution increases, Molar conductivity (Conductance of 1 mole of electrolyte in the total solution) should INCREASE in accordance with Ostwald's Law

Q3. How does dilution affect Molar Conductance?

Q4. How is Conductance affected upon dilution?

I suppose if the above statements are proof-read and the queries answered, I might get fairly good idea about this....

Also if you feel there is are any additional points worth mentioning, by all means go ahead and put it in the answer.

And finally, if anyone could recommend a decent site that deals with the above-mentioned terms and concepts in a fairly lucid manner, it'd be appreciated.


texts: In an equilibrium, why are partial pressures not affected by the coefficients of the balanced equation?

texts:
It's probably easiest for me to explain in an example. For the following reaction: $$\ce{2NOBr(g) <=> 2NO(g) + Br2(g)}$$
At equilibrium, if the partial pressure of $\ce{NOBr}$ was 6 atm, the partial pressure of $\ce{NO}$ was 4 atm, and the partial pressure of $\ce{Br2}$ was 3 atm. Why is the equilibrium constant: $$Kp = \frac{3\cdot 4^2}{6^2}$$ instead of the individual pressures multiplied by their coefficients like in molar solubility: $$Kp = \frac{3\cdot \left(2\cdot 4\right)^2}{\left(2\cdot 6\right)^2}$$


texts: Are there any other acids of noble gasses besides xenic acid? Why other ones seem to be very unstable (like perxenic), or completely unknown (acids of any other noble gases). Particularly are there fluoroxenic acids, for example $\ce{HXeF5}$?


texts: How much heat is required to dehydrate a hydrate?

texts:
If I have a hydrate, such as copper (II) sulfate pentahydrate, $\ce{CuSO_4 \cdot 5H_2O}$, what is the amount of heat to required to dehydrate it? I assume that it is equal to or greater than the amount of heat required to evaporate the water molecules. Does the required heat vary for every hydrate?

The formula for dehydrating copper (II) sulfate pentahydrate is:

$$\ce{CuSO_4 \cdot 5H_2O ->[\Delta] CuSO_4 +5H_2O}$$


texts: Meaning of the symbol “$\Delta_\mathrm{sub}H^\circ[\ce{I2,s}]$”

texts:
One of the back exercises (13(C)) from the book for practice provided at my school asked whether the following relation is true:

$\Delta_\mathrm{f}H^\circ(\ce{I2,g}) = \Delta_\mathrm{sub}H^\circ[\ce{I2,s}]$ at $\pu{25 °C}.$

I know how to solve the question, but the answer would depend on the meaning of  $\Delta_\mathrm{sub}H^\circ[\ce{I2,s}].$ Which of the following reaction does the symbol $\Delta_\mathrm{sub}H^\circ[\ce{I2,s}]$ represent?
$$
\begin{align}
\ce{I2(g) &-> I2(s)}\tag{a}\\
\ce{I2(s) &-> I2(g)}\tag{b}
\end{align}
$$


texts:
I have hard water in my house. All the taps have tartar around. It generates some problems in some of my home appliances so I have bought polyphosphate salt but when I boil water I don´t get the expected results.
I´m looking for some product or filter that would make the water in my house better for drink and use. That´s is why I´m evaluating to install a filter with polyphosphate salt or a floating dispenser (like a buoy).
I´m now trying to make a test before installing the floating dispenser I have recently bought in my water tank so, this is what I have done:
First I have filled a pan with water and boil it until it got empty and this was the result:

Then, I have use the floating dispenser in a pan with polyphosphate salt for 30 mins. After that I took out the dispenser and boil it until it got empty. This was the result:

It seems like there is no difference.
How can I make a better measurement or treatment? Is this the right product for my problem? 30 minutes is enough to the polyphosphate salt? Do you think that will be better a floating dispenser or the filter with that product? Maybe I have to buy another kind of filter?


texts: Greater entropy: an atom or macromolecule?

texts:
A question that appeared on my last chemistry exam was :

  Which of the following has greater entropy A) An atom
  B) A
  macromolecule

The question doesn't specify anything else(i.e. type/size of atom or macromolecule). The macromolecules we learned class were proteins, sugars, nucleic acids(DNA/RNA) or lipids. What is the correct answer and why(hypothetical calculation, if possible) ?


texts: How much of the anion species is left over after the first precipitation?

texts:
Some barium chloride is added to a solution that contains both $\ce{K2SO4}$ ($\pu{0.050 M}$) and $\ce{Na3PO4}$ ($\pu{0.020 M}$).
  (a) Which begins to precipitate first: the barium sulfate or the barium phosphate?
  (b) The concentration of the first anion species to precipitate, either the sulfate or phosphate, decreases as the precipitate forms. What is the concentration of the first species when the second begins to precipitate?

