texts: Is it realistic to have a natural oxygen source in a cave? I am writing a story, about people who live underground in a land that is freezing outside. Heat is taken care of by geothermally heated groundwater. How do I make it realistic for these people to breath in the caves?


texts: Silicon degassing with negative pressure

texts: I am planning to use polydimethylsiloxane (PDMS) to create phantom for mimicking tissue for imaging. For this, I plan on using SYLGARD® 184, which is a viscous liquid. When adding other components to it, the air bubbles will be introduced. I have learned that one way (available to me) is using the negative pressure/ vacuum pump to remove bubbles / de-gas the solution. Does any one knows what negative pressure is sufficient to remove the air from the gel-like solution?


texts:
Methanol forms adducts with $\ce{CaCl2}$ but I am not finding much information about the nature of these adducts & their stability. Are these solid adducts? Crystalline?  Is the reaction substantially exothermic etc.?

In this link, it is written that:-

  At temperatures below 55°C, $\ce{CaCl2}$ forms $\ce{CaCl2·4CH3OH}$ with methanol and below 55°C, $\ce{CaCl2·3CH3OH}$ is formed.

Obviously, they seem to have gotten their Temperatures wrong. Any more authoritative information about methanol adducts?


texts: How the alkali molecules can dissociate completely in the reaction of weak alkali and strong acid?


texts: Do alkanes evaporate faster than alcohols?

texts:
If so, is it because alchohols have hydrogen bonds?

Which type of compound evaporates faster, and why?


texts: Computational modeling of steric repulsion between two polymer mediated magnetic Nanoparticle?

texts:
Can you recommend any modern article or research papers on steric interactions and forces between two or multiple magnetic nanoparticles with polymer brushes in a nonpolar solvents? something with more physics and mathematical formulas not just text and graphs. My goal is to learn how brushes create osmotic pressure, what are the forces, and then create a simulation of two particles interacting together.

I am new to this field and currently reading Israelachvili's Inter-molecular Forces and Flory's Polymers books they are very general and don't have detailed Physics in case of steric repulsion.


texts: How to make acetic acid more volatile so that it can be removed by vigorous aeration of an acetic acid-water mixture?

texts:
I want to remove acetic acid from a mixture of acetic acid and water by aeration. The concentration of acetic acid is 200 ppm (mg/L). The pH of the water is more than 5. I want to reduce the acetic acid concentration by around 80%.
I understand that acetic acid can be removed by addition of sulphuric acid to bring down the water pH to around 2 and then boiling the mixture to separate the acetic acid.
I however the water quantity I have is very huge, so it is not practically possible to boil the water. The water temperature is more than 60 deg C. Also, I do not want to put lots of sulphuric acid in the water due to various other issues and my practical limit of using sulphuric acid is around 80-100 ppm which lowers the pH to around 3.0. I can also providing aeration to the water at 0.2-0.5 vvm.
I want to know that under these conditions, can acetic acid be removed from the water?
Is there any other other method by which we can remove acetic acid by aeration at 60 deg C, by adding not more than 100 ppm of any additive?
Is there any other chance that acetic acid would be removed by aeration at 50-70 deg C temperature? If yes how to enhance the efficiency by minimum inputs?


texts: Do materials exist that absorb Visible light and emit Near InfraRed light?

texts:
I am thinking about the possibility of making a hat or other clothing item that might show up funny on cameras, as they are more sensitive to infrared light than human eyes.
Therefore, I was wondering if there are any (non hazardous) materials that emit InfraRed light when they are exposed to visible light.

Do these exist, and would they be suited for this kind of application?


texts: Can one component of a mixture penetrate the skin if the whole mixture cannot?

texts:
There's a general rule that says that compounds under 500 dalton are able to penetrate the skin without any special vehicle (such as ethanol).

I've started using castor oil, which contains different acids that are believed to be good for the skin (not discussing this here now). The oil is very thick, and each acid has different molecular weight. I'm mostly interested in ricinoleic acid, which has about 300 dalton.

