texts:
I was given a problem to identify whether the given statement is true or false.

And the statement was:

"Consider an ideal gas which is expanded from $(P_{1},V_{1},T_{1})$ to $(P_{2},V_{2},T_{2}).$ Then, the work done on the gas is maximum when it is compressed back irreversibly from $ (P_{2},V_{2}) $ to $ (P_{1},V_{1})  $ against a constant pressure $P_1$".

I concluded that the statement is false, as:

It is nowhere mentioned what is greater $P_1$ or $P_2$ as there is no information on how the expansion process was done.
Even if I assume that $ P_1 > P_2$, still during irreversible compression I can vary the pressure such that the pressure goes beyond $P_1$ in the middle of the process but finally returns to the required final state $ (P_{1},V_{1})  $ , which would mean that I am doing more work than what I would be doing if I keep the pressure constant.

However the answer says that the statement is true.

Where am I wrong?


texts:
I would like clarification on the role of oxygen as a hydrogen bond acceptor in Lipinski's Rule of 5 (for drug absorption). I have learned in my medicinal chemistry class that both electron pairs from an oxygen atoms are able to individually form hydrogen bonds.

I was wondering if every sp3 hybridized oxygen would account for 2 possible hydrogen bond acceptors in this rule for drug absorption? If not, what other mechanisms or in vivo findings are not causing oxygen to not count as double?


texts: Mechanism of reaction of alcohol with NaBr + H2SO4

texts:
My teacher told that the mechanism for reaction of alcohol with $\ce{NaBr + H2SO4}$ follows SN1 when alcohol is 2°/3° and SN2 when it is primary or methanol. He told that the reactivity of alcohol also follows the order 3° > 2° > 1° which is that of SN1.
But I couldn't understand why is it the case. The nucleophile is $\ce{Br-},$ which is anionic nucleophile—so it should always follow SN2.


texts:
Theoretically, is it possible to make a large, transparent piece of armor or a shield from a diamond?

Say, a piece of the said armor with a size  $7^\prime \times 7^\prime \times 6^{\prime\prime}$?

What kind of forces could this put up with?


texts: What is the equation that demonstrates the relationship between molar conductivity and temperature?

texts: Can someone please help me find the equation that defines the relation between molar conductivity and temperature. I have found some information, but it was not really that much complete.


texts: The effect of pressure on equilibrium constant

texts:
What will happen to the $K_\text{eq}$ in the following reaction if volume is increased?

$$\ce{2NO(g) + O2(g) <=> 2NO2(g) + energy}$$

From le Chatelier's principle I know that it must be constant unless temperature is changed, however it doesn't make sense because if

$$K_\text{eq}= \frac{[\ce{NO2}]^2}{[\ce{O2}][\ce{NO}]^2},$$

then by increasing the volume we know that equilibrium will shift left and favor reactants. Hence concentration of reactants would increase while concentration of products would decrease. If we plug that back into the equilibrium constant equation we see that if numerator decrease and denominator increase that must yield a smaller number than the initial number. Hence the equilibrium is not constant. Why this occurs?


texts: Hyperconjugation is often illustrated with C-C and C-H bonds donating electron density to the p orbital in the adjacent carbon atom. Since the concept revolves around sigma bonding orbitals donating electron density to p orbitals, would other bonds such as Si-Si or Si-H bonds be able to take part in hyperconjugation as well? If they are not able to do so, why not?


texts: Equilibrium between R and S configuration?

texts:
We have learnt that the energy evel of both R and S optical isomer of a compoud is same, just as well the entropy of each isomer is also same. If we consider the conversion of R form of a compound to it's S isomer we observe that the change in gibbs free energy is "0". This implies that the two isomers must exist in equilibrium. But we also know that any compound does not change from its R configuration to its S configuration for example inversion of configuration in Sn1 mechanisms lead to only one configuration and not both are obtained after the reaction.

So the question is that why don't any compounds R isomer convert into its S isomer on its own so as to maintain equilibrium ?


texts: I am trying to work out the ground state symmetry of electronic states. The paper states the GS symmetry is $^6A_1$ for the right hand side electron configuration and $^4B_1$ for the LHS in the D$_{2\mathrm{d}}$ point group. I understand that the symmetry is determined from direct products of the molecular orbital symmetries of the singly occupied orbitals. However I cannot get to the two symmetries listed. For the left electronic configuration it is $b_1 \times a_1 \times b_2 \times e \times e = [a_1+a_2+b_1+b_2]$ so I'm unsure of how to get $A_1$. Likewise the product e x e for the right electronic configuration produces the same results and again I'm unsure of how to arrive at $B_1$.


texts: Supporting electrolytes and increased conductivity?

texts:
Hi a question about supporting electrolytes (SE) I hope you can help with.  I found some related questions here through searching but looking for a simple answer (if there is one!):
If SE are electroinactive (in the potential range of interest) and so do not pass or receive electrons at the electrodes to complete the circuit then how to they "increase conductivity"?  I am referring to typical DC experiments, e.g. chronoamperometry.  It's not like electrons hop through the solution from one electrode to the other using SE ions as a shuttle.
I understand that one role is that they migrate to the opposite electrodes to neutralize ion charge imbalances that would build up due to reagent consumption or product generation from the electroactive species you are measuring (e.g oxidizing an enzyme product), thereby facilitating these redox reactions that do occur to continue. Is this the answer?  So in just water + SE, for example, it is more conductive because they facilitate the electrolysis of water (H2 and O2 generation (e.g for SE without Cl-) by this method?
I also understand that movement of ions is considered current, but with DC wouldn't this migration slow down and exhaust as time went on? Is it this transient conductivity due to ion movement that they refer to?
Thanks!

Thanks for your answer Maurice.  What you describe sounds like this (maybe not clearly written) part of my own possible answer to my question: "I understand that one role is that they migrate to the opposite electrodes to neutralize ion charge imbalances that would build up due to reagent consumption or product generation from the electroactive species you are measuring,  thereby facilitating these redox reactions that do occur to continue".
I think my confusion arises because the IUPAC definition is:  "A supporting electrolyte, in electrochemistry is an electrolyte containing chemical species that are not electroactive (within the range of potentials used) and which has an ionic strength and conductivity much larger than those due to the electroactive species added to the electrolyte", which makes it sound like the the SE ions themselves are conductive.  Plus the most common explanation offered is along the lines of "because they are ions and ions conduct".
If I understand correctly now as discussed, they actually facilitate the reaction of the true electroactive species (which produce faradaic currents through redox - the current being a measure of conductivity), by maintaining neutrality around the electrode, rather than being "conductive" themselves (along with other roles such as making results more purely diffusion controlled, etc).
Put simply, the SE ions do not increase conductivity directly by contributing to the current (like an electroactive ion would), but increase conductivity by increasing the rate of faradaic processes of the actual electroactive species that are present (by using the SE ions to maintain electrical neutrality around the electrode).
Is this it?
Again, thanks for your time!


texts:
I am having a lot of trouble with this question. We have to determine if $K$ is greater or less than 1. I at first thought the equilibrium would favor the right side because this could have to do with ligand binding where the negative charge would probably cause binding to occur tighter than the left side.
I was told by someone else that it could favor the left side however due to resonance stabilization present in the molecule. Now I am not sure how to judge if $K$ will be greater or equal to 1.


texts: Additive to an aluminum sulfate and water solution to lower pumping pressures

texts:
I am currently looking for a surfactant (powder form) that I can add to a solution of aluminum sulfate and water.  My current solution is comprised of 34 gallons of water and 4 (four) 50 lbs bag of aluminum sulfate.  It has a specific gravity of 1.275

It is used as an additive to a gypsum based fireproofing product to lower the density as well as help with a quick set of the fireproofing material.  It is injected into the fireproofing material at the base or a 1" hose that is 20 feet long.  I was hoping to find an additive (surfactant?) that would reduce the pumping pressure of the fireproofing material thru the 1" hose without affecting the chemical nature of the aluminum sulfate and water combination.

The aluminum sulfate and water are mixed in a 50-gallon drum with a high propeller blade that is fairly aggressive.  I worry that a normal surfactant will foam up too much and make the product unusable.

If a non-foaming agent can be added to the water that will offer to lower the pumping pressures of the material thru the 1" hose that would be what I am looking for.


texts: How to show that when the equilibrium constant is larger than one, some real-life equilibria are still reactant favoured?

texts:
My instructor assigned us with this question:

  When real examples of chemical equilibrium are used, the conclusions about reactant- or product-favoured versus the value of $K$ must be modified (e.g. real equilibria can have $K > 1$ but still be reactant-favoured). Discuss this idea, using examples of real chemical equilibria and assumed values of equilibrium concentration.

I was taught that when $K > 1$, it will be product favoured, assuming it’s already at equilibrium ($Q = K$).

How would I go about answering this question? Do I approach it with regards to initial concentrations in the system, their initial states (mixed vs. unmixed), pressure and volume changes?


texts:
When preparing a known mass of something (e.g. when producing a standard solution) it is often that in my school lab that we first use a weighing boat to measure the mass and then once transferred into a beaker we reweigh the boat and calculate the mass transferred.

Do we this even though we zero the scale anyway?

Now to my knowledge would this not increase the uncertainty as instead of just using the beaker on the scale and adding the mass directly which would lead to one uncertainty we instead weigh it twice which would thus have 2x the uncertainty in the scale.

Could somebody explain where my reasoning is wrong and why this method is more accurate?


texts: What are the implications of having different conformations?

texts: I have seen videos explaining what conformations are. I am curious about whether different conformations can give rise to slightly different properties. Particularly of interest is whether you can modify the smell of something by just rotating some bonds.


texts: How does change in entropy influence the tendency of a reaction to occur?

texts: I know that entropy is the measure of the randomness of particles within a system, but how would it affect the tendency of the reaction? Would it just increase or decrease the chance of the reaction occurring, based on what change in enthalpy is?


texts: Does Wurtz-Fittig-reaction involves Sn1 or Sn2?

texts:
Following mechanism is commonly proposed for the Wurtz-Fittig-Reaction:

Picture from Wikipedia

The red marked reaction steps is a nucleophilic substitution (SN). I suppose that this is a SN1 reaction, with an intermediate carbocation, rather than a SN2 reaction. In my opinion the resulting carbocation is good enough stabilized throughout the aromatic ring and therefore SN1 should be preferred, moreover because of the steric hindrance of the aromatic ring.