I've figured out the first part of this problem, that barium phosphate is the first to precipitate (due to lower $K_\mathrm{sp}$), but I can't seem to figure out the other part. I even read about selective precipitation and I can't get the answer that was in the back of the book (namely, $\pu{1.1 \times 10^{-6} M}$).
Granted, sometimes I'm pretty there are errors in the books I use to teach myself, but this is not one of those instances where I am so sure.


texts: What does m± represent in the equation for mean activity of a salt solution?

texts:
I need to find the activity $a_\pm$ for a $\pu{0.0120 M}$ solution of $\ce{Na3PO4}$, and have calculated the activity coefficient, $\gamma_\pm = 0.389$.

I know that $$a_\pm = \frac{m_\pm}{m_0}\gamma_\pm,$$

but I must be plugging in the wrong numbers. What does the top $m_\pm$ mean? And isn't the bottom $m_0$ simply $1$?


texts: sp, sp2 and sp3 hybrid orbitals are actual solutions of Schrodinger's equation or only a heuristic?

texts:
According to Wikipedia's article about orbital hybridisation:

[...] today it is considered an effective heuristic for rationalising the
structures of organic compounds. [...] Hybrid orbitals are assumed to be mixtures of atomic orbitals, superimposed on each other in various proportions.

So are $\mathrm{sp}$, $\mathrm{sp^2}$, $\mathrm{sp^3}$ hybrid orbitals 'real'? Are they solutions of Schrodinger equation? Are they a superposition of atomic orbitals?


texts: Why is $\ce{H2O2}$ named hydrogen peroxide and not dihydrate dioxide?


texts:
From all we know only tautomers should get the same InChI key, or, in case of the second block, if there are lots of stereo centers. However these cases are just collisions, they still have different InChI. I have found a class of molecule pairs, with four real-world examples in ChEBI and PubChem, where both web input pages of ChEBI and PubChem generate identical InChI and keys, despite there being a different E-Z configuration on a double bond. And these are also entries in the said databases. My question:
Is this normal/expected? Is it a bug in both software, which part of it?
The pairs:

5,7-dihydroxy-2-(4-hydroxy-3,5-dimethoxyphenyl)-1-benzopyran-1-ium-3-yl 6-O-[(2Z)-3-(3,4-dihydroxyphenyl)prop-2-enoyl]-β-D-glucopyranoside and 5,7-dihydroxy-2-(4-hydroxy-3,5-dimethoxyphenyl)-1-benzopyran-1-ium-3-yl 6-O-[(2E)-3-(3,4-dihydroxyphenyl)prop-2-enoyl]-β-D-glucopyranoside

2-(3,4-dihydroxy-5-methoxyphenyl)-5,7-dihydroxychromenium-3-yl 6-O-[(2Z)-3-(4-hydroxyphenyl)prop-2-enoyl]-β-D-glucopyranoside and 2-(3,4-dihydroxy-5-methoxyphenyl)-5,7-dihydroxychromenium-3-yl 6-O-[(2E)-3-(4-hydroxyphenyl)prop-2-enoyl]-β-D-glucopyranoside

5,7-dihydroxy-2-(4-hydroxy-3,5-dimethoxyphenyl)chromenium-3-yl 6-O-[(2Z)-3-(4-hydroxyphenyl)prop-2-enoyl]--β-D-glucopyranoside and 5,7-dihydroxy-2-(4-hydroxy-3,5-dimethoxyphenyl)chromenium-3-yl 6-O-[(2E)-3-(4-hydroxyphenyl)prop-2-enoyl]-β-D-glucopyranoside

5,7-dihydroxy-2-(4-hydroxy-3-methoxyphenyl)chromenium-3-yl 6-O-[(2Z)-3-(4-hydroxyphenyl)prop-2-enoyl]-β-D-glucopyranoside and 5,7-dihydroxy-2-(4-hydroxy-3-methoxyphenyl)chromenium-3-yl 6-O-[(2E)-3-(4-hydroxyphenyl)prop-2-enoyl]-β-D-glucoside-glucopyranoside

Addendum: I also confirmed with two different SDF files that the current inchi-1 Linux binary generates the same InChi.
P.S. This is a pair of minimal molecules:

Both have the InChi InChI=1S/C11H10O3/c1-14-8-11(13)7-4-9-2-5-10(12)6-3-9/h2-8H,1H3/p+1. If the methyl is removed, leaving a =OH+ group at the end, both isomers get different InChi.


texts:
I was wondering if there is any natural process which breaks down PCBs (Polychlorinated biphenyl).

This is an extremely harmful contaminant that was pumped into various lakes by chemical plants up until about the 1950s. It is very stable, which is why it was used a coolant in these chemical plants. However this toxic substance has greatly impacted lake systems, as the concentration of the PCB is increased in each trophic level of the lake ecosystem (due to biomagnification). Anyways, I was wondering if there was any method to break down the PCBs.

