texts: How can every atom have unique spectral lines?

texts:
Why does every element have unique spectral lines?

I have studied that spectral lines help us to identify the properties of an element. This is because after excitation when the excited electron(s) fall back to their original energy level(s), photons of certain frequency corresponding to the difference between the energy levels are emitted.

Now I have a question,  every substance consists of atoms, and each atom consists of electrons, electrons are fuzzy clouds and are described by wave-functions given by the solutions of the Schrodinger equation, so what makes the spectral lines different although every substance has the same thing?

I searched on the site and discussed with various members of the community and some of the conclusions I drew are mentioned below:

Electron-nucleus attraction and the electron-electron repulsion.
Hydrogen is a special case because it has only a single electron so there is no electron-electron repulsion.
Helium has two electrons so now we have some e-e repulsion, Lithium has three electrons so there is even more e-e repulsion and so on...
Every atom has a different number of electrons and a different nuclear charge, so the balance of nuclear attraction and e-e repulsion is different. So every atom has its own set of atomic orbitals that are specific to it and are different from every other atom.
The spectrum comes from transitions between orbitals, and since the orbitals are different for every atom the spectrum is different for every atom.

Are my conclusions reasonable or is there something else I missed to note?

But this answer creates one more question in my mind,

Do all noble gases or alkaline earth metals have similar spectral lines considering the above points I mentioned?


texts: Is it more precise to measure a substance as a solid or as a liquid?

texts:
If I have a substance and want to obtain an exact quantity of it, is it better to measure it as a solid or as a liquid?

In other words, if I have, for example, NaCl crystals I can weigh the crystals in an analytical balance, or alternatively I can dissolve them in water and then determine the concentration by, for example, titrating with silver nitrate.

Which method would be more exact?


texts:
I made a galvanic cell with the anode electrode being aluminum and the electrolyte being aluminum sulfate. The salt bride was magnesium chloride. I am a little confused on what my oxidation equation would be for this set up.

So I did some research and I found out that aluminum sulfate in water will go to aluminum hydroxide and sulfuric acid, so I proposed this half cell equation:

$$\ce{2Al_{(s)} + Al2(SO4)3_{(aq)} + 6Cl- + 6H2O_{(l)} -> 3H2SO4_{(aq)} + 2Al(OH)3_{(s)} + 2AlCl3 + 6e-}$$

So this would then become:

$$\ce{2Al_{(s)} + 2Al^3+ + 3(SO4)^2- + 6Cl- + 6H+ + 6OH- ->
6H+ + 3(SO4)^2- + Al(OH)3_{(s)} + 2Al^3+ + 6Cl- + 6e-}$$

The spectator ions cancel off to give:

$$\ce{2Al_{(s)} + 6OH- -> 2Al(OH)3_{(s)} + 6e-}$$

This equation makes sense but aluminum hydroxide should form a precipitate. However, when I ran my cell, there was no visible precipitate, so it makes me question whether my anode half cell reaction is correct.

What am I doing wrong? Is the process I used to describe the half reaction right?


texts: Why does electrode potential depend upon enthalpy of hydration and sublimation?

texts: It's given in text that "Electrode potential among other things depends upon: enthalpy of sublimation,ionization enthalpy and hydration enthalpy." I could understand why it would depend upon ionization enthalpy as less is the IE easily we could remove the electron thereby reducing the other reactant. But I couldn't figure out why the other two enthalpy comes. But after some thinking I thought maybe we are adding the enthalpy of the three with sign and substituting in ∆G°=∆H°-T∆S° and obtaining ∆G° to substitute in ∆G°=-nFE°cell to find E°cell value. I couldn't think further clearly after this. Could you help me? ( I'm trying to understand why lithium because of its high hydration enthalpy overweighs its high ionization enthalpy and becomes the strongest reducing agent in aqueous solution)


texts: Titration of acid with base or base with acid: can I always use the same indicator?

texts: If you are doing a titration with $\ce{NaOH}$ and $\ce{HCl}$, does it matter which one goes in the burette, and will this change the outcome of whether the solution in the beaker will turn pink due to phenolphthalein?


texts: Separation of sulfur dioxide and sulfur trioxide in the contact process

texts:
When gases leave the catalytic reactor in the contact process of sulfuric acid generation, both $\ce{SO2}$ and $\ce{SO3}$ will be present. According to descriptions I have read, the trioxide reacts with the water spray, but the dioxide does not, and instead rises as a gas and is recirculated into the system.

I thought that sulfur dioxide was highly soluble in water. If so, should it not dissolve into the water spray and thereby contaminate the oleum?


texts: I have a solution containing many different organic compounds (originally from leek and potato soup) and I would like to extract the starch from it. However, starch is insoluble in water. How could I go about extracting the starch?


texts: Chemical function of Mg and Conjugated bonds in Chlorophyll

texts:
This question has 3 parts, each related to the title.

In biochem, we were shown the chemical structure of chlorophyll.  The light-absorbing head has many carbon-rings with alternating single and double bonds (conjugation).  We were taught that this arrangement of bonds is what allows the molecule to absorb light energy.

Question 1: I understand that pi-bonds are generally better at absorbing photons than single bonds, but why do conjugated bonds increase this ability?

Question 2: Also, this molecule does not seem to be have any resonance structures needed for delocalized bonds and thus does not have the light absorbing capabilities like that graphene/graphite or benzene rings.  (If we could engineer an artificial chlorophyll molecule would this increase its efficiency?)

The head of the molecule also contains a Mg ions that is coordinate bonded to four surrounding nitrogen atoms.

Question 3:  If the alternating double and single bonds are responsible for the absorption of light, what role does this metal complex serve in the molecule?  Other pigments like carotenoid don't have this metal complex and they're still able to absorb light.


texts:
What is the difference between "reaction pathway" and "reaction mechanism"?

Are these expressions synonyms?

Some textbooks authors use both without making clear to the learner if they are synonyms or not.


texts: Do core electrons in bulk material have discrete energy levels or continuous energy band?

texts:
The energy band of valence electrons gets smaller and smaller when the lattice (bulk) atoms are more and more separated from each other, until discrete energy levels are formed, due to the isolation of the atoms from each other (see image below).

What happens with energy levels of core electrons in the bulk, as the lattice constant is changed? Do they form a continuous energy band in the first place? Why?

(source)

If core electrons form a continuous energy band, how come K,L,M,... shells are differentiable in xray spectroscopy? In other words, if all electrons form one continuous band, how can xray have element specificity?

(source)


texts: Problem in anode in experiment of electrolysis of brass

texts:
I am studying the electrolytic determination of copper content in brass (~58% copper, ~40% Zn and other trace elements) by using standard method BS EN 16117-1:2011.

Now the electrode used for the electrolysis are both platinum material electrode. Normally the copper ion in electrolyte moves to platinum cathode to form copper. After the electrolysis done, the electrolyte is colorless, the cathode is brown because of copper. Normally the platinum anode is unchange in its "silver" color however it is not in my experiment, the anode is brown too! I don't understand what happen in anode.

I try to put the "colorized" anode in a nitric acid solution (50%) to try to dissolve the "color" but it didn't work. Can anyone tell me why this happen and how to solve the problem in reserving the platinum anode? Please and thanks for reading my question.

(Some information in making electrolyte:
2.5g of brass was dissolved in (15mL 40g/L boric acid, 2mL HF, 30mL 50% nitric acid, neutralized with NH3 solution and reacidify with 50% nitric acid, make up to ~300mL with water and add one drop of HCl, as stated in the stardard method)
(Electrolysis environment: constant current, about 1-1.5A)


texts: Reason for three phases in total fatty matter test on soap

texts:
I am currently trying to perform the Total Fatty Matter (TFM) test on soap and for some reason I am getting three phases instead of two.
The surfactant used is SLES and other reagents include hot water, $\ce{HCl}$, petroleum ether.
I have no idea as to what could be causing the 3 phases and my knowledge in organic chemistry is very little. Any help would be greatly appreciated. Below is the procedure:
I dissolve soap in hot water and then I transfer the cooled solution to a decantation flask. I add concentrated $\ce{HCl}$ (37% stock solution) and then petroleum ether to increase extraction ratio.
I repeat this extraction two more times (and after this I am getting 3 phases) and then I purify the organic phase twice using hot water to eliminate any $\ce{HCl}$.
I then heat the organic phase to vaporize ether and calculate TFM %.
The surfactant used in the soap is sodium laureth sulfate (SLES), and I think that it may relate to why I have 3 phases but I can't tell why. What is the reason for this?


texts: What results from the reaction of 5-bromopentan-1-ol and NaOH?

texts:
In our chemistry class, we noted three molecules that result from the reaction:

pentane-(1,5)-diol

This one is simple to understand, simply a nucleophilic substitution between $\ce{Br^-}$ and $\ce{OH^-}$.

(1,5)-epoxypentane

This is the main result, resulting from the intramolecular esterification of the two $\ce{OH^-}$ groups of the previous molecule. This is wrong, please see the explanation
by  ringo

4-penten-1-ol

This one, I don't understand. How is this a possible result? Could anyone help me understand? Thank you for your time.


texts: Is reducing nitrogen oxides with ammonia practical in a gasifier?

texts:
Sorry if this is an outright stupid question. I am no chemist.

For nitric oxide:

$$
\ce{2NH3 + 2NO -> 2 N2 + H2 + 2H2O}
$$

For nitrogen dioxide:

$$
\ce{2NH3 + 2NO2 -> 2N2 + H2 + 2H2O + O2}
$$

or

$$
\ce{4NH3 + 2NO2 -> 3N2 + 2H2 + 4H2O}
$$

As you can see, I'm trying to find if it is practical to take two toxins and convert them into non-volatile substances. Also, of course, harvesting this hydrogen gas would also be preferred; you could just add it back into the resulting Syngas. And I suppose ammonia doesn't have to be used. It just seemed convenient and the above reactions (producing useful Hydrogen and other non-volatiles) somehow came into my mind.

And it seems for every $\ce{O}$ (or $\ce{N}$) in the $\ce{NO_{x}}$ it can make another $\ce{O2}$ (or $\ce{N2}$, respectively). Or double the ammonia, to effectively double up on the first reaction.

If its the case that one reaction is more practical than another (as it usually is). I have noticed that conversion is simple:

$$
\ce{2NO + O2 -> 2NO2}
$$

readily happens in air and at 150C it reverses:

$$
\ce{2NO2 -> 2NO + O2}
$$

Most of this leads to gasification. Gasifiers stratify the combustion process to extract producer gas (Called Syngas. It is $\ce{H2 + CO}$, and it burns clean.). If a gasifier is built a certain way, the only pollutants could be $\ce{NO_{x}}$, and since some gasifiers can use biowaste, then ammonia is not hard to reconstitute on-site in some applications. Plus, I think it might be possible to extract ammonia directly from the pyrolysis stage when using garbage in certain gasifiers. As well, I think Ammonia is in the resulting trace gases sometimes depending on the gasifier/fuel setup.