If I were to apply this bare oil on my skin, would it be a correct to think that some acids would penetrate the skin and some others wouldn't (because of the 500 dalton rule), assuming this oil didn't have any special treatment (except, well, the process of extracting the oil itself)?


texts: Would a redox reaction still happen between the two electrodes only connected by a wire?

texts: The galvanic cell I'm studying has Pb as reducing agent and Cu as oxidizing agent, and as I understand it the reason that the electron flows from the Pb electrode to the Cu electrode without anyone doing anything is because it's thermodynamically favorable, ie a spontaneous reaction. Would this flow of electron still happen if I only have two electrodes only connected by a wire? This doesn't seem possible, but I'm not sure.


texts: Why is the zero of standard enthalpy of formation a convention?

texts:
The standard enthalpy of formation $\Delta H_f^°$ of pure elements is zero by definition. Why is that a convention? It is true that enthalpy is defined unless a constant (like energy and entropy), but enthalpy of formation is actually a variation of enthalpy, so we don't really care.
Also, how could we possibly choose something else than zero if there's no heat transfer?
Note: I'm using General Chemistry (Ralph Petrucci)


texts: The effect of pH and solubility on coagulation in water treatment

texts: In water treatment, a specific pH range must be met in order for the process of coagulation to occur properly. Sources have stated this is due to the pH affecting the solubility of the coagulant, but why is solubility significant?


texts:
I was trying to silanize the glass coverslips using a protocol mentioned in some papers that say to make up a solution of 595µl N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TCMP-TAC) and 216µl of vinyltrimethoxysilane (VTS) in 300ml ultrapure water and incubate overnight at 65ºC.

However, I don't know about the concentrations of each of the components of the mixture containing TCMP-TAC and VTS individually. Gelest provides TCMP-TAC in 50 % methanol and VTS as a solid. How should I go about making the individual components?


texts: How can batteries reach equilibrium if the reactions are irreversible?

texts:
My book says that the batteries we have considered so far (Daniell cells) have a low life span because they reach equilibrium too quickly.

In the next paragraph, it states they are also made by irreversible reactions and we call them "primary batteries."

How can a reaction reach equilibrium without being reversible?


texts: Is it environmental to throw ordinary keys in the regular household trash?

texts:
I have several keys on my chain that I do not need any more, so I'm thinking about throwing them away, but I'm not sure if it is okay to throw away in the regular household trash. I looked it up to see what are keys made of and I see that it's usually nickel-plated brass, sometimes with silver in the mix (see here and here for example). Is there any environmental harm in throwing away such keys in the trash?

(I am guessing that due to the small size and mass of a key, it would probably not have a significant impact anyway, but I want to know the proper answer nonetheless)


texts: What's the difference between aqueous hydrogen chloride and hydrochloric acid?

texts: From my understanding, both aqueous hydrogen chloride and hydrochloric acid are written as $\ce{HCl(aq)}$, is there an actual difference between them?


texts: Why is mercury much more toxic when inhaled than injected?

texts:
Following wikipedia:

  Cases of systemic toxicity from accidental swallowing are rare, and attempted suicide via intravenous injection does not appear to result in systemic toxicity,[1] though it is still causes damage by physicaly blocking blood vessels both at the site of injection and the lungs.

Shouldn't both inhalation and IV injection of elemental mercury produce the same result, namely, mercury in the bloodstream?


texts:
What kind of glass can I purchase that will melt in a Bunsen burner flame?

Is there any way to treat glass such that the melting point is lowered? I tried adding some sodium hydroxide but the glass shattered when heated.


texts: Why is Hessian Matrix called 'force-constant' matrix?

texts:
Hessian Matrix is a square matrix containing the elements as the second-order partial derivatives of energy-function of a molecule; the derivative is done with respect to geometric coordinates of the molecule.

However, I couldn't get why Hessian matrix is referred to as force-constant matrix; as is done in the book I'm following viz. Computational Chemistry: Introduction to the Theory and Applications of Molecular and Quantum Mechanics by Errol G. Lewars and in many other sources.

If the energy function is a quadratic function which is mostly the case for a molecule following 1D PES; the function which a Hookean spring follows for small displacement, then the second derivative does indeed give the value of force constant, that is $$\begin{align}E- E_0&= k(q-q_0)^2\\ \implies \frac{\mathrm{d}^2 E}{\mathrm{d}q^2}&= 2k\;.\end{align}$$

However, for molecules following multidimensional PES, most of the time, the energy function is not simple quadratic; how can the second order derivative give the force constant? Second order derivatives vary from point to point unlike the simple case above.