Since they are a chlorine-containing compound, would I have to use something like a sodium or potassium based compound to safely break them down chemically. What do you guys think? Thanks!


texts: What is an effective coagulant/flocculant for an acidic solution?

texts: The acidic solution is a mixture of dissolved ammonium sulfate and mono-ammonium phosphate (pH about 4.5-4.8) along with an inorganic sludge with a similar consistency to clay I am looking to remove through coagulation. Preferably the coagulant would have negligible negative impact on soil health.


texts: What is Hydroxy Methylbutyrate-Ca and what is it's relation to butyric acid

texts:
First of all, I am nowhere near familiar with chemistry. But I really need help with this question. A certain product contains "Hydroxy Methylbutyrate-Ca" and I need to translate this ingredient in two languages (German and Dutch). After some research I found it very unclear what exactly I am dealing with.

The first thing I found was "beta-Hydroxy beta-methylbutyric acid" $\ce{C5H10O3}$. According to Wikipedia this has a form with calcium:

  calcium β-hydroxy β-methylbutyrate monohydrate (HMB-Ca, CaHMB).

Would this calcium form still be considered "Hydroxy Methylbutyrate-Ca"?

The Dutch wiki named the same page "3-hydroxy-3-methylbutaanzuur". "Butaanzuur" would translate(NL > GB) to "Butanoic acid". Is "Butanoic acid" the same thing as "Butyrate" and "Butyric acid"? According to the Dutch wiki 3-hydroxy-3-methylbutaanzuur did have the same composition ($\ce{C5H10O3}$).

Someone told me "Hydroxy Methylbutyrate-Ca" would also be known as "Butyric acid". Someone else told me it turns into Butyric acid once broken down inside the body. What would be correct?

My main goal here is to translate "Hydroxy Methylbutyrate-Ca" but all resources I found have all kinds of names for this substance and I am completely lost. I'm not even sure if some of the dutch equivalents are talking about the same thing as their English counterparts.

My apologies if this is the wrong place to ask for help.


texts: interaction of grape juice or wine with marble

texts: I have a marble cup which I drink wine from. If I leave a little bit of wine in the cup and wait maybe 30 minutes, the wine becomes discolored and appears black (photos attached). My conjecture is that this is the acid from the wine interacting with the calcium carbonate of the marble to produce calcium choloride? If so, is it toxic to continue drinking wine from the cup? Thanks.


texts: So I am a clueless undergraduate student trying to get a glass substrate sputtered with a 100 to 200 nanometer copper thin film from one lab to another. I need to know how much time I have before the copper begins to oxidize, or at least how I could figure out how long it would take in room temperature.


texts:
What is the value of enthalpy change for the following reaction

  $$\ce{X + 2Y -> 2Z}$$

  given

  \begin{align}
\ce{W + X &-> 2Y} &\qquad &\Delta_\mathrm{r}H_1 = \pu{-200 kcal} \tag{1}\\
\ce{2W + 3X &-> 2Z + 2Y} &\qquad & \Delta_\mathrm{r}H_2 = \pu{-150 kcal} \tag{2}
\end{align}

I have the answers, and the correct answer is $\pu{250 kcal}$, so I'm assuming you do $400-150$, but not sure how you would go about it.


texts:
Which one is more basic: acetamide or aniline?

I had approached the question by protonating both of the compounds. Then I judged them on the basis of the stability of the corresponding conjugate acid.

In $\ce{CH3CONH3+}$, due to resonance, a positive charge is created on the oxygen atom. So, resonance is not very effective here. Hence $\ce{ CH3CONH2}$ is not a good base.
In $\ce{C6H5NH3+}$, there is far better resonance which takes place.

From the above observations, I concluded that aniline is more basic.

I had another view that $\ce{C6H5NH2}$ is a basic type of compound rather being salt-like as is $\ce{CH3CONH2}$.

Am I going in the right direction to solve the problem?


texts:
I was reading about Bohr's atomic model in our textbook when came up with this question:
Since the electron in hydrogen atom is most stable in the first orbit, why should it descend from higher orbits to any orbit except the first orbit(that means balmer series for example)?


texts: I have seen literature refer to catalyst supports being doped with another chemical, such as Nb doped $\ce{TiO2}$. What does it mean if a catalyst support is doped?


texts: How to calculate mass of water of crystallisation?

texts:
How do you work out the mass of water of crystallisation for 13.5 g of

$$\ce{Al2(SO4)3*6H2O}$$

The correct answer is 3.24 g of water but I'm unable to derive the answer.

What I have tried:

I worked out the mols of aluminium sulfate which is approx 0.038 mol by dividing 13.5 g/353.5.

Since the ratio of aluminium sulfate: water of crystallisation is 1:6, I multiplied the number of mols by 6 to result in 0.228 mol of water.

To work out the mass, I multiplied mols of water by molar mass to result in 4.101 g which is NOT the answer of 3.24 g .

What am I doing wrong and what is the correct method?


texts: What is physically responsible for different compounds with the same types of atoms?

texts:
I only have a GCSE in Chemistry but I have discovered a lot of resources myself. One thing I cannot find an answer to is this: What is physically responsible for the different compounds you can get with the same types of atoms.