There are some resources to be had. Gasifiers also have to typically filter out sulfur and mercury from the resulting Syngas. If those can help at all here and/or could also be included in this detoxification. As well, there are usually sources of heat (up to 1100C), tar, char (hot carbon), and hot or cold ash (burnt charcoal), $\ce{H2 + CO}$, $\ce{CO2}$, and other trace gases like $\ce{CH4}$ or whatever, depending on the gasifier and fuel. These resources could be utilized if needed, but most already have a role to play. Carbon dioxide, methane and tar are used to make more Syngas. The wasted byproducts are: sulfur, mercury, cold ash, and the "whatever" trace gases. I believe sulfur is in the form hydrogen sulfide. There is also probably substantial unsued hot Char (hot reactive carbon), but it burns quick, and only exists in the heart of the machine, then once all the heat is extracted it turns to ash.

Actually, I wonder if I could pump the $\ce{NO_{x}}$ (or other pollutants) back into the pyrolysis stage, if they would might reform into something else. Less toxic, eventually.

Of course, I feel like I'm barking up the wrong tree. As $\ce{NO_{x}}$ gases are closely scrutinized by municipalities, any practical reduction would probably be used already and emission of $\ce{NO_{x}}$ gases into the environment wouldn't be a problem, but that is assuming way too much for humans. So, I have to ask:

Do any chemists see a way, using these resources (or other practical external ones), to detoxify the nitrogen oxide from the resulting burnt Syngas fumes?


texts: I came across something called overlap integrals. I could understand that it is something about the overlapping of orbitals. What is it actually?


texts: Find Equilibrium Constant with only balanced equation?

texts:
Calculate the value of $K_p$ for the following equation:
$$\ce{PCl3 (g) + Cl2 (g) <=> PCl5 (g)} ,\qquad \mathrm{R = 0.0821 \frac{L\times atm}{mol\times K}}$$

This question appeared on my test. I know how to find $K_p$ if I was given $K_c$ $(K_{\mathrm{p}} = K_\mathrm{c} \times (\mathrm{R} \times T)^{n})$ or if I was given the partial pressures of all of the parts at equilibrium, but none of those values were given; only the equation. My professor marked the answer as $0.041$ (no units), but I have no idea how to calculate that if I wasn't given any values.


texts: Why is nitric acid often used to digest any solid sample?

texts:
Why is $\ce{HNO3}$ often used to digest any solid sample?

I heard many solid samples often digested with $\ce{HNO3}$ solution because nitrate compound always dissolve in water.

Is the concept correct or not?


texts: How reliable is spectrometry in the determination of the oldest material Startdust?

texts:
After reading one of the latest findings by scientists, Stardust was considered the oldest material on earth. However having not much of an experience with chemistry, I was intrigued upon how scientists were able to find such finding therefore from my understanding, scientists used spectrometry to determine composition of stars to then determine the age of the material(hopefully I am not wrong). However, reading one of the news article, it said that “ stardust that predated the formation of our solar system by billions of years, scientists said on Monday.” This gabbed my attention because it says that scientists found that it was on Monday but the question that came to mind is, how reliable is spectrometry in the determination of such exact findings? Please let me know what you think?
Thanks a lot.
News article: https://www.aljazeera.com/news/2020/1/14/stardust-oldest-material-on-earth-found-inside-meteorite


texts: Why is CCSD(T)/aug-cc-pVTZ not a suitable method for the geometry optimisation of omeprazole?

texts:
I know that CCSD(T) with the aug-cc-pVTZ basis set for geometry optimization of omeprazole (5-methoxy-2-[(4-methoxy-3,5-dimethylpyridin-2-yl)methanesulfinyl]-1H-benzimidazole, the active substance in Losec) is not suitable using normal computers. The substance is:

(omeprazole)

Can someone explain to me what exactly makes these methods too expensive for this substance?


texts: Methyl orange coordination compound chemistry

texts: Methyl orange changes colors depending on the acidity or basicity of the solution. But I have read that it forms complexes with certain ions. Can anybody suggest any resource regarding the coordination complex-formation chemistry of methyl orange?


texts: How does this brominated intermediate lose its methyl group?

texts:
The problem is such:

So far my working has been:

I'm concerned about the last step where the ester forms a ring. The methyl group doesn't look like a plausible leaving group, but it does not appear in the product so how can I get rid of it?


texts: What will be the product when 3,4-dibromocyclohexene is reacted with sodium followed by heating with selenium?

texts:
I'm tutoring few Class 12 students for their chemistry exams. I'm stuck with few problems. I don't know, if the key is wrong or I am wrong.

According to me product (A) must be the cyclic diene, as given in option (A). Now, I don't know, what happens when you heat cyclic diene with selenium. But I do know that,  $\ce{SeO2}$  oxidizes allylic positions of alkenes into alcohols. But, none of the options given are fitting into that argument.

The answer given in the book is option (B).
How can that be explained?


texts:
I wish to use lauryl glucoside in the solution of citric acid. I tried to add it to 5% w/w solution of citric acid in water but after about 24h in the concoction which was previously clear I observed a kind of sediment. It looked like a "white smoke" disspersed in the clear liquid. I wonder whether it can be the effect of hydrolysis of glucoside due to the low pH (about 2) of the solution...
I used:

distilled water,
clear citric acid,
clear lauryl glucoside.

Can someone provide an information in what pH values lauryl glucoside is stable? Do you know how to explain what happened with my solution?


texts: Can benzyne be trapped inside a polycyclic hydrocarbon?

texts:
I came across an article in my organic chemistry textbook, which told about how benzyne was trapped within a molecular container and stabilized for short periods of time before undergoing a Diels-Alder reaction with the molecular container.

Obviously the container molecule must have had double bonds, which caused the powerful dienophile benzyne to react with it. While thinking about fully saturated molecular containers, dodecahedrane came into my mind:

The volume enclosed inside a dodecahedrane molecule was found to be approximately $2.8 \times 10^7 \text{pm}^3$. If I approximate the dodecahedrane to be a sphere, I get the diameter of the dodecahedrane to be approximately $5970 \text{pm}$.

Benzyne was conveniently prepared by diazotizing o-anthranilate, followed by heating simultaneously removes both $\ce{N2}$ and $\ce{CO2}$, and creating the benzyne molecule:

I am unsure on exactly how to find how much transverse space an anthranilate ion would occupy when stuffed into a dodecahedrane, but benzene itself is $496 \text{pm}$ wide, so I can suspect anthranilate maybe a bit wider, but nontheless can easily fit inside dodecahedrane.

And another advantage is, since both $\ce{N2}$ and $\ce{CO2}$ are linear molecules, they can easily escape through the pentagonal faces, leaving the benzyne trapped inside.

Edit: I made a mistake in calculating the diameter of the dodecahedrane. I now get it as $377 \text{pm}$, which is slightly smaller than a benzene ring width, so this compound won't work.  Still if we used bigger molecule, it could fit in. Can this be done? Will this work? Are there any complications involved?


texts: How to choose the parameter to scan in finding transition state by using Gaussian 16?

texts:
I have problems in finding the TS of reaction dehydrogenation of an organic compound. I read many tricks to find the TS and see scan is an effective method. As I know we can use the product of the reaction as a starting point to scan. But what parameter should I choose if there are two bonds were broken (the bonds in the red circles in the picture)?  I already tried to scan with one broken bond, and for the other one I just elongated it a little.  Unfortunately, the result has not converged. And one more question, does the orientation of the initial structure affect the result of the scan?
I am just a very new person in DFT as well as with Gaussian. Thanks in advance for any help.


texts: What is the Gibbs Free Energy in Zinc Electroplating?

texts: In zinc electroplating process, where zinc metal (anode) is deposited on an iron plate (cathode), there is no net equation. Then why do we need to apply voltage to the system to produce zinc metal on iron? Does Gibbs Free Energy change, regardless of how much voltage is applied, after electrolysis?


texts: Why is one lobe of an sp3 hybridized orbital smaller than its other half?

texts: A hybrid sp3 orbital is drawn with one lobe smaller than its other half, the latter which is of equal size when drawing the p orbital. Why is it so?


texts:
Is the phenoxide ion aromatic? I read that technically it isn't aromatic because it violates some arcane rule, but I can't find any references in the literature.

I don't see why it couldn't be aromatic, since it's

flat/planar
has a system of conjugated p-orbitals.
has 4n+2 pi electrons: 2 from the oxygen lone pair that is delocalized and n = 0.
is cyclic.


texts: What is the substituent on this benzaldehyde? (MS attached)

texts:
I have no clue what the substituent may be.

The molar mass of the unsubstituted benzaldehyde is 105 g/mol (subtracting one H, where the substituent will be). So the substituent is around 30–33 g/mol. Also I'm having trouble identifying the molecular ion. Is it the really small 138 peak or the 137 peak?


texts: Why was Nobel Prize given to Baeyer for his "faulty" Baeyer's Strain Theory?

texts:
Baeyer Strain Theory said that using the formula

$\frac{(109^ \circ 28' - \alpha)}{2}$, where $\alpha$ is the angle between 2 sides of the cycloalkane, the most stable cycloalkane could be found. Thus he proved cyclopentane to be the most stable.

But later using the value of heat evolved during combustion, cyclohexane was found to be the most stable.

Then why was the Nobel Prize given to Baeyer for a faulty theory, still resides beside his name?

For a theory which no longer could explain the maximum stability of cyclohexane?


texts:
This is a worked example about solubility equilbrium I am new to this subject and I am really confused first of all I know that Q is the product of concentration of Ag and Cl in the solution and ksp is the product of molar solubility of Ag and Cl then why the difference of these two is not amount of precipitation
second: if we are not given ksp value of AgCl and we are given only the last part ( part b) how can we find the ksp value?
P.s: after change the amount of cl become zero and amount of Ag become 99*10^-6 so it means that after mixing two solution precipitate is formed and amount of dissolved Ag ions become 99*10^-6 and all of Cl ion is precipitated am I right?
(Sorry if my questions doesn't make sense for you it is because I am new to subject and I don't have any teacher I really tried hard on this example and I saw lots of videos about this subject but I didn't understand it)


texts: $E^\circ_\mathrm{cell}$ is the EMF of the cell for a reaction with respect to standard hydrogen electrode (SHE). So why don't we represent $E^\circ_\mathrm{cell}$ or $E_\mathrm{cell}$ by $\Delta$ symbol, in the same manner in which we represent $\Delta H^\circ$, $\Delta G^\circ$, $\Delta S^\circ$, etc., with respect to initial absolute zero temperature?


texts: Elegant solutions to non-conjugate buffer systems: ammonium carbonate, pyridinium dihydrogen phosphate, lysine and glutamic acid etc

texts: Okay, this has really been frustrating me as a tutor because there is such few materials online on what to do in this case (besides use a brute-force method with systems of equations). Almost every pedagogical resource assumes a weak base and strong acid, or weak acid and strong base, and stops there. Oh, sometimes they will cover ammonium acetate, which is honestly cheating because pKa + pKb of both species add up to 14, so it's really a conjugate system in disguise. Is there a pedagogical resource for these general situations? I also realize my knowledge is lacking because I only was taught the system of equations method as a backup.


texts: Why is the number 2 needed for 2-methylpropanal?

texts: I think there is just one possible position for the methyl group to 'fit in' to propanal, however, my textbook and wiki suggests the correct names should be '2-methylpropanal'. Why is the '2' needed?


texts: How to calculate probability of finding an electron at a point?

texts:
In school i learned how to calculate probability of finding electrons in some volume but how can we calculate the probability of finding a electron at a particular point.