Is this assumption right? Thanks a lot for your help.


texts: Catalytic poison in Pt catalysed manufacture of H2SO4

texts:
I came across a question that goes as:

  In manufacturing of sulfuric acid in presence of platinum catalyst, which metal impurity acts as a catalytic poison?

  Fe
  Cr
  Cu
  V

I searched everywhere I could but did not find anything that talks about this.
I read about $\ce{As2O3}$ being a catalytic poison in this reaction and recommendations for using the Contact process using $\ce{V2O5}$ instead of this reaction.

I can understand that this is more of a fact based question but reasons or explanation (if any) should please be included.


texts: When is it realistic to model diffusion without advection?

texts:
Brownian motion abounds in nature, but so does drift current.  In theoretical models of solutions and colloidal suspensions it is sometimes assumed that advection is negligible.  I'm wondering if this is a natural assumption to make, or if it is generally better (e.g. more informative, whether in a positive or negative sense) in settings where accuracy is desired to account for correlated motion owing to mesoscopic currents from the beginning.
This question is partly motivated by the following paradox (or non-paradox, as the case may be): correlated motion of solute and suspended particles from bulk currents is only irrelevant when the particles are near enough to a solid surface, like a porous material or substrate, for those currents to be negligible.  But no surface is perfectly rigid, and to some extent each exposed surface may act as an additional source of random current: could vibrations transmitted by the substrate introduce additional correlations in particle diffusion that depend on the substrate-solvent interface?
Finally, is it known to what extent hydrodynamic interactions between suspended particles account for drift induced by boundary fluctuations (e.g. deformations or perturbations to the container walls), or would these be better modeled as an independent source of randomness?
A related question would be, is it possible to reproduce Brownian dynamics with hydrodynamic correlations through a randomly fluctuating flow field? (and if so, to what extent should these fluctuations involve independent activity or spontaneous motion of the particles, i.e. as though they were pulled along by invisible forces, and to what extent should the particles be driven by currents that are induced by fluctuating boundary conditions?)
References:
Hydrodynamic coupling to a wall (i.e. effect of random currents on the diffusion tensor, both away from and near a perfectly rigid wall)
https://physics.nyu.edu/grierlab/leshouches2/node20.html
"Currents" induced by fluctuating surfaces:
https://www.scientificamerican.com/article/making-sound-waves/


texts: In the bicarbonate ion, why can the hydrogen not bond to the carbon?

texts:
I've been studying electrophiles and nucleophiles recently, including how the carbonate ion ($\ce{CO3^2-}$) is stabilised through resonance. While drawing the model for bicarbonate, however, I suddenly asked myself why a different design of this ion would not be possible. The design I am proposing features the hydrogen atom attached to the carbon, with single bonds for all of the three oxygens. This is shown below:

Now, I know that this is not what we usually see, which is:

The question is, why is my own design not feasible? If it is, is it not energetically favourable due to the numerous charges that would have to be created?


texts: Dead trees or charcoal is generally used as a reductant in the production of pure silicon for use in industry what other reductants could be used?

texts:
What other known reductants for SiO₂ could potentially be used for producing silicon from silica in an arc furnace?

Read more: http://www.madehow.com/Volume-6/Silicon.html#ixzz6uKynirns


texts: Are there any non-Jahn-Teller type distortions?

texts:
My question is essentially, if ANY gradual type of deviation from a higher possible symmetric arrangement of the nuclei in a molecule is covered by the Jahn-Teller model.

More specifically I have in mind some lets say "ionic complexes" between a very small cation and some larger (possibly weakly coordinating) anions.

Very specifically, I remember I have seen for example a calculated equilibrium structure of a beryllium bis-2-fluorobenzoate $\ce{(Be[o-C6H4FCOO]2}$, isomer with $\ce{F\bond{...}Be-O}$ coordination), which showed a distinct deviation from $\ce{C2}$ symmetry. The only type of JT-distortion this would qualify for is 2nd order one. But then since its largely an ionic species I suppose the HOMO-LUMO gap should be so large that 2nd order JT is very unlikely (I am aware that $\ce{C2}$ is not Jahn-Teller active but through vibronic coupling of close-lying $\ce{^2A}$ and $\ce{^2B}$ also JT-like distortions can occure).

I imagine that if the cation is very small so that it "dangles" in the gap between the anions it might be energetically more favourable if the cation decides to stick on one than to balance in the centre. Just a naive picture. But would such a thing - if it exists - be subsumed under JT as well?

So, is distortion possible for ionic aggregates and would such a thing also be described by JT?


texts: No indicator is suitable when titrating weak acid with weak alkali

texts:
This was a statement in my book:

A solution of a weak acid cannot be titrated with a weak base using an indicator to find
the end-point because the pH change is too gradual close to the equivalence point.

Could someone please elaborate the bold text.


texts: How to determine the equivalence point of a titration of a mixture.

texts:
Today, I'm graphing the titration curve for a mixture, to be precise, this particular case:

In order to get this done, i've been following wisely the mantra of "The strongest species (oxidizing and reducing agent determine the E(V)" and from there, I construct appropriately the Nerst Equation to suit the situation. This has given me positive results until the end point of Fe, where this doesn't seem to work for me.

At this point, my logic is the following; we have Fe3+, Ce3+, and Sn4+, and we don't have any complete redox pair. Given this, the stronger oxidizer is Fe3+, and the strongest (and only) reducing agent is Ce3+; However, when I try to calculate the weighted average for the E(V) associated to these species, the value obtained (1.2) isn't anywhere near 1.05, my theoretical value, but closer to the upper limit of E(V).

For me, it makes sense that it isn't 1.2V as there is another ion that lowers the potential, but I'm not really landing these ideas to determine the second end point nor the upper limit.

I'd appreciate any thoughts on this, thank you.


texts: How to identify the ratio of oxidation states in terbium ions in its mixed oxide?

texts:
Estimate the ratio of $\ce{Tb^3+}$ to $\ce{Tb^4+}$ in  $\ce{Tb_6O_11}$.

For my solution I knew that I had to get a sum of 22 positive charges from 6 $\ce{Tb^3+}$ and $\ce{Tb^4+}$ ions, so I just added different combinations until I found that $4(\ce{Tb^4+})+2(\ce{Tb^3+})$ gave me the desired value to have an overall neutral oxidation state on the molecule. This gives a $2:1$ ratio also. Is this the correct way to do this, or is there a more formal method?


texts: How could you accomplish the following transformation in sufficient yield?

texts: I've considered Riley oxidation but the major product would have a hydroxyl group at the benzylic carbon to the left of the double bond instead of the methyl group as shown. Is there a way to make the reaction favor oxidation of the methyl group?


texts: Why does SYBR green emit more signal when bound to DNA?

texts:
Principle of SYBR Green

  SYBR Green I (SG) is an asymmetrical cyanine dye used as a nucleic
  acid stain in molecular biology.

  (wiki)

This molecule is commonly used in qPCR to meassure the amount of double stranded DNA. The fluorescent dye SYBR Green I binds to the minor groove of the DNA double helix. In solution, the unbound dye exhibits very little fluorescence (left figure below), however, fluorescence is greatly enhanced upon DNA-binding (right figure below).

(image source)

Question
Although its common use I cannot figure out why SYBR green fluorescence more when bound to DNA.

*I first doubted whether I should have posted this on biology stackexchange due to its relevance in this field, however I think this question covers way more chemistry than biology.


texts: Is there a reason for all the bottles being 70% ethanol, or is it convention.


texts:
I know that when making a bond the reaction is exothermic (positive)
and breaking a bond the reaction is endothermic (negative).

Lattice enthalpy or lattice formation enthalpy is defined as the enthalpy of formation of 1 mole of an ionic compound from gaseous ions under standard conditions, which is endothermic (negative).

My question is ..
Why lattice formation is negative? It should be positive when making the ionic lattice because we are releasing energy.

Is bond making/breaking different than lattice making/breaking?


texts: Which is the most acidic proton of (3Z)-3-ethylidenecyclopent-1-ene-1-carbaldehyde?

texts: At first glance, I thought the most acidic protons would be the ones in red due to their proximity to the carbonyl. However, the answer key has the hydrogens in green as the most acidic. Can someone explain how that is? (I'm guessing resonance, but I need a more concrete explanation.)


texts:
My science teacher says that all ions are stable, which seems wrong to me.

For example $\ce{He^{-1}}$ is an unstable ion of helium, and although it might not exist in the real world, it is still technically an ion of helium. Is it right?


texts: How do I analyze 17 different gases from a sample?

texts:
I am designing a test setup in which I heat a battery until it releases its gases, and I need to analyze the composition of the fumes. Below is the list of gases that are believed to be present in the battery's fumes. I was planning on just using a bunch of gas detection tubes, but they don't seem to be available for all these gases. I was thinking about moving on to buying a gas chromatograph instead since, so far, it seems cheaper than getting a bunch of tests, but I have never used a GC, so I don't know if this would even work for so many gases.
If I were to go the GC route, what would I need to learn and buy in order to test for these gases? Is there a handbook that demonstrates the proper setups for different gases since I think you need to change some physical components for proper testing of different gases (I didn't find any)? Or is there a better method to test for this?


texts: How can I relate the conductivity (uS/cm) at various temperatures of an aqueous solution of NaCl with ionic strength?

texts: Can someone give the relationship between conductivity (uS/cm) with ionic strength please ? In some sources they that there is a linear relationship with a constant, but with no explanation to come up with it.


texts: How to interpret the activation energy calculated via the Arrhenius equation?

texts:
In solution phase, the activation energy of a reaction is usually determined through the study of kinetics and the Arrhenius equation. However, I am confused by the notation, and have trouble interpreting the Ea term, almost universally called "activation energy". Is it free energy? Or is it enthalpy?
This is important, because I want to compare some experimental and theoretical values and in the output of quantum chemistry software the differences between energy/enthalpy/free energy are quite clear, and I want to be sure that I compare the right ones.

So my question is:
The Ea calculated via the Arrhenius eq. is the enthalpy change going from the reactants to the transition state, or is it the free energy change?


texts:
Problem
   A synthesis of azetidine is shown below. Provide a mechanism for all the steps. Why does the formation of azetidine in the last step require high temperature?

My working is thus:

I am stuck on the last step and my version seems wrong. Can someone please guide me in the right direction?


texts: Is there any way to determine if the compound is oxide or peroxide or superoxide?

texts:
I know that in an oxide oxygen's oxidation number is $-2$, in a peroxide oxygen's oxidation number is $-1$ and in a superoxide oxygen's oxidation number is $-\frac12$. So, how will I be able to detect that any compound is oxide or peroxide or superoxide?