For example, if you were to mix a bunch of carbon and hydrogen what exact process determines if you get methane, butane, ethyne etc.? Is it the different concentrations of carbon and hydrogen? Then what is the physical explanation? If there is 4 times more hydrogen than carbon might a carbon atom more likely find itself surrounded by four hydrogens by chance and then bond with them to form methane? Similarly if there is equal carbon and hydrogen is it just morel likely that ethyne will form? If this is the case then in general if you mix carbon and hydrogen in different concentrations would you always get different concentrations of methane, butane, ethyne as products just by chance? For example if there is 4 times more hydrogen than carbon then is there still a small chance that at least some ethyne will form?


texts:
I made some organic surf wax with 4 parts beeswax and 1 part coconut oil. The wax turned out to be sticky but had no tack.

I'd like to make wax for warm water that forms a layer of hard bumps on the board when wax is applied.

Not sure how I can achieve this w all organic items.

Any suggestions?


texts: How can I get more information about the Voronoi integral in Gaussian09?

texts:
I am working on metal based organic complexes to find out catalytic characters. I am using the B3LYP density functional level of theory in Gaussian09.
I need to know the possible keywords for getting effects of Voronoi integral where I use the keyword EmpiricalDispersion = GD3. This is not a cluster, but the central metal atom is $\ce{Fe}$. How can I obtain more output about it?


texts: Most endothermic room-temperature reaction

texts:
In terms of energy per gram of reactants, the evaporation of water at -2.2 kJ/g, is much higher than any chemical endothermic reaction that I have seen demonstrated. At extreme temperatures there is no real limit, but for reactions that occur at a reasonable rate at room-temperature it seems water is hard to beat. And it isn't even a chemical reaction.

I have reason to think water is hard to beat: the entropy of gases is much higher than liquids. The strong hydrogen bond network of water makes the liquid phase lower entropy than non-polar liquids because it structures the liquid. Finally, water is a very light molecule so you get many moles of gas per kg of liquid. Despite this huge entropy gain, the phase-transition proceeds sluggishly because it takes so much dry air to shift the equilibrium forward, if it took much more energy it wouldn't happen at a meaningful rate.

Can any chemical reaction approach this at room temperature? If so, can any non-gas-evolving reaction come close?


texts: carbon dioxide in liquid and gaseous phase with liquid water

texts:
What are the differences between carbon dioxide solubility (miscibility, reaction) in liquid water when in gaseous ($\pu{<38 bar}$) and liquid ($>\pu{38 bar}$) phase? The temperature in my experiments is usually between $0$ and $\pu{5\!^\circ C}$. Is there more phase - interface for the reaction between water and $\ce{CO2}$ in the gaseous phase?

According to Henry's law for real gases (including a Poynting correction), the solubility should rise with the fugacity of the vapor. How is it however, when the carbon dioxide is liquid? When observing a pressure drop in a closed stirred vessel with liquid water and $\ce{CO2}$ on top of it, the pressure drop is much larger for gaseous $\ce{CO2}$ than for the liquid $\ce{CO2}$, this does not however imply a larger solubility? In my understanding it just means, that the liquid $\ce{CO2}$ is not that compressible and will mix in a different manner than gas and liquid water, resulting in a lower pressure drop.


texts: What happens to a radioactive carbon dioxide molecule when its carbon-14 atom decays?

texts:
When carbon-14 decays, the decay products are nitrogen-14 and an electron (and an electron antineutrino, but that's chemically irrelevant*):

$$\ce{^14_6C -> ^14_7N + e- + \overline{v_e}}$$

Let's assume that the carbon atom in question is part of a carbon dioxide molecule in the atmosphere. What would happen to the molecule when the atom decays into nitrogen? Will it be converted into a $\ce{NO2}$ molecule, or will it split apart? Will the electron created in the decay have sufficient energy to escape the molecule and form a positive ion?

Here's a somewhat related question dealing with the formation of radioactive carbon dioxide.

* Of course, not all the energy from the defect will be transferred to the beta particle's kinetic energy, so this is in fact relevant for the rate. See Loong's answer for details.


texts: How to find pH of an aqueous ammonia solution at high pressures?

texts:
Here's the simplified question: I start with $15~\%$ of $\ce{NH_3}$ and I want to find the $\mathrm{pH}$ of the following reaction at $25~\mathrm{^\circ C}$ and $5\ \mathrm{kbar}$:
$$\ce{NH_3 + H_2O -> NH_4^+ + OH^-}$$

Now I believe I understand the basic procedure. I was able to find the pH at STP, but there are a few things that confuse me about finding the pH at high pressures. Here's the procedure I followed for STP:

$$[\ce{NH3}]_\mathrm{eq} = 0.15-x\tag{1}$$

$$[\ce{NH4+}]_\mathrm{eq} = x\tag{2}$$

$$[\ce{OH-}]_\mathrm{eq} = x\tag{3}$$

$$K_\mathrm{b} = \frac{x^2}{0.15-x}\tag{4}$$

where $x = [\ce{OH-}], \mathrm{pOH} = -\log[\ce{OH-}],$ and $\mathrm{pH} = 14 - \mathrm{pOH} = 11.2$

Now for my questions about applying this to $5~\mathrm{kbar}$:

Unfortunately I'm not entirely clear about what they mean by $15~\%$—whether it's a mass fraction or in g/ml or what.