Point here has negligible volume.


texts: I get it that transition metal salts have colour due to d-d transition from $\mathrm{t_{2g}}$ to $\mathrm{e_g}$ orbitals in octahedral and the opposite in tetrahedral but why would $\ce{Mn^2+}$ not have any characteristic colour? Is it so because the orbitals are degenerate in $\ce{MnSO4}$? or because d-d transition only takes place when there is completely empty d orbital?


texts: What is the dipole moment of the most stable conformer of 1,1,2,2-tetrafluoroethane?

texts: I want to know about the dipole moment of this molecule. I think the molecule has no dipole moment, but a book says me that it has a dipole moment.


texts: Is it safe to mix potassium alum powder with magnesium oil (made from water and magnesium flakes)?

texts: Will mixing these two together cause a reaction of any sort? If so, is it safe and is there an order in which one should be added to the other?


texts:
I was visiting an elements exhibition in the Ulster Museum (Northern Ireland) and there were these native sulfur crystals on display.

My question is how do sulfur crystals like these form in nature? Does the sulfur precipitate out of a solution? Are they the product of a chemical reaction?
I am confused because of sulfur's negligible solubility in water and I couldn't imagine any other way such perfect crystals could form.

I am really interested in making such crystals myself but as I have said, I don't know by what process or under what conditions this crystallization of sulfur occurs.


texts: Suitable first-year experiment idea - stability of coordination complexes in TLC?

texts:
I'm a first-year in university and we have to carry out a "measurement" project next term. I'm fascinated by coordination chemistry (though I haven't taken the course yet), and while our equipment list is pretty limited it does include a thin-layer chromatography setup (and a colorimeter & a pH probe, which I would love to use if there was a way).

I was thinking of using TLC to look at the stability of different complexes (either different ligands or central metals), similar to the experiments in these papers:

Stability of mixed-ligand $\ce{zinc(II)}$ carboxylate complexes in thin-layer chromatography
Thin-layer chromatographic determination of the stability of complexes of substituted styrenes on silver nitrate-impregnated silica

However, I'm struggling to come up with examples of complexes that can be made easily (without a fume hood) and inexpensively. I'm not very knowledgable about this topic so I apologize if this is a bad question, I was just wondering if this seemed like a feasible yet worthwhile project given constraints in equipment/money and my knowledge. In previous years, people have mostly done biology or physics related projects so I'm a little doubtful if this idea—in particular, synthesizing a variety of complexes—is realistic. I'd appreciate any advice, specific or general! Thanks!


texts: Between $\ce{[Rh(Ph2PCH2PPh2)3]^{3+}}$ and $\ce{[Rh(Ph2PCH2CH2PPh2)3]^{3+}}$, which one is the most stable thermodynamically? I think it's about the size of the chelate ring effecting their stability, but i'm not sure.


texts: A substance that is immisiscible with water and that can be made cloudy

texts:
I need to identify a substance that is immiscible with water that is or can be made cloudy.

At the moment I'm using glycerol, but I don't know how to make glycerol cloudy nor is it perfectly immiscible with water.

Clarity:

I need to make a bottle containing two liquids. One part being water mixed with rhodamine and the other part another liquid that is immiscible with the rhodamine water mix that is cloudy. The other chemical can either be cloudy already or be mixed with another substance so that it can become cloudy.


texts:
I am currently doing a experiment in the lab which is using a continuous wave NMR, by sweeping the magnetic field, and I am having trouble understanding how the theory works for this type of experiment.

So I currently understand if a proton is not placed in a magnetic field it will spin on it axis of rotation due to the magnetic moment.

My first question is on what causes this magnetic moment, from what I have found so far that the proton can be modelled a sphere with infinitely  many of  tiny circular current loops which run along the axis, but what I can understand is that for a dipole moment to be formed a current going in a circular loop generate the dipole moment.

  So dose the dipole cause the proton to spin which generates the magnetic moment and if so what causes the tiny dipoles along axis? It seem to me there a rotation being caused by a rotation.

So moving on when the proton is placed in the a uniform magnetic field it will either align it self with parallel or anti parallel. It would not align it self fully due to the rotation of the proton so the proton will actually precess around the axis in which is in the direction to the static magnetic field. Now when the proton is in a state parallel to the static magnetic field it is in a low energy state and when anti parallel it is in a high energy state so the energy difference is given by:

$$\Delta E=hf=g\mu _nB_0$$

Now applying this to a sample of high hydrogen 1 like glycerine that has been place in CW NMR. When the sampled is placed in the static filed according to the Boltzmann distribution there will be more protons parallel to the field that non-parallel so now in cw as I understand a constant RF signal is being applied and a varying magnetic field perpendicular to the static field.

So my second question is

  Dose the varying magnetic field vary the energy levels until resonate occurs?

I believe it dose as this would explain the nmr of glycerine that was take in the lab, as show below.

Now the real trouble I am having with these graphs is that one it looks to me that there is a dampening effect occurring, which I believe to be the relaxation time of the sample, but what I cant visualise is how the resonance is occurring within the sample it self in terms of the physics with respect to all the protons precessing.

  Are the individual proton within the sample at different depths become out of phase with each other and the varying magnetic field is decreasing over time, and why dose each resonance peak have a negative voltage associated with it? How dose this negative voltage tell me about what is occurring with in the sample?

If anyone could with any of the theory behind CW NMR and how the signals being receive can inform me on what occurring with in the sample it would, it would be appreciated. Thanks in advance.


texts:
Why is the empirical atomic radius for both Co and Rh 135 pm, the same?

Source


texts:
Why does $\ce{C6H5COOH}$ in benzene form dimers? Also why only in benzene, why not in other solvents such as water?

In general, what are the properties of compounds which form dimers or polymers in benzene?


texts: Why is it important to know the spin of bioinorganic complexes?

texts:
During a bioinorganic chemistry course, my teacher gives a lot of importance to spin states of metal ions and how they changes (or not) after the formation of a complex.

For example, when hemoglobin's Fe(II) ion couples with oxygen molecule, it's spin changes from high spin to low. My teacher says that is very important but he doesn't give a reason.


texts: What is some advance reference books about alloy that gives a lot historical background and applies a lot of theoretical equation or formulas

texts:
What is some advance reference books specifically about alloy that gives a lot historical background and applies a lot of theoretical equation or formulas with explanation?

I seem to find nothing really very interesting for myself to learn general theory of alloy while searching the google books because these books is too wordy in detail but too few formula and laboratory skill to support it.


texts: Which has higher priority (Cahn-Ingold-Prelog)?

texts:
Which group gets higher priority and why?

$\ce{R-CH_2OCH_3}$

$\ce{R-CH=O}$


texts: Is there a coating substance that is very visible through a lens?

texts: I'm trying to find a way to easily spot golf balls, and I was looking for some chemistry help. I was wondering if there is a substance that I could coat a golf ball in, that would be very visible through a specific type of lens?


texts: Order of solubility of sodium halides and potassium iodide

texts:
Order the following ionic compounds in decreasing order according to their ease to dissolve in water.
a) NaBr; b) KI; c) NaF; d) NaCl.

d > a > b > c
a > b > c > d
b > c > d > a
c > d > a > b

So, according to what I researched the solubility $s$ for each one of these compounds in water (at $\pu{20 °C})$ is:
$$
\begin{array}{lc}
\hline
\text{Compound} & s/\pu{g L-1}\\
\hline
\ce{NaBr} & 905 \\
\ce{KI} & 1400 \\
\ce{NaF} & 40.4 \\
\ce{NaCl} & 359 \\
\hline
\end{array}
$$
Therefore, my answer would be, from more soluble to least soluble:
b) KI > a) NaBr > d) NaCl > c) NaF
But this answer is not among the list. I think option 4 might be "correct", but it's kind of backwards.
Are the given answers wrong or am I doing something wrong?


texts: Organic nomenclature of substituted diamines

texts:
Nomenclature of substituted amines is done with the N-locants, with the N being used to indicate that a group is connected to the methyl group. I was wondering, therefore, on how to properly name a substituted diamine.

I found this source from the University of Calgary, here, which recommended to use N, N', N'', etc locants for compounds with multiple substituted amines. However, their examples are all with symmetrical diamines, and it is apparent that using the N, N' locants only works because of the molecule's symmetry. Thus, my question is: how can we name substituted diamines properly, such as the one below?

Would it be N,N,N'-trimethyl,3,5-diaminopent-1-ene or N,N',N'-trimethyl,3,5-diaminopent-1-ene, or something else?


texts: Calculating the number of neutrons in a sample

texts:
Which of the following contains one mole of neutrons?
A. $\pu{1 g}$ of $\ce{^1_1H}$
B. $\pu{1 g}$ of $\ce{^{12}_6C}$
C. $\pu{2 g}$ of $\ce{^{24}_{12}Mg}$
D. $\pu{2 g}$ of $\ce{^{23}_{10}Ne}$

Here's a question which I don't know how to answer. I tried using the equation:
moles=mass/mr
but that did not match the answer given, which is (C). I keep doing 2/24 which doesn't appear to equal 1 mole.


texts: Why aren't the hydrogen bonds in carboxyllic acids like this?

texts:
Why don't carboxylic acids form H-bonds in this formation with the red dots (diagonal) instead of the black dots (horizontal)?

I was always taught that H-bonds formed between partially negative and partially positive atoms. I agree that the $\ce{=O}$ carboxyl oxygen is partially negative, so there should be a H-bond there from the partially positive H.
However, the $\ce{O}$ in $\ce{OH}$ is also partially negative. So why aren't the H-bonds denoted with red dots formed?


texts:
The question says:

A proton is accelerated to one tenth of the velocity of light. If it's velocity can be measured with a precision $\pm 1\%$. What must be its uncertainty in position?

Therefore,
$v=0.1 \times c =3\cdot 10^7\ \pu{m/s}\\
 \Delta(v)=\frac{1}{100}\\
 m= 1.6\cdot10^{-27}\ \pu{kg}$
Then I directly substituted these values into the formula:
$$\Delta(v)\cdot\Delta(\text{position})\cdot \text{mass}=\frac h{4\pi}$$
To get the uncertainty in position, however, the answer I got was approx. $3.5 \cdot 10^{-6}\ \pu{m}$ which is way too different from the correct answer:

$0.5\cdot10^{-13}\ \pu{m}.$

Can anyone please explain me how to solve this question?


texts:
Which of the following pair of molecules have identical bond dissociation energies (approx)?