So, can anyone tell why Hessian matrix is called force-constant matrix?


texts: How do I calculate the ensemble-average net charge of an amino acid at given pH?

texts:
I am given an amino acid with an ionizable side chain at a certain pH. How do I determine the net charge of that amino acid when there are mixed protonation states of one or more of the groups at that pH (pKa of side chain, for example, is really close to the pH)?

Amino acids have terminal carboxyl and amino groups; some amino acids have ionizable side chains. When determining the charge of an amino acid, you have to take into consideration the pH and the pKa's of each of these groups. When the pKa of one group (or more) is close enough to the pH, a fraction of the amino acids will be deprotonated at that group and the other fraction of amino acids will be protonated at that group in solution. Thus, when determining the average net charge across the ensemble (or a time-averaged charge of a single particle), you have to take this into account.

I am asking for the expected value of the net charge (which would not be an integer); this number is relevant, for example, for the migration speed of the amino acid (or a protein) in gel electrophoresis or the strength of interaction with ion exchange chromatography media.

For example, a carboxylic acid/carboxylate group at a pH equal to its pKa would have an average charge of minus one half because half of the functional groups would be protonated (charge of zero) and half would be deprotonated (charge of minus one).


texts: How to find the concentration of potassium permanganate in this experiment?

texts:
I completed a titration experiment in a lab. The aim was to find the concentration of the titrant $\ce{KMnO4}$ solution by titrating it with a sodium oxalate solution of a known concentration.

I first made a standard solution of sodium oxalate solution, using $\pu{0.826 g}$ of sodium oxalate powder, then poured $\pu{50ml}$ of distilled water along with $15$-$\pu{20ml}$ of $\pu{3 M} \,\,  \ce{H2SO4}$. Then I pipetted out $\pu{25 ml}$ of the solution and poured it in to a volumetric flask. Then I filled the rest of the volumetric flask with distilled water, to form the standard solution. I then did the Mcbride experiment to find $75\%$ of the volume of $\ce{KMnO4}$ need to titrate the solution.

I then did the experiment three times to get an average volume of $\ce{KMnO4}$ to be $\pu{25.48 ml}$. And the volume of sodium oxalate solution is $\pu{25 ml}$.

I should find the concentration of $\ce{KMnO4}$ now.

I know the molar ratio is 2:5. How do I calculate this?

I know I need to find the moles of sodium oxalate then I multiply it by $\frac{2}{5}$ and then divide that value by the volume of $\ce{KMnO4}$ which is $\pu{25.48 ml}$. But how do I calculate the moles of sodium oxalate? What would the concentration be? I know the volume is $\ce{25 ml}$.

This is what I have done, but I am not sure if it is correct:

Moles of sodium oxalate = $\frac{\pu{0.8265 g}}{\pu{133.96 g mol-1}} = \pu{0.006169752 mol}$

$\frac{0.006169752}{\pu{0.025L}}$ = concentration of sodium oxalate is therefore $0.246790086$, $0.0248$ to 4 s.f.
($\pu{0.025 L}$ is the volume of the sodium oxalate)

I then multiplied that by $\frac25$.  $0.0248 \cdot \frac25$ gives me the concentration of $\ce{KMnO4}$ which is $0.09872$.

But I think this is wrong because I have not used the volume of $\ce{KMnO4}$ used, which was the whole point of the experiment.


texts: Why do people commonly refer to Na2HPO4 as Sodium Hydrogen Phosphate, rather than Disodium Hydrogen Phosphate?

texts: First of all, I am aware of this question.  The purpose of my question is to understand why people seem to break the rules that IUPAC has set (See example five on page 76 of the book), especially since this is not a compound that has a historic name, like $\ce{NH3}$ being ammonia or $\ce{N3-}$ being azide.  This compound has two species of cations, with sodium having a 2:1 ratio to hydrogen.  According to example five on page 76, compounds that have multiple cations are supposed to give prefixes to every compound in an ion that has a quantity greater than one.  Why do we not do this for sodium hydrogen phosphate?


