texts: Why is hypochlorite a stronger oxidizing agent than other oxychlorides?

texts:
The reduction potentials of perchlorate, chlorate, chlorous acid and chlorine dioxide in acidic and basic solutions are listed in the table below:
$$
\begin{array}{lcc}
\hline
\text{Oxychloride} & E^\circ_\text{acidic}/\pu{V} & E^\circ_\text{basic}/\pu{V} \\
\hline
\ce{ClO4-} & 1.19 & 0.56 \\
\ce{ClO3-} & 1.21 & 0.63 \\
\ce{HClO2} & 1.65 & 0.78 \\
\ce{ClO2}  & 1.63 & 0.89 \\
\hline
\ce{}
\end{array}
$$

Why is $\ce{ClO-}$ such a strong oxidizing agent compared to other chloride oxyanions, despite its low oxidation number? Is oxidation number representative of oxidizing strength?


texts: Ice Crystal Matrix measurements of H2O molecules?

texts:
I want a mathematically generated 3D STL copy of this image, however it's represent algorithmically.

If I do all the H2O's as individual pieces with female connections prepared for chopped bike spokes, are all the H2O's the same and what angles do they have?

Is there a written array of positions and degrees of rotation of the water molecules of a regular ice matrix?


texts: Why do ethanethiol molecules have stronger London dispersion forces than those of ethanol?

texts: I know that, molecules with higher molecular weight tend to form London forces. Is there any other reason which makes Ethanethiol to have strong London dispersion forces as compared to Ethanol?


texts: Why isn't Cahn Ingold Prelog principle used to name the isomers of complex compound having square planar geometry & different ligands attached to it?

texts:
For a complex compound with coordination number 4, say having square planar geometry, and say all the ligands attached to the central metal atom are different, then we know that we will get 3 geometrical isomers.

Now my doubt is like in organic chemistry if we had 4 different groups around a carbon atom, we still named those isomers as Z and E isomers (by Cahn Ingold Prelog principle) . Similarly why can't we name the isomers as Z and E for the case of complex compound with square planar arrangement having four different ligands attached to it?

That is why can't we name those 3 geometrical isomers as Z and E isomers of the complex compound by Cahn Ingold Prelog principle?


texts: Theoretical comparison of critical constants of real gases

texts:
We know that for a real gas, its critical constants are: $T_\mathrm c=\frac{8a}{27Rb}$, attempt to $P_\mathrm c=\frac{a}{27b^2}$ and $V_\mathrm c=3b$. Now, let's compare the value of these critical constants for three real gases, say, $\ce{CO2}$, $\ce{NH3}$ and $\ce{H2O}$.

Knowing that $V_\mathrm c=\frac38\cdot\frac{RT_\mathrm c}{P_\mathrm c}$ (for one mole), experimental data from Wikipedia is:

$$
\begin{array}{|c|c|c|c|}\hline
&T_\mathrm c&P_\mathrm c&V_\mathrm c\\\hline
\text{Carbon dioxide}&\pu{304K}&\pu{7380 kPa}&\pu{0.1284L}\\\hline
\text{Ammonia}&\pu{406K}&\pu{11280 kPa}&\pu{0.1122L}\\\hline
\text{Water}&\pu{647K}&\pu{22060kPa}&\pu{0.0914L}\\\hline
\end{array}
$$

We will now attempt to justify this regular trend in the values qualitatively.

For $T_\mathrm c$, we know that it is the maximum temperature above which a real gas cannot be liquefied. If a gas has stronger intermolecular forces (IMFs), its molecules possess greater attractive forces to be able to overcome separatist forces that might separate them, and thus they'll still be able to liquefy. Thus, if a gas has higher IMFs, its $T_\mathrm c$ would be higher.
We know that H-bonds formed by water are much effective than those by ammonia (read), and carbon dioxide is a non-polar molecule with only London dispersion forces. Hence, we would expect $T_\mathrm c(\text{water})>T_\mathrm c(\text{ammonia})>T_\mathrm c(\text{carbon dioxide})$ by our qualitative reasoning, which agrees with the experimental order.

By definition, the critical pressure is the pressure needed to liquefy a real gas at its critical temperature. Now, since water molecules have the highest attractive forces, one would expect that they require the least external "support" (aka force per unit area) to be able to liquefy themselves (by bringing the molecules closer). Hence, we would expect that $P_\mathrm c(\text{water})<P_\mathrm c(\text{ammonia})<P_\mathrm c(\text{carbon dioxide})$. However, this does not match with the experimental trend! (which happens to actually be in the reverse order)

Moreover, I am unable to come up with a way to predict the trend in the critical volume at all.

Hence, my questions are:

Since $V_\mathrm c$ depends on the ratio of $T_\mathrm c$ to $P_\mathrm c$, am I correct in saying that its trend cannot be determined without actually being given the values for the other two constants? Or is there some clever way that I am overlooking?
Is there any other way to justify the trend in $T_\mathrm c$?
What is the fault in my reasoning for the trend in $P_\mathrm c$? And what is the correct reasoning?


texts: Why left and right circularly polarized light have different index of refraction in chiral media?

texts:
This is a followup question of (Dependence of the angle of rotation on the wavelength of plane polarized light).

Ron's answer tells about the difference between left and right circularly polarized light. But the explanation isn't in the answer.

So, what's the reason behind different index of refraction?


texts: Why can't oxygen in furan be sp-hybridized?

texts:
From the Chem LibreTexts article on Aromaticity and the Huckel $4n + 2$ Rule:

So far, you have encountered many carbon homocyclic rings, but compounds with elements other than carbon in the ring can also be aromatic, as long as they fulfill the criteria for aromaticity. These molecules are called heterocyclic compounds because they contain one or more different atoms other than carbon in the ring. A common example is furan, which contains an oxygen atom. We know that all carbons in furan are $\mathrm{sp^2}$ hybridized. But is the oxygen atom $\mathrm{sp^2}$ hybridized? The oxygen has at least one lone electron pair and is attached to an $\mathrm{sp^2}$ hybridized atom, so it is $\mathrm{sp^2}$ hybridized as well.

Is this a general pattern - if an adjacent atom is $\mathrm{sp^2}$-hybridized, and if there's at least one electron pair, then our atom it $\mathrm{sp^2}$-hybridized as well?
Why can't oxygen in furan be $\mathrm{sp}$-hybridized? Is this only because the overall structure will not be consistent, because sp-hybridization will make the $\ce{C-O-C}$ line straight, and thus the $\ce{O-C-C}$ angles would have to be lesser than the carbons' $\mathrm{sp^2}$-hybridization would allow?


texts:
I did an experiment to determine enthalpy change when Zinc is added to Copper(II) sulphate solution.

I recorded values and plotted a temperature-time graph to obtain values of the temperature change to calculate heat transfer .

The trend line that I obtained is when temperature of the mixture started to drop.

I never knew why I needed to extend that trend line and draw a vertical line at the point when Zinc is added and thus never understood why the difference between the interception point and the point when Zinc is added is $\Delta T$

To summarise, I don’t understand why I need to extend the trend line and the interception point gives the highest ‘T’ value...


texts: Equilirium mixture of nitrogen dioxide and its dimer

texts:
When an equilibrium mixture of gaseous, colorless $\ce{N2O4}$ and brown $\ce{NO2}$ is warmed at constant volume, which of the following is correct?

  The density remains constant.
  The degree of dissociation decreases.
  The average molar mass increases.
  The pressure decreases.
  The color becomes lighter.

The correct answer is (1).  But all the other answers except (4) seem reasonable to me.

The equilibrium we are looking at is: $\ce{N2O4<=>2NO2}$

Upon heating at constant volume, the pressure will increase, and so the equilibrium will shift to the left, which means that there is less dissociation of $\ce{N2O4}$, the average molar mass will be closer to the molar mass of $\ce{N2O4}$, than before warming, thus the average molar mass will increase.

Finally, as the equilibrium shifts to the left, more colorless $\ce{N2O4}$ will be present, lightening the color of the gaseous mixture.

Obviously, the density will also remain constant, as density of gas = $\frac {\text{mass}}{\text{volume}}$ and since no mass is lost and we are at constant volume, the density remains constant.


texts:
Related: Covalent Bond/Hydrogen Bond

What is the half-life of hydrogen bonds in a glass of water at room temperature, say 18 degrees Celsius? I guess values may be different for distilled water and for tab water, but both may be intersting.

My attempts to get an answer involve searching with google, google scholar, and google books. Complications were that I cannot get access to all articles using my universities database.

From this page we have

  The half-life of a hydrogen bond is about 10 seconds

Is this correct?


texts:
Both this and that question seem to indicate that the hydrogenation of alkenes to alkanes or alkynes to alkenes is always a syn process.

However since hydrogenation is not a concerted process, I do not see why we could not have a non-negligible (although small) portion of the trans product.

Following this reaction mechanism for syn additions :

before the penultimate step (the addition of the second hydrogen), can't the molecule simply rotate around the $\ce{C-C}$ axis (I expect this should be possible with small enough alkenes) ?

The Wikibooks article on alkenes does indicate that typically the hydrogenation of alkenes leads to only $98\%$ of the syn product, but I have been unable to find more precise information elsewhere.


texts: Why the etching profile of HF and HCl on titanium surface is different?

texts:
Why the profile of etched titanium with HF-HNO3 looks like a hill, while the profile of etched titanium with HCl is U-shaped? Can you please put your source if you know it? Thank you

Note: the picture above is the profile of etched titanium with HF


texts: how do you enable result summary in gaussview

texts: On G2:M1:V1 window, result summary is grayed out. Does anybody know how to enable so that I can see my calculation summary?


texts:
A question on the 1996 AP Chemistry Free Response asks:

  The $\ce{N-O}$ bonds in the $\ce{NO2-}$ ion are equal in length, whereas they are unequal in $\ce{HNO2}$. Explain.

Since the nitrogen dioxide ion has resonance, the $\ce{N-O}$ bonds are equal as resonance is in reality a hybrid of all of the possible structures for a certain molecule. However, the answer then assumes that $\ce{HNO2}$ has no resonance but rather one single and one double bond ($\ce{N-O}$ and $\ce{N=O}$), and therefore not all of the $\ce{N-O}$ bonds are equal.

How is this possible? Why can $\ce{HNO2}$ not have 2 possible structures where the single and double bonds switch between the two oxygens?


texts: Finding pKa from equivalence point on titration curve

texts:
Is there a mathematical proof/explanation of why $\mathrm{p}K_\mathrm{a}$  corresponds to the $\mathrm{pH}$ at $\text{Volume of titrant}/2$  at the equivalence point?

A concise proof will suffice.


texts: Why does 'softening' of lead oxidise only elements other than lead?

texts:
In a flowchart describing the steps to refine lead obtained after the reduction step, my book1 gives a short note on the process 'Softening of lead' where the crude lead is melted in the presence of air. It's stated that this removes scum of oxides of copper, tin, arsenic, antimony and bismuth which constitute the hard lead. After this soft lead with silver and gold is obtained.
Earlier, under the section which explained about refining of gold, the book described about the process cupellation where crude gold is melted in the presence of air. This method was meant to remove lead and the success behind this method was attributed to the high oxygen affinity of lead. The lead oxide being volatile gets easily separated from the system.
I understood the above two scenarios independently. However, when I thought about the lead refining process with the volatile nature of lead oxide in mind, it seems contradictory on why in the first case lead remains in the molten state whereas in the second it gets oxidised and escapes into the atmosphere.
My question is, why does 'softening' of lead oxidise only elements other than lead? Why doesn't the lead get oxidised and escape into atmosphere as volatile lead oxide? Compared to the impurities, as per the Pauling scale of electronegativity, lead is more electropositive and this seems to suggest it must get oxidised before the impurities which is opposite of what must be inferred in order for the lead softening process to be successful.
References

Guha, Sudarsan. Concise Inorganic Chemistry for JEE (Main and Advanced). 4th ed., Wiley India Pvt. Ltd., 2017.


texts: How to pool fractions after chromatography?

texts:
I used chromatography to purify my protein and now I have fractions with different concentrations ranging from 1-16 mg/ml. Should I pool all these fractions or just the ones with high concentration (where under the actual peak)?