  $\ce{H2}$, $\ce{F2}$
  $\ce{F2}$, $\ce{I2}$
  $\ce{N2}$, $\ce{CO}$
  $\ce{HF}$, $\ce{O2}$

I think it's either (2) or (3). (Single correct type).

Bot $\ce{F2}$ and $\ce{I2}$ bonds are weak because of inter electronic repulsions and due to large sizes respectively.

In case (3), both molecules have bond order 3.


texts: Gaussian16 Raman calculation from IR checkpoint file

texts:
I already did an IR frequency calculation for my molecule. Is there any possibility to just run a Raman frequency calculation with the chk file from my IR calculation?
Or do I have to do the calculation again with the freq=raman keyword? I checked the Gaussian manual and found the raman=polar keyword, but I think this is not exactly what I am looking for.


texts: Order of rate of acid catalysed dehydration of alcohols

texts:
The relative rate of acid catalysed dehydration of following alcohols would be:

According to me, we have to arrange them in order of their carbocation stability.
Q will be the most stable as it is stabilized by Resonance and Hyperconjugation. P should come next. After that I think it should be S>R as in case of R there is no hyperconjugation and hyperconjugation is a “stronger” effect than the Inductive effect.
But in my Book R>S is given. Is Inductive effect stronger here? Or is there some other reason to it?


texts:
As a non scientist I several times wondered how can an Organic chemist successfully isolate a single molecule which a natural product of an organism;
Whether a plant-part/mushroom-part/algae-part or a coral-part or even from an animal or human organ in autopsy (neurotransmitter/hormone and so forth).

I also wondered how could she go further to know the natural product's (exact?) chemical formula and give such newly discovered molecule a name.

Given that molecules are such small entities, way smaller than the smallest uicellular organism and are hard to be photographed uniquely with current microscopal technologies (AFM/STM); it is unclear to me How could she know if a plant part contains a certain molecule (say caffeine or nicotine) so precisely that she could tell:

  This is what I will now name Caffeine → not Theobromine
  or any other Methylxantine → just Caffeine, pure and exact and unequivocal.

Practical examples for my problem are:

How did organic chemists isolated THC from various Cannabis plant-parts and gave it a formula and a name, although today it is known that Cannabis plant parts has tens of cannabinoids?
How did organic chemists isolated Ganodermadiol in some Ganodrma mushroom part/s and gave it a chemical formula and name and claimed it is similar to steroidal hormones?
How did they know they weren't wrong?

My question

How can an Organic chemist know the chemical formula of a natural product she isolated from an organism?


texts: Interpreting equilibrium equations correctly

texts:
I've watched over this Khan video titled "Reactions in Equilibrium" and am still confused on the interpretation of equilibrium. Reactions in Equilirbium

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

Whenever I see an equilibrium like the one above, the amounts of each molecule are only what happens at the start of the reaction, correct? In the video, it was made out as if the starting coefficients next to each molecule were what was needed to reach equilibrium. However, each reaction at a different temperature has a different equilibrium constant. With that said, the amount of each molecule will change which also changes the concentration so the amount of $\ce{NH3}$ would not necessarily be 2. He does this in other videos too. He starts off with something such as:

$\ce{aA + bB <=> cC + dD}$

and immediately plugs those into an equilibrium equation. I guess what he is getting at is that we figure out the final concentrations necessary to reach equilibrium but I'm not positive.

Towards the end of the video, arbitrary (I guess) concentration amounts of each molecule were plugged into the formula to output the matching equilibrium constant. He raised each concentration to the power of the starting coefficient for that molecule. If you start out with $\ce{3 H2}$ and you need a wildly different concentration to reach equilibrium, why are we raising the concentration to the power of the starting amount of $\ce{H2}$?

Finally, let's say the concentrations I have for a particular reaction were not the concentrations at equilibrium. If I still plugged them into the equation, that would tell me not only if I were at equilibrium (if I looked up the constant) but also if the forward or backward reactions were favored right?


texts:
In which of the these structures C-3 carbon is not a chiral centre?

I think that the answer to the above question should be both (b) and (c) as C-3 is attached to same groups and also they have a plane of symmetry hence making it achiral. But, the answer given to this problem is (d) with the reasoning that only in (d) option configurations of the both the carbon attached to C-3 is same while the configurations of both the carbon attached to C-3 is different in (b) and (c).
Should the configurations of C-2 and C-4 carbons even matter here?


texts:
If two electrons that get paired occupy the same orbital, then wouldn't there be a heavy amount of repulsion between the two?
As is, since electrostatic force ${\displaystyle \propto }$  $\ce{ 1/ (distance)^2}$   so since the distance between two electrons is way smaller than between the electrons and nucleus, I don't really assume it has any role here.

Does this have anything to do with the strong nuclear force? As far as I know its range is too short and exists only between protons and neutrons.

Summing up, what causes two paired electrons to stay in the same orbital rather than get thrown away due to "the force"?


texts:
Look for the following data for Nickel
IE1+IE2  2490 kj/mol
IE3+IE4.  8800kj/mol
Total.       11290kj/mol

Hence Nickel can show +2 oxidation state but not +4.
But according to me Ni in +4 oxidation state can acquire 3d6 and 4s0 which has t2g3 configuration.
Why do it has high ionisation energy?


texts:
The hybridization of $S$ in $SO2$ is sp2 which means it has only one unhybridized p orbital to form a $\pi$ bond. How does it form two?
Could it be one electron from a $p$ orbital getting promoted to a $d$ orbital leading to one $d-p$ and one $p-p$ $\pi$ bond. Is this even possible or are $\pi$ bonds only between p orbitals? Could the electrons possibly be delocalized in the $d-p$ and $p-p$ $\pi$ bonds?


texts: Why does mesitylene absorb at a longer wavelength than benzene (UV-Vis)?

texts:
According to UV-Vis spectroscopy, mesitylene (1,3,5-trimethylbenzene) absorbs at $\lambda_\text{max} = 210\ \mathrm{nm}$ while benzene absorbs at the slightly shorter wavelength of $\lambda_\text{max} = 204\ \mathrm{nm}$.

Why is that? One would think that $\pi$-ring's hyper-conjugation with the $\sigma^*$ orbitals of the methyl hydrogens would help stabilize the system thereby increasing the gap between the HOMO and LUMO (in turn decreasing absorption wavelength).

An opposite effect is observed when nitrobenzene ($\lambda_\text{max} = 252\ \mathrm{nm}$) is compared to 2-nitrotoluene ($\lambda_\text{max} = 250\ \mathrm{nm}$) and 2-isopropylnitrobenzene ($\lambda_\text{max} = 247\ \mathrm{nm}$). In these cases, the addition of larger and larger alkyl groups seem to be decreasing the absorbed wavelength (therefore increasing gap between HOMO and LUMO).

Is that because of sterics? Or because the the strongly electron withdrawing nitro group (conjugation) is being "counteracted" by the alkyl electron donating groups and therefore electrons are more concentrated in the ring rather than being spread though the molecule?

EDIT:

My question in more general terms: I understand HOW more conjugation results in a decrease in absorption frequency (due to molecular orbitals overlapping constructively vs destructively therefore decreasing gap between HOMO and LUMO). What I don't understand is HOW pumping electron density into a conjugated system (or withdrawing) effects the HOMO and LUMO. An explanation from a MO perspective would be greatly appreciated.


texts: Does the volume change when the reactions occur?

texts:
I have this reaction (all substances are gaseous):

$$
\begin{align}
\ce{A + 4.5 B &→ C + 2 D + 2 E}\tag{R1}\\
\ce{C + 7.5 B &→ 8 D + 2 E}\tag{R2}
\end{align}
$$

Does the volume change when the reactions has occurred?
Because if so, the concentration changes too, right?


texts: Significant figures in pH calculations: does pH 0.30 count as 2 or 3 significant figures?

texts:
Just say I wanted to give a pH calculation to three significant figures.
Eg: the $\mathrm{pH}$ of a $0.500 M$ solution of $\ce{HCl}$ is $-\log(0.5) = 0.3010299957...$

Would 3 s.f. be $0.301$ or $0.30$?

I know normally when zero comes before a number, it isn't considered a significant number (i.e $0.00034$ and $0.34$ both have two significant figures). But since pH is a scale, can I treat $0.30$ as three significant figures?


texts: How to purify sodium chloride table salt that contains sodium ferrocyanide

texts: I wish to obtain pure sodium chloride crystals from ordinary table salt.  But all proprietary table salts seem to contain the anti-caking agent sodium ferrocyanide which I should like to remove.


texts: How to identify a compound as chiral or achiral

texts:
I read my book and learned everything about enantiomers, racemization, $\mathrm{S_N1}$ and $\mathrm{S_N2}$ reactions, but when I'm trying to identify molecules as chiral or achiral, I get confused.

Consider the two molecules below:

1.CH3-CH-OH
      |
      Br

2.CH3-CH-Br
      |
      Br

How can I tell if a compound is chiral?


texts: I was thinking is there really bond present at microscopic level or atoms/molecules are just nearby and are connected with force which is not visible(like gravitational force between earth and sun) and we make bonds just for understanding.


texts:
Can someone please explain the bonding in a bridged metal carbonyl (like diiron nonacarbonyl)?

I cannot understand what kind of bonds (sigma/pi) exist between the bridging carbonyls and the metals.

Also why aren't the metals charged in such a case?
What is the bond order in such a case?


texts: Effect of relative strength on nature of solution

texts: If a solution has equal no. of gram equivalents of a week acid (say acetic acid) and a strong base say NaOH , will the soltution be neutral or the relative strength has some role making solution slightly basic?


texts: Why does CO2 diffuse through a butyl rubber membrane more readily than air?

texts:
I am a cyclist, and not a chemist. When I or my cycling buddies get a flat tire out on the road, after removing the offending sharp object (if any) remaining in the tire, we will typically replace the punctured butyl rubber inner tube with a new one, and then inflate the tire using a $\ce{CO2}$ cartridge.

Inflating the tire in this way takes less than a second to bring the pressure up to 120 psi. At home, naturally, we fill our tires with air rather than a $\ce{CO2}$ cartridge, using a floor pump.

When we fill our tire with an air pump the tire remains inflated for several days. But after filling it with $\ce{CO2}$, the tire is severely flat again by the next morning. $\ce{CO2}$ clearly diffuses through the butyl membrane very much more rapidly than air, even though $\ce{CO2}$ is a larger molecule than either $\ce{N2}$ or $\ce{O2}$. Is it the shape of the molecule? Or its chemical properties?


texts: Is there any kind of reaction with two types of reactants (gases) and one product (also gas) such that the total volume after the reaction increases?

texts:
I would like to think of the following equation:

$$\ce{aA(g) + bB(g) -> cC(g)}$$

where $a + b < c$ and $\ce{A},$ $\ce{B}$ and $\ce{C}$ are different gases.

Is there such chemical reaction?


texts:
We know that if a system's equilibrium is exposed to a stress, the system shifts to relieve that stress. According to my teacher, certain kinds of pressures are stresses and others are not.