For example, to get the oxidation number of $\ce{Mn}$ in $\ce{KMnO4}$ how will I determine whether $\ce{KMnO4}$ is an oxide, superoxide or peroxide? Is there any way?


texts:
I'm trying to do Normal Mode Analysis for my MD trajectory. I'm following Amber tutorial (http://ambermd.org/tutorials/advanced/tutorial3/py_script/section5.htm) which uses an example of estrogen receptor protein and raloxifene ligand. Since I'm only getting errors from this, I'm having a couple of technical questions.

As for solvent, my system is explicitly solvated. Skjaerven et al. in J Mol Str: THEOCHEM 898 (2009) 42–48 claims as follows:

  "normal modes of proteins are most often calculated in the absence of solvent or with simple solvent models, as opposed to explicit solvent molecules in molecular dynamics simulations. (…) a common approximation is the absence of (explicit) solvent. Studies have shown that explicitly present water yields an increase in the density of local minima compared to vacuum simulations. In addition, water is found to increase the friction and amping on the atomic fluctuations."

Could NMA be used for proteins? I've heard an opinion that rigid rotor model used in NMA is not appropriate for proteins which are flexible.
The molecule in Amber tutorial example is a protein and it's solvated in explicit solvent (I think).

So, to conclude, how does it all make sense?


texts: Is this stoichiometric question answerable? (unknown variable)

texts:
This question kind of borders on the fields of both semantics and math, as well as chemistry, but I still believe this is the right place to ask.
On a test I took, a question was posed as such:

Via titration we are adding a solution of 25 ml, with 0.5 M NaOH, to 25 ml of HCl. What will the concentration of the acid be?

Now, this question seemed a bit strange to be, and it was definitely new. I'm used to calculating concentrations after dilution and other stoichiometric calculations, but this question seemed like a misworded version of those other questions I've grown familiar to.
So, I asked my teacher if she could clarify. First I asked whether the 25 ml of HCl was pure HCl, or a water solution with HCl in it. She said it was pure HCl. Then I asked if she was looking for the concentration of the acid before ANY reaction between the NaOH and the HCl had occured. To this, she also said yes.
The options were:

0.25 M
0.5 M
0.75 M
1 M

I answered 1 M, my reasoning being that 25 ml of HCl is the same volume as 25 ml of water with NaOH. Obviously, this reasoning is quite flawed, but I didn't have anything better. The answer was wrong. However, when my teacher told me what was meant by the question afterwards, her explanation did not align with the question, nor her previous clarifications. She said that this was a simple case of:

$$C_1 \times V_1 = C_2 \times V_2$$

Where $C_2$ was the unknown, since the concentration of HCl was not specified. I don't see how this makes sense. All the question is saying, is that there is a 25 ml container, with HCl in it. It doesn't even say that this 25 ml consists of a water solution with HCl in it, but a more knowledgeable chemist would've known that HCl cannot exist outside of a water solution (that's what my teacher said at least).
Then the the question says that 25 ml of water, with a concentration of 0.5 M of NaOH is added. And from those two values, I'm supposed to find the concentration of HCl. That basically means:

$0.025$ l of H$_2$O$ \times 0.5$ M NaOH(aq) $= 0.025$ l of water $\times x$ M HCl (aq)

Which would then make the answer 0.5 M. Maybe she wanted me two add the two volumes, which would make sense:

$0.025$ l of H$_2$O$ \times 0.5$ M NaOH(aq) $= 0.05$ l of water $\times x$ M HCl (aq)

Which would then make the answer 0.025, which wasn't even an option.
But even if it was, it still wouldn't make sense to me. Just because you have a solution with a given volume and an unknown concentration, adding another solution with a known volume AND concentration won't just magically let you know what the unknown concentration in the original solution is, now in this new solution. Or am I wrong?


texts: How to deal with exact numbers on error propagation?

texts:
In Analytical Chemistry, 7th edition by Christian et al., in its Example 3.10 (screenshot below; see blue circle for the main matter), when it computed for the standard deviation after getting the average of the three measurements, the authors further divided the standard deviation by 3 to get its absolute uncertainty.

However in its Example 3.12 (screenshot below; see blue circle for the main matter) it did not divide further the calculated standard deviation by 100 to get the absolute uncertainty, even though it's essentially the same operation as in Example 3.10. In addition, you can see in the price calculation near the end of the solution that he multiplied it too to the standard deviation to get the absolute uncertainty.

Of the two, which is the correct action for the error when dividing or multiplying with an exact number? If they're both wrong, or if they're both right and I'm just misinterpreting the concept, what is, then, the proper way to deal with this situation?

Follow-up question:

On the other hand, what should I do with the error when adding/subtracting a measured number from an exact number or vice-versa?


texts: Which of the compounds give the same SN1 and SN2 products?

texts:
Which of the following compounds give same SN1 and SN2 product?

I think (b) should be the answer, but the given answer is (c). I think so as it is the only compound where carbon is not chiral. While in others racemic mixture in SN1 and enantiomer in SN2 are formed, in (b) there is no question about this. Please tell me if I got it right.


texts: Nomenclature for two cyclohexane rings linked by a single bond

texts: From my current basic organic chemistry knowledge, I suppose it is 1,1-dimethylcyclohexane-4-methylhexane. I considered one of the hexane ring as parent chain. But I'm looking for the correct answer with appropriate explanation for it.


texts: What does the following sentence mean - "Li is least reactive but the strongest reducing agent among all alkali metals"

texts:
Isn't it contrasting? Is reactivity only concerned with kinetics of reaction ?

PS - I am a high school student, probably I might be missing small detail!


texts: Why does a Lower Concentration of SO2 call for an increase of equipment dimensions in a Contact Process Plant?

texts:
I'm working on a presentation based on an article about the Contact Process (production of sulfuric acid), and it says that using a low concentration of SO2 at the entrance of the converter (in which the oxidation of SO2 to SO3 takes place as an equilibrium reaction) is better in terms of conversion, but disadvantageous in that it would require using bigger plant equipment dimensions.

Why does using a lower concentration of SO2 require a higher volume of such equipment?

Wouldn't using more gas require more size?


texts: Will distillation do the job of purifying the water?

texts:
I asked about my sophisticated water purification system for a generation ship on Worldbuilding Stack Exchange, and somebody mentioned this:

  If you're gonna go to all the trouble of distilling it, why not just
  have that be your only step?

And it is a good question. But, from my chemistry knowledge, this just won't work. Here are the problems I see with distillation being the only step:

Proteins in blood and urine are going to froth up from the heat. If these get into the water, the water is going to smell like urine and nobody is going to want to drink it.

This is the easiest issue to fix. Just make the apparatus tall enough and no urine froth will make it to the distallate. That or adding a trap to react with the urine froth and solidify it in between the 2 ends of the apparatus would work.

Any hydrochloric acid that is present from vomit is still going to be there because it changes the boiling point of water. You simply can't get rid of the acid via distillation alone, not even repeated distillation. You need either microbes that can break down hydrochloric acid or an acid base reaction to get rid of the acid.

Hydrochloric acid forms an azeotrope with water. In fact it forms several depending on the acid concentration. So at some point, strongly acidic water will come over. Worst part is that a mixture of hydrochloric acid and water is colorless and odorless, so the only way you could tell is by density. Start to see those lines that occur when you mix liquids of different densities and you know strongly acidic water is coming over. Also, checking for pH would help but that would mean either an acid resistant pH sensor in the container with the distillate or stopping the distillation periodically and using pH strips. Checking for a change in density is much easier.

If acid vapors escape the system, as I think some will, then everybody on the ship will get irritated lungs, and some might get "Acid Pneumonia" and die from both the irritation due to the acid and the infection that the hot acid predisposes them to. There would be some infectious agents on the generation ship to keep their immune system in their prime and to help prevent autoimmune disorders from spreading like wildfire. But if this is combined with acid vapors, it is basically a death sentence for whoever gets infected. This is not even considering the fact that acid in your eyes can make you go blind

No distillation system can 100% prevent vapors from escaping. Not even a vacuum distillation with a trap will do it.

So in my opinion, distillation is necessary but can't be the only step, otherwise WCS, you get water that smells like urine that nobody wants to drink and hot acid vapors spread all over the ship causing lung irritation and blindness and everybody dies from a combination of the acid vapors and dehydration related both to heat and infection very quickly and you just have an empty hull in space. BCS, everybody gets heartburn from drinking the acidic water.

So, is there a way to get rid of the hydrochloric acid when distilling the water? Or would the people distilling the water have to resort to an acid base reaction followed by a second distillation to get rid of the acid and any excess base?


texts: Suppose I take three bases in a solution, $\ce{NaOH}$, $\ce{Na2CO3}$ and $\ce{NaHCO3}$, and I titrate this solution with $\ce{HCl}$. Since the strengths of the bases are different, does it mean that $\ce{HCl}$ would first react with the strongest base completely and then start reacting with the next strongest base?


texts: Is the transformation of pi bonds to sigma bonds always energetically favorable?

texts:
Is the move from pi bonds to sigma bonds always favorable?

My professor claims so, except in the case of conjugated pi bonds. I can see how pi bonds going to sigma bonds might be favorable; I know that double bonds are actually not twice as strong as single bonds because of poorer overlap ... but are there any exceptions to this guideline that the reduction of pi bonds to sigma bonds is favorable except in the case of conjugated systems?

EDIT: what about in the case of organic chemistry? It certainly seems that hydrogenation (a way of transforming pi bonds to sigma bonds) is generally a favorable move.


texts: Does a bulky nuclephile react faster by Michael or direct addition?

texts: Between Michael or direct addition on a $\alpha,\beta$-unsaturated ketone, I think that Michael addition is faster than the direct addition as the nucleophile can attack orthrogonally to the $\ce{C=C}$ which is a less hindered approach than the Bürgi-Dunitz angle required to attack the $\ce{C=O}$.


texts: Regioselective enolate formation, choosing major and minor products

texts:
This question came in my organic chem assignment. The options highlighted are the answers.
The end carbon(adjacent to the carbonyl group) should have more acidic alpha-hydrogen and the alkene formed is more substituted (as compared to the one in F). Still it is given as the minor product. Could someone explain why?


texts: What is the largest molecule (synthetic or natural) that isn't a polymer -- let's say, bigger than 3000 dalton?


texts: Diagonal relationships in the Periodic Table

texts:
I have often wondered about diagonal relationships between elements on the periodic table, and the most often cited explanations revolve around charge-density considerations.