Thanks in advice


texts: Organic chemistry - alkanes step up reaction

texts: Well I was studying organic chemistry, and I came across this reaction for increasing the length of the carbon chain. Upon asking my teacher about the following reaction, she said she was unsure about it. Is this a valid reaction? And if it is, can you please provide the name of the reagent and the actual mechanism?


texts: Where does the characteristic peak for phtalic acid diethyl ester at m/z 149 originate?

texts:
Which fragmentation is possible at this m/z value for phthalic acid diethyl ester?

I tried McLafferty but it didn't solve my problem.


texts: Why is SnCl2 produced when tin reacts with hydrochloric acid?

texts:
$$\ce{Sn + 2HCl -> SnCl2 + H2}$$
Our teacher told us that it's because $\ce{Sn^2+}$ is more stable, but I can't find that in any textbook.

Why is $\ce{Sn^2+}$ in the chloride product over any other oxidation state?


texts: Why are lab coats required in chemical laboratories?

texts:
Well at first it seems kind of awkward but let me tell you what I was thinking from past few days. Currently I am studying and go to school. In school, whenever we have to go inside a chemistry lab then it’s compulsory for us to wear a lab coat; without one we were not allowed to enter and do experiments. But then one question arises is: Why it is compulsory?

Then I started finding solution for this question. I thought that we wear lab coat just for safety against all those chemicals we use for experiments but then if accidentally someone drops any concentrated acid then I guess that lab coat won’t be able to protect us. So if we wear something solid or something hard which can protect us from those chemical that might be helpful but we only wear a lab coat.

Then I thought that lab coats have so many pockets on them so it might help us to carry a few things but then again why don’t we use something else which is handy rather than a lab coat (still this example is quite useless).

After hours of thinking I am not able to come up with anything.

And also whenever anyone goes inside chemistry lab he/she wears a lab coat which is quite similar to everyone else’s. I.e. everyone wears same type of lab coat (a long, white colored coat) which is quite fascinating.

So my question is really simple: Why do we have to wear a lab coat when we go inside a chemistry lab and how come everyone uses same type of lab coat?


texts: Energy of orbitals under a crystal field

texts:
It is shown in octahedral crystal field splitting that both the $e_g$ orbitals have equal energy. But how can that be possible ?

The $d_{x^2-y^2}$ is directed along both the axes (x and y) whereas the $d_{z^2}$ is directed along only the z-axis, shouldn't the later have less energy than the former ?


texts: Is every substance in equilibrium with its vapours?

texts:
In one of my previous questions, I got an answer from user Jan:

The smell of a compound as we perceive it usually depends on which receptors in the nose will bind the molecule (or not).
These receptor, being proteins, are usually rather specific for certain shapes, not for bonding patterns. So chlorobenzene might fit into similar receptors as toluene which would lead to at least partly a similar smell, but that is it.

This means that a substance must be in the vapour phase in order to smell it, which brings me to my question:

Do all substance (at least those which have a characteristic smell) maintain an equilibrium with their vapours (if the substance is in closed container)?

But if it's true for those solids, then it must be true for all other solids, as well as nonvolatile liquids that do not have a characteristic smell to humans. Is this not the case? Also, if this substance is placed in open air, will it evaporate totally?


texts: NMR calculations with NWChem quantum chemistry program


texts: Question regarding the colour of Benzoic acid and Benzyl alchohol

texts:
This question is primarily based on the Cannizzaro reaction, where a base induces a disproportionation reaction of non-enolizable aldehydes (benzaldehyde, formaldehyde, etc) to form an alcohol and a carboxylic acid.
In the video by Nile Red exploring the Cannizzaro reaction (https://www.youtube.com/watch?v=qEBC204WTKs), the product mixture contained both Benzoic acid and Benzyl alcohol and had an orange color. I am aware that the benzoic acid was in the form of sodium benzoate due to sodium hydroxide also reacting with the acid produced.
My question is, where does the colour come from?
I am guessing it is either from the benzyl alcohol or sodium benzoate, but I have learned that most organic compounds are colorless.
Moreover, if the aldehyde used was something like formaldehyde, will the orange color also form?
Thanks in advance for the clarifications.


texts: Psi4 gradient calculation with complete basis set?

texts:
I'm trying to set up a gradient calculation for psi4. In my input.dat file, I have tried the following keywords:

set basis cc-pVTZ
gradient('CCSD(T)')

which is not working. Does anyone have any recommendations on what key words to use at the end of my input file to run a gradient calculation with a CBS? Any suggestions welcome.


texts: Calculating the solubility for chromium(III) hydroxide using the complex ion constant

texts:
Problem

$$
\begin{align}
\ce{Cr(OH)3(s) &<=> Cr^3+(aq) + 3 OH-(aq)} &\quad K_\mathrm{sp} &= \pu{6.7E-31} \\
\ce{Cr^3+(aq) + 4 OH-(aq) &<=> Cr(OH)4-(aq)} &\quad K_\mathrm{f} &= \pu{8E29}
\end{align}
$$
The solubility of $\ce{Cr(OH)3}$ in pure water is $\pu{1.3E-8 M}.$
The solubility of $\ce{Cr(OH)3}$ in $\pu{0.50 M}$ $\ce{NaOH}$ when the complex ion $\ce{Cr(OH)4-}$ is formed is:
a) $\pu{0.32 M}$
b) $\pu{0.59 M}$
c) $\pu{0.27 M}$
d) $\pu{0.18 M}$

Answer

 d) $\pu{0.18 M}$

My approach
$$\ce{Cr(OH)3(s) + OH-(aq) <=> Cr(OH)4-(aq)} \quad K = K_\mathrm{sp}\cdot K_\mathrm{f}$$
$$\pu{6.7E-31}\times\pu{8E29} = \frac{s}{\pu{0.50 M}}$$
$$s = \pu{0.27 M}$$
As you can see I got c), which is not the correct answer. Could anyone point out what I did wrong?


texts: Largest alkane having a given alkane as its base name

texts:
What is the largest (most carbon atoms) alkane having heptane as its base name?
For example, 2,2,3,3-tetramethylbutane is the largest (most carbon atoms) alkane retaining butane as its base name.


texts: The rate of hydrogenation is faster for which alkene : cis or trans. I know it depends on steric hindrance on the carbon, but both have steric hindrance. Can someone please help


texts: Why do the field of study "Chemical biology" often return papers that are in general anything disease related?

texts:
For example, if one tries to look up research opportunities or browse papers in the field chemical biology, most often return research fields related to biological sensing, drug activity etc. and which the ultimate goal of all these researches are related to treating diseases of some kind.

http://pubs.acs.org/journal/acbcct

and only occasionally, do the other non disease treatment related sector of chemical biology (those related to proteins, environmental biochemistry, microbial reactors etc.) can be found

http://www.ch.cam.ac.uk/rig/biological/about

http://chemistry.mit.edu/research/biological

http://www.kemi.uu.se/research/molecular-biomimetic/microbial-chemistry/

  Why are most chemical biology research dominated by disease treatment goals despite the chemistry of biological systems are not limited to the medical sector, or is it because the non disease related sector of chemical biology are often lumped into the environmental science, biotechnology and engineering sectors?


texts: Can Fe and Ca react and become unusable in some foods?

texts:
In Turkish cuisine there is a popular food called "tahin pekmez" (tahini with grape molasses).
According to a 2017 article on some Turkish news site, mixing these is supposedly counter-productive due to the calcium in the tahini bonding with the iron in the molasses and becoming unusable to the human body.[1]  From what I can tell, the article doesn't cite any study for this claim.
Obviously I'm inclined to believe that the claim is click-bait, but I thought let's give it a chance and ask people who know their chemistry.
I hope this isn't too basic or otherwise off-topic for Chemistry StackExchange.
[1] https://www.yenisafak.com/gundem/tahin-ve-pekmezi-karistirmayin-2804300 (in Turkish)


texts: Why is the disordered CuAu structure more stable at high temperatures?

texts:
I know that the disordered CuAu structure is based around FCC whereas the ordered CuAu structure is tetragonal. Why would the FCC structure be more stable at high temperatures?
For context, I was asked to explain this with the aid of a graph. I don't really know where to start


texts: How many types of 3D packing are possible?

texts: In my book  it's said that there are 3 types of unit cubic cell - primitive , face and body centered . But for 3d packing types they have only mentioned FCC and HCP . I know that these 2 concepts- unit cell and packing types are different but it's the packing that determines the type of unit cell , right ? So are there any packing types like primitive packing and body centered packing ?  .


texts:
In the second chapter, Methane Energy of activation and Transition state in the textbook Organic Chemistry by Morrison and Boyd, Energy of activation is given the following definition:

  The minimum amount of energy that must be provided by a collision for a reaction to occur is called the energy of activation, Eact.

The Eact for the reaction:

Cl(free radical) + CH3-H ---------> H-Cl + CH3(free radical)

is 4 kcal/mol. Therefore, on an average, it is 4/NA kcal per individual collision (where NA is the Avogadro number).

However, the bond energy of the carbon-hydrogen bond in methane is 104 kcal/mol. Therefore, on an average, it would be 104/ NA kcal for a single molecule of methane. In other words, 104/ NA kcal should be the energy provided by a collision that involves a methane molecule in order to break the carbon-hydrogen bond. Why does this not agree with the statement above which says 4/NA kcal per individual collision is what is required?


texts:
$\ce{CH3NHCH(CH3)CH2CH3}$
Should this be named as 2-(N-methyl)butanamine or 2-(methylamino)butane?

In other words, do we name the compound as 'alkanamine' or treat amino group as a substituent of butane?


texts:
I can see that these compounds are identical as we have basically just done a 180 degree rotation of the molecules.

But if we go by the concepts of chirality, the carbons 2 and 4 are chiral centers and since they have inverted configurations at both chiral centers, they should be enantiomers. Or is it just that I cannot assume the hydrogens not shown to be out of plane?


texts: Comparing IR stretching bands in molybdenum complexes

texts:
Why would the infrared stretching frequency of $\ce{CO}$ (which is about $2140~\mathrm{cm^{-1}}$ in gaseous form) be $1982~\mathrm{cm^{-1}}$ in $\ce{[Mo(CO)_6]}$ and even lower in $\ce{[Mo(CO)3(η^6$\text{-}$Mes)]}$ ($\ce{Mes} = $1,3,5-trimethylbenzene)?

I think it may be due to the π* orbital being used in the $\ce{CO}$ ligand which reduces the bond order and lengthens the bond. The stretching frequency is proportional to the bond strength so if the bond gets weaker then the frequency is lowered.


texts: Will piperine endure heating for several days of soxhlet extractions?

texts:
I'm extracting piperine for use with curcuminoid supplements using a soxhlet apparatus and 91% isopropyl alcohol. My first extraction is right about done but I still need to do two more because of the limited size of my soxhlet.