Normally, if we just say that the total pressure of a container with a reaction occuring inside is increased, the reaction shifts toward the side with a small sum of the mole ratios (i.e. $\rm 2A +3B \longleftrightarrow C + D$, if increasing pressure reaction shifts to the right to decrease pressure). I understood this formerly, but another case erases this understanding.

My teacher also said that if we add a noble gas to the container in which this reaction is occurring, although the pressure increases because of a new gas, the equilibrium does not shift to counteract this pressure increase. She says it has to do with the partial pressures of the reactants and products of only the particles In the reaction, but not in the total balloon. But this makes no sense to me because by increasing the total pressure of the system as described before, how does this cause an equilibrial stress and this case doesn't? How does increasing total pressure even cause an equilibrium shift? By increasing total pressure we have a proportional increase in the collision rates of all particles involved, do we not? If this is true, then why wouldn't the reaction rates both be doubled, and hence cause the equilibrium to not shift?

If I'm missing some fundamental principle, please let me know.

Thanks!


texts: Colliding particles and activation energy

texts:
If two particles collide and they are under activation energy, why do they JUST “bounce apart”? Isn’t the activation energy steadily decreasing if those particles continuously collide?

I always viewed the activation energy as a "barrier" that prevents collisions from producing a reaction, if sufficient energy is not met. I thought that if particles collide and they do not have enough energy to cause a reaction, the "barrier" gets weakened. Therefore, I found it surprising that this "barrier" doesn't get weakened, and the activation energy isn't reduced.


texts: What is the reaction of pentane-2,4-dione with chlorine in presence of NaOH?

texts:
We know that in haloform reaction alpha acidic hydrogen are substituted by halogen atom. But in the above case we find two acidic hydrogens in between the two keto groups (due to -R effect) which are more acidic than the hydrogens on the terminal methyl groups.

So what should be the products of this reaction?


texts:
What are the differences between:

van der waals surface area
solvent accessible surface area
topographical polar surface area

What is the significance of these differences, and what are the differences in how each of the three is used?


texts: Mechanism for chloromethylation of benzene with formaldehyde and HCl

texts:
What is the mechanism of the above reaction? I have thought of one possibility:

Would this work? How exactly is the chlorine installed on the alkyl chain?


texts: Designing a device to separate water from water-ethanol mixture using dry ice baths

texts:
I've been trying to design a device to increase the percentage of ethanol and water, or to at least concentrate the water-alcohol mixture without using distillation.

The way I'm trying to do this is by using a dry ice bath (dry ice+propanol). I then insert a stainless steel vessel in the bath with the said water-alcohol mixture (between 30-60% ethanol to begin with). Going by the ethanol-water phase diagram and the temperature of the ice bath (-78C), I should, in theory, be able to concentrate the mixture up to ~80% ethanol.

Where this goes wrong is that instead of cleanly separating into water ice and concentrated water-ethanol mixture, what I get is a kind of ice-alcohol slushy.

Any suggestions on how to get a clean separation and get ice that I can scoop out?

Thanks!


texts: On heating in the Earth's atmosphere, can magnesium react with nitrogen to form magnesium nitride?

texts:
This question is derived from a question asked in my school test.

What happens when a magnesium ribbon is heated in air?

My first response was the formation of magnesium oxide $(\ce{MgO})$ when oxygen in air reacts with magnesium at a high temperature which can be expressed in the form of a chemical equation like this:
$$\ce{2 Mg(s) + O2(g) ->[\Delta] 2 MgO(s)},$$
but I was wondering if magnesium could react with any other gas in the air to form a compound with that gas and I found out that magnesium does react with nitrogen in the air to form magnesium nitride too:
$$\ce{3 Mg(s) + N2(g) ->[\Delta] Mg3N2(s)}.$$
What determines whether the heated magnesium ribbon will react with the oxygen in the atmosphere or the nitrogen in the atmosphere?
Two possibilities that I can think of are:

composition of the air;
temperature.

I don't think that composition is the answer because on average the atmosphere of Earth has more nitrogen than oxygen, so I think that the answer may be temperature.
I'd also like to know how the factor affects the chemical reaction on an atomic level.


texts: Fleshing out the stochiometric/molar quantities

texts:
Any help appreciated, it's been 37 yrs. since I was in univ. chemistry class.

Trying to flesh out the stochiometric/molar quantities (grams) of magnesium oxide to be combined with monoammoniumphosphate (MAP, a common fertilizer) to create ammonium magnesium phosphate x 6 H2O ?

MAP (NH4H2PO4) is an acidic dihydrogen compound, MO is an alkaline oxide, so it appears at 1:1 mix ratio I already have a problem of excess protons - -  not enough hydroxyls.

I'm guessing I can simply heat it the combination in distilled H2O on a magnetic stirrer overnight, then try cooling it to separate by crystals , but I have read that AMP is sparingly soluble in water, so maybe just push pH slightly above 7, cool in fridge, decant and harvest the "sludge" or crystals ?
Combining the two should ultimately yield H2O as the byproduct, plus I have excess protons.

This substance is a common problem in sewage treatment plants where it precipitates on pipes, as well as kidney stones in humans and dogs.


texts: Mechanism with hypohalite in haloform reaction

texts:
The haloform reaction is usually done in a solution of NaOH and $\ce{I2}$ (or indeed, any halogen). Now the first part of the reaction mechanism in the wikipedia page and in the most organic books describes the reaction between the enolate and a halogen molecule ($\ce{X2}$).

[Picture source: Wikipedia, URL:https://upload.wikimedia.org/wikipedia/commons/8/8d/Haloform_Schritt_1.svg ]

Now, one of the things that I read in the wikipedia page is that the haloform reaction can also be done with sodium hypochlorite($\ce{NaOCl}$). We also know that hypohalite ions are produced in a solution of base and halogen, which is what we use in case of haloform reaction. So, I was wondering, is there any way to draw the mechanism with hypohalite only, without bringing in the halogen molecule? What would that mechanism look like?


texts: Why must the ground state of hydrogen molecule be gerade?

texts:
As we know, the electronic ground state of hydrogen molecule is $\Sigma_g^+$. My question is, how do we know it from the theoretical perspective?

The nuclear potential in the hamiltonian of hydrogen molecule is of the inversion symmetry, so the electronic wave function of the system must be gerade or ungerade. However, how can we derive that the ground state is of gerade symmetry?


texts: Why does orbital optimization remove spin contamination?

texts:
I've come across numerous articles asserting that orbital optimized methods, where minimization of the energy is achieved through a series of unitary rotations (achieved by exponentiated single-electron excitations from the ground state reference) of the reference determinant, are exceptionally good at removing spin contamination. I've seen the numbers they report, and I believe them! I get the gist that orbital optimization allows us to overcome the error introduced by the UHF orbitals, but nowhere can I find the actual explanation of why these rotations effectively cure spin contamination.

Both references and explanations warmly welcomed.


texts: What is the exact meaning of the term 'isostructural' molecules?

texts:
Wikipedia:

Isostructural

  Isostructural chemical compounds have similar chemical structures.

Chemical Structure

  A chemical structure determination includes a chemist's specifying the molecular geometry and, when feasible and necessary, the electronic structure of the target molecule or other solid. Molecular geometry refers to the spatial arrangement of atoms in a molecule and the chemical bonds that hold the atoms together, and can be represented using structural formulae and by molecular models;[citation needed] complete electronic structure descriptions include specifying the occupation of a molecule's molecular orbitals.

My Doubt

Given that, while practicing, I encountered a question asking whether $\ce{NO3-}$ and $\ce{SO3}$ are isostructural or not. If we go as per the geometry, they are isostructural ($\ce{sp^2}$ hybridization). But if we consider the electronic structure, the former has bond order 4/3, the latter has 2 (assuming $\ce{S=O}$), and so may be, they are not isostructural. (In addition, they also have different total number of electrons.) This (that they are not isostructural) is the answer.

So, this question. Is the term defined or is it used without any strict definition?


texts: Energy and impurities balance for adsorption with a fixed bed (with description)?

texts:
Do you have any suggestion where to look for a source of information about energy and impurities (component) balance for adsorption of mixture CO2/H2O in fixed bed?

I have looked into many articles / some books (Ruthven: Principles of Adsorption and Adsorption Processes etc.) and most of them describe mass balance into a very details. I understood that, but these books do not contain information about how to express energy and impurities balance within the column.

Some articles focusing on adsorption modelling use energy, impurities, macro-micro pore balances etc. but their expression of these equation significantly differs (there are also difference in boundary and initial conditions). They also do not explain expressions used in the balances which I would very welcome while this is not my area of expertise.


texts: I made $10~\mathrm{M}$ of $\ce{NaOH}$ solution by diluting $40~\mathrm{g}$ of its pellets in distilled water. I'm not sure if it's really $10~\mathrm{M}$ or at least close enough, but I don't think standardize can be done in such concentration. I've been careful enough in making the solution such as measuring the mass in low humidity room and closing it with plastics/glass.


texts: Why is the residual proton resonance in deuterated benzene a singlet?

texts: In deuterated benzene ($99\%$) the residual protio peak is a singlet at $\pu{7.16 ppm}$. This however doesn't make sense since the protons will be randomly distributed among various benzene molecules. Therefore there won't be a mixture of $99$ $\ce{C6D6}$ molecules and $1$ $\ce{C6H6}$ but $94$ $\ce{C6D6}$ and $6$ $\ce{C6D5H}$. Considering that deuterium has a spin of $1$ the residual solvent peak in D6-benzene should be a septet. Any thoughts?


texts:
My solution manual implied that we can have a racemic mixture of a meso compound.

Is this possible?

I was able to rotate the molecule to make it symmetrical. Sure, the bromination in the nucleophilic solvent gives you an anti product, but from my understanding, if you can rotate the molecule so that it is symmetrical, the molecule can be meso.

I'm thinking no because meso compounds by definition have no enantniomers and a racemic mixture has both enantiomers.


texts:
I am currently researching as too which is better for purifying a water sample. I have obviously tried the standard Google search for 'Aluminium Sulphate or Ferric Chloride' and have come up with lots of results. The only problem, is that most of these results are based more around peoples opinions or psuedo-scientific observations. So, to the question:

What chemical reasons are there for choosing Aluminium Sulphate over Ferric Chloride to refine a water sample?


texts: Spectrochemical Series - Sigma Donor Capability

texts:
I fully understand and recognise the manner and which the series works.

I cannot find any references for the change in sigma donor capability moving up the series.

For example, comparing $\ce{Cl-}$ and $\ce{NH3}$. Which of the two would be more a more willing sigma donor ?

Does this have something to do with how diffuse the orbitals are ?


texts: Complete Mechanism for Oxidation of an Alkene to a Glycol

texts:
My organic book does not write out the full mechanism for the reaction of an alkene with osmium tetroxide in a basic aqueous solution with sodium bisulfate. I have made an attempt at a mechanism and am looking for a confirmation or a correction to it. Thanks and I appreciate the help.