But other than that, what other factors could possibly contribute to this phenomenon?

EDIT: What I mean by "diagonal relationships" is that there are certain similarities in chemical properties that have been observed in diagonally adjacent neighbors in the 2nd and 3rd period example: Li-Mg, Be-Al, and B-Si.

Link to a wikipedia article (not much to be found here though)

The explanation that I personally have most often encountered is that the  charge-to volume ratios (charge density), say for Li-Mg cations is roughly the same, and hence could account for some of the similarities in behaviors.

What I am looking for is what can be some other contributing factors (if any) to this phenomenon. I am not expecting very concrete answers because I believe this phenomenon is not very well understood.


texts: Comparing bond angles in carbonyl dichloride and carbonyl dibromide

texts:
Background
I was studying VSEPR and hybridization theory and one of the popular questions in many textbooks was comparison of bond angle of $\ce{NH3}$, $\ce{NF3}$ and $\ce{NCl3}$.
$\ce{NF3}$ had smaller bond angle as electrons were nearer to the more electronegative fluorine atom, thereby reducing bond pair - bond pair repulsion (of N-F bonds) and thus allowing contraction of bond angle.
Further, in $\ce{NCl3}$ bond angle was larger than both $\ce{NH3}$ and $\ce{NF3}$ due to steric repulsion between large Cl atoms. So the order was $\ce{NCl3}$>$\ce{NH3}$>$\ce{NF3}$.
Now, a question that I later saw in one of my textbooks was the analysis of bond angles of $\ce{COCl2}$ and $\ce{$\ce{COBr2}$}$, which have trigonal planar geometry. According to my textbook, $\ce{COCl2}$ has smaller $\ce{O-C-Cl}$ angle, less than $\mathrm{120^{\circ}}$, (and thereby greater $\ce{Cl-C-Cl}$ angle). The angles for $\ce{COBr2}$ were not given.
My Approach
Now if we apply the reasoning given for $\ce{NCl3}$ and $\ce{NH3}$, $\ce{NF3}$ in this question comparing $\ce{COCl2}$ and $\ce{COBr2}$, we would find that the $\ce{C-X}$ bond pair electrons would be more polarized towards X, if X is Cl, and thus analogously to $\ce{NF3}$, it should contract leading to a smaller bond angle than in $\ce{COBr2}$.
Also, due to steric repulsion, $\ce{C-X}$ bond angle in $\ce{COBr2}$ should be greater than $\ce{COCl2}$.
Solution given in the book
The author has stated that there are four electrons in the $\ce{C-O}$ bond
Thus, bond pair repulsion between electrons of $\ce{C-O}$ bond and $\ce{C-X}$ bond would be much greater than any repulsion between the electrons of the $\ce{C-X}$ bonds.
As electrons in the $\ce{C-X}$ bond would be closer to carbon atom (and thus $\ce{C-O}$ bond pair electrons) in $\ce{COBr2}$, therefore a greater amount of repulsion would be present between them. This repulsion would lead to contraction of Br-C-Br bond angle leading to an angle less than that of $\ce{COCl2}$.
However, no data was provided in support or against it. Also no reasoning was given why they would be greater or less than $\mathrm{120^{\circ}}$, only the above reasoning for comparing the bond angle was provided.
I have not been able to find any bond angle data. My teachers are also not sure. Also, the textbook I referred to is infamous for having lots of errors.
Which reasoning is correct, or is it something else entirely?
What is the actual data?


texts: Which of the following species has an enthalpy change of formation = 0 kJ/mol?

texts:
Below was a question in the 2012 Australian Chemistry Olympiads:

  The enthalpy change of formation ($\Delta_\mathrm{f}H^\circ$) for a species at
  $\pu{298 K}$ is defined as the enthalpy change that accompanies the
  formation of one of the following of one mole of a substance from its
  constituent elements in their standard states. Which of the following
  species has $\Delta_\mathrm{f}H^\circ = \pu{0 kJ/mol}$?

  a. $\ce{H2O(l)}$  b. $\ce{Na(g)}$  c. $\ce{Na(s)}$  d.
  $\ce{CO2(g)}$  e. $\ce{O3(g)}$

Original

Solutions stated the answer is b, but isn't the standard state of $\ce{Na}$ solid?


texts: What is the literature value of the activation energy of the reaction between iodate and bisulfite?

texts: I explored the Arrhenius equation using the reaction between potassium iodate (containing the IO3- iodate ion) and sodium metabisulfite (bisulfite ion), however I can't find a literature value to draw a comparison. I was wondering if anyone had the lterature value for this particular reaction's activation energy?


texts: Why does the pressure equilibrium constant exist?

texts:
Since $K_c$ can already be used for calculating the equilibrium constant for a reaction involving gases, but $K_p$ cannot be used for calculating the equilibrium constant for a reaction involving aqueous solutions, what is the use for $K_p$?

It doesn't seem like there is ever a situation where $K_c$ cannot be used and $K_p$ must be used, especially since partial pressures can be readily converted to concentration through the ideal gas law. If anything, it just seems like the existence of two equilibrium constants that more often than not don't equal each other could cause more confusion.

Thoughts?


texts: Which has hotter temperature, blue flame or yellow flame?


texts: Why does the pH before the equivalence point of a titration depend on the initial concentration only when the acid is strong?

texts: SO, in this picture, two different titration curves are shown: one for a weak acid, one for a strong acid. I'm confused as to why for a strong acid, if you vary the concentration of the acid, (and the concentration of the acid and titrant are the same) the pH lines are spread apart below the equivalence point, but for a weak acid, where the pHs are initially slightly different, the lines converge to a common path


texts:
From the Wikipedia article on dimedone,

  Dimedone is prepared from mesityl oxide and diethyl malonate.

I can't really figure out the mechanism for the reaction. Could someone please help me out?


texts: What happens to the t-butyl cation in the TFA deprotection of a t-butyl ester?

texts:
I am a first-year chemistry graduate student and I am currently learning how to synthesize proteins. I have reached a stage in the process where I need to deprotect a carboxylic acid moiety protected by t-butyl using trifluoroacetic acid (TFA).
I went online trying to find the mechanism for this step, but in terms of step-wise mechanism with electron movement arrows, the only thing I was able to find was this:

(Taken from here, no references therein)

While this looks legit, I am wondering about the t-butyl cation and its fate.
My reaction is a bit simpler, and is presented below:

And my question is: is this truly where the deprotection ends? Does the t-butyl cation remains in solution as pictured?

(I know that a t-butyl cation is considered to be relatively stable on account of it being a tertiary carbocation, but still I was not sure that it can remain in solution like that.)


texts: Stabilization of multiple bonds through inductive effects

texts:
In the conversion of m-chloroanisole to m-anisidine using $\ce{NaNH2}$ and liquid $\ce{NH3}$, apparently the reason the $\ce{NH2-}$ goes for the meta- position instead of the para position is that, in the reaction mechanism for the conversion to m-anisidine, the benzyne intermediate involved has the triple bond closer to the $\ce{-OCH3}$ group than in the reaction to the para product, thus stabilizing the intermediate due to the stronger inductive effects of $\ce{-OCH3}$.
I know the triple bond in benzyne isn't exactly your typical triple bond, but is there always some(if negligible) stabilization of all multiple bonds through electron-withdrawing inductive effects?


texts: Quantifying CO2 generated/released by the soft drink industry and breweries

texts:
I need some help in developing a method by which to calculate how many tons of "evil" $\ce{CO2}$ are routinely being released into the atmosphere SOLELY due to our beverage addictions, notably beer and soft drinks.  I realize that not all manufacturers and products are consistent in their carbonation levels, and that an average probably has to be applied industry-wide (unless individual companies are required to record and publish such data) per unit measure or monthly/annual volume output.

Is this the proper forum to ask such a question?  If not, suggestions on where else I go?

On a previous post I got part of the answer, relating to an individual 12 oz can, or 1 liter, but I'm wondering if there is an easier way in which I can go about plugging weekly, monthly or annual volumes of beverages into formulas which will yield the results I'm looking for, notably a discussable unit of measurement in tons or ?  I'm willing to do all the numbers work once I'm pointed in the right direction.

I'm not sure if anybody's ever thought about this before, because I've never heard it discussed.  But if, according to some environmentalists, we should all watch our carbon footprint (and I'm not debating that here), then it seems like the most logical place to start would be with our hundreds of millions of daily beverage choices?  Isn't it?


texts: Rutherford's Alpha Ray Scattering Experiment & Plum-Pudding Model

texts:
My teacher said, "Rutherford thought that all the Alpha particles would directly go through the gold foil without any collision if the plum pudding model was right. Because, as said in plum pudding model, positive charges are arranged in a balanced way in the atom with electrons like plum in pudding. As there is no densely accumulated charge in the center, so the Alpha particle will not deviate by anything."
But two question raised on my mind.

Is my teacher right?
If not, then why?
If yes, then why evenly accumulated positive charge will not deviate the Alpha rays? I mean, when the alpha ray will come near to the pudding like positive charges, it should deviate more sooner nah? Moreover, as there are evenly arranged positive charges, so, no empty space is in the atom. So, no alpha particles would come across the foil. Is my assumption true if thought from plum pudding model?


texts: How to extract force constants for normal modes from ORCA?

texts:
I am following the computational method described in Scientific Reports.[1] Where the authors analyze the contribution of each excited state normal-modes to the shift of the transition energy. For this calculation they use the force constants of each normal mode.
I am using ORCA but could not understand how to generate the force constants. I did find that the orca_vib program generates force constants, but I did not find how to use the output to generate a force constant for the specific normal modes.

I also found this question,[2] I am not sure if it solves my problem. I saw the great answer by Jan Jensen who following the equation: $$\tilde{\nu}=\sqrt{k_i^{\prime\prime}}/(2\pi \times 137 \times 5.29\times 10^{-9}).$$
Do I just need to plug in my vibrational frequencies and rearrange the equation to get $k$?

References:

Schweighöfer, F.; Dworak, L.; Braun, M.; Zastrow, M.; Wahl, J.; Burghardt, I.; Rück-Braun, K.; Wachtveitl, J. Vibrational coherence transfer in an electronically decoupled molecular dyad. Sci. Rep. 2015, 5 (1), No. 9368. DOI: 10.1038/srep09368.
How to calculate wavenumbers of normal modes from the eigenvalues of the Cartesian force constant matrix?


texts: Ring expansion from a given cyclic carbocation

texts:
How will the cyclobutane ring behave in the case of cyclobutylmethylium (cyclobutylmethyl cation)?