My question is, instead of distilling off and reusing the distilled IPA could I just use the same solvent that contains the black pepper extract for three subsequent extractions?

I tried googling but could not determine if piperine is stable enough.


texts: Terminology of redox reactions: which species are the oxidizing and reducing agents?

texts:
I've got a question regarding 'notation' for redox reactions. Suppose you are asked to identify the oxidizing and reducing agents for a simple reaction like this one:

$$\ce{Cl2(aq)}+\ce{2KI(aq)} \longrightarrow \ce{2KCl(aq)}+\ce{I2(aq)}$$

Now are you supposed to say $\ce{Cl}$ is the oxidizing agent or $\ce{Cl2}$? Also, is $\ce{KI}$ the reducing agent or $\ce{I}$ or $\ce{I^-}$?

By the way, if you were instead asked to identify which species got oxidized, would you again say that $\ce{KI}$ is oxidized or $\ce{I}$ or $\ce{I^-}$?


texts: Lewis dot structures and exceeding the octet

texts:
I'm confused about the octet rule.  As far as I understand, you need to complete the valence shell of the elements by sharing electrons.

Now, carbon has 6 electrons which means it has 4 valence electrons, but because it has 6 electrons in total it exceeds the first shell with 4 electrons. The second shell has 4 orbitals with 2 electrons each, so to complete the second shell I need 8 valence electrons, but I had read somewhere that the octet rule holds true until down to the 4th period. How can that be when say, magnesium, has 12 total electrons and thus it exceeds the the second shell with 4 electrons but the third shell needs 18 valence electrons to be complete, not just 8?

Secondly, I read that if the central atom has more then 8 electrons, then that's ok too? What happens if I have a choice of exceeding the 8 electrons by forming another bond with an adjacent atom or sticking those electrons on the opposite side of the adjacent atom?

Is one strictly wrong/preferable?


texts: Hydrogen bonding in acetylene and other terminal alkynes

texts:
My textbook says that hydrogen bonding is possible only when there is acidic hydrogen connected to an electronegative atom like $\ce{N}$, $\ce{O}$ or $\ce{F}$ and a basic lone pair of electrons on another electronegative atom.
Recently, when I was going through a material on organic chemistry online, I read that $\ce{sp}$ hybridised carbon atom is more electronegative than $\ce{sp}^{3}$ hybridised nitrogen atom. Assuming that is true, we can infer that $\ce{sp}$ hybridised C-H bond is more acidic than $\ce{sp}^{3}$ hybridised N-H bond.
I already know that ammonia has strong hydrogen bonding and the nitrogen atom in ammonia is $\ce{sp}^{3}$ hybridised. So I wanted to know if acetylene has strong hydrogen bonding.
I asked my teacher about this but he simply replied by saying 'no'. I tried googling my doubt but couldn't find any resource which gave me a satisfactory answer. I also wanted to know that, if acetylene shows hydrogen bonding, can other terminal alkynes show hydrogen bonding?


texts: Why can't unimolecular reactions be 2nd order?

texts: Why can't unimolecular reactions be second order? For example, doubling the concentration of a single reactant would result in four times the original rate of reaction.


texts: Why use glacial acetic acid in bromination of anisole?

texts: In my organic chemistry lab (next week, the experiment has not been conducted yet) we are being asked to react anisole with bromine to get 2-bromoanisole (as well as 2,4-dibromoanisole and all the others).  In our lab instructions we are told to add anisole, bromine and glacial acetic acid to our mixture.  No mention of other compounds (such as $\ce{FeBr3}$) was made.  I was under the impression that bromine is not reactive enough to brominate an aromatic without $\ce{FeBr3}$.  What purpose does the acid serve, and how does it make this reaction work without the iron compound?


texts:
Caluculate the collision density between $\ce{O2}$ and $\ce{N2}$ in air at $T = \pu{10 ^\circ C}$. Assume that the air is an ideal gas and that the molecules are spheres with diameters $\pu{0.36 nm}$ for $\ce{O2}$ and $\pu{0.37 nm}$ for $\ce{N2}$.

This is what I have done so far, the collision density equation is:

$$ Z_{AB} = \frac{N_A}{V} \frac{N_B}{V} π d^2_{AB} c_A$$

And since we assume that air is an ideal gas, we can use:

$$\frac{N_A}{V} = \frac{N_B}{V} = \frac {p}{kT}$$

$$\frac {p}{kT} = \frac {1.01325 \cdot 10^5}{(1.38 \cdot 10^{-23}) \cdot 283} =2.6 \cdot 10^{25}$$

The collision cross-section can also be calculated:

$$ \sigma = \pi d^2_{AB} = \pi \left((3.6 \cdot 10^{-10})+(3.7 \cdot 10^{-10})\right)^2 = 1.67 \cdot 10^{-18} m^2  $$

But to calculate the average speed I need the mass of the molecules, which I don't have and I am not sure if I can determine it from the information given either. I thought about calculating the volume of each molecule and then looking up the density of oxygen and nitrogen to get the mass, however I am not sure if this is the correct way that the problem should be solved. Is there a specific assumption I need to take in order to determine the masses?


texts: Algae Cultivation Using Polyethylene Film Reactor Vessel Floating In Pool with Algicidal ClO2 Concentration

texts:
I'm attempting to grow chlorella algae in a polyethylene film bag (which contains the growth medium) submerged in a temperature-moderating, above-ground swimming pool.  This presents a challenge in that I would like to kill algae in the pool with  $\ce{ClO2}$ while cultivating it in the bag despite diffusion of $\ce{ClO2}$ across the polyethylene film.

How often must I replace the growth medium?

The constraining quantities:

7.62e-16kg/m/m^2 Pa $\ce{ClO2}$ diffusion across polyethylene
Polyethylene film thickness 0.5mm
Bag volume to surface area ratio 5cm
5mg/L average $\ce{ClO2}$ concentration in the pool
0.1mg/L maximum $\ce{ClO2}$ concentration in chlorella growth medium

Justifications for my choice of constraints:

Chlorella 30 minute kill rates:

0% @ 3ppm (and below)
80.7% @ 4mg/L
87.2% @ 5mg/L
99.0% @ 6mg/L

High concentrations of $\ce{ClO2}$ are desirable for disinfectant power.  I'd like to keep the pool at an average of 5mg/L (swinging between 6mg/L and 4mg/L) to suppress infection and keep the chlorella growth medium at 0.1mg/L since according to the below table, the "Experimental phenomenon", shows "ball in shape" morphology at 0mg/L which is lost at some concentration below the sublethal 2mg/L.  Such loss of morphology implies a potential impact on growth rate.

Table 5 of "Disinfection effect of chlorine dioxide on viruses, algae and animal planktons in water":


texts: Why are electron configurations more stable when there are 8 electrons in the outer shell?

texts:
In this video on Khan Academy, Sal remarks that 'all atoms envy the noble gases, which are the most stable because they have eight electrons in their outer shell'.

I can't think of much of a reason that the number of electrons in the outer shell would affect the stability of the electron configuration. Additionally, I read that more electrons in the outer shell slightly increases the atomic radius. A larger atomic radius usually indicates a less stable electron configuration.

However, perhaps I've been thinking about this the wrong way. I've been wondering whether some property obtains when there are eight electrons in the outer shell that causes the configuration to be more stable. Perhaps, I ought to think about thus: atoms tend toward having eight electrons in their outer shell (i.e. eight electrons in the outer shell coincides with configuration stability, but doesn't cause it). The fact that the unscreened Coulomb force increases from left to right along a period is what explains why atoms tend toward having eight electrons in the outer shell: The atoms near the left of a period exhibit relatively little unscreened Coulomb force, and so are prone to giving up electrons and, so are prone to giving up the few electrons that constitute their valence shell. Whereas, those atoms near the right of the period exhibit much Coulomb force, relatively. Accordingly, those atoms are prone to attracting more electrons, and thereby prone to filling their valence shells.

Why does the stability of the electron configuration increase when the outer electron shell is full?

NOTE: I have reviewed the question Can an atom have more than 8 valence electrons? If not, why is 8 the limit? That question asks about the maximum number of valence electrons. This question asks why eight electrons in the valence shell are more stable than 1, 2, 3, ... 6, or 7 electrons in the valence shell.


texts: Solubility of Calcium Oxalate in Aqueous Alcohol?

texts: In searching through the literature for the solubility of calcium oxalate, I came across this post https://www.researchgate.net/post/Are_there_any_organic_inorganic_solvents_for_dissolving_Ca-oxalate I am not sure where the people answering this question have gotten the information that calcium oxalate is soluble in an aqueous solution of alcohol, but I can't view the only article that I could find agreeing with them past its abstract (I can't see the full text).  https://www.ncbi.nlm.nih.gov/pubmed/641826  Does anyone know if this is true?


texts:
If I have a cyclohexene with no substituents and add HBr, how do I know what side of the former double bond to place the Br anion? I think I understand Markovnikov's rule, but in my chemistry book they always show one carbon specifically that the Br attaches to and I seem to always pick the other. Does it matter or are they equally likely? Is there some way to decide which carbon is more substituted if there are no other groups attached to it and it's just a carbon ring?

Hopefully I've worded this in a way that makes sense, thanks for any help!


texts: Number of configurations/states for electrons in orbitals

texts: I'm performing complete active space calculations for the prediction of X-ray absorption L edge spectra. This involves an excitation from 2p orbitals to the 3d orbitals of the metal. For the electronic configuration of 2p5 3d5 I can calculate the total number of microstates from "n choose k" to be 1512 however the total number of pure spin states is 600. Could someone please explain how to obtain this number?


texts:
I prepared a compound "$\ce{SO2}$-Quinolclathrate" by dissolving hydroquinone and sodium sulfite with hydrochloric acid in warm water.

After this, I tested a little sample of the product on a flame and it vaporised, following which I smelled the gas. I am supposed to define this gas and my prediction is that this could be $\ce{SO2}$(with orange flame).

Clathrate compounds include a trapping system with guest molecules (held "guest" in cages) and the host (hydroquinone here).
$\ce{SO2}$ is guest in the cages of hydroquinone and the gas is held due to crystal lattice forces. Does this mean there are no bonds?

What can be the reason for $\ce{SO2}$ vaporizing?

Additionally, the product was added to starch/iodine solution to find out if it is soluble in that solution and it is so. What can be the reason of this solubility.


texts:
I am struggling with a very basic concept and I think the issue lies in the definition of standard states.

When calculating standard state free energy change via Gibbs equation $$\Delta G^ \circ = \Delta H^\circ  – T \Delta S ^\circ$$  one simply plugs in the standard state entropy and enthalpy, and the corresponding temperature, assuming that $\Delta H^\circ$ and $\Delta S^\circ$ are relatively temperature independent. Since these are standard state values, all species are at $1~ \mathrm{M}$ (in solution). But if all species are at $1~ \mathrm{M}$, then using the equation $\Delta G^ \circ = -RT ~ \ln K$ yields $\Delta G^ \circ =  0$. What am I missing?


texts:
This is a technical question. I have a real-space representation of a potential in a grid of points, however I have the grid in the format:

x  y  z  w  v

meaning: the coordinates of each point, the weight and the value of the potential.

I would like to visualize this potential but I need to re-write this potential in a cube file. I haven't found any particular software or script to do that.

I know how to get the header of the cube file. However I don't know how to re-write the points.

Is there a specific format to write the points?