I am concerned because the mechanism I wrote creates hydrogen gas and I have not done the reaction so I don't know if a gas evolves.


texts:
Vapour-liquid equilibrium of a two-component ideal solution of trichloroethene (C2HCl3) and trichloromethane (CHCl3) is established at 25 °C. The mole fraction of CHCl3 in the vapour phase is 1. What is the mass fraction of C2HCl3 in the liquid phase?
The vapor pressure of trichloroethene and trichloromethane at 25 °C are:

Pvap, C2HCl3 = 73.0 mmHg

Pvap, CHCl3 = 199.1 mm Hg

I'm confused about this problem, if the mole fraction of one element equals to 1, would not be the mole fraction of another element be 0? Can someone advise me on how to approach this problem?


texts: How would one compare the magnitude of covalent character between SnCl4 and SnF2 using Fajan's Rules?

texts: It is easy to compare two ionic compounds when one of the ions is same. However, how do we compare two compounds if one of the ions is the same element but just has different charge and the other ion is completely different?


texts: Why is Ka constant when volume is increased?

texts:
The following graph shows $\ce{Ka}$  vs ${V}$  (Volume) at constant temperature, as ethanoic acid is diluted:

However, I thought it would instead produce the following graph (see below).

$\ce{Ka=[H3O+]*[A-]/[HA]}$

As ${V}$  increases, I would think all of $\ce{[H3O+]}$,$\ce{[A-]}$ and $\ce{[HA]}$ would decrease similarly. As there are two concentrations decreasing in the numerator, and only one decreasing in the denominator, this leads me to believe I can write this as $\ce{Ka ∝ [X]}$, where $\ce{[X]}$ decreases as ${V}$ increases (i.e. that I could cancel out one of the concentration in both the numerator and denominator, leaving only $1$ concentration in the numerator; noting that during ionisation $1$ mole of $\ce{[HA]}$ turns into $1$ mole of $\ce{[H3O+]}$and $1$ mole of $\ce{[-A]}$)

Giving the following graph:

Why is the top and not the bottom graph produced?


texts: how to define proper ppm concentrations for water solvent vs alcohol solvents?

texts:
1 ppm is 1 mg / kg
Water density: 999.97 kg/m³
methanol density: 791.80 kg/m³

solution 1 with water as solvent: at 1 $\ce{\mu}$g / mL is considered 1 ppm

solution 2 with methanol as solvent: at 1 $\ce{\mu}$g / mL, should it be considered 1 ppm?

If this is adjusted by the density of methanol, it wouldn't be 1 ppm. I heard it is a common practice that at the ppm / ppb levels, the density of the solvent is often omitted by only focus on the volume. Is this true?


texts:
Both have similar resonance energy per ring, even Naphthalene has a little higher Resonance energy (127.5 KJ per mol per ring v/s 127 KJ per mol per ring )

Can we prove , why there is a small difference between them and Anthracene has lower resonance energy ?

Is there significant difference in their reactivity ?


texts: Which has more metallic character: aluminium or magnesium?

texts:
Which element has more metallic character - aluminium or magnesium?

I know that metallic character decreases along a period (from left to right) and increases down a group.

Aluminium comes after Magnesium in the same period (period 3) in the periodic table. So, I thought Magnesium would have greater metallic character.

However, I read in a book that Aluminium has greater metallic character. Is this true? If this is true, why?


texts: What solutes will give the largest reduction in volume when dissolved in water

texts:
This question is inspired by another question.

If you take some common salt (NaCl) and some water and mix them, then the volume of the solution is less than the volume of the constituents.

I did some calculations with;

5.75 L salt
44.25 L water
total initial volume 50 L

Density of salt is 2.170 kg/L so resulting solution is 22% concentration, which has a density of 1.164 kg/L. Therefore resulting volume is 48.73 L. This means the solution has a volume 1.27 L lower than the constituents.

My question is in two parts;

Are my calculations correct?
Is there another solute that would give a solution with volume 4 L lower than the constituents, given the volume of the constituents must be 50 L.


texts: Why is the probability of finding an electron in an orbital not 100 %?

texts:
Here is what I know and please correct me if I am wrong:
An orbit can have 2 electrons only but electrons do not exist in defined orbits. An orbital is like a hollow sphere where the 2 electrons are most likely to be found. In other words the 2 electrons of an orbit are not confined to that pathway and can be found anywhere in the orbital.

Now my question is:
Why isnt the probability of finding the two electrons of an orbital $100~\%$? Most websites say the probability is $95~\%$, where else could they be and why?


texts:
I want to understand why the p$K_{\mathrm a}$ of $\ce{HCO3-}$ is approximately 10.2 and not less.

My hypothesis is this :

Bicarbonate could react in two ways in an aqueous solution:

$[1]\qquad\ce{HCO3- + H2O -> CO3^2- + H3O+}$

$[2]\qquad\ce{HCO3- + H2O -> H2CO3 + OH-}$

Since $\ce{H2CO3}$ is more stable than $\ce{CO3^2-}$ (because it has a lower charge and all the octets are completed), the p$K_{\mathrm a}$ must be high (more alkaline than acid).

In [1], the equilibrium will be shifted to the left and in [2] the equilibrium will be shifted to the right.

Is my line of thought correct?


texts:
I have a water softener for showers and dishwasher and a reverse osmosis filter for drinking water.  For convenience of the install, the RO filter is using softened water (some calcium carbonate has been exchanged with sodium chloride -- this is my basic understanding; correct me if I'm wrong).  I don't fully understand how an RO filter works except that it is essentially just a molecule-sized physical filter.

My question is, Does the RO filter care whether the supply water is salty or hard?  Is it more effective at filtering one or the other?  Is one going to influence the life of the RO filter more than the other.

My apologies if this is not a "true" chemistry question, but I'm looking for a bit more of an thorough explanation than I got at diy.stackexchange.


texts: How are the hybrid orbitals of sulfur hexafluoride shaped?

texts:
On the fluorine end the fluoride atoms are simply completing a $3p$ orbital.

On the sulfur end one could posit a hybrid of one $3s$ orbital, two $3p$ orbitals and a three inner $2p$ orbitals. However, I think this would result in a geometry which sulfur hexafluoride does not exhibit.

The explanation I read online is that the orbitals are a hybrid of an $s$ orbital, three $p$ orbitals and two $d$ orbitals.

This confuses me because the $3d$ orbital is quite high energy and I don't think it is possible to have a $2d$ orbital even in a hybrid.

The ground state of a neutral sulfur atom is:

$$ [\ce{Ne}] \underset{3s}{[\uparrow \downarrow]} \underset{3p}{[\uparrow \downarrow \vert \uparrow \vert \uparrow]}$$

With this hybrid the state would be something like the following but with the electrons paired up with the orbitals they are bonded with (also the orbitals are hybridized):

$$ [\ce{Ne}] \underset{3s}{[\uparrow]} \underset{3p}{[\uparrow \vert \uparrow \vert \uparrow]} \underset{3d}{[\uparrow \vert \uparrow \vert \; \; \vert \;\;\vert \;\;]}$$

One approach is that sulfur hexaflouride could be thought of as a less extreme case of $\ce{S^{+6} + 6F^-}$.

Another approach is that sulfur hexaflouride could be a hybrid of a bunch of $\ce{2F2 + SF2}$ arrangements. The $\ce{SF2}$ part has a tetrahedral geometry and so $sp^3$ character. The bonds are then $sp^3-p$ bonds. The total result would be a bunch of partial $sp^3-p$ bonds between the center sulfur and outer flouride atoms and some outer partial $p^3$ bonds between flouride atoms. But I'm not sure what the actual geometry this interpretation would predict or how it would differ in properties.

How are the hybrid orbitals of sulfur hexaflouride shaped?


texts: Physical interpretation of the Gibbs-Duhem equation

texts:
For a binary system at constant temperature and pressure, the Gibbs-Duhem equation can be reduced to
$$\mathrm d\mu_B=-\frac{n_A}{n_B}\mathrm d\mu_A$$
How does one make sense of the Gibbs-Duhem equation in terms of intermolecular forces and lattice packing? Why does the chemical potential of one component decrease (relative to the other) by a factor of $n_A/n_B$?


texts: What is the real gas equation at high pressures?

texts: Is it correct to ignore the $\frac{n^2a}{V^2}$ term at high pressures as is done? I think that, as pressure increases, this term also increases as Volume decreases so it is not safe to ignore it!


texts: Identification of Sir Raman's handheld scope

texts:
I read an article somewhere around 5-10 years ago that talked a little bit about the life of Sir C. V. Raman. The focus was on the effect of Raman spectroscopy but included an interesting little tidbit.

Sir Raman apparently used to carry a small handheld scope of some description which allowed him to examine an object and only see the scattered light. He would always keep it in his pocket so that he could pick a flower or look at an everyday object and see how it changed. The article included a photo of him using it. I think I even remember seeing a video of him using it. As I recall, it was a small tube, about a hands length in size, and I think it was made from brass.

What was that tube, how did it work, and is there a resource for me to get one of my own?


texts: How can a substance be diluted to nothing?

texts:
If I start with a small amount of a substance, and I dilute that substance with billions of gallons of water, what is the scientific explanation for there being no (actually zero) remaining molecules of that original substance?

This question is related to the practice of homeopathic dilutions. I was reading some articles which stated that homeopathic dilutions don't work because at most homeopathic levels of dilution, there are very few or no molecules or the original substance.

What I'm confused about is how there can no longer be any molecules of the original substance (or even fewer molecules) of an original substance when diluted.

If there are X number of molecules in a solution, and Y liters of water are poured into the solution for dilution, don't the X number of molecules remain? How can a molecule just "disappear"? How can even one molecule just "disappear"? It makes more sense if these molecules are undergoing a chemical reaction, but if two kind of molecules (the substance, and water) are not undergoing any chemical reaction, then how can one molecule of either kind simply vanish?


texts: Why are phosphate-phosphate bonds weaker than phosphate-water bonds?

texts:
According to the Wikipedia entry on ATP,

  ATP is an unstable molecule in unbuffered water, in which it hydrolyses to ADP and phosphate. This is because the strength of the bonds between the phosphate groups in ATP is less than the strength of the hydrogen bonds (hydration bonds), between its products (ADP + phosphate), and water

Why are the bonds between a water and a phosphate stronger than the bonds between two phosphates?

I'm studying first year chemistry, so an explanation that appealed to basic principles would be best.

(I've thought about this for a bit, and looked at the molecular diagrams in hope of seeing the answer. I'd include my thoughts on the matter in this question, however those thoughts amount to a half dozen inconclusive lines of speculation, so I opted to leave them out. Saying that to say, I have put effort into trying to figure out the answer, but I haven't gotten anywhere.)


texts: Why is ethanol written as C2H5OH not C2H6O?

texts:
This is balanced equation of fermentation of glucose:

$$\ce{C6H12O6(aq) -> 2C2H5OH(aq) + 2CO2(g)}$$

I know that the result of glucose fermentation is ethanol ($\ce{C2H6O}$). What represented in the aforementioned equation is slightly different. I would like to know what $\ce{C2H5OH}$ is?