I initially thought there would be ring expansion to a five membered ring so that there may be less angle strain and a secondary carbocation instead of a primary one. But I have also been told that there will be ring contraction for stability purposes. I would be highly obliged if someone could explain the mechanism involved here.


texts: How can absolute binding free energies be calculated?

texts: In the calculation of binding free energies, such as between a protein and a ligand, I learned that absolute values cannot be obtained from simulation (such as taught in this lecture, slide 2). Rather, with the appropriate reference state, only relative free energies can be calculated. However, there are a number of papers that discuss calculations of absolute free energies (ex. recent JACS paper). What does this mean? Are the absolute values--even among different papers--using some kind of general reference state?


texts: When you are going to burn magnesium you need to wait a few seconds before it actually starts to burn. To get to this point it needs a certain amount of energy/heat. How much does it need?


texts:
Spin magnetic moment of a octahedral complex having CFSE = $– 0.8∆$ and surrounded by weak field ligands can be:
A. $\sqrt{15} \space \mu_B$
B. $\sqrt{8} \space \mu_B$
C. (A) & (B) both
D. None of the above

The CFSE value given in the above question corresponds to only $d^2$ configuration for weak field ligands. Hence, according to me, the value of spin magnetic moment should be only $\sqrt{8} \space \mu_B$.
For the answer to be $\sqrt{15} \space \mu_B$, the configuration would have to be $d^7$ requiring the CFSE value given in the question to have an additional 2P(twice of pairing energy) but that is not the case.
Hence answer should be option (B) but the source of the question says that the answer is option (C).
I am unable to understand the consideration of both $d^2$ and $d^7$ configurations.
Can anyone please explain?


texts: Isopropyl Alcohol Vs Acetone for Dissolving Organic Contaminants on PCB

texts: Acetone is widely used in the labs as a solvent to clean the vials and tubes as it is good solvent for organic materials. While Isopropyl alcohol is used as a rubbing alcohol for cleaning contaminants on the body before injection. Both are good solvents for organic materials. I would like to know which one is more suitable for cleaning the organic contaminants on the PCB's (Printed Circuit Board) with minimal residue?


texts: If gases turn into liquids under pressure, what does carbon dioxide turn into?

texts: Since there is no liquid state of carbon dioxide, what will carbon dioxide turn into when exposed to high pressure?


texts: How to determine number of structural isomers?

texts:
I have come across many questions where I'm asked to give the number of possible structural isomers. For example number, structural isomers of hexane is 5, while the number structural isomers of decane is 75.

How can I determine the possible number of structural isomers of a given organic compound?


texts: Predict the product of reaction of quinone and hydrochloric acid

texts:
This is the question:

And this is my solution:

In the last step, I have tautomerised, and in the second last step, there is no double bond between carbon attached with Cl and OH (just some cutout work)

The answer given is B, but my answer comes out to be C.


texts: I heard aluminium doesn't produce fumes when burnt but the opposite happened, how?

texts: One day I took aluminium foil(sanitary brand,  don't know if you've  heard it)  then I casually burned it over  a gas lighter then it burned and gave off Grey fumes and the foil became a dull Grey where it had burnt.  I mistakenly may have inhaled a bit of fumes.  I had a slight pain in my right nostril the whole day. How is that?  Is that dangerous?


texts: How do I make PDB 1HIG's data usable for producing ball-and-stick models?

texts:
PDB: 1HIG, when opened using Accelrys DS Visualizer, Avogadro and Jmol produces a series of dots in space and cannot be displayed as 3D ball and stick models. Is there any way to overcome this problem?

This is the output from Accelrys DS Visualizer 4.0:

This is the output of Avogadro:

This is the output of Jmol:


texts: Why do the trends in reactivity not apply for francium?

texts:
Why is francium not included in the reactivity series?

Why is potassium considered more reactive than francium?

I know that reactivity increases down the group, but why does it not apply here?


texts: Dehydration of carboxylic acids with phosphoric acid

texts:
To find Z one must find X. Finding Y is of no use to find Z.

I get X as:

After addition of $\ce{H2/Pd-C}$, the unsaturated portion becomes saturated and the carboxylic acid remains unchanged.

However I am unsure what does $\ce{H3PO4}$ do to this (new) carboxylic acid? I was unable to find any information. I did find information regarding dehydration with $\ce{P2O5}$, but unsure what to make use out of it.

After looking at (unofficial/3rd party) solutions, I saw that $\ce{H3PO4}$ protonates the $\ce{-OH}$ part of the carboxylic acid (since it is a much stronger acid than the organic acid?) then $\ce{H2O}$ leaves, rendering a carbo-cation at the carbonyl carbon, followed by EAS at the ring.

However, I do not see how $\ce{H3PO4}$ exactly works with the carboxylic acid. I have merely guessed that the $\ce{-OH}$ portion gets protonated (since, this was the only thing I predicted would happen). I really do not know why this happens and how it happens.

Hints and reference material or examples would be appreciated.

The original question is taken from the JEE (Advanced) [2018] Paper-1.


texts: Why does the size of hybrid orbitals vary as sp³>sp²>sp?

texts:
In my text book it said that

  Size of hybrid orbitals vary as sp³>sp²>sp

Does this size variation in hybid orbitals means that S orbitals are smaller than P orbitals?

But we know that larger the quantum number "n" is, the larger the orbital. I guess it has nothing to do with type of orbital.

What could be the reason for this variation in sizes?


texts: How can I make a better whiteboard cleaning solution?

texts:
I just started work as a lab assistant in a chem lab. The whiteboard the instructor uses for classes gets very dirty very quickly. The woman who started at the same time as I did spent over 3 hours scrubbing it with a solution of a powdered soap-like product in a milk-carton style container to get it anything like clean.

I'd rather not watch her do that again (or, worse, do it myself). Can I make a better cleaning agent without using too much of an expensive chemical?

So far  I've seen large quantities of Ethanol, Acetone, Alcohol, and milliQ water. What else we may have, you folks would probably know better than I.


texts:
What does cell walls mean in the context of lath martensite? Are they grain boundaries?

Quote (page 66 Structure and properties of engineering alloys - Smith): In the lath martensite of low-carbon steels, there is a high density of individual dislocations and many cell walls.

Sorry for the stupid question, I don't find any image to understand it.

Thank you for your time.


texts: Mechanism for acid-catalyzed dehydration of 2,3-dimethylcyclopentanol

texts:
How do you get from 2,3-dimethylcyclopentanol to 1,2-dimethylcyclopent-1-ene?

I know the -OH group leaves as water (being protonated by acid) forming a carbocation. Then the weak nucleophile (water) attacks the beta-hydrogen to form what I think is 2,3-dimethylcyclopent-1-ene. But why is it 1,2-dimethylcyclopent-1-ene?

I know Zaitsev's rule wants the more substituted alkene, but forming the 1,2-dimethylcyclopent-1-ene would leave the carbocation hanging there, wouldn't it (the carbocation would still be unsatisfied)?

Update:


texts: Is zero-point vibrational energy an intensive or extensive property?

texts:
The zero-point vibrational energy (ZPVE) is the non-zero amount of non-electronic energy that molecules have even at zero kelvin and is purely quantum mechanical in nature. For a molecule with $c$ countable normal modes, it is defined as

$$
E_{\text{ZPVE}} = \frac{1}{2} \hbar \sum_{c} \omega_{c}
$$

where $\omega_{c}$ is the energy or frequency of each normal mode.

Intensive and extensive variables have always confused me. This reference gives the following concise bulleted definition:

  Extensive:

  Additive
  State variables (only sometimes)

  Intensive:

  Not additive
  Field variables
  Point variables (i.e., same at each point in a system at equilibrium)

with further examples of each (also on Wikipedia):

  Extensive: $Q$, $W$, $U$ (and other free energies), $N$, $V$, $M$, $C$, $n$
  Intensive: $P$, $T$, $\mu$, $\xi$ (electric field), any field variable, ratio of extensive/extensive

To use an example, the total energy of a system is extensive. If I have one molecule of caffeine, calculate $U$, and then take two caffeine molecules (even at infinite separation), and calculate $U$, they'll be different.

Now consider the ZPVE. For a nonlinear molecular system, there are $3N-6$ normal modes, where $N$ is the number of atoms. Take caffeine again, which has 24 atoms. There are 66 normal modes for one molecule and 138 for two molecules. If the ZPVE is considered to be a bulk or macroscopic property, then clearly it increases as the total number of normal modes increases, independent of whether or not the resulting normal modes are localized to one molecule. If the ZPVE is considered to be a single-molecule property (I hesitate to call it microscopic), then a single molecule is a single molecule, and it would make sense to "isolate" it in a way that doesn't make sense for other properties; that is, it doesn't make sense to only consider the temperature of a single molecule assumed to be in isolation that would in fact be part of some bulk phase.

So, perhaps a better wording of the question is: is ZPVE a microscopic (ugh) or macroscopic quantity? A property like polarizability also exists in a weird gray area for me as well.


texts:
On what basis can the SRP value of different elements in the periodic table be explained?
For example why does Cu have a greater tendency to accept an electron and Zn have a tendency to lose electrons in a Daniel cell?


texts: The Health Effects of Alkaline Ionized Water?

texts:
I came across alkaline ionized water as my aunts bought a system called Kangen Water from Enagic Inc. The water produced by this system is claimed to contain smaller water clusters (4-6 molecules) compared to tap water with 10-12 molecules. Besides, the ORP (Oxidation Reduction Potential) of the water is negative (-250 to -350 mV), which the company claimed to battle ROS (Reactive Oxygen Species). Of course, the company also advertised the water as having other incredible properties such as emulsifying grease, thereby can be used to remove pesticides on fruits and vegetables.

So, let alone the validity of the claim on benefits, my questions are:

How can one produce negative-ORP water? Is it possible to do so with added minerals? (Just the only way I can think of, is there any other way?)
What chemical/physical process is happening in the emulsification demo? Why can't tap water do so?