Thank you


texts:
I was wondering whether someone could explain me if nifedipine is a weak base or a weak acid.
I barely can find any information about nifedipine's physicochemical properties in studies, however some suggested that it is a weak acid. If it is a weak acid, which hydrogen atom is dissociable and what would the pKa of that group be?

Thanks in advanced.

Nifedipine's structure, as shown on wikipedia:


texts:
Williamson ether synthesis is conducted using vanillin, $\ce{KOH}$, $\ce{EtOH}$, water and benzyl chloride.

Why is water needed for the synthesis?
Why must the solution be refluxed for an hour to gain the desired product?
Why is water added after reflux to create a cloudy solution?


texts: Is carbonyl-enol tautomerization only intermolecular or can it be intramolecular?

texts:
During workup of a conjugate addition reaction, it is likely that protonation occurs at the oxygen of the enolate formed. See discussion here: Do enolates get protonated at the carbon or oxygen atom? In that discussion, it is essentially said "The oxygen is probably protonated, but it really doesn't matter." However, I think this could be important in select instances, specifically in the protonation of enolates with diastereotopic faces (which isn't all that rare). But this mostly depends on if tautomerization can occur intramolecularly.

An example of what I'm getting at:

This is an example I just made up. This reaction likely would not actually happen like this. In actually, I could see some γ-deprotonation happening.

In this reaction, one chiral center is formed, and an enolate is formed, and the most likely atom to be protonated upon addition of an acid is the oxygen:

That enol could go on to form one of two products. The intramolecular reaction, I think, would likely give much more of the thermodynamic product (shown below) than an intermolecular reaction, though I'm not certain on that. The reactions here are simplified; I realize both would most likely make some mixture of the two products:

My thoughts are that the four-membered intermediate required for the intramolecular reaction will just be too strained for this to occur. I realize that in basic or acidic solution, catalysis will occur, as the Wikipedia page mentions. I guess the best way to phrase my question is this: In the hypothetical situation that a single ester enol molecule (like that shown as the product of O-protonation above) is dissolved in pure hexane, would that molecule be stuck in in the enol form or would it be able to rearrange? I realize this is more feasible with an dienol, but I'm specifically trying to figure out if the enol can do this.

For the sake of this question, ignore the basicity of the nitrogen. Maybe I should have used the diphenylmethane anion or something. Doesn't matter, it wouldn't reach the proton, either.


texts: How to perform molecular dynamics simulations of charged systems?

texts:
The GROMACS official documentation (see here) states that a system with non-zero total charge will yield an error:

System has non-zero total charge
Notifies you that counter-ions may be required for the system to neutralize the charge or there may be problems with the topology.
If the charge is a non-integer, then this indicates that there is a problem with the topology. If pdb2gmx has been used, then look at the right hand comment column of the atom listing, which lists the cumulative charge. This should be an integer after every residue (and/or charge group where applicable). This will assist in finding the residue where things start departing from integer values. Also check the capping groups that have been used.
If the charge is already close to an integer, then the difference is caused by rounding errors and not a major problem.
Note for PME users: It is possible to use a uniform neutralizing background charge in PME to compensate for a system with a net background charge. There is probably nothing wrong with this in principle, because the uniform charge will not perturb the dynamics. Nevertheless, it is standard practice to actually add counter-ions to make the system net neutral.

If I understand this correctly, it means that a uniform background charge will be added to a net-charged system. What if I wanted to study a charged system, e.g. a peptide with basic groups in the gas phase, where counter ions are absent. Is it still possible to perform a gromacs calculation on such a system and how will the introduction of the compensating background charge affect the molecular dynamics?
I then looked into other packages and noted that net-charged systems seem to be generally problematic in mm calculations. Can anyone point me into a direction like literature on this?


texts: Do I have to change my sample buffer before IEX chromatography?

texts:
I will use IEX chromatography to purify a protein and will then use a equilibration buffer Tris-HCl, pH 8 to set the start conditions for my column and optimize the binding of my protein. Then inject my sample and further on elute with the same buffer but with a salt gradient.

My sample will contain my protein as well as the PBS buffer (pH 7) that I used in previous purification steps.

This question might be dumb but is this applicable, i.e. can I inject my sample with the PBS buffer to the column after equilibration with another buffer, or do I have to change my sample buffer in some way before the chromatography?

Thanks!


texts: What are the resonance structures for chlorite anion?

texts:
What are the possible resonance structures for $\ce{ClO_2^-}$? Assigning one double bond to the structure makes for formal charges of $\ce{O(-1)-Cl(0)=O(0) <-> O(-1)=Cl(0)-O(-1)}$. It appears that the same set of formal charges can be achieved with two double bonds (expanding the octet on $\ce{Cl}$ to 12 electron capacity, using the d orbital). That is, $\ce{O(0)=Cl(-1)=O(0)}$.

Is this feasible, and if not, why not?


texts: What is the meaning of "no Hessian Eigenvalue "?

texts:
When running GAMESS for finding Hessian Eigenvalues and frequencies ( using Optimization with hessian calculation at the end ) , I have seen there are times that it comes out "without any frequencies".

I think even a non-optimized system should have some vibrational properties and I can not understand what such a " no-frequency state " means physically.


texts: Are all compounds named according to International Union of Pure and Applied Chemistry (IUPAC) recommendations or is there another system?


texts: Are esters and amides soluble in cold acids/bases?

texts: The main problem I have is that we say amines are soluble in acids because they are bases, and they will thus react with acids. But if A reacts with B, how does that imply A is soluble in B? Yes, esters and amides do not react with cold acids/bases, but why does that imply that they are insoluble? Ethanol does not react with water, but it's soluble in it.


texts: Equilibrium constant for the thermal dissociation of phosphorus pentachloride

texts:
Thermal decomposition of $\ce{PCl5}$ is studied in a closed vessel. Partial pressure of $\ce{PCl5}$ in gaseous equilibrium mixture is $\pu{1 atm}.$ $\pu{50 \%}$ $\ce{PCl5}$ dissociates. Find equilibrium constant.

I am aware of the formula of equilibrium constant, but I am finding difficult determining concentration of reactants and products from partial pressure and $\pu{50 \%}$ dissociation.

I know the formula

$$K_c = \frac{[\ce{PCl3}][\ce{Cl2}]}{[\ce{PCl5}]},$$

but how to calculate the concentration?


texts: I was interested in knowing if Low Energy Nuclear Reactions are practical or just mythical. What is the current stance of the scientific society about their feasibility?


texts: How can we calculate the "degree" of conjugation?

texts:
So a conjugated system is a system of connected p orbitals or alternating single and multiple bonds.

I know that conventionally, we count the number of adjacent parallel p orbitals or alternating single-double bonds to see which molecule is "more conjugated" or not. However, when considering the following molecules:

I cannot seem to find out which molecule is "more" conjugated or not.

Is there a way to calculate the degree of conjugation? And in this case, would the rhodamine B be the most conjugated compound in the list?


texts: Why do different metal ions release different colors of light?

texts:
For example, potassium chloride released a purple colored flame?
Does it have to do with the energy level of the valence electrons in the metal cation that is being burned?


texts: Finding formula of hydrated potassium chromium(III) sulfate through experimentation

texts:
I'm in Year 13 and this is a past paper question which I don't have a mark scheme for and I'm confused on the chemistry.

  Hydrated potassium chromium(III) sulfate has the formula $\ce{KCr(SO4)2.xH2O}$

  An experiment using heating can determine $x$.

  Give a step by step description of how you would carry out the experiment

  Include all measurements taken

  Outline how you would use your results to find $x$.

  You are provided with solid $\ce{KCr(SO4)2.xH2O}$ and apparatus usually found in a school laboratory

I think mostly I want to know how would begin with this type of question, like what part of my knowledge do you think this is testing me on because I don't know where to start.


texts: Why do most character tables include an $(x^2 + y^2)$ term?

texts:
Why do most character tables (e.g. $C_{3h}$ but not $C_{2h}$) include an $(x^2 + y^2)$ term?
Is it an abbreviated form for $d_{z^2}$, applying only where $3d$ (and higher) orbitals might be involved, or just a generic binomial term with no specific relevance?
The only clue I can find is on this page where it lists the full expression for the angular wave function for $3d_{z^2}$ as
$$Y_{3d_{z^2}} = √(5/4){2z^2-(x^2 + y^2)}/r^2 × (1/4\pi)^{1/2} $$
where it also comments that "the $3d_{2z^2-x^2-y^2}$ orbital is abbreviated to $3d_{z^2}$ for simplicity".
Thoughts appreciated.


texts: Calculate the pressure of the gas samples as indicated by the manometer

texts:
Part A) Given a barometric pressure of $\pu{764.0 mmHg}$, calculate the pressure of gas sample (a) as indicated by the manometer.

Part B)
Given a barometric pressure of $\pu{764.0 mmHg}$, calculate the pressure of gas sample (b) as indicated by the manometer.

For Part A) I tried to subtract $764.0-40.0$ to get $724$ but the answer is wrong.
For Part B) I tried to add $764.0+40.0$ to get $804$, but the answer is also wrong.


texts: Does fluorine in FNO3 have +1 oxidation number?

texts:
According to my textbook and also Wikipedia, fluorine nitrate is a compound which can be created (though it is unstable). Also my textbook says that fluorine has a $+1$ oxidation state. But how is $+1$ state of fluorine possible?

I read in another textbook that fluorine can only show $0$ and $-1$ oxidation states (even Wikipedia says so).

Can someone explain as to how fluorine nitrate exists with a $+1$ oxidation state of fluorine?


texts: Which karat gold is harder, 24 kt or 18 kt?

texts:
$\pu{24 kt}$ gold indicates that $24/24$ part of it, i.e. $100\%$ of it is gold. $\pu{18 kt}$ indicates that $18/24$ part of it is gold. As gold is a soft element, I reckoned that $\pu{18 kt}$ gold would be harder than $\pu{24 kt}$ gold.

I recently saw on a website that $\pu{18 kt}$ gold is harder than $\pu{9 kt}$ gold, which surprised and confused me. Now I want to know which karat gold is harder of $\pu{18 kt}$ and $\pu{24 kt}$.


texts: Finding a substance which has a continuous gradient in refractive index

texts: I need to find a substance whose refractive index is constantly changing and directly proportional to the square root of the depth. I know I'm looking for a lot, but I'd really appreciate any ideas or advice from anyone. Thanks a lot


texts: Are these molecular structures of cyclodecapentaene identical?

texts:
I think that the above structures are identical compounds as I doesn't exist in the shown form but it would exist naturally in the II form, so these should be identical.
But these are mentioned to be geometrical isomers in a book that I was reading. Even if I assume that I existed in it's given form, then how can they be geometrical isomers? In I, there are two trans alkenes, three cis alkenes and in II, all five are cis alkenes.
So, are these compounds isomers or identical?


texts: Mixing solvents, or how does paint thinner work?

texts:
I would like to understand how a mixture of solvents works together.

For example, there are two solvents combined, and each one alone can dissolve some material, but one acts faster.

How do they interact when used in combination on the same material?

An example would be paint thinner, for example a mixture of toluene and xylene.

One reason to use multiple solvents in a paint thinner is to make it dissolve more kinds of paints etc. (In German, this is called "universal thinner".)

But does the combination of multiple solvents somehow make it work better dissolving a single compound or mixture?

I had dissolved some polycaprolactone in that universal thinner above, and it seemed to dissolve quicker than in either toluene or xylene alone.
I do not know exactly what is in the thinner, so it does not mean much – but it made me wonder about this!