texts: How many of different types of chemical species are in a certain volume of aqueous solution of an acid

texts:
The acid in question has $\mathrm{p}K_\mathrm{a}$ about 1.29. Density of 98% w/w solution is $d=\pu{1.323 g/cm^3}$. I would like to find the number of undissociated acid molecules ($\ce{HX}$), water molecules ($\ce{H2O}$), dissociated acid molecules ($\ce{X-}$), and hydronium ions ($\ce{H3O+}$).
The molar mass of the acid ($\ce{HX}$) is $\pu{125.1 g/mol}$. Thus 98% w/w solution corresponds to $\pu{10.57 M (mol/L)}$. If I'm not missing sth, the solution contains 1.5 mole of water and 10.57 mole of acid. What I'm not sure is how these numbers convert into the number of ions/molecules which are, let's say in a volume of $1~\pu{\mu L}$ (one microliter).
Though my attempt would be:

Firstly I have to determine $\mathrm{pH}$ of the 98% (w/w) solution in question; I did some rough calculations and got $\mathrm{pH}$ = 0.509

Then, I need to establish the ratio $\dfrac{[\ce{X-}]}{[\ce{HX}]}$; this can be done using Henderson-Hasselbach equation; I got 0.166

Thus, for let's say 1000 $\ce{HX}$ molecules and 172 $\ce{H2O}$ molecules (this stems from 10.57:1.5 molar ratio), I have at equilibrium: 834 $\ce{HX}$, 166 $\ce{X-}$, 166 $\ce{H3O+}$ and 6 $\ce{H2O}$ molecules.

The solution, seems to be correct. 834 $\ce{HX}$, 166 $\ce{X-}$, 166 $\ce{H3O+}$ and 6 $\ce{H2O}$ molecules should have a total mass of $2.129\times10^{-19} \pu{g}$. Since the density is known, such a group of molecules should occupy a volume of $\pu{160.9 nm^3}$ which is perfectly reasonable.


texts: Why is it that every snowflake is unique?

texts:
It's pretty hard to believe in around 4.5 billion years of this planet's existence, no snowflake pattern was repeated, and that's not including potential earth-like planets.

Is there a proof to the structure or is the probability even more statistically insignificant than I thought, or what?


texts: Why does Cl- corrode aluminum containers?

texts: I heard that $\ce{Cl^-}$ will corrode aluminum containers. Why? Is it because it would form a galvanic cell or produce coordination compounds?


texts: Do Lewis acids and bases turn change colour of litmus

texts:
Well, the question is short. Can lewis acids and bases change the colour of a litmus paper? I can't seem to find the answer online (at least according to my high school level chemistry search history).
The intuitive answer I feel is that they shouldn't be able to, as lewis acids and bases are defined only by their ability to donate or accept electrons. On the other hand, Arrenhius and Broensted-Lowry acids seem to be able to change the colour of litmus, possibly due to the presence of H+ or OH-
As a bonus question, is there any indicators that can be used to test the presence of lewis acids that change their colour after donating a lone pair of electrons?


texts: Are IR signals affected by nearby atoms?

texts: E.g. If there is a methyl from an aldehyde vs a methyl at the end of a hydrocarbon chain, will the difference in neighboring atoms have an effect on the location of the IR signal?


texts: How can I have iron powder without a fast reaction with oxygen?

texts:
I've seen this video in which fine iron powder reacts immediately with oxygen when exposed to the air, turning into rust.

Now, will this reaction always occur with iron powder? Or is there something special with this specific sample?

I'm writing a steampunk story where people are liberating iron powder in the air. Now, I know that iron powder exists without creating sparks, but I don't want to make some huge mistake, so I'd like to understand a little more about this reaction.

Also, the presence of coal combustion smoke or water steam would have some influence in the reaction?


texts: The heat of combustion of neo- pentane is lower than n-pentane.This clearly means that neo-pentane is more stable than n-pentane.What is the reason for this?


texts: How do the stored chemicals in batteries drive electronic current from their terminal to outside devices?

texts:
I have got around to at least read on Wikipedia, and it does not clarify how this works in any sensible manner.

I wondered how the chemicals make electrons "move". How is the basic understanding of this?


texts: Effects of potassium hydroxide & carbonate on metals?

texts:
BACKGROUND

I am in the process of restoring an old computer. The problem with the computer is that it has a NiCad battery fitted to the motherboard, which powers a real-time-clock circuit. The NiCad battery has leaked onto the motherboard. The leaked material has caused quite extensive damage, which I am cleaning and repairing.  See here and here.