Please refrain from discrediting the company too quickly as I think I might have and please tell me if I formulated my question clearly enough because I acknowledge this is a fairly vague question.


texts: Influence of protic and aprotic solvents on SN reactions

texts: How does protic and aprotic solvents influence reaction mechanism considering SN1 vs SN2?


texts: Finding/Calculating Thermal Conductivity of Magnesite

texts: Our research group is having a very difficult time locating anything about the thermal conductivity of $\ce{MgCO3}$. It is a pretty commonly mineral, so we were pretty surprised by this. Is any way to derive thermal conductivity from other properties of magnesium carbonate? (Magnesite)


texts: Why do other sugars melt whereas sucrose decomposes?

texts:
Sucrose decomposes at 186 °C. It doesn’t melt but when it reaches decomposition temperature, sucrose decomposes into fructose and glucose.

After cooling and hardening it is no longer sucrose. Am I right?


texts: Bleach turned towel bright pink before fading to white

texts: We have some relatively new white towels that were getting dirty, so we decided to clean them with bleach (standard Clorox). When we sprayed the diluted bleach on the towels they immediately turned bright purplish pink, but the color faded back to white within seconds. We initially thought it was somehow transferring color from the pink nozzle on the spray bottle, but we noticed the same effect when the diluted bleach was poured directly onto the towels. No harm appears to be done, but what would cause the towel to turn pink, especially since it fades almost immediately?


texts: I am confused as to how an order of a reactant (n or m) in the rate law can be negative. This means that increasing the concentration of a reactant would actually decrease its rate of disappearance. How does this make sense? Doesn't a higher concentration always allow for more collisions? Also, when the order is 0, this means that concentration has no effect on the rate of disappearance. How does this make sense chemically/at the atomic level?


texts: How does electrophoretic separation work in terms of separating soil into minerals?

texts:
I found this diagram and would like to know how it works with soil.

Google searches yield protein/biology things, anyone know how this method would work with soil?


texts: Order of priority for including functional groups in the parent chain compared to order of priority for numbering the parent chain

texts:
The following is about the IUPAC naming system.

So as far as I understand the rules for numbering a chain are as follows:
Compare the locants of functional group 1 in both cases if the are lower in one of them it wins. Compare the locants of functional group 2 in both cases if the are lower in one of them it wins. And so on for all functional groups in order of priority. And then in the end we compare the locants for all substituents in alphabetical order.

But the rules for choosing a parent chain are the same, except we firstly want to maximize its length and after that we want to maximize the number of functional group 1s, functional group 2s and so on. And after that we want to minimize the locants for functional group 1, functional group 2 and so on until any of them is better. I am not sure what we do after that though.

My main 2 questions are the following:

Is the ordering of the functional groups the same for all 3 steps (maximizing the number of functional groups in the parent chain, picking a parent chain with minimized locants of the the functional groups, and then the same but for directing it)?

Where can I find the ordering of all functional groups or at least the following functional groups: alkyl (are alkylidenes in the same category as alkyls?), halogen, OH, double bond, triple bond, and  NO2?

And I know that sometimes two or more of these are grouped together in a set (for example double and triple bonds) so an ordered list of these is not enough.

Can you please provide something like (Set of double and triple bonds)>(double bonds)>alkyls but for all of the listed? If not where can I find such a thing?

Please tell me if any of that is wrong.


texts: General justification for steady state approximation

texts:
I want to understand the assumptions that have to be fulfilled in order for the steady state approximation to work. I did some research myself and was able to deduce assumptions of the form $k_1\gg k_2$ for some systems, by solving the system exactly and taking the limiting case in which the exact system reduces to the approximative system. (Later I found this answer doing the same thing Meaning of steady state (kinetics)) This approach will not work for most systems though, as no closed exact solution exists for most non-linear differential equation systems.

I want to develop a clear chemical intuition in which case it is justified to use the approximation. Most literature seems to just tell the reader that it's fine to use the approximation in the reaction thats discussed. This is unsatisfying. From a mathematical standpoint this approximation is all but trivial.


texts: When I burn isopropyl alcohol (IPA), it burns orange. But when I burn ethyl alcohol, it burns totally blue. Why is this?

texts:
I burned them in a small aluminium tray. While IPA is burning orange, it produced the smell of soot, but while ethanol is burning blue there isn't any smell.

Also, ethanol made the tray really cold when I poured it on the tray before burning it, compared to isopropyl alcohol. How can this be explained?

Note: IPA concentration is 99%, Ethanol is 97%


texts: Frequency Factor of the Arrhenius Equation

texts:
The question came to my mind as to whether the effect of a catalyst on a reaction included the modification of the frequency factor (or pre-exponential factor) of a reaction, shown in Arrhenius' Equation below as "$A$":
$$ k = A\exp{\left(\frac{-E_\mathrm{a}}{RT}\right)}$$
On the one hand, we know that catalysts reduce the activation energy of a reaction, thus enabling more particles of reactants to acquire the minimum energy needed to break bonds and form products, therefore speeding up the reaction. But, does the frequency factor stay the same? My guess is that it does, and the effect of the catalysis is manifested solely on the change in activation energy. My question is if this intuition is correct and, if so, why.
Maybe it would help if someone could give a little more insight into the actual meaning of the frequency factor. Is it constant a constant specific to each reaction? What does it represent?
Thanks!


texts: Why are halogens base sensitive groups (Wolff-Kishner Reduction)?

texts:
So while studying about Wolff-Kishner reduction reaction to form alkanes from carbonyl groups. I read that it is not suitable for base sensitive groups as the environment is highly basic and as an example the following reaction was given:

Now the desired product that should've formed is

But this doesn't happen as -Cl is a base sensitive group and so reacts with KOH. But how can a halogen be base sensitive when it already  has 7 e- and is highly electronegative? How is it possible for it to react with OH-?
Also, I don't understand the reaction mechanism of this reaction so can someone please explain how this takes place?


texts: How can I make a reference humidity environment with NaOH pellets?

texts:
I have NaOH pellets at my disposal. Some of the pellets are degraded, but most are not, and I can provide a new batch if needed.

I would like to test several humidity sensors in an environment with a humidity value around 10%. NaOH should be able to reach about 7% humidity when pure.

How should I proceed? I have tupperware and a stone mortar and pestle, if needed.

Should I take some good pellets, crush them without making them too fine, and place the resulting powder in a container, which I will enclose in the tupperware together with the sensors? or should I place the pellets in water but leaving the solution oversaturated (undissolved pellets visible in the water)?

The pellets would probably have a much higher contact surface with air, but time is not an issue, I can leave the sensors in the container for a day, if needed. Accuracy of the result is more important.

I can tolerate 2-3% errors.


texts: Electrode potential for metal-metal ion and metal-metal insoluble salt-salt ion electrode

texts:
So I read it in a book that

The potential of metal-metal ion electrode and metal-metal insoluble salt-salt anion electrode is same while their standard potentials are not same. Standard potential are related by the following equation:
$$E^\circ_{\ce{X-/MX/M}} = E^\circ_{\ce{M+/M}} + \frac{2.303RT}{F}\log_{10}K_\mathrm{sp}$$

My question is that $E^\circ$ is just the potential at some given standard condition, i.e. 1 bar and 25 °C, but when $E$ is same for both at all other conditions, why is it that it is not valid for the standard  particular case/condition?


texts: Is it possible to calculate electrostatic interactions using QM methods?

texts:
I'm trying to calculate an accurate electrostatic repulsion (and possibly attraction) energy term for various small molecules, using Quantum Mechanics (QM) methods. These may include molecules such as bifuran, bipyridine, etc... I'm mainly interested in, for example, the electrostatic interaction energy of the two oxygens in a bifuran.

I've already tried using Molecular Mechanics-based methods, which use point charges (ie. GAFF charges) but they seem to be unable to account for the nuance orbital interactions, especially when molecules are in close contact. I was wondering if there exists a robust QM method, which is able to give accurate electrostatic interaction energies for molecules?


texts:
I have three factors in mind:

1) vdW repulsions

2) Bond length

3) Electron-electron repulsions.

I know that vdW repulsions between ligand atoms push the atoms apart. And bond length obviously influences bond angle; if the bonds were very long, then the bond angle can shrink without bringing the ligand atoms too close together.

Are there any other factors or are these it?


texts: Does the current of an electrolytic cell increase if the surface area of the Cathode is increased

texts: I am currently in high school and will be conducting an experiment looking at the effect of surface area on electroplating. I will be changing the surface area of the Cathode during my experiment but am unsure whether the amp and voltage would be controlled or dependant variables.


texts:
I'm doing some statisitcal research and I have come across an acronym for a chemical. I have tried googling it but it comes up with very little and I can't find the name.
I only have HMOBA. Can anyone tell me what this stands for?


texts: Could we bond hydrogen to the edges of covalent network structures like diamond?

texts: I know that diamond is just carbon atoms structured in a way that differs from graphite and charcoal. The carbon atoms on the edges do not have full valence shells. Would it be possible to attach hydrogen atoms (or other elements) to complete these shells? And if this is possible, would it change the properties of the diamond?


texts: Do pipettes always outclass glass syringes?

texts:
I was previously working in a lab preparing lots of samples for gas chromatography that exclusively used glass pipettes and was able to get really high precision between replicates. Now I'm working on my own project doing a lot of liquid dilutions that need to be very accurate with an older pipette that I am looking to potentially replace for better results. I'm specifically looking at 1 mL volumes.
Tolerances for glass syringes seem to be about +/-1% (not as much info), where pipettes are +/-0.6% accuracy and +/-0.2% precision. There were definitely some other reasons to use syringes vs pipettes at my old lab, but are syringes really always outclassed by pipettes? Can an experienced syringe operator beat a pipette?
I realize tip choice, needle, calibration, and ambient temperature controls probably have larger effects than these differences (though seemingly favor syringes), so I am wondering more about the relative optimal performance of each.


texts:
The wikipedia article on nitric acid mentions the following structure of $\ce{HNO3}$ in which the two $\ce{N-O}$ bonds (other than that of $\ce{N-OH}$) are of different length i.e.,  $119.9\,\pu{pm}$ and $121.1\,\pu{pm}$.

But it also mentions that $\ce{HNO3}$  molecule is a resonance hybrid of - (only major contributing ones)

I can't understand how can both be simultaneously correct since the resonance hydrid should have same two $\ce{N-O}$ bond lengths (other than $\ce{N-OH}$ one). How is it correct or is the source itself wrong?


texts: Why is silver nitrate used for cyanide titration?

texts:
Or more to the point, since silver isn't exactly cheap: Why can't cuprous nitrate ($\ce{CuNO3}$) substitute for the pricier ($\ce{AgNO3}$) in cyanide titration?