So, in which ways interact multiple solvents in the context of the example, and are there other mechanisms in general, not covered by the example?

Addendum:

For discussing a simple example, let's just assume the thinner contains only the two solvents above.

But for context, I looked up the Sicherheitsdatenblatt (MSDS) for my example thinner, which shows some more solvents on the list of ingredients:

Compound                                Mass %
----------------------------------------------
Toluol                                  15- 45
Xylol                                   10- 40
Ethanol                                  2- 15
Aceton                                   5- 20
Ethylacetat                              5- 20
n- Butylacetat                          10- 20
aromat. hydrocarbon mixture (C8-C10)     5- 15
aliph. hydrocarbons (C7-C9)              2- 10


texts: What do D and L stand for in the Fischer-Rosanoff convention?

texts: In R and S configuration, the R stands for rectus and the S stands for sinister. Similarly, do the D and L descriptors in the Fischer-Rosanoff convention stand for something?


texts: Why does 3-hydroxy-butan-2-one give positive Tollens' test?

texts: Why does 3-hydroxy-butan-2-one give a positive Tollens' test despite the absence of an aldehyde group? What is the mechanism?


texts: Coupling constant (Jab) - Why more unpaired electrons means a smaller coupling?

texts:
I hope this is not a "homework" question, but I'm having a bad time trying to figure this out.
Available literature proposes 3 equations to calculate the coupling constant during a Broken-Symmetry approach:

\begin{align*}
J(1) = \frac{-\left ( E_{HS}-E_{BS} \right )}{S_{max}^{2}} \\
J(2) = \frac{-\left ( E_{HS}-E_{BS} \right )}{S_{max}\left ( S_{max}+1 \right )} \\
J(3) = \frac{-\left ( E_{HS}-E_{BS} \right )}{\left \langle S_{HS}^{2} \right \rangle-\left \langle S_{BS}^{2} \right \rangle}
\end{align*}

I'm intrigued by the fact that, from the equations, the more the system have unpaired electrons, the minor will be $J_{ab}$. Why does this happen? Doesn't more unpaired electrons increase magnetic momenta (and an increase in magnetic coupling))?


texts: Why do we use coke instead of coal in order to reduce FeO as basic reaction in ironmaking process?

texts: Why is coke used as a reducing agent to reduce FeO to produce iron instead of coal.I admit that coke is carbonaceous but what is it that compels us to use coke instead of the naturally available coal?


texts: In the last step of Kjeldahl Method, is the reaction of ammonium to NaOH not taken into account?

texts: In the last step of Kjeldahl method, the unreacted $\ce{HCl}$ in the solution is back titrated with a standard $\ce{NaOH}$ and the concentration of $\ce{HCl}$ that has been used to neutralize the ammonia is then calculated. However, other than $\ce{HCl}$, there also exist an acid in the solution that can be titrated with $\ce{NaOH}$ which is the protonated form of $\ce{NH3}$. How is this not considered when calculating the nitrogen presence in a sample?


texts: Why does lithium move on the surface of water during the reaction?

texts:
If someone asks me to number the most notable "textbook experiments" I would definitely name "the comparison of the reactions of alkali metals with water" among the most favorites.

We just happened to do such a reaction with small pieces (approximately $\text{7.5 g}$) of Li, Na and K. As we were supposed to write down anything that we observe, I came across an interesting phenomenon.

It seems that the answer is so simple, I didn't get it through many resources.

  Li piece is moving rapidly (better call it spinning) on the surface of water as it is reacting with it and a subtle explosion sound is heard.

Why does the motion of Li on the surface of the water in the beaker take place? Could the heat released by the reaction be causing current in the water (I don't believe so, as the possibly hot water isn't involved in any convection currents)? Info you might need:

Our chemistry teacher cut a non-oxidized piece of well-preserved lithium. The piece of the reactant wasn't of any distinguishable geometrical shape. After repeating the experiment for several times, I sensed a headache that as I believe is because of release of the impurities of the sample.


texts: How do I get the m/z = 101 peak for 3-methylbutyl propanoate?

texts:
(reference, second source here)
I've found the bigger peaks like m/z = 57, and 70 but how do I get 101? I've tried everything I could think of, like inductive cleavage or McLafferty rearrangement. Since it's 101, using rule of 13 I get the most likely formula to be C5H9O2. But the alcohol-chain has 11 hydrogens, how do I take 2 hydrogens away and end up with 5 carbons?


texts:
I got an unexpected reaction which I'm trying to explain to myself:
I mixed 10 parts glycerol with 1 part glycine at ~90C and to my great surprise the mixture turned from transparent to a tint of red. I had maybe 1-2% water in there too. There might have been a very slight evolution of gas but that most probably was just the water boiling out.
I googled to try to find an answer to no avail. Does anyone know what could have happened?


texts: What software is used to generate the PDB molecule of the month images?

texts:
What software does the PDB use to generate these "cel-shaded" protein models with outlines around foreground atoms?

(Leptin: May 2012 Molecule of the Month by David Goodsell)


texts: Simplified Chromatography - will this work?

texts:
I am interested to separate a sample matrix via a method very similar to chromatography. The reason I am asking about this is because I am planning to integrate this method with my SERS application.

This is what I have in mind:

A droplet of sample is placed at position X.
50/50 Methanol/water is dropped at position Y.
The chromatography plate is outlined as red. It is made of silica gel.
This plate is placed flat on a table.

Assuming:

The solvent does not overflow to the sample drop area.
The solvent can only travel via the direction of the arrow
The solvent will dissolve the sample while it is travelling.

Will this actually work?


texts: Looking for a non-volatile liquid less viscous than water

texts:
I have tried searching everywhere for a stable, non-volatile, bio-safe, low viscosity (< .8cST) fluid. Everything I have come across that is low viscosity is inflammable - acetone, ether, silicone oil, fuel, etc.

I have found some confusing things in my research. Acetone has a viscosity 3x less than water but weighs 2.5 times more. I would like to know how water weighs less but flows slower. Google says viscosity is from low intermolecular forces, but I do not know how to quantify those forces or how to find chemicals that match.

I am trying to make a science project that shows the principle of siphoning, but I want a lower viscosity liquid to show how viscosity effects flow rate. I am working with glass right now and PVC tubes, but I can change my materials based on whatever low viscosity liquid you can find.

Also if anyone knows anything about siphoning, viscosity or material chemistry please let me know if there is a database I can search or if you know chemical that is less viscous than water and meets my specifications.

Is there something I can add to water to lower the viscosity aside from heating? I do not want to have boiling water in my hands. I hear there are surfactants that lower the viscosity of water, but google says surfactants increase viscosity.


texts:
I have a new grain mill that I am hesitant to use because the rollers are anodized aluminum.  As I understand it the anodized aluminum is actually aluminum oxide and supposedly non-toxic.  I realize that the aluminum/alzheimer connection is in doubt (but I have seen it fluctuate as so many "certainties" do).  I do not wish to take a chance playing with aluminum in my food, so can you answer the following questions:

Given that eventually the aluminum oxide would wear off, exposing me to the aluminum.  Would the aluminum form a new protective oxide and if so, how fast would the aluminum re-oxidize and reform a protective barrier? (instantaneously, days, weeks?)


texts: Name of a proton bonded to a hydroxyl carbon

texts:
What do you call the proton in a CH-OH configuration?

When discussing an NMR spectrum, I can talk about the hydroxyl proton, but it seems clumsy to refer to "the proton on the hydroxyl carbon".


texts: How does mixing lemon juice in hooka water affect the composition of the mixture?

texts:
The other day I saw one of my friends, who was mixing lemon juice directly into the flavour chimney (or wind guard) and water pot of hooka. When I asked why are you doing as such, he said that it makes inhaling hooka smoke passive.  By passive, I mean easily inhalable without any hiccups or harshness.  I have tried it, it really makes the smoke passive. But how did this happen?
Here is a diagrammatic view of working principle of hooka:

Here is a list of ingredients of hooka flavour which he used, it was of about 200 grams:

glycerol 70 %
18 % mollases
5 % synthetic edible flavours
5 % sodium xanthate
0.05 % nicotine and 1.95 % water

the temperature at which glycerol boils (and hence the smoke appears) is 290 °C,
By adding lemon juice, we are actually adding citric acid to it, so what would be the products obtained heating that flavour at the given temperature which reduces harshness of hooka.
My friend says the water present at the bottom in the hooka pot, serves for the purification of nicotine present in the flavour (which I can't believe), and he further adds that adding lemon juice to it will act as a filter for nicotine, hence reducing its harshness. [I think there shouldn't be any harshness due to nicotine as it is in a very low concentration i.e. measurable in the order of milligrams per puff, see the comments beside the answer below]
So the harshness must be due to other substances present in the mixture, such as glycerol ( which wouldn't cause harshness as it is in the vapour state), mollases and other flavoured substances along with sodium xanthate, here is molecular structure of mollasses

is mollasses causing harshness, then what is the left over debris after all the flavour is exhausted, many individuals say that the left over & exhausted part of the flavour is nothing but the molasses itself.
and coming to the other substances present in the flavour.
the knowledge which i have gathered from online sources is, the reaction between glycerol and citric acid yields a polymer in a controlled and catalysed reaction, called PGC, which is generally obtained at the temperature of 150°C,  but here in this case the temperature is above 290°C i.e. boiling point of glycerol.
so the fact is that, no polymer is obtained while inhaling hooka, as the glycerol is in its vapour state and citic acid being, very acidic {1M citric acid has a pH value of 2}, so it is nearly in its dissociated state {the lemon juice was mixed in water present in the water pot},

Citric acid

Glycerol


texts: Nucleophilicity of bonding vs lone pairs

texts:
Does the bonding pair in $\ce{FeCl4^-}$ attack a proton or does a lone pair on the chlorine attack the proton?

My prof has an argument for the first one; the first one involves fewer steps, so it is probably more favorable. My proposed mechanism has three steps of electron pushing versus two, so okay.

However, I can see an argument for the second mechanism - the first one involves a bonding pair acting as a nucleophile rather than a lone pair on chlorine. The bonding pair is stabilized by the chlorine and the iron atom, while the lone pair is stabilized by only the chlorine.

So, which one wins? I'm guessing both mechanisms are operative here.


texts: In molecular orbital theory when two different atoms are combined, how do you tell which one is higher energy?

texts:
So in the picture above, see that there is an Atom A and Atom B and they combine. Notice that Atom A is higher in energy than Atom B (as indicated by how the 2s and 2p lines are drawn higher). Suppose I say that this is the diagram for NO. How would I tell which atom and which is O? What determines which atom has higher energy in the orbitals?

Thanks.


texts: Understanding a chemical reaction from kegg

texts:
I came across a reaction that looks as follows:

In this reaction the polyphosphate is common in both the sides of the reaction. Does this act as enzyme? But from the website it seems that the enzyme is ADP-specific glucokinase(in the enzyme section click 2.7.1.63). Then what is the function of polyphosphate here?


texts:
The US defines the "proof" of an alcoholic beverage to be twice the alcohol per volume percentage at 60° F (about 15.5° C)

As someone who does not have a chemistry background, I am wondering what the 60°F requirement means.

Given a mixture of alcohol and water that is 80 proof (40% alcohol by volume at 15.5°C), what is the alcohol by volume at room temperature 20°C?


texts:
I tried drawing out (R)-1,1,2-trimethylcyclohexane but I can't seem to figure it out. I think I"m getting hung on assigning priorities.