But I did manage to get the right $\mathrm{pH}$ using $0.15$ as my initial $[\ce{NH3}]$ … though maybe that was just a coincidence. Actually if I assume that it's a mol fraction and then convert it to molarity, I do get something close to the right answer but not quite … if anyone has any ideas about this please let me know.

Also if I am missing some conversion from $15~\%$, is there any reason $[\ce{NH_3}]_\mathrm{initial}$ would be different at STP vs $5\ \mathrm{kbar}$? If both start with $15~\%\ \ce{NH3}$?
From what I've read, the value for $K_\mathrm{b}$ shouldn't have any pressure dependence at all. And for this specific reaction, $K_\mathrm{b}$ should be equal to $K_\mathrm{p}$ since there are two molecules on the left and two molecules on the right sides of the equation.

However when I calculate $K$ using $\Delta H$ values at $5~\mathrm{kbar}$, I do get a different value (at STP, $K = 10^{-4.754}$ and at $5~\mathrm{kbar}$ $K = 10^{-2.81}$). So does $K_\mathrm{b}$ really not change with pressure or is this just an approximation at low pressures? Or am I dealing with two different $K$ values? Does the $K$ that I calculated from $\Delta H$ only equal $K_\mathrm{b}$ at STP?

Actually now that I think about it, the value for $K_\mathrm{w}$ definitely changes at high pressures. At STP $K_\mathrm{w} = 10^{-14}$ and at $5~\mathrm{kbar}$ $K_\mathrm{w} = 10^{-12.559}$

So if $K_\mathrm{w}$ changes at high pressures, shouldn't that mean that $K_\mathrm{b}$ does as well?
Is there some sort of step I'm missing at the end? Because I tried solving for $\mathrm{pH}$ using both K values (the value at STP and the value I found at $5~\mathrm{kbar}$) but I still don't get the right value for $\mathrm{pH}$.

If I had to guess, I'd say that $[\ce{OH-}] = a_\ce{OH-}$ at STP which is why $-\log a_\ce{OH-}$ gives me the right $\mathrm{pOH}$ and $\mathrm{pH}$ at STP. But at $5~\mathrm{kbar}$ $[\ce{OH-}] \neq a_\ce{OH-}$ so I'd need the activity coefficient? But if activity coefficients were needed, their source should have been cited which it wasn't … Unless there's a straightforward way to solve for the activity coefficient?

Let me know if any clarifications are needed.

Edit: I've just found that if I take the ratio of the vapor pressure of Ammonia (~10.1 bars) to the total pressure (5000 bars) and multiply that by .15, I do get very close to reproducing the 5 kbar results. Any ideas why that might be?


texts: Why is the iron(II) on the heme molecule depicted as having 6 electrons in its 5 d non- and anti-bonding orbitals?

texts:
Approximating the $\ce{Fe}$ complex as a square base pyramid ($D_\mathrm{4h}$ symmetry) with 5 $\ce{N}$ ligands, My electron count of the system gives me 16 electrons – 10 from the $2\times 5$ $\ce{N}$ electron pairs and 6 from the iron(II). Filling the molecular orbitals of the valence shells, I ended up with $\ce{4 e-}$ in the d non-bonding orbitals – for there to be 6 in the d orbitals, I am under the impression that there must be 18 electrons, as suggested by the 18 electron rule (which I am aware is a loose guideline).

Looking at depictions of the orbital diagram however, such as this one:

and this one:

I've seen that there are consistently 6 electrons in these orbitals — which would be consistent with iron(0) but not iron(II) as I understand it. Can anyone help me make sense of this situation?

If I'm being a little unclear about my approximation, just look at the $\ce{Fe}$ molecular orbitals on the lefthand side of the images and subtract 2 electrons


texts: Thermal decomposition results: repeatable in ordinary temperatures?

texts:
In thermal decomposition studies where very high temperatures are used (see below for four reactions and their respective temperatures, coming from one paper), can I directly relate these decomposition processes to the ones that happen in room temperature?
Is it OK to assume those same reactions will take place even if those temperatures are not reached (instead taking more time to happen or with the requirement of other variables to compensate for the absence of the same heat, but still existing the same mechanism)?

117–170° C: $\ce{Cu(CH3COO)2·H2O → Cu(CH3COO)2}$
170–309° C: $\ce{Cu(CH3COO)2 → Cu2O}$
309–479° C: $\ce{Cu2O → CuO}$
946–1016° C: $\ce{CuO → Cu2O}$

Obs.: these reactions are neither complete nor balanced.


texts: Finding the equivalent weights of the oxide and the metal when reduced by hydrogen

texts:
A metal oxide ($\pu{1.80 g}$) required $\pu{833 ml}$ of hydrogen at NTP to be reduced to its metal. What are the equivalent weights of the oxide and the metal?