I assume that free cyanides bind eagerly with all Group 9-11 metals, since they're used industrially to leach the heavier ones.

I'm guessing that there's something relatively quirky about the Period 4 metals Co, Ni, and Cu that prevents their use as a titrant of aqueous cyanide: E.g., it appears that nickel nitrates are very hygroscopic.


texts: What concentration of sulfur hexafluoride is safe to inhale

texts: I want to do a density demonstration, and I want to inhale helium and sulfur hexafluoride as a fun demonstration. I am open to using any source to purchase from, and money is not an issue (but preferably as inexpensive as possible), but what concentration should I buy (what concentration is safe to inhale), and from where?


texts: What changes occur when adding differing amounts of acids & bases?

texts:
In an experiment, $\pu{5 cm^3}$ of $\pu{1 mol/dm^3}$ sodium
  hydroxide are gradually added to $\pu{10 cm^3}$ of $\pu{1 mol/dm^3}$ hydrochloric acid containing methyl orange. What changes occur in the mixture?

  The concentration of $\ce{H+}$ ions increase (decreases)
  The methyl orange changes colour
  More water molecules are formed (water is formed, but use of the word 'more'??)
  A precipitate is formed (no ppt formed, $\ce{NaCl}$ is soluble)

I thought the answer would be (2). However when thinking about the question the methyl orange would be red in the acid and given the proportions of the reactants and the 1:1 mole ratio, the $\ce{HCl}$ would be in excess, so would it still change colour?


texts: A chamber to control concentration of a vapor: Is there a name for this equipment?

texts:
Mechanical engineer here so please excuse me if my question seems dumb to you!

I want to have a chamber $(\approx 40 \times 30 \times \pu{30 cm})$ to control concentration $(\pu{ppm})$ of a flammable material (e.g. alcohols or ketones) at a specific temperature $(T\approx \pu{24 \pm 10 ^\circ C})$ and pressure $(P\approx \pu{1 \pm 0.5 bar})$

What should this chamber be called? I need the the name to be able to search for it and also mention in my publication.

Candidate names so far:

Incubator --> mostly for biological entities
Reactor
Environmental chamber --> too expensive
Atmospheric controlled chamber
Autoclave --> for sterilization(high temperature/pressure)
Flash drum
Vapor inhalation chambers --> for animal testing

P.S. I have posted the question also on Reddit here and here. There are some good points mentioned there.


texts: Calculate molecular orbitals of high-lying or Rydberg states in GAMESS (US)

texts:
I am trying to calculate the high-lying or Rydberg orbitals (i.e. unoccupied orbitals with their energies just below the ionization energy) of a nitrogen molecule.
I use GAMESS(US) with the following input file.

!   File created by the GAMESS Input Deck Generator Plugin for Avogadro
 $BASIS GBASIS=N311 NDFUNC=3 NFFUNC=0 NPFUNC=3 DIFFSP=.TRUE.
 NGAUSS=6 DIFFS=.TRUE. $END
 $CONTRL SCFTYP=RHF RUNTYP=ENERGY DFTTYP=SLATER MAXIT=99 $END
 $SYSTEM TIMLIM=1440 MWORDS=500 $END

 $DATA
Title
C1
N     7.0     0.00000     0.00000     0.00000
N     7.0     0.00000     0.00000     1.12001
 $END

The output file contains 70 orbitals, but the high-lying orbitals seem to have too big energy.
For example, LUMO+62 has 42.8618 Hartree (or 1166 eV), which is far above the ionization energy of a nitrogen molecule.
How can I correctly get the high-lying or Rydberg orbitals?


texts: The carbon is $\mathrm{sp^2}$ hybridised and is therefore planar and should also, theoretically be $120^\circ$. However, VSEPR theory suggests that the π bond would "need more space" due to greater electron repulsion. As a consequence the $\ce{H-C-H}$ bond angle would be smaller. However, since the π bond is out of the plane of the molecule does this actually happen?


texts: How is the hydrazone formed in the Wolff-Kishner reduction?

texts:
In the Wolff-Kishner reduction the first step is to react a carbonyl with hydrazine to form a hydrazone. The later steps of the reaction requires a strong base to cause loss of nitrogen.
However, the mechanism for the formation of the imine/hydrazone is acid catalyzed:

Wikipedia mentions that the formation of the hydrazone is typically done in situ.  So how does the formation of the hydrazone occur in basic conditions?
References:

https://www.organic-chemistry.org/namedreactions/wolff-kishner-reduction.shtm
https://en.wikipedia.org/wiki/Wolff–Kishner_reduction


texts: Why only two atoms share an electron and not three?

texts:
In a covalent bond between two atoms, an electron from one of the either atom is shared by overlapping of their orbitals.

So,
Why can't three atoms share an electron and overlap their orbitals?


texts: entropy calculation in an irreversible process

texts: I found out that if we want to find the entropy change in an irreversible process let's say $\text{state A} \to \text{state B}$ , we find or make an reversible path for the same process and find the entropy change for that irreversible process. The thing I don't get is that, even if entropy is a state function, does it mean that the change in entropy for the irreversible process we needed to find is the same as the change in entropy for the reversible path we constructed? Or am I being mistaken? If its the latter, please provide me a solution for it. Thanks.


texts: Gaseous state: Boyles, Charles and Lusaac's law

texts: We know that pressure is inversely proportional to volume (Boyles law) and volume is directly proportional to temperature ( Charles law). So then won't pressure be inversely proportional to temperature?


texts: Possibility of SET mechanism of Wurtz reaction

texts: I was studying the Wurtz reaction, and I wanted to figure out the mechanism. When I searched the web, I came across the single electron transfer (SET) mechanism explanation. How can the alkyl group and the halogen form free radicals when the halogen is clearly much more electronegative then the alkyl group?


texts: Can gold recovery with acid peroxide (ap) method be done under vacuum or left in sealed chamber, as opposed to placement in open air?


texts:
I tried to put the 'Ferrofluid' and the clear liquid in a large glass tank.
My glass tank was bonded with silicone. However, silicon reacted with 'Ferrofluid' ('Ferrofluid' became sticky and hardened).
Perhaps 'Ferrofluid' seems to have chemically reacted with silicon because 'heptane' is the base.
What kind of glass glue can replace silicone?
Perhaps the epoxy is good, but it is not elastic.


texts:
Can dry ice be used as a explosive chemical? I am intrigued by this chemical dry ice and seen various experiments with it, and seems to have potential to be a   explosive.

So can dry ice explode?


texts: Are there pressure driven reactions such that the product remains stable even after it is depressurised?

texts:
High pressure chemistry tend to return compounds with very interesting and unusual bonding structures, such as $\ce{NaCl7}$, metallic hydrogen and $\ce{Na2He}$
However, for most of these, the resulting product is only at best metastable (e.g. diamond) when returning to ambient conditions, and does not survive when pressure returns to ambient conditions (r.t.p.).
For the following requirements, a compound that has unusual bonding similar to those 3 reported above, that is things like n centre m electron bonds is desired

Are there exceptions to this rule, where the high pressure is mainly needed to overcome the energy barrier and the resulting product is more stable than the reactants such that the product stays stable (instead of metastable) even when it is decompressed (That is, a spontaneous but kinetically slow reaction where pressure is the major factor to activate the reaction)?
If there are no known exceptions, what are possible theoretical reasons that products formed from high pressure are usually metastable and cannot survive at low pressures. Put it simply, why are most reactions reversible under the change of pressure?


texts: If I can't draw resonance structures for a pi system, does that mean it doesn't exist?

texts:
Whilst trying to answer this question I came across an interesting situation regarding the relationship between resonance structures and molecular orbitals. There are two places that you can deprotonate this compound. The two different deprotonated forms are shown below along with their resonance structures.

Both compounds have a continuous system of p orbitals which can align in a plane and overlap to form a $\pi$ system. However, in the first example it is not possible to draw resonance structures that delocalise the negative charge over all five atoms that have the available p orbitals. Does this mean that the negative charge is not delocalised over all five atoms? @Martin said in his comment on this answer that valence bond theory and molecular orbital theory ultimately give the same result so this should also apply here. In the molecular orbital description, what is the reason why the negative charge is not delocalised over all five atoms? What do the molecular orbitals for these anions look like?


texts: How does the Rf value change when changing the eluent composition?

texts:
A non-polar molecule X is analyzed by TLC chromatography on silica to determine its $R_f$ value.
The first eluent was hexane:EtOAc = $9:1$ and the $R_f$ value was $0.5$.
In the second run, the eluent was changed to hexane:EtOAc = $7:3$. Will the $R_f$ value be smaller or greater than $0.5$?

I am confused because there are two important interactions: because the 2nd system is more polar, it will form weaker interactions with substance X, and the $R_f$ value will decrease; on the other hand, the molar polar eluent will form stronger interactions with stationary phase, so the $R_f$ value will increase because the substance X is more easily eluted.


texts:
A 2% (weight %) solution of a salt with Mr = 190.6 g mol-1 was prepared at 25 0C. The density of the prepared solution was 1.00926 g cm-3. The density of water at 25 0C is 0.99707 g cm-3, and the density of the crystalline salt was 3.00845 g cm-3.
a) ) What is the molar volume of the crystalline salt?
molar volume of salt=(190.6g/mol)/(3.00845g/cm^3)= 63.4cm^3 /mol
b) what's the partial molar volume of the salt at infinite dilution
assuming the mass of solution =100g, w%:(mass of salt)/(mass of solution) x 100
w%:  (mass of salt)/100g*100= 2%
mass of salt= 2g
mass of water=100-2=98g
no.of mole salt= 2/190.6=0.010493mol
no.of mole of water=  98/18.02=5.4384mol
x_salt=  0.010493/(5.4384+0.010493) = 0.001925
x_water=1-0.001925=0.99881
these are my workings for part a and b. My understanding of part b is to find partial molar volume via dV/dn, but I can't seem to find the difference in volumes, let alone infinite dilutions...I'm not even sure if I'm on the right track. Do I have any misconceptions?
-struggling physical chem student


texts: Energy levels in non-hydrogen-like atoms

texts:
The energy $E_n$ for a hydrogen like atom is given as

$$E_n = -hcR_\ce{H}\frac{Z^2}{n^2}$$

However, aside from on wikipedia where there is

$$E_n = -hcR\frac{Z_\text{eff}^2}{n^2},$$

I can't find anywhere that relates to the energy of an atom that has more than one electron. Is there an equation that gives the specific (or approximate) energy or is there an 'easy' way to calcuate a value for $Z_\text{eff}$?


texts: Would nodal planes of participating Atomic orbitals be nodal planes of molecular orbital?

texts:
As I take sigma 2p antibonding molecular orbital as an example

Would it have 3 or 1 nodal planes. The two supposed nodal planes pass through the centres of the two atoms and are same as in the original atomic p orbitals. By LCAO A and B, I suspect that there will be some electron density due to the wave function of B where A is zero. Is there a fault in my logic?