I've labeled the chiral carbon with an asterisk. I've also drawn out all the groups it is attached to. I gave the hydrogen the lowest priority (4) and I'm giving the methyl carbon a priority of 3. I am giving the other carbons priorities of 1 and 2 (as can be seen in the picture). However, this doesn't seem to make any sense; I get a molecule that I can neither assign S nor R to since the numbers are out of order.

Also is this really an image of (R)-1,1,2-trimethylcyclohexane?


texts: What does solubility limit mean in practical terms?

texts:
I am not really a chemist guy so please bear with me. Glycerol monolaurate has an upper limit of solubility in water of 20 μg/mL, which is enough for my experiment. Does this mean that no matter how much glycerol monolaurate I add to water the concentration will always stay at 20 μg/mL? Glycerol monolaurate is in powder form so does this mean that the powder would flow on top of water and the concentration of 20 μg/mL glycerol monolaurate would be in the water below?

Thanks.


texts: Why do Cu⁺ ions spontaneously form copper metal and Cu²⁺ ions in solution?

texts:
The standard electrode potentials for three reactions involving copper and copper ions are:

  $$
\begin{align}
\ce{Cu^2+(aq) + e- &-> Cu+(aq)} &\quad  E &= \pu{+0.15 V} \\
\ce{Cu^2+(aq) + 2e- &-> Cu(s)} &\quad   E &= \pu{+0.34 V} \\
\ce{Cu+(aq) + e- &-> Cu(s)} &\quad   E &= \pu{+0.52 V} \\
\end{align}
$$

  Which statement is correct?

  A. $\ce{Cu^2+}$ ions are a better oxidizing agent than $\ce{Cu+}$ ions.
  B. Copper metal is a better reducing agent than $\ce{Cu+}$ ions.
  C. $\ce{Cu+}$ ions will spontaneously form copper metal and $\ce{Cu^2+}$ ions in solution.
  D. Copper metal can be spontaneously oxidized by $\ce{Cu^2+}$ ions to form $\ce{Cu+}$ ions.

Why is the answer C, and not B? I thought that because copper is more likely to get oxidised than $\ce{Cu+},$ it is a better reducing agent and thus B is the answer. But I cannot explain why C is the correct answer. Why is this?

Any help would be greatly appreciated.


texts: Determining the composition of basic copper sulfate by titrimetry

texts:
A colleague shared an undergraduate level classical gravimetry/titrimetry experiment on determining the stoichiometry of basic copper sulfate. I am looking for a reference for this type of experiment. Unfortunately, my colleague does not know the original reference and despite our search we could not find any similar experiment on titrating copper sulfate with $\ce{NaOH}.$ Has anyone seen this type of experiment in any paper or book?
Here is the gist of the experiment.

Basic salts of metals have structures based on the polymeric metal hydroxide lattice with some of the hydroxide groups replaced by other anions. The formula of basic copper sulfate is $\ce{Cu_{(x+y)}(OH)_{2x}(SO4)_y}.$ In this experiment increasing amounts of $\ce{NaOH}$ are added to fixed amounts of $\ce{CuSO4}$ to form the basic copper sulfate salt according to the following reaction:
$$\ce{$(x + y)$ CuSO4 + 2x NaOH -> Cu_{(x+y)}(OH)_{2x}(SO4)_y + x Na2SO4} \tag{Eq. 1}$$
Increasing amounts of $\ce{NaOH}$ are added to different portions of fixed amounts of $\ce{CuSO4},$ resulting in variable amounts of $\ce{CuSO4}$ remaining in excess for the different portions by iodometric titration.
Using the stoichiometry of the reactions, the amount of excess $\ce{CuSO4}$ can be
determined. This, together with the original amounts of $\ce{NaOH}$ and $\ce{CuSO4}$ mixed together, can be used for the determination of the stoichiometric coefficients of reaction (1), allowing the determination of the formula of the basic copper sulfate salt.


texts:
Question
  A linear regression line was obtained; $$\log(\ce{[NaF]})~(\mathrm{mol~L^{-1}})~ \mathrm{vs~EMF}:
y = 59.8x +600.8$$
  $0.7540~\mathrm{g}$ of toothpaste was diluted in a$50~\mathrm{mL}$ and tested to obtain a EMF value of $390$. what is the ppm of $\ce{F-}$ in $198~\mathrm{g}$ of toothpaste?

I plugged in $390$ into the eqn to get $-3.525$, taking the antilog to obtain $0.0002985$, and times it by the volume $0.05~\mathrm{L}$ to get the moles of $\ce{NaF}$.

Due to stoichiometry, this also equals $1~\mathrm{mol}$ of $\ce{F-}$. I multiplied by $18.998~\mathrm{g~mol^{-1}}$ to obtain $0.000283527~\mathrm{mol}$ of $\ce{F-}$. I then multiplied by the factor: $\frac{198}{0.750}$ to obtain $0.074454015~\mathrm{g}$ of $\ce{F-}$ in the $198~\mathrm{g}$ of toothpaste.

I'm stuck here, how can I calculate the ppm?

The expected value of fluoride in toothpaste is $1000~\mathrm{ppm}$


texts: Graphitic acid-Its structure and properties?

texts: What exactly is graphitic acid? I know that it's obtained when you react graphite with concentrated $\ce{HNO3}$ and that its structural formula is $\ce{C11H4O5}$. But I can't find or deduce its structure. And also I am unable to find any of its properties, except that it's a yellow-green liquid insoluble in water.


texts: What chemical explosives detonate when exposed to alpha particles or nuclear fission products?

texts:
Wikipedia's article on nitrogen triiodide $\ce{NI3}$ claims that

  Nitrogen triiodide is also notable for being the only known chemical explosive that detonates when exposed to alpha particles and nuclear fission products

referring to the article published 60 years ago [1]. Are there any other examples of chemical explosives capable of that discovered afterwards, or is it still a prerogative of nitrogen triiodide?

References

Bowden F. P.; Young D. A. The Initiation of Explosion by Neutrons, α-Particles and Fission Products. Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences 1958, 246 (1245), 216–219. https://doi.org/10.1098/rspa.1958.0123.


texts:
Is it possible to recycle an alkaline battery?

The application I am thinking about is that in 3rd world countries often access to western markets is limited. You can't just pop into a store and buy batteries. Would it be possible for a small factory to be in these places and the locals could bring their batteries in for recycling?

The reactions for an alkaline battery are the conversion of zinc to zinc oxide and MnO2 to Mn2O3. So, to recycle a battery of this type you would have to reverse these reactions. Is that easy to do?


texts: Is Tkatchenko's MBD-NL method self-consistent?

texts:
I have a question regarding Tkatchenko's [1] new nonlocal many-body dispersion method (MBD-NL). Does anyone know if it's a self-consistent method? I read this paper many times but I'm still not sure.

References

Hermann, J.; Tkatchenko, A. Density-Functional Model for van Der Waals Interactions: Unifying Atomic Approaches with Nonlocal Functionals. arXiv:1910.03073 [cond-mat, physics:physics] 2019.


texts: Why is the order of reflection simplified to n = 1?

texts: My professor told us that for the sake of simplicity, we will assume that the order of reflection for Braggs' Law is always equal to 1 but failed to explain why. Is it because d(h,k,l) for materials has been determined using an order of reflection 1?


texts: Standard electrode potential of a galvanic half cell is zero at equilibrium at standard conditions?

texts:
At standard conditions(at 1atm pressure and unit activity(1molal or 1molar concentration)of all dissolved compounds),the electrode potential is equal to the standard electrode potential by the Nernst equation. $$ \Delta E = \Delta E^0 $$
At the same time,while the electrochemical reaction is at equilibrium,the electrode potential of the cell, $$ \Delta E =0 $$

So this must mean,that when ANY reaction is at equilibrium under the standard conditions, $$ \Delta E = \Delta E^0 = 0 $$
Which is quite surprising.Is this correct?please explain.


texts: Is silicon dioxide decomposition possible?

texts:
I was thinking about this, I made Gibbs free energy calculations and I can't figure out if

$$\ce{SiO2(s) -> Si(s) + O2(g)}$$

is actually possible, even at a ridiculous high temperature.


texts:
Can an isotope have a charge, i.e. the number of neutrons and electrons differ in that atom?
If it does exists, is it correct to call it an ion isotope or isotope ion?


texts: Is magnesium sulfate basic, neutral or acidic?

texts:
A question in my college test was whether $\ce{MgSO4}$ is neutral, acidic or basic. I was told to solve this kind of problem by hydrolyzing any ions that do not "come from" a strong acid or a strong base, and if nothing is hydrolyzed, then the salt is neutral. So by this logic, as $\ce{Mg^2+}$ comes from $\ce{Mg(OH)2}$ and $\ce{SO4^2-}$ comes from $\ce{H2SO4}$, I answered "neutral".

My professor marked it as wrong, and said that the salt $\ce{MgSO4}$ is basic. How can you explain this?


texts: Resonance forms of deprotonated hydroquinone

texts:
What resonance forms stabilize deprotonated hydroquinone?

Deprotonated hydroquinone looks like this:

Possible resonance forms include:

1 and 2 look reasonable: they don't carry multiple charges. My question is: how much do these two structures contribute to the stability of deprotonated hydroquinone? I am thinking that they should be much higher energy than the structure on top, because the negative charge is on C, which is not nearly as electronegative as O.

Can this be quantified (by and for amateur chemists)?

Per Michael Lautman's suggestion, here are partial charges as calculated in Avogadro:

The pattern expected from the resonance forms above, with more negative charge on carbons 2, 4, and 6, is not there.

Why is C4 -0.20?

For comparison, deprotonated cyclohexane-1,4-diol:


texts: Is there a list of must-have columns for LC-MS/MS used in biochemistry/clinical lab setting?

texts:
Considering a wide variety of chromatographic columns used for (U)HPLC based on

phase type (normal or reverse);
column dimensions (geometry, length, inner diameter);
particle material $(\ce{SiO2},$ $\ce{ZrO2},$ $\ce{TiO2},\ldots),$ size, shape and porosity;
dopants/modifiers etc.,

as well as proprietary manufacturing techniques involved, is there a narrowed-down list of the bare-minimum column types that every analytical lab doing specifically liquid chromatography tandem mass spectrometry must have to cover the majority of the analytical routines (qualitative and quantitative analysis of short-chain fatty acids, primary metabolites, amino acids etc.)?

Background: a new LC-MS/MS lab is being created within a university's biochemistry division from the ground up both for the fundamental research and providing analytical services, so listing the most versatile and recent columns would be appreciated.
I do realize the question is borderline off-topic being somewhat opinion-based, so it would be nice if the answer were based on a trustworthy source.


texts:
Part 1: According to what I've learned so far, helium is in the first row of the periodic table, so its $n$ should always equal $1$. However, a question in my text asks about helium 2s. What is helium 2s? If helium 2s exists, why does the periodic table list helium in the first row instead of the second?
Part 2:
I believe that He 1s is more stable than He 2s. I've reasoned thus:

The numerals '1' and '2' in 'He 1s' and 'He 2s' express the size of the orbital. The greater number represents a larger orbital.
The electrons of smaller orbitals exist closer to the nucleus than the electrons of larger orbitals do.
The intensity of the attractive force between electron and protons increases the nearer the protons are to the electron
Therefore, the attractive force between the protons and the electron will be greater in He 1s than in He 2s.
The greater the attractive force between the protons and the electron, the greater the stability of the electron.
Therefore the electrons in He 1s are more stable than the electrons in He 2s.

Is that correct?