What is the OH functional group doing here? Does it make ethanol acidic? Does it mean that ethanol is diluted with water?


texts: Curtin-Hammett principle to evaluate alkene insertion

texts:
Given an unsymmetrical alkene in a simple non-stereoselective catalytic hydrogenation reaction. If one would want to investigate the nuances in the catalytic cycle of a dihydride complex leading to the alkane, there are two important transition-states that have to be considered.

Insertion of the alkene into one metal-hydride bond
Reductive elimination of the alkyl and remaining hydride to give the alkane.

We assume the boundary condition that the transition-state for the second step (TS-2) is always higher in energy than the transition-state for the first step (TS-1).

Moreover, I want to look at the elementary steps of the insertion, e.g. a 1,2-insertion (1-position of alkene binds to the metal and the hydride is transferred to the 2-position of said alkene) or 2,1-insertion (2-position of alkene binds to the metal and the hydride is transferred to the 1-position of the alkene).

If I now have a catalyst where the transition state for the first step (TS-1) lies lower in energy for a 2,1-insertion compared to a 1,2-insertion, but the transition-state for the second step (TS-2) lies higher in energy for the 2,1-insertion product than for the 1,2-insertion product, which pathway is the right one? E.g. does the mechanism proceed through the 2,1-insertion since TS-1 favors this pathway, or does the mechanism proceed through a 1,2-insertion since TS-2 is lower for this pathway.


texts: Why isn't orthoboric acid soluble in cold water even though it has polar B-OH bonds?

texts:
This is the information I found regarding orthoboric acid's solubility:

Textbook (NCERT India): Sparingly soluble in water (didn't say what temperature - presumably cold) and highly soluble in hot water.
Wikipedia: "Boric acid is soluble in boiling water."

My question: why is it only sparingly soluble in cold water even though it has polar $\ce{B-OH}$ bonds? Also, what happens on increasing the temperature that increases the solubility?


texts: Does the methyl rotation in propene have a symmetric or asymmetric potential energy surface?

texts:
Depending on how one imagines the methyl rotation of propene to occur, it seems like it could exhibit either a symmetric or an asymmetric potential energy surface.  If the $\ce{H2C=CH\! -}$ portion were held fixed, the rotating methyl would seem to be symmetric due to the local $\mathrm C_3$ axis:

On the other hand, if the methyl group were held fixed, the rotating $\ce{C=C}$ portion would seem to be highly asymmetric:

Obviously this rotation can't be both symmetric and asymmetric. So which is it, and why?

Intuitively, given the logical contradiction of the above, my inclination is to assume that the rotor is asymmetrical. My best guess as to a more rigorous argument for it being asymmetrical is that it's not valid to imagine any part of the molecule as being "held fixed", since it's not actually anchored to anything.  Thus, both of the above images are probably subtly incorrect.


texts:
I am looking for ways of removing water hardness from tap water, specifically permanent hardness.

I have tried working on some methods, e.g., to perform precipitates using sodium hydroxide and calculated calcium hydroxide, but it seems that either my methods or something else is wrong.

Please recommend me some methods (or resources) on how to remove the hardness from tap water.


texts: Quick-and-Dirty Molecular Dynamics by Mass-Weighted Atom Translations?

texts:
I'm thinking about a quick-and-dirty approach to molecular dynamics, mostly for teaching purposes.

At a given temperature, statistical mechanics tells us molecules have translational and rotational and vibrational energy as given by the equipartition theorem. At a basic level, all three motions derive from movement of the individual atoms along Cartesian axes.

So it seems like a very simple quick-and-dirty approximate molecular mechanics could be implemented by "shaking" the individual atoms with mass-weighted random displacements. You'd need to implement some sort of force field to make sure the added displacements would fall into the correct potential energy distribution for a given molecule.

Quick searching doesn't seem to find this as an approach, likely because it won't obey a particular canonical ensemble.

I'm curious... Has anyone implemented such a method for qualitative visualization? What are some of the pitfalls compared to "proper" molecular dynamics? (e.g., presumably ensuring the proper velocities?)


texts: Combination of several unit symbols when finding new pressure from ideal gas law

texts:
As a car is driven, the tires heat up and the volume and the pressure change. Calculate the new pressure of a 35.0 L tire initially at 235 kPa that expands to 36.5 L when it heats up from 15.0 °C to 43.0 °C. (4 marks)

$P_1 = \pu{235 kPa}$
$P_2 = ?$
$V_1 = \pu{35.0 L}$
$V_2 = \pu{36.5 L}$
$T_1 = \pu{15.0 °C} = 15.0 + 273 = \pu{288 K}$
$T_2 = \pu{43.0 °C} = 43.0 + 273 = \pu{316 K}$

The number of moles of gas in the balloon is not changing, so $n_1 = n_2$.

$$P_1V_1/n_1T_1 = P_2V_2/n_2T_2$$

(since $n_1 = n_2$ we can cancel them from both sides)

$$P_1V_1/T_1 = P_2V_2/T_2$$

(cross multuple to allow for isolation of $P_2$)

$$P_1V_1T_2 = P_2V_2T_1$$

(divide both sides by $V_2T_1$ to isolate $P_2$)

$$P_2 = P_1V_1T_2/V_2T_1$$

(now plug in values)

$$\begin{align}
P_2 &= (\pu{235 kPa})(\pu{35.0 L})(\pu{316 K})/(\pu{36.5 L})(\pu{288 K})\\
  &= 2 599 100 / 10 512 \\
  &= \pu{247 kPa}
\end{align}$$

The new pressure of the tire would be 247 kPa.

I like keeping track of the units throughout solving, but not sure how to do that with three units...

Can I write $P_2 = 2599100\cdot\pu{kPa/L/K}/10512\cdot\pu{L/K}$ (L and K cancel out and leave me with kPa), or is it recommended not to record the units in that step and only write the final unit with the final answer?


texts: Does cyclooctatetraene also have a diradical anti-aromatic electronic state?

texts:
I read that the molecular orbital diagram of cyclobutadiene predicts that it should have a diradical nature as it has two unpaired electrons in two degenerate non bonding orbitals (one in each).
Why does this diradical state exist only in cyclobutadiene? Shouldn't other anti aromatic compounds, like cyclooctatetraene, also exist in a similar diradical state?


texts: How to decide at which end to start the numbering of the parent chain when the options for locant sets are the same?

texts:
I would like to know whether the blue or purple way of numbering is preferable? Following the two possible ways, I get the following names:

4-(1,1-dichloro ethyl)-5-(1-chloro-2-bromo ethyl)-octane
4-(1-chloro-2-bromo ethyl)-5-(1,1-dichloro ethyl)-octane

In each case, the locant set is (4, 5), so from which side should I start numbering from?


texts: NaCl electrolysis with copper electrodes

texts:
Considering the aqueous $\ce{NaCl}$ is already concentrated. If we were to use copper electrodes instead of inert graphite electrodes:
Would copper react with the evolved chlorine gas to give $\ce{CuCl2}$ in solution, whilst still giving hydrogen gas at the cathode? Since in my experimentation, I obtained a teal blue green colored salt that was soluble in water. I do not have appropriate lab equipment to test for the identity of the salt, so I am hoping someone here could shed some light on the reactions taking place and the identity of the obtained substance. Thanks.


texts: What is ultimate decomposion product of Teflon (PTFE) in environment

texts:
There is a lot information available regarding thermal decomposition e.g. burning, but what happens to PTFE in ordinary environmental circumstances? Or if time for degradation is short enough, what happens in households (indoor air) which contains some PTFE impregnated materials? As far as I understood fluorotelomers might be also involved here somehow, but this is maybe due e.g. some dirt repellent product product which contains those fluorotelomers among PTFE.

One answer can be that PTFE is inert and stable and so fort, yes but I assume that some degradation happens still?


texts: (How) Does ICP-OES determine the quantity of detected elements, or just their occurance in the sample?

texts:
ICP-OES is a very common analytical method (Wikipedia page here), and I have heard a number of times (from chemists, too) that it is used for quantitative analysis.

However, from the description of the process, I'm not certain if it really does give quantitative information, how it does so, and whether it can do so on its own, or whether there are additional methods run in combination (like with gas chromatography and mass spectrometry) to achieve that result.


texts: What's the usual agent added to discourage drinking of hazardous substances

texts: I've once read somewhere that in materials that are hazardous to swallow, a chemical is used in very small quantities to assure any accidental drinker to retch. This also helps to prevent suicide by drinking. Am I correct about this info or just myth? And what is the name of the substance?


texts: Why do no known atoms have electrons in the g or h subshells?

texts: I'm learning about orbital quantum numbers. While checking several elements on the periodic table I noticed that there aren't any atoms that have electrons in the g or h subshells. Why is this?


texts:
My general chemistry textbook discusses how cations behave as (Brønsted-Lowry) acids in water. There's a picture of a $1.0~\mathrm M$ solution of Calcium nitrate with a pH indicator indicating a pH of around 6.9. How is it that $\ce{Ca^{2+}}$ ions behave as acids at all?

The book does explains how transition metals behave as acids: they form coordination spheres with water, and one ligand water molecule loses a proton to a free water molecule. The hydroxide is bound to the transition metal, thus not affecting pH.

However, to my knowledge, non-transition metals, such as $\ce{Ca^{2+}}$ or $\ce{Al^{3+}}$ do not form coordination compounds. Even if they can solvate some hydroxide ions, isn't the bond much weaker and therefore the hydroxide not effectively removed from solution like by a transition metal?

What would be the acid equilibrium expression for these cations?


texts: Software for chemical reaction simulation in ICE

texts:
I want to study what happens in a internal combustion engine in which fossil fuels are mixed along with other chemical additives.
Example:
Acetone drastically reduces surface tension.
Most fuel molecules are sluggish when it comes to their natural frequency. But acetone has inherent molecular vibration that "stirs up" the fuel molecules, to break the surface tension.
This results in a more complete vaporization with the various other factors remaining the same. More complete vaporization means less wasted fuel, hence the increased gas mileage from the increased thermal efficiency.
Along with this I also want to study the emission of $\ce{CO2,\  O2\,\ H2O}$ and more.
Is it possible to carry out the above phenomena/process in a virtual simulator ?


texts:
What precisely is the Franck-Condon region? My understanding is that the FC region is the "bonding" or "equilibrium" region in a potential energy surface, i.e. near the minimum. But when a transition takes place from S0 to S1, it is said that molecule is excited to the FC region of the S1 state - but there is no guarantee that going vertically from an S0 minimum will lead to a near S1 minimum. So something is probably incorrect with my current understanding.

Also, in theoretical minimum energy path calculations, we start from an optimised high energy state, often in a "Franck-Condon region" of an excited state.