My attempt:
$$\text{equivalent of metal oxide = equivalent of } \ce{H2}$$
$$\frac{\pu{1.80 g}}{E \ \pu{g/eq}} = \frac{\pu{833 ml}}{\pu{22400 ml/eq}}$$
$$E = \pu{48.4 g/eq}$$
Now, since $$E_\mathrm{oxide} = E_\mathrm{oxygen} + E_\mathrm{metal} $$
$$48.4 = 8 + E_\mathrm{metal} \Rightarrow E_\mathrm{metal} = 40.4$$
where $E$ is equivalent weight.
However, my textbook says that the equivalent weight of the metal oxide is $\pu{24.2 g/eq}$ and that of the metal is $\pu{16.2 g/eq}$ (it does not provide a solution). Is the book's answer correct? If yes, what did I do wrong?


texts: Confusions regarding oscillator in black body and value of one quantum

texts:
Q 1 By saying oscillator I.e atoms in the wall of black body. Do we mean electron ? Because boundary of any atom is electron right.
Q2 My textbook say that quantum is the smallest value of energy that can be emitted or absorbed. On web , it says charge of an electron i.e 1.6*10$^{-19}$C
so , is this the smallest value and there can be a value greater than this ?
“The value of one quantum is equal to the magnitude of the charge on an electron”


texts: The reason behind the alphabetical order in nomenclature

texts:
I hope my question is not too dumb but hey I am learning from the beginning
so when we have a compound such as 6-ethyl-3methylnonane, obvioysly we arrange the alkyl groups alphabetically. Then if we just follow the numbers, we can get somethign like 3-methyl-6-ethylnonane and that saves the extra step of arranging alkyl groups alphabetically. it's much easier to follow.
So I assume the extra step of arranging things alphabetically comes with a reason behind it? otherwise doesn't make sense to make things harder?


texts: A general definition of bond order in molecular orbital theory?

texts:
I stumbled upon this problem upon learning organic chemistry after learning the foundations of MO theory in physical chemistry. It seems that VBT and MOT can coexist with each other in many scenarios. One problem that especially confuses me about their compatibility is that how can we define a general notion of bond order in MOT. This question arises naturally as we assign integer values to bonds between atoms in VBT but this is definitely not true in MOT.

It's often taught in general chemistry course that bond order is 1/2 times number of bonding orbitals minus antibonding orbitals, but this definition only works for diatomics. I wonder if there's some more general definition that works for each adjacent(perhaps this is ill defined) pair of atoms, perhaps in the spirit of Mulliken population analysis that assigned partial atomic charges based on MO coefficients of AOs.


texts: rate constant via flux-flux correlation function for linear potential energy surface

texts:
How does one calculate fully quantum mechanical rate ($\kappa$) in the golden-rule approximation for two linear potential energy surfaces?

Attempt:

Miller (83) proposes $\kappa=\int{Tr[\exp{(-\beta\hat{H})}\hat{F}\exp{(-i\hat{H}t/\hbar)}\hat{F}\exp{(i\hat{H}t/\hbar)}]}dt$

Where integrand is simply the flux-flux correlation function: $C_{ff}(t)$. Which can be calculated under Feynman's path integral formalism. My attempt (which is in vain) at calculating $C_{ff}(t)$ is as follows:

$C_{ff}(t)=Tr[\exp{(-\beta\hat{H})}\hat{F}\exp{(-i\hat{H}t/\hbar)}\hat{F}\exp{(i\hat{H}t/\hbar)}]$

=$Tr[\exp{(-\beta\frac{\hat{H}}{2})}\hat{F}\exp{(-\beta\frac{\hat{H}}{2})}\exp{(-i\hat{H}t/\hbar)}\hat{F}\exp{(i\hat{H}t/\hbar)}]$

By cyclicly permuting the operators we reach at:

=$Tr[\exp{(i\hat{H}t/\hbar)}\exp{(-\beta\frac{\hat{H}}{2})}\hat{F}\exp{(-\beta\frac{\hat{H}}{2})}\exp{(-i\hat{H}t/\hbar)}\hat{F}]$

The boltzmann operator and quantum mechanical propagator can be combined as follows:

=$Tr[\exp{\hat{H}(\frac{it}{\hbar}-\frac{\beta}{2})}\hat{F}\exp{\hat{H}(\frac{-it}{\hbar}-\frac{\beta}{2})}\hat{F}]$

In the golden-rule (non-adiabatic) case, we have two electronic states 0 and 1. So F is simply a projection operator. Hence one can obtain:

=$Tr[\exp{\hat{H_0}(\frac{it}{\hbar}-\frac{\beta}{2})}\exp{\hat{H_1}(\frac{-it}{\hbar}-\frac{\beta}{2})}]$

This basically is kernel corresponding to two potential energy surfaces $V_0$ and $V_1$. For trajectory starting at $x_a$ and ending at $x_b$, we have