Note the following is the original question:

For each pair of orbitals determine which is more stable and explain why:
(a) He 1s and He 2s;
(b) Kr 5p and Kr 5s;
(c) He 2s and He+ 2s


texts:
Recently I came across this equation:

$$\ce{WO_3 +SnCl_2 +HCl\rightarrow W_3O_8 + H_2SnCl_6 +H_2O}$$

The compound $\ce{W_3O_8}$ that appears in the right hand side of the equation seems to be mixed oxide. Normal calculation of the oxidation state of W in the compound yields $\ce{\frac{16}{3}}$ which is a fraction. A google search on the compound does not give any good results too.

So, is $\ce{W_3O_8}$ a mixed oxide? What are the oxidation states of the different tungsten atoms?


texts: When is it permissible to use the stoichiometry of a reaction to determine rate laws?

texts:
I have read in a general chemistry textbook that rate laws can only be determined by experiment. This seems intuitive because if a mechanism is not elucidated and tabulated reaction data would be one way of bypassing that info to reach the rate law. However, I have seen instances where the rate law is simply determined by using the reactants and raising them to their respective stoichiometric power...which I thought contradicted the idea of needing an experiment? I highly speculate that this is only acceptable if it a singular reaction that the reaction order can be determined experimentally? For example:

$$\ce{2A -> B_2}$$

Can be surmised as:

$$\text{rate} \  = k[A]^2$$

Is this true? My speculation is based on the notion that if one reactant is splitting to a product and that stoichiometric equivalent is needed for the conversion of reactant to product, then the rate law is determined by stoichiometric equivalent number of molecules hence the justification for the "raise to the power" method. Or is there another underlying factor when the exponents have been raised and no detail is given to rate laws determine by experiment?


texts:
I noticed while heating some PbI2 powder that it reversibly changes from a yellow to a dark red. However, I was unable to find anything on this thermochromism.

There are related cases in TlI and AgI but there it is mostly about occupying the free sites in the crystal structure or if Ag is present there is also the possibility of Ag coming close to Ag (so-called argentophilia). This, however, doesn't seem to be the case for Pb(II).

It is also no thermal charge transfer, for Hg(II) + I(-) a thermal charge transfer to Hg(I) + I(0) was often mentioned and it makes sense there but Pb(I) is not really useful here.

The structure is also different forming layers. I read they have weak VdW-bonds so perhaps those break in the process of heating it? If impurities are introduced there is the possibility of forming a perovskite structure but I doubt this would be reversible. So this has to be a smaller shift in the structure.

PbI2 has quite many different room temperature and high-temperature polytypes, so perhaps it's really a change in the crystal structure? I couldn't really find much on this because I don't know how the colors change for the different polytypes.

Does anyone have an idea what might be the dominating effect for a reformation in the structure, like an actual effect that might take place here?

You see often it is the case in these solid-state thermochromic compounds, that the high-temperature form seems to be the best situation, but cooling it down allows weaker forces like this argentophilia, for example, to distort the structure a bit. Like TlI is more or less an orthorhombically distorted NaCl in its low-temperature form.

Given the fact however that Pb(II) still has a lone-pair that can be positioned quite well in the gap between the layers I don't see a real demand for any change at all.


texts:
Is it possible to heat a material above its solidus without melting occurring?

More specifically, at a heating rate of approximately 200K/s, will a metal alloy exhibit superheating and if so by what order of magnitude i.e. fractions of a degree versus tens of degrees. What is the mechanism behind this?

There is a lot of information about supercooling but I am not certain whether this applies!


texts: Which of these thermodynamic relationships is true for a system at equilibrium?

texts:
Which of the following is true at equilibrium

$$T \Delta{S} = \Delta{H}$$

$$T \Delta{s} = \Delta {G}$$

I think it's the first one but I just wanted to be sure.


texts: Interpretation of Coloumb operator in Hartree Fock equation

texts:
I have read in a textbook (Modern Quantum Chemistry Szabo and Ostlund) that the Coulomb operator of the form
\begin{equation}
\mathcal{J}_{j}\left(\mathbf{x}_{1}\right)=\int d \mathbf{x}_{2}\left|\chi_{j}\left(\mathbf{x}_{2}\right)\right|^{2}r_{12}^{-1}
\end{equation}
describes the average local potential at $\mathbf{x}_{1}$ arising from the charge distribution from an electron in $\chi_{j}$. And therefore the term $\sum_{j \neq i}\left[\int d \mathbf{x}_{2}\left|\chi_{j}\left(\mathbf{x}_{2}\right)\right|^{2} r_{12}^{-1}\right] \chi_{i}\left(\mathbf{x}_{1}\right)$ for an N-electron system gives the total averaged potential of $N-1$ electrons in other spin orbitals on the electron in $\chi_{i}$.
However, if one expands the sum
\begin{equation}
\sum_{j \neq i}\left[\int d \mathbf{x}_{2}\left|\chi_{j}\left(\mathbf{x}_{2}\right)\right|^{2} r_{12}^{-1}\right] \chi_{i}\left(\mathbf{x}_{1}\right) = \left(\int d \mathbf{x}_{2}\left|\chi_{1}\left(\mathbf{x}_{2}\right)\right|^{2}r_{12}^{-1} + \int d \mathbf{x}_{2}\left|\chi_{2}\left(\mathbf{x}_{2}\right)\right|^{2}r_{12}^{-1} +...\right) \chi_{i}\left(\mathbf{x}_{1}\right)
\end{equation}
it is indeed a sum over the spin orbital but not of the electrons in the system. My interpretation for the sum is as follows: the total averaged potential acting on electron 1 due to the charge distribution of electron 2 in N-1 spin orbitals . I think it has something to do with the fact that electrons are indistinguishable so one cannot assign an electron to an orbital. However, I think the Hartree Fock integro-differential equation
\begin{equation}
h\left(\mathbf{x}_{1}\right) \chi_{i}\left(\mathbf{x}_{1}\right)+\sum_{j \neq i}\left[\int d \mathbf{x}_{2}\left|\chi_{j}\left(\mathbf{x}_{2}\right)\right|^{2} r_{12}^{-1}\right] \chi_{i}\left(\mathbf{x}_{1}\right)-\sum_{j \neq i}\left[\int d \mathbf{x}_{2} \chi_{j}^{*}\left(\mathbf{x}_{2}\right) \chi_{i}\left(\mathbf{x}_{2}\right) r_{12}^{-1}\right] \chi_{j}\left(\mathbf{x}_{1}\right)=\epsilon_{i} \chi_{i}\left(\mathbf{x}_{1}\right)
\end{equation}
was derived for hydrogen molecule. Is it the same for an N-electron system?


texts: What is the difference between graphite oxide and graphene oxide?

texts:
I am considering making a sheet of graphene using the LightScribe technique and I have read that I need graphite oxide. However when I look up graphite oxide for sale, graphene oxide pops up.

Are these two oxides similar? What is the difference?


texts: Which of these can undergo decarboxylation reaction readily

texts:
Which of these carboxylic acids can undergo decarboxylation readily?

According to what I know beta-keto acids undergo decarboxylation easily and readily due to formation of a stable intermediate. So my general answer was option (A) however the answer key states that (A),(B) and (D) are correct. I am not able to understand, based on my current theory what is the reason for (B) and (D) to undergo decarboxylation readily.


texts:
I faced a question

  How many cyclic isomers are possible for $\ce{C4H6}$?

I and my friend found the following four.

But the answer key says there are 5. So what's the other one?


texts:
According to me the answer should be (c),(b),(a),(d). As we move left to right in a period the electronegativity increases and hence the tendency to donate electrons will decrease so nitrogen is better electron donor than oxygen. Now to select between three oxygen donating species we can use the steric hindrance concept and hence my answer.

  But the correct answer is (b),(c),(a),(d).

Please tell me what is my mistake.


texts:
I have a zinc-body garden spray head with a brass garden hose thread stuck inside.  This is actually an irritatingly common problem.

Which got me wondering: What chemical means exist to dissolve copper but not zinc?

(Going the other way is easy: just dipping in HCl acid dissolves the zinc but doesn't touch the copper.)

Boiling in lime sulfur will oxidize a thin layer of copper, but I don't think that will be sufficient to extract the hose thread.

Tryggvi Emilsson supposedly used KCN and $\ce{K2S2O8}$ to dissolve copper without touching zinc, but claims it was a very tricky process to get right.

Is there a clever way to extract the copper using electrolysis?$%edit$


texts:
I am using TINKER package to calculate the external reorganization energy for pentacene crystal. But I have problems with that - I've generated .xyz file of 5 molecules with VESTA and I need to perform the calculation on those five molecules (image below) with periodic boundary conditions (PBC).

How can I find the proper size of cell and keep it fixed for calculations? When I use keywords A-axis, B-axis, C-axis and alpha, beta, gamma and assign lattice vectors and angles to them after optimization or minimization for the charged system like that apparently cell gets broken and molecules are distorted out of box:


texts: Origin of Virtual Molecular Orbitals in Hartree-Fock equations

texts:
Let's look at scheme
Do I understand correctly, the origin of Virtual Orbitals is a solution of (for, exampre, restricted) HF equation eigenfuncions?


texts: Why do metals tend to lose electrons, as opposed to maintaining electric neutrality?

texts:
Metals tend to lose electrons to obtain the stable noble gas configuration of 8 valence electrons.

Why do they want to obtain this configuration, and how does the strength of their "desire" to obtain this configuration compare with the "desire" to maintain neutral charge.  If the answer depends on the chemical, I'm happy for you to provide some examples.

Thanks.


texts: Entropy change of isothermal irreversible expansion of ideal gas

texts:
Two mole of an ideal gas is subjected to isothermal expansion from $\pu{2 atm}$ to $\pu{1 atm}$ at $\pu{300 K}$. Calculate entropy change of the system, surrounding and total, if the process is irreversible.

Since

$$ΔS_\mathrm{system} = nR\ln\left(\frac{P_1}{P_2}\right),$$

I got the $ΔS$ for the system as $1.4R$. I know that for reversible process the entropy should not change, hence the entropy of surroundings decreases by $1.4R$. But how do we calculate the same for an irreversible one?


texts: Why is carbon dioxide considered a Lewis acid?

texts:
$\ce{CO2}$ is considered a Lewis acid. How it is an acid? According to Lewis: “species that accept an electron pair are acids”. But $\ce{CO2}$ can't accept electron pairs because oxygen and carbon both are electron sufficient (have complete octets). If the reason is within a lone pair of electrons on oxygen then ammonia ($\ce{NH3}$), which also has a lone pair of electrons, should be acidic, too. But ammonia basic in nature.

So why can carbon dioxide be considered a Lewis acid?


texts: Why assume a neutral amino acid is given for acid-base reaction?

texts:
The questions is:

  $1.812\ \mathrm{g}$ of a crystallized α-amino acid ($\mathrm{p}K_\mathrm{a1} = 2.4, \mathrm{p}K_\mathrm{a2} = 9.7$) has a $\mathrm{pH}$ of $10.4$ when dissolved in
  $100\ \mathrm{mL}$ of $0.1~\mathrm{M}\ \ce{NaOH}$. Calculate the molecular mass of this amino acid.