I am curious about this leaked material. Here is what I (think) I understand so far:

NiCad batteries use potassium hydroxide as an electrolyte, and this
is the material which has leaked from the battery.
The potassium hydroxide forms potassium carbonate when it reacts with
the carbon dioxide in the surrounding air.

MY QUESTIONS

Some white(ish) powder has formed on the battery terminals themselves. Is this potassium carbonate?
The effect of the battery leakage has been quite widespread corrosion of metals, mainly electronic components. The corrosion has spread much further than the leakage site. How?
Why does the material attack metal? Do both materials (potassium hydroxide and potassium carbonate) attack metal, or does one of these have more of an effect on metals than the other?
Are any other chemicals likely to have formed that I have not considered? (e.g. there are green/blue deposits to be found in areas affected by the leakage)

CONJECTURE

Having pieced together some information from reading on the internet, I have formed a bit of an opinion about the process which has unfolded here. And I'd like to run it by you all to see what you think about it:

When the battery started to leak, the potassium hydroxide reacted with the air and formed potassium carbonate, as a white powder on the battery terminals.
When all of the carbon dioxide in the air was depleted (due to closed computer cover), the potassium hydroxide stopped forming potassium carbonate. And this is when it began to attack the metals.

THANK YOU IN ADVANCE!

The purpose of my questions is purely to satisfy my curiosity. If someone takes the time to respond, and share their knowledge, then I respect that and I am grateful. So I just wanted to say thank you in advance!


texts:
So I've come across this lovely spectrum of a compund where only its chemical formula is given with C5H9NO.
I have made the pictures of the spectrum available below.
obviously there is some pretty hefty coupling going on but I cant really figure out what it could be.
So far I think we definitely have a CH3 group that could be attached to either heteratom. On the other side, the single proton at 6.66 ppm could also be an H attached directly to the N-atom (maybe?).
Anyways, I hope you guys can help me here and maybe also explain me the couplings that are going on.

EDIT: to not get marked as homework, because it isnt, I suggesting that it should be some sort of pyrrole or pyrrolidine structure type. Further I think that the CH3 group must be shielded from other protons and is either near or is sitting at a heteroatom.
Next I have narrowed down two structural possibilities: either we have a proton sitting at the nitrogen and the other sitting on a double bound, or we have diastereotropic protons.
My best candidate so far is the picture below (please let me know if it would be possible):


texts: How can I mask the Chromium (III) and Chromium (VI) ions in my solution?

texts:
I want to conduct a quantitative analysis on my acid etching solution for my Aluminum pre-treatment process. The easiest way for me to conduct my quantitative analysis of Al is through complexometric titration with EDTA and back-titration with standardized Zinc solution.
My problem is that there's also Chromium ions in my solution and it can bind with the EDTA which reduces the volume of Zn solution I utilize in my back-titration. [I have confirmed my dilemma because the solution I am using was analyzed through Atomic Absorption Spectroscopy (AAS).]
How can I mask the chromium ions in my solution so I can proceed with the complexometric titration?


texts: Products of Lead(II) nitrate decomposition

texts:
It is known, that decomposition of Lead(II) nitrate is one of the ways of generating $\ce{NO2}$ for lab use.

I recently did this in order to acquire $\ce{NO2}$ in liquid form (ambient temperature was ~0 °C), and got quite strange results. First, liquid $\ce{NO2}$ had 2 visible layers, usual brown one at the top and transparent at the bottom:

Also, during condensation liquid initially had green color (I know that Graham condenser is not safe in this configuration - I wouldn't see this color change in conventional condenser setup).

Can anyone clarify why I got such variety of products instead of pure $\ce{NO2}$?


texts:
I'd like to use Hill notation (i.e. CH, then alphabetical), but I am not sure how to include isotopologues (i.e. carbon-13) in this notation.

For example, what would be the preferred form of ethylamine (with 13C)?

C13CH7N
CH713CN
12C13CH7N
12CH713CN
Other

I'm leaning toward using #2 but was trying to find the std practice, but I didn't see anything about isotopologues.  Thanks.


texts: I'm doing an assignment where we must research the separation of a mixture to obtain a useful final product. I thought about the separation of uranium from its ore after it has been mined, but I did not know if the ore counted as a mixture, or