$C_{ff}(t)=\int{\int{K_0(x_a,x_b,\frac{it}{\hbar}-\frac{\beta}{2})K_1(x_b,x_a,\frac{-it}{\hbar}-\frac{\beta}{2})}}dx_adx_b$

For a linear potential energy surfaces (PES), where my PES looks as follows:

$V_0=k_0 x$

$V_1=k_1 x$

My kernels are:

$K_0=\sqrt{\frac{m}{2\pi t_0}}\exp{(-S_0)}$

$K_1=\sqrt{\frac{m}{2\pi t_1}}\exp{(-S_1)}$

$S's$ correspond to action which is:

$S_n(x_a,x_b,t_n)=\frac{m(x_a-x_b)^2}{2 t_n}-\frac{(x_a+x_b)k_nt_n}{2}-\frac{k_n^2t_n^3}{24m}$

The problem is the integral for flux flux correlation function doesn't seem to be converging with the imaginary argument for $t$'s. I am trying to integrate w.r.t $x_a$, $x_b$ and $t$ from -Inf to +Inf. My final answer for rate should look something like this:

$\exp{\frac{k_0^2k_1^2\hbar^2\beta^3}{24m(k_0-k_1)^2}}$

Is it a gaussian integral with respect to $x_a$ and $x_b$? One has to be careful because there is also an imaginary parts in the exponent. How does one reach the final answer for rate with those integrals? Really confused! Any help is appreciated.


texts:
I am going to be doing a gender reveal for my sister's pregnancy. To do this, we wanted to light a huge fire pit and throw in a chemical to change the fire into the color (red/pink for girl, blue/violet for boy).

From my research, I found that strontium chloride is the best option for red/pink and copper I chloride is the best for blue. I found that Iron Filings make great gold sparkles, as well as magnesium shavings make for a great silver spark.

It is my goal to have my sister and brother in law throw a satchel full of chemical-enriched wax pucks into the fire pit fire and have the fire first glow many different colors, a rainbow of colors until the other colors die down and the pink or blue for the gender remain.

To do this, I was going to create many wax discs with many different colored chemicals and methanol (to create a more vivid color) by first melting wax, adding methanol and the chemical, mixing and setting to dry. The pink or blue one would be the LARGEST wax puck/disc and would, hence, color the longest after the rest of the colors died down.

I was going to add all the discs and the iron filings into a satchel with the largest disc (the gender color in it's own satchel so it remains last), and then when they throw it in, it will create this spectacle.

My question is, does this sound like a viable option and experiment?
Is using methanol in the wax an unnecessary step?
Is it ok to mix methanol with wax? Will it still harden?
How can I insure that the blues, yellows, oranges, greens will die down and the gender color (lets say RED in this case/girl), remains?
How long will it take the color to shine through? How can I make sure this is done within the course of a minute or so?
How much of a chemical should I use to ensure it is seen in a large fire pit (about 3-4 feet in height)?

Any further advice? Tips? Tricks?


texts: Are all solutions of weak acid/bases buffers?

texts:
I am having a difficult time understanding what makes a buffer a buffer.

Buffers in my textbook are defined as a solution of a weak acid or base and their conjugate acid/base. So if I were to just dissolve acetic acid (a weak acid) in water why would this not be defined as a buffer. Acetic acid incompletely dissociates into an acetate ion (the conjugate base) and a Hydrogen ion. Why is it that for a base to be made the acetic acid would have to be mixed with something like Sodium acetate if acetic acid incompletely dissociates into a conjugate base in the first place? Could someone please help me understand why this is the case?


texts: How to find number of moles of HNO3 behaving like acid in a redox reaction?

texts:
In the reaction $(1)$, how to find the number of moles of $\ce{HNO3}$, which is behaving like acid?

The reaction is given as follows:
$$\ce{Sn + HNO3 -> Sn(NO3)2 + NH4NO3 + H2O} \tag1$$
To find number of moles of $\ce{HNO3}$ behaving like acid, I first balanced the reaction using oxidation number method which gave me:
$$\ce{4Sn + 10HNO3 -> 4Sn(NO3)2 + NH4NO3 + 3H2O}$$
But I could not proceed any further. I am unable to find any hint. How should we proceed to reach the answer? Answer mentioned in book is 9.  This is a question from chapter "Redox Reactions".


texts: The question has its roots in why only carbon mainly shows catenation. I don't see why such a compound cannot be formed. Why don't we have a whole branch dealing with such compounds other than organic chemistry? If this compound can exist then such atoms will also be able to form a large number of compounds like the organic compounds.


texts: Calculating Enthalpy Changes at Different Temperatures

texts:
To calculate $\Delta H$, the change in enthalpy at $\mathrm{100^\circ C}$ for the reaction below, one needs what addition information?