As usual we can obtain the ratio of the conjugate base and acid around $\mathrm{p}K_\mathrm{a2}$ by using the Henderson-Hasselbalch equation. However, once we get the ratio, the solutions key says that we know $c(\text{Base}) = 0.1$ because all of the $\ce{OH-}$ reacted with our acid. While I totally agree that all the $\ce{OH-}$ reacted with the acid, since it is a strong base, how do we know there was no $c(\text{Base})$ before the addition of $\ce{NaOH}$? Thus making the concentration $c_0(\text{Base}) + 0.1$.
Is this because it came from a solid crystal where all of the amino acid was in the acid form?


texts: When we heat hydrogen the energy of the molecular orbital of H2(1s) is increased .What happens to the energy of the antibonding molecular energy of hydrogen(1s*)?


texts: What determines whether iodination or reduction will occur?

texts:
Alkyl Iodides are formed by reaction of alcohols with iodine and red phosphorus.  I already am well aware that this forms $\ce{PI3}$ in situ, which acts similarly to $\ce{PBr3}$ and allows alkyl iodides to be prepared from alcohols.

However, when the same reaction is performed on ephedrine, the hydroxyl group is reduced rather than iodinated.  What determimes whether iodination or reduction occurs?

I have a few theories, one being temperature may be kept lower to form the alkyl iodide.  Or is it to do with the benzylic position of the hydroxyl group?  Or perhaps the red phosphorus is in excess to favor reduction?  Any incite will be helpful.


texts: Why is the Van der Waals constant of water lesser than benzene?

texts:
Van Der Waals constant of water and benzene ($a$) are $5.537$ and $18.82$ respectively.
I have read that the value of Van Der Waals constant indicates the extent of attractive forces.
By this, shouldn't it be greater for water instead because water has hydrogen bonding?
Also, what are the factors(with priority) on which the Van Der Waals constant depends on ?


texts: What are the pros and cons of using Gilman reagent over Grignard reagent to synthesize a hydrocarbon?

texts:
As far as I know, in order to synthesize a hydrocarbon $\ce{R-R'}$, Grignard reagent or Gilman reagent could be used.

$\ce{RMgX + R'X -> RR' + MgX2}$

$\ce{R2CuLi + R'X -> RR' + LiX + RCu} $

What are the pros and cons of using Gilman reagent over Grignard reagent? Gilman reagent is significantly harder to prepare and involves a reactive organolithium compound. I'm not looking for the pros and cons in terms of cost and yield, but rather specificity:

Are there any $\ce{RR'}$ groups that must be synthesized via Gilman reagent and not Grignard reagent?
Are there any $\ce{RR'}$  groups that must be synthesized via Grignard reagent and not Gilman reagent?

Someone (outside of SE) pointed out to me how pointless it is for chemists to synthesize hydrocarbons using these methods (as they are readily available to purchase). While I agree with him, I'm still interested to find out "theoretically" if Gilman/Grignard reagent is specific to certain R/R' groups.


texts:
In one of my books it is written that boron does not react with alkali but in another book it is written that it reacts with alkali.
Can any one help in clearing this confusion?


texts: Hydrocortisone cream seems to be sold as 1% w/w, but my cream is 1% m/m, which is confusing. Are they the same units or the same concentrations?


texts: How is Standard Gibbs free energy measured?

texts:
I have seen hole theory of thermodynamics but almost nothing about the experiments that measure $\Delta G^\circ$. I know how to measure it by electrodes, when the reaction is a redox one. But what with other reactions?

What are the experimental ways to determine $\Delta G^\circ$? Some examples would be helpful


texts: Finding the binding energy iof methylated miRNA to an mRNA

texts:
I'm working on a project in biophysics and I need to find if there is a difference in binding of an miRNA to an mRNA when in one case the miRNA is methylated and in the other it isn't.
What tools should I use to calculate the binding energy in each case?
I have the binding sequence of the miRNA.


texts:
From Schroeder's Introduction to Thermal Physics.

Parts $(a)$ and $(b)$ are quite simple, and we find that $ \Delta H =-2808\ \mathrm{kJ}$ and $\Delta G =-2879\ \mathrm{kJ}$, so by $\Delta G = \Delta H -T\,\Delta S $, we find that $T\,\Delta S = 71\ \mathrm{kJ}$ at room temperature.

What I absolutely cannot understand is how $(c)$ and $(d)$ work. It intuitively makes sense that entropy is increasing. Assuming $1$ mole of glucose, we start the reaction with $7$ moles of reactants and end with $12$ moles of products. Entropy obviously increases, as we can arrange these molecules in many more ways. However, this implies that we are getting usable work from increases in entropy – meaning that the muscles are somehow absorbing heat energy from the environment. But this isn't true in real life – metabolism reactions obviously release heat. What's going on here?


texts: Balancing by oxidation numbers method multiple atoms

texts:
In my Chemistry textbook, the rules for balancing a chemical equation using the oxidation-Number method are as follows:

Assign oxidation numbers to all the atoms in the equation.
Identify the atoms that are oxidized and the atoms that are reduced.
Determine the change in oxidation number for the atoms that are oxidized and for the atoms that are reduced.
Make the change in oxidation numbers equal in magnitude by adjusting coefficients in the equation.
If necessary, use the conventional method to balance the remainder of the equation.

I understand how to do this for simple equations, such as $$\ce{SnCl4 + Fe -> SnCl2 + FeCl3}$$

Following the steps:

$\ce{Sn^{4+} + 4Cl- + Fe^0 -> Sn^{2+} + 2Cl^- + Fe^{3+} + 3Cl^-}$
Oxidation: $\ce{Fe^0 -> Fe^{3+} (Fe)}$ reduction: $\ce{Sn^{4+} -> Sn^{+2} (Sn)}$
oxidation: +3; reduction -2
$\ce{3SnCl4 + 2Fe -> 3SnCl2 + 2FeCl3}$
(no change necessary, already balanced)

The Problem: Notice how Sn and Fe (the reduced and oxidized atoms) all have subscripts of 1. However, when their subscripts differ, I'm not sure how to balance it.

For example, I can easily balance the following equations by inspection, but not so easily by this method of oxidation numbers:

$$\ce{KClO3 -> KCl + O2}$$ (O is oxidized, subscripts of 3 and 2)

$$\ce{NH3 + NO2 -> N2 + H2O}$$ (N is oxidized and reduced, oxidation numbers of -3, +2, and 0)

And this gets even more complicated when the subscripts differ and there are more than two elements whose oxidation numbers changed (are reduced or oxidized), e.g.,

$$\ce{NH4ClO4 + Al -> Al2O3 + HCl + N2 + H2O}$$
(Al and N are oxidized, Cl is reduced)

For all of these, I get stuck on the fourth step. Determining oxidation numbers and calculating the change is not the problem, but figuring out how to do it with larger or different coefficients as in the examples above is the problem.

The five general steps in my textbook don't help me understand this method much with more complicated methods such as this. Could you give me a more thorough explanation - a better explanation or a general rule - of how to solve all of these?


texts:
While solving for weak acid and weak base salt hydrolysis, why do we take the degree of hydrolysis for both the anion and cation to be the same?

If we assume they are the same, when solving for $K_\mathrm{a}$ and $K_\mathrm{b}$ for the cation and anion using simultaneous equilibrium, I always get them to be the same, resulting in the solution always being neutral. I feel that both should have different degrees of hydrolysis.


texts: I have read in my textbook that $\ce{CI4}$ is more stable than $\ce{PbI4}$ due to inert pair effect. But shouldn't we also consider the effect of steric repulsions? In $\ce{CI4}$, four large iodine atoms surround the small carbon atom, which should make it less stable than $\ce{PbI4}$.


texts: Why does the Gibbs Free Energy change determine spontaneity of a reaction?

texts:
Here is a doubt that arose in my mind while studying the chapter Thermodynamics of the 11th standard. (It might be silly, but I would love it if you try to understand what I mean to ask before down voting. Also, I want the doubt cleared.)

We have been told that if the value of $\Delta G$ or Gibbs' free energy change is negative or zero the process is spontaneous or in equilibrium, respectively. If otherwise, it is non-spontaneous.
Why? What does $\Delta G$ exactly signify that if it is positive the process won't happen by itself. I mean, I know what $\Delta G$ is equal to, but why does spontaneity of the reaction depend on its sign?


texts: Why do atoms "want" to have a full outer shell?

texts: Okay, so I know that this is about filling the orbitals of the atom, and I understand that. What I don't understand is why? For example, an Oxygen atom has 8 protons and 8 electrons spinning around it. Oxygen wants to have 8 valence electrons so it takes 2 electrons from other elements when bonding. But, since Oxygen has 8 protons and now has 10 electrons around it, it has a charge of -2. I don't understand how having a charge is more stable than having no charge at all, shouldn't the most stable version of an element be its neutral state? Why do the atoms want to look like the next noble gas?


texts: How can a ketone be enantioselectively reduced, in the presence of an ester?

texts:
I'd like to reduce enantioselectively a ketone in presence of an ester (which should NOT be reduced to an aldehyde and further to an alcohol).

Adding $\ce{LiAlH4}$ would also reduce the ester and gives no enantioselective reduction of the ketone.
In the following reaction (Frater-Seebach Alkylation) they used Bakers yeast:

Probably S-BINAP also give 2. I think there is a $\ce{RuCl2BINAP}$ transition metal complex in combination with $\ce{H2}$ used.
I would first use KOH, then adding Evans auxiliary, adding LiCl for chelation of acid carbonyl to Evans auxiliar carbonyl, then adding $\ce{NaBH4}$ and to a standard Felkin Anh reduction. And as a last step I would use $\ce{LiOEt}$. Does this work or will the chelating ketone also be reduced?

May be my own suggestion is easier to reproduce in lab than the use of asymmetric reduction using $\ce{H2}$ under high pressure.

I'm looking for further ways to get the (S)-hydroxy compound 2. Are there easier ways?


texts: Nomenclature priority of prefixes consisting of identical letters but containing different locants

texts: I have no idea how to name this compound. Can someone please help give the IUPAC name for this? Also mention the IUPAC nomenclature rules followed while naming.


texts:
I am trying found a relation between cp - cv for a real gas. I know how to calculate for an ideal gas, but when I try to do the same for a real gas I stopped at some point and I don't know how to continue.
The EOS used is Van der Waals equation.
If someone could help me, please, I am glad for it.


texts: Does Intercalation and Deintercalation of Lithium ions occurs in Half Cell?

texts: The important feature of Lithium ion batteries is the ability to  intercalate and deintercalate lithium ions in  anode and cathode . However when we use  half cell, using lithium metal foil as anode, intercalation and deintercalation process occurs in this case too. How the lithium ion moves and what process cause the current to flow in discharge?


texts: Test for Fe2+ ion in salt using potassium hexacyanidoferrate(III)

texts:
It's given in my book that $\ce{Fe^3+}$ ion reacts with potassium hexacyanidoferrate(III) to give brown colour.
$$\ce{Fe^3+ + [Fe(CN)6]^3- -> Fe[Fe(CN)6]}$$
Both the reactants have the same oxidation states.

My question is, can I use the same test for $\ce{Fe^2+}$?

First, the hexacyanidoferrate(III) will oxidize $\ce{Fe^2+}$ to $\ce{Fe^3+}$ like this:
$$\ce{Fe^2+ + [Fe(CN)6]^3- -> Fe^3+ + [Fe(CN)6]^4-}$$
Then the reaction will continue to give brown colour.


texts: What's the driving force of this reaction?

texts:
The question is to find the major product in this reaction-

And this is the answer given-

The first step seems to be a kind of intramolecular SN2 reaction. But how can it occur on this carbon which has a lot of steric hindrance. What is the driving force of this reaction? I have never seen such a reaction that occurs solely on giving heat except, of course, dehydration reactions.
Edit- I am asking about the driving force of the first step.