So, what is the precise description of the Franck-Condon region?


texts: Why is ionization always an endothermic process?

texts:
My textbook says removing an electron always requires an input of heat. That makes sense because of coulombic force between electron and nucleus. But it also says that the process is endothermic always.
Why is that? In the case of Na, after the input of "activation energy", isn't Na+ more stable than Na? So therefore it would be exothermic?
Furthermore, this is not always true for electron affinity like it is for ionization. Adding an electron to Helium is an endothermic process because He- is less stable than He.* But it's exothermic for Cl and Cl-.
*Not totally sure about that. Contradicting information on the internet. Some sources say electron affinity of He is 0. Others say its negative (thus endothermic).


texts: Explanation of bond angles in the aluminium chloride dimer

texts:
In order to attain stability $\ce{AlCl3}$ dimerises to $\ce{Al2Cl6}$ whose structure is depicted as:

I want to understand why one of the bond angles is $79^\circ$ and the other $118^\circ$. Is it possible to justify this using Bent's rule?


texts: Can electrons switch orbitals within a shell?

texts: I know that electrons can move from say 2s orbital to an unoccupied 2p orbital, as in Carbon atom which can form 4 bonds this way. But I want to know is it possible for an electron say in orbital 2p to switch its place with an electron in 2s? I know only 2 electrons are allowed in an orbital, but is it possible for one electron to oust another and take its place so the ousted electron would have to take the other one's place? Is this theoretically possible?


texts:
I have been tasked to find the $\lambda_{\text{max}}$ of 3,4-dimethyl-1,2,3,4,4a,5-hexahydronaphthalene.

This was supposed to be fairly easy. I used the base value for homoannular diene ($\pu{253 nm}$) and added the increments for the three ring residues attached to the diene ($\pu{+(3\times 5) = +15 nm}$). This should get me a value of $\lambda_{\text{max}}=\pu{268 nm}$. However, checking the solution this question, they have also added the increment for an exocyclic double bond, and have got the answer to be $\pu{273 nm}$ instead.

As far as I know, an exocyclic double bond means exo+cyclic, where exo means "outside" and cyclic means, well "cyclic", or more simply, a double bond that is outside the ring. I'm looking at this compound, and I dont see any exocyclic double bond at all.

Am I dealing with a key mistake here or is there something that I'm not aware of?


texts: Why does ice crack when a drink is poured on it?

texts:
I think most people have experienced this, but while pouring a beverage over ice I noticed the ice cracked.

Before

After

My initial thought was that because the beverage has an antifreeze property to it, that some sort of thermal shock might occur due to the rapid local cooling from dissolving the ice, but I know that this also occurs when other beverages such as various flavored carbonated sugar water products are poured on ice which do not depress freezing as much. So then What would cause the ice to crack?


texts: How do I figure out the relative polarity of organic compounds?

texts:
It's a question on my quiz which I guessed right and couldn't do the reasoning:

Based on the intermolecular forces, predict the boiling points of the following substances and list them in the order of increasing boiling point. State your reasons accordingly.

Dimethyl ether $(\ce{CH3OCH3})$
Ethanol $(\ce{CH3CH2OH})$
Propane $(\ce{CH3CH2CH3})$

Right away, I see the hydrogen bond in ethanol, so it must have the highest boiling point.
I couldn't decide on the other two, so I drew lewis structures (kind of) for both

I ignored the hydrogens because they don't affect the polarity (correct me if my lewis strctures are wrong).
This is what I guessed, and I was right. When my teacher takes this question up, he said that propane is non polar, which means it only interacts via london forces, which means it has the lowest boiling points out of these three.
But how is propane non polar though, when I asked, he said "I don't have an answer for this, life is hard."
I mean, if I draw the structure in the bad way, it does look symmetrical and balanced out:

But if I draw it in this way, it doesn't help me when I'm trying to figure out the polarity, because everything will look non polar. I can even say water is in a linear shape because the H's and the O line up perfectly in a line, which is not the correct picture of reality.
My biggest question is, how do I figure out if something is polar or not.


texts: Compounds with aluminum and nitrogen atoms directly bonded to each other as part of an aromatic ring?

texts:
Just hours ago, I asked a question about whether aromatic organoaluminum compounds with aluminum and carbon bonded together as part of an aromatic ring would be stable in water. The answer seemed to be that "it wouldn't even work at all since aluminum and carbon have relatively poor pi-overlap, and even then the resulting compound would still end up complexing with nitrogen- or oxygen-based protic solvents due to the high affinity for nitrogen and oxygen of aluminum", implying that aluminum-nitrogen bonds are reasonably stable, at least when they're alone by themselves.
My questions are- do aluminum and nitrogen have sufficient p-orbital overlap to be directly bonded to each other as part of an aromatic ring, and, if they do, how stable are they to different kinds of solvents (protic, aprotic, polar, non-polar etc), and is there any specific compound reported in the literature that is water-stable and in which there is a direct aluminum-nitrogen bond as part of an aromatic ring? (Note that these need not be organoaluminum compounds- that is to say, the aluminum atom in question need not be bonded to any carbon atoms)


texts: Relative etch rates of nitric acid on metals and oxides

texts:
I am trying to either find or calculate the etch rate of nitric acid ($\ce{HNO3}$) for various different metals and oxides. The ones I am interested in are titanium ($\ce{Ti}$), zirconium ($\ce{Zr}$), and lead ($\ce{Pb}$); and their oxides $\ce{TiO2}$, $\ce{ZrO2}$, and $\ce{PbO/PbO2}$.

I have checked lots of sources, including the CRC Handbook of Metal Etchants, and have not been able to find anything that describes comparative etch rates for those six materials. Where can I find this information or, alternatively, how can I estimate these quantitites?


texts: Constitutional isomers for four carbon thioesters

texts:
Question:

  How many isomers are there for thioesters with the formula $\ce{C4H8OS}$?

Answer given is four.

I can see that the following two are possible constitutional isomers:

But what are the other two?


texts: What happens when adding swimming pool salt to a freshwater pool?

texts: Why does adding swimming pool salt to a freshwater swimming pool cause a white sediment to build up and stick to the floor of the pool?


texts: Would the 1st excited state of Li2 be vibrationally excited?

texts:
I'm quite torn about an interesting past paper question that's come up during my revision, shown below.

On the one hand, you're promoting an electron in a bonding orbital. In general, since this means you would substantially change the electronic wavefunction, I would expect overlap from the initial vibrational state with a range of excited vibrational states and so due to the Franck-Condon principle the molecule would be vibrationally excited in the electronically excited state.
But the bond order of the excited molecule is 0, and so it will presumably dissociate as soon as it vibrates.
Which of these considerations wins out?


texts: Can I use fluorescence microscopy with a solution of hydrogen peroxide?

texts: I want to use microspheres which have been dyed with a fluorescent dye for fluorescence microscopy in a solution that has a 1-5% concentration of hydrogen peroxide. Is this possible or will the hydrogen peroxide always bleach any particles I put in?


texts:
I don’t know much about chemistry but I recently found the below bond-line structural formula painted on a wall near my place. I really can’t let go of trying to find the name of the compound. If anyone would be so inclined as to relieve me of my suffering, I sure would be grateful!
Thank you and greetings from Sweden!


texts: Why is the principal quantum number irrational?

texts:
My textbook says that for a $d$-electron, the orbital angular momentum is: $$ \frac{\sqrt{6}h}{2\pi} $$
But since:
$$ mvr = \frac{nh}{2\pi}$$
$$ n \in N$$
where $N$ is the set of natural numbers, how is the value of $n$ an irrational number?


texts: detection of psilocybin with ehrlichs-reagenz

texts:
I tried to form the product of the detection reaction,
however i dont know which product is correct or both products are wrong!


texts: Which compound is more reactive towards acetylation, 4-aminophenol or 4-aminocyclohexanol?

texts: Does the delocalisation of the lone pair of electrons in the NH2 group mean that they are less available to attack the carbon making the 4-aminocyclohexanol more reactive? Or does the polarisation of the neighbouring molecule due to the higher electron density of the benzene ring make the 4-aminophenol more reactive?


texts:
My book says

  Aluminium is extracted from its ore bauxite $\ce{Al2O3.nH2O}$

What does "n" stands for?
Does it mean that there is no fixed amount of water in bauxite?


texts: There is a reference of 1.48 value at room temperature which is a different value from an experimental study.


texts: Sorry if the question is silly but this is troubling me more than enough. Here's what I know about chemical formula: Reverse the valencies of the combining elements. But in this case, $\ce{NO2}$ is the formula for nitrogen dioxide while N valency is 3. Please explain it to me if I am wrong somewhere.


texts: Why does strong Lewis acid-strong Lewis base interactions prevail over hard-soft acid-base interactions?

texts:
In Pearson's paper, he mentions that strong acid-strong base interactions are more favourable compared to hard-soft acid-base interactions. He cites the example of  $\ce{H+ + H- -> H2}$. In this example, the hydrogen cation is a strong and hard Lewis acid while the hydride ion is a strong yet soft Lewis base. By just considering hardness and softness of the acid and base, we would not expect a particularly favourable interaction between the two species. However, Pearson says it is because of a more favourable interaction which is the strong acid-strong base interaction which is at work in this case.

Some background information:

When the HOMO of the Lewis base and the LUMO of the Lewis acid are similar in energy, the bonding molecular orbitals produced are significantly lower in energy and thus, electron occupation of these bonding MOs give rise to significant stabilisation. This occurs when hard Lewis acids and hard Lewis bases react and also when soft Lewis acids and soft Lewis bases react. This is the molecular orbital basis of Pearson's Hard Soft Acid Base Principle.

Can we explain the favourable interaction of strong Lewis acids and strong Lewis bases using molecular orbitals as well?

Reference: Pearson, R. G., & Songstad, J. (1967). Application of the Principle of Hard and Soft Acids and Bases to Organic Chemistry. Journal of the American Chemical Society, 89(8). Retrieved June 5, 2017 (link to paper)


texts: The connection of the "R" in the ideal gas law and osmotic pressure

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I am studying chemistry and biology at the same time, and have encountered a problem. In the ideal gas law, the $R$ is the ideal gas constant, and its value is $\pu{0.0821 L atm mol-1 K-1}.$

However, in the osmotic pressure formula $\Psi_s = -iCRT,$ the $R$ is called the pressure constant, and its value is $\pu{0.0831 L bar mol-1 K-1}.$ Is it a coincidence that their values are identical (after adjusting for the $\pu{atm}$ and $\pu{bar}$ conversion)?


texts: Can a π bond form between the py and d(x2-y2) orbitals along the x-axis?

texts:
π bond does not form due to overlap between $\ce{d_{x^2-y^2}}$ and $\ce{p_y}$ along x axis? True or false?

Here is a diagram of the orbitals.

This pair of orbitials should be distingished from $\ce{d_{xy}}$ and $\ce{p_y}$, which are shown below.


texts: What properties of carbon dioxide make it a greenhouse gas?

texts: Why is it that heat from the Earth reflects back off carbon dioxide and other greenhouse gases but not gases like nitrogen or oxygen?