For pi there is no problem, there are 1 nodal planes for pi bonding mo and 3 for antibonding mo as there is a common nodal plane to both MO.


texts: Why does equilibrium for the addition of the Claisen enolate to an ester not favor the product?

texts:
I am currently reading chapter 26 of Clayden's Organic Chemistry, and a diagram for the elementary steps of the Claisen condensation with ethyl acetate in ethoxide is provided. It is obvious why the net reaction is favorable. The 1,3-dicarbonyl compound has a pKa of ~10 while the pKa of ethanol is 16 (so the more acidic 1,3-dicarbonyl compound will be the product in its deprotonated form). Even though the first few elementary steps may not favor the product, the last step is essentially irreversible.
I am having trouble understanding why the second equilibrium arrow claims to favor the formation of the reactants and not the products.
The first equilibrium arrow is obvious, the pKa of ethanol is 16, and the pKa of the ester enolate is ~25 (when protonated), so the less acidic ester will be favored in equilibrium. However, in the second equilibrium arrow, the pKa of the starting enolate is ~25 (when protonated) while the pKa (when protonated) of the product alkoxide is likely somewhere around 16. Wouldn't this mean the product for the second equilibrium arrow would be favored thermodynamically? I have considered that this step does result in a decrease in entropy, but I wouldn't expect this to have a drastic impact on the direction of the equillibrium.


texts: How can you explain the energy change in this phenomenon?

texts: Tagged is the diagram of the apparatus used in this thought experiment. Pure water is taken in one side of the beaker and a solution of common salt in water in the other. After a very long time, the pure water should get transferred to the NaCl solution side because according to Raoult's law, the NaCl solution should have lesser vapor pressure than pure water, thus causing the water-vapour equilibrium in the pure water side to move forward, resulting in the condensation of the vapour in the other side (the solution side) . But how has the potential energy (=mgh) of the pure water increased during the process?


texts: Why can't the hydrogen attached to the bridge head carbons take part in tautomerism?

texts:
I've read that hydrogen attached to bridge head carbons in bicyclo compounds cannot take part in tautomerism. For example, I read that the below ketone cannot underground an enol tautomerism.

What is the reason behind it?


texts: What is the correct electronic configuration of darmstadtium?

texts: Some of the places, the electronic configuration of darmstadtium ($\ce{Ds}$) is given as $\mathrm{6d^9 7s^1}$ while at some other places, it is $\mathrm{6d^8 7s^2}$. Which among the two is correct?


texts:
The easiest carcinogenic thing for me to grasp is radiation, as it directly messes with DNA. Then it seems there are other compounds that simply mimic hormones, but these shouldn't necessarily cause cancer, right? Then there are things that can accelerate mitosis or mess with other processes, which can inadvertently mess with DNA. So my question is, in general, how many different flavors of carcinogens are there? I know there are a lot, but can someone list a good few? Maybe some examples? I'm most interested in how plastics and things like smoke cause cancer. I think a few examples would be best in aiding my understanding.
Thank you!
Edit: I also just realized this is the Chemistry Stack Exchange, I think I am more interested in the chemistry side of this question, but it might need to be migrated.


texts: Addition of inert gas to equilibrium mixture under constant pressure

texts:
Adding inert gas under constant volume will not disturb equilibrium. But I want to know what would happen if inert gases are added at constant pressure.
If total pressure remains constant and inert gases are added, then mole fraction of any gas participating in equilibrium decreases and hence partial pressure decreases.
If $\Delta n$ is non zero, then $K$ changes. But how can $K$ change if temperature remains constant?


texts: Can a polymer have different resonance structures?

texts: Several organic compounds have resonance structures, but can a polymer have resonance structures?


texts: Explain isotopic uranium/perchloric acid digestion

texts:
What is happening in this video? Can you explain this technically as well as in layman's terms?

I'll summarize it. I see a technician moving fuming mixtures of presumably uranium and organic compounds on and off hot plates. Perchloric acid is mentioned, and a large bottle is present.


texts: How can molecularity be the order of the rate determining step?

texts: In my textbook the molecularity is defined as(along with the standard definition) the order of the rate determining step(RDS). It is also given that the order can be a fraction but molecularity is always a whole number. But, then if the order of RDS is a fraction molecularity will be a fraction which is a against the definition. So, where is the problem? Is it that the order of RDS can only be a whole number?


texts: How will the pressure of a gas in manometer change if it goes to a place with higher pressure?

texts: Imagine a manometer where air pressure is $\pu{0.8 atm}$ and the gas pressure is more. We move it to sea level which the air pressure is $\pu{1 atm}$. How will the gas pressure change? (the temperature is constant)


texts: What makes sulfur-containing compounds such good antioxidants?

texts: Many sulfur-containing compounds (like glutathione and cysteine groups) have high antioxidant activity. Why?


texts: When an electron returns to it's ground state does it release the same wavelength of light that promoted it in the first place?

texts:
If this is true, I fail to understand why we see colour at all -- wouldn't any wavelengths absorbed by electron promotion be inconsequential to colour because there would an equal amount, and identical wavelength of light emitted when the electrons returned to their ground state?

The only way this would make sense to me is if the energy of the photon absorbed by the electron is given off as heat or something besides an identical photon when the electron returns to its ground state.


texts: Plotting a calibration curve for Gas-Liquid Chromatography

texts:
Question:

The given graph of abundance of different samples of butanol with respect to time is-

Textbook solution:

But why aren't the points like this:
$(20,5);(40,10);(60,15);(a,7)$
after which, to plot the curve we can use $y=mx+c$ and then find the value of $a$?


texts: What is the exothermic reaction of superglue with cardboard?

texts:
I glued a sheet of paper to a cardboard package using superglue (labelled with ethyl 2-cyanoacrylate).
To my surprise the paper became very warm.
What kind of reaction is it?


texts: How to breakdown wax, preferably beeswax

texts: I have a project that I'm working on at the moment, but I'm stuck on this detail. I'd like to find out what can I supplement beeswax with that is organic, non toxic, and safe if accidentally consumed, in order to speed up decomposition rate of beeswax to a time frame of about 1-6months. Any ideas?


texts: Why do Asn-Ser and Gln-Thr have different H bonding patterns?

texts:
I noticed that Asn-Ser H-bonding is different from the H-bonding between Gln-Thr.
However both have the same functional groups. I wasn't able to find any information about this. Maybe it's due to steric effects, but because these striking similarities between Asn and Gln and on the other side Ser and Thr I don't think that is an explanation (but maybe it is, I'm just guessing).

excuse me for the drawing, but I couldn't find an image showing this clear

I found these H-bonding patterns in Fundamentals of Organic Chemistry, McMurry, seventh edition.

update

Are al these H-bonds possible?


texts:
So my teacher started the explanation of Chemical Equilibrium saying..
The concentration does not change with time.
And, gave us certain graphs asking which ones show chemical equilibrium.
I cannot understand what's written in my copy since I took the lesson two years ago. I need to be explained what I wrote in my copy.

I know that the concentration does not change with time.
If concentration is same or not, does not matter. That only the rate of forward reaction and the rate of backward reaction needs to be same.

These are the graphs: (I am sorry I could not draw better.)
:
Now, I know 1,4,5 and 6 show chemical equilibrium.Reasons:

The concentration of the reactant is lost but same amount is achieved by the product.So here, the rate of forward reaction and rate of backward reaction is same.
For 5 and 6- The concentration of reactant and product may not be the same but it does not change with time.

I need help regarding :

1.Explanation as to how the other graphs do not show chemical equilibrium(if possible in terms of how the answer for the other graphs are explained).

2.Explanation for graph 5 and 6. I cannot understand the reason I had written.

3.An overall explanation and answer of the question.

Thank you very much for your help and understanding!!


texts: How does the inverted Marcus region explain chemiluminescence?

texts:
The invert Marcus region offers one explanation of chemiluminescence, the process by which light is one of the products of a chemical reaction.

I tried reading one of Marcus's original papers on the subject [1], but I don't really get his argument. I get confused about which of the potential energy surfaces in his Figure (copied here, hopefully that's okay) that refer to the ground state reactant, ground state product, excited reactant, and excited product.

[1] R.J. Marcus (1965), "On the Theory of Chemiluminescent Electron-Transfer Reactions", The Journal of Chemical Physics 43(8):2654-2657


texts:
Why does an excess of neutrons leads to instability?
For example, both $\ce{^{3}H}$ and $\ce{^{4}H}$ are unstable, with respective half-lives of $3.89\cdot 10^8$ and  $1.39\cdot 10^{-22}$ seconds.
By my reasoning,  neutron-rich nuclei should be strongly bound by the strong nuclear force, and should therefore be more stable. Additionally, neutrons, unlike protons, are neutral and therefore do not contribute to repulsive electromagnetic forces.


texts: How do I find change in Gibbs free energy of water formation?

texts:
How do I find the change in Gibbs free energy of the reaction

$$\ce{H2 + \frac{1}{2}O2 -> H2O}$$

when it is at $\pu{75^\circ C}$ and $\pu{1 atm}$? Do I calculate the Gibbs free energy of each species and then do

$$\sum\Delta G{\mathrm{(products)}} - \sum\Delta G{\mathrm{(reactants)}}?$$


texts:
For strong electrolytes, according to Kohlrausch, molar conductivity decreases as the concentration increases.

( i don't know why I'm not allowed to attach a photo here in order to show you the diagram ), but however I'm trying to explain how the diagram looks.

In the diagram we have strong electrolytes like $\ce{HCl,\, H2SO4,\, KCl,\, LaCl3,\, Na2SO4}$ whose molar conductivity decreases as the concentration increases. But, what I don't understand is that in the diagram we have also $\ce{CH3COOH}$ which is a weak electrolyte, and his molar conductivity also is decreasing and even far more rapidly, as the concentration increases.

Can somebody explain this ?