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

  $\Delta H^\circ = \pu{-92.0 kJ}$ at $\mathrm{25^\circ C}$

  (a) The equilibrium constant for the reaction at $\mathrm{100^\circ
 C}$

  (b) The molar heat capacities of the reaction and the products as a
   function of temperature

  (c) $\Delta E^\circ$, the standard internal energy change for the
   reaction

  (d) The partial pressures of the reactants and products at
   $\mathrm{100^\circ C}$

  (e) The entropies of formation for the reactants and products at
   $\mathrm{100^\circ C}$

The correct answer is (b), but I'm not entirely sure why.

I know it can't be (a) because I think we need $\Delta S$ as well.  Also, (c) won't be helpful because it is at standard temperature, and we are wanting information at $\mathrm{100^\circ C}$.  Finally, (e), seems correct but they are actually talking about entropy instead of enthalpy.  However, I'm not sure how to rule out (d) or justify (b).


texts: How to numerically solve a reaction network with fast equilibrium steps?

texts:
For example If I have to solve the following reaction numerically

\begin{align}
*\ce{ + A(g) &<=>[K1] [A*]} \tag{1}\\
\ce{[A{*}] &<=>[k1][k-1] [B{*}]} \tag{2}\\
\ce{[B*] &<=>[K2] [B](g) +}* \tag{3}
\end{align}

Where the first and third reactions are fast equilibrium steps.

[* ] represents vacnt site and [A*]  and [B*] represent adsorbed species.

The reaction is carried out in a closed container, therefore the concentrations of A(g) and B(g) are not constant.
Given initial A(g) and B(g) pressure and assuming zero coverage of reactants initially, how do I solve a system like this numerically.


texts: Nuclear fusion reactions violate law of conservation of mass, but it has not yet been taken into account. Why?

texts: According to the law of conservation of mass, during any physical or chemical changes, the total mass of the products is equal to the total mass of the reactants. But in nuclear fusion reaction if considered an example, energy that sun emits in its core is due to collision of hydrogen nuclei and formation of helium nuclei. Here conservation of mass is not obeyed as certain part of mass is converted into energy. So, law of conservation of mass is violated here. Then law of conservation must be redefined as: during any physical or chemical change, the total mass of the products is equal to the total mass of reactants provided mass has not undergone conversion into energy.


texts: Molecular weight determination from freezing point depression

texts:
Which is the better solvent for molar mass determinations by freezing point depression, benzene or cyclohexane?
  Which is the better method for molar mass determination, freezing point depression or boiling point elevation?

What is the correct approach for solving these?

In my opinion, resonance structures might be the key concept, but I don't know how it would help or hurt.
I think boiling has a decomposing effect that we must avoid, meaning freezing the compound(s) is preferable.

But, both of these statements are inadequate.


texts:
What would happen if water is to flow through a microchannel where its top is hydrophilic and bottom hydrophobic?
If an external pressure is applied, for example, a syringe pump is used, it is expected that water will flow through the microchannel, even if the channel is completely hydrophobic.
I wonder what is the situation when only the capillary force is the driving force, when the two surfaces of the channel are different in their wettability.


texts: Cis/trans interconversion of crotyl-boron compounds

texts: Why is the following interconversion slowest for crotyl boronates and fastest for crotyl boranes while crotyl borinates are somewhere in-between?


texts: Estimating the protein concentration of an unpure protein solution

texts:
I'm confused on this problem for estimating protein concentration. Upon first glance, it looks like a simple Beer's law problem. but then there's the issue that the protein is not pure. How do I account for that?

  E. coli Maltose binding protein, like alkaline Phosphatase is a periplasmic protein. Audrey, has a solution containing solublized E. coli periplasmic proteins and maltose binding protein and she just read the absorbance of the solution at $280~\mathrm{nm}$ which was $0.84$, path length $1~\mathrm{cm}$.
  Help Audrey estimate the protein concentration of her solution. Also note Audrey knows the extinction coefficient for maltose binding protein ($\mathrm{MW} \approx43,000$) is $32,290~\mathrm{M^{-1}cm^{-1}}$.
  (Hint: not pure protein solution.)

As mentioned above I think it would just be Beer's law
\begin{align}
A &= \epsilon cl\\
A &= 0.84\\
l &= 1~\mathrm{cm}\\
\epsilon &= 32,290~\mathrm{M^{-1}cm^{-1}}\\
\end{align}

Solving for $c$ gives $0.26~\mathrm{mM}$. My guess would be to say that it is less than that. How do I approach this?


texts: Total number of stereoisomers of 1,2-dimethyl-4-(propan-2-ylidene)cyclopentane

texts:
I don't think there is any change of showing geometrical isomerism across the double bond because the two groups on the right side (two $\ce{-CH_3}$) are the same.

Also I don't think there should be optical isomerism as there is plane of symmetry. Can someone please explain the solution?


texts: Stereoselectivity solvolysis of cyclohexenyl halides

texts: When a functionalized cyclohexenyl halide undergoes $\ce{S_{N}1}$, does a racemic product form (due to ring flipping) ?


texts: Why are more easily oxidized elements more reactive than less easily oxidized elements?

texts:
Why do the more easily oxidized elements displace the less easily oxidized elements?

Question inspired by Activity Series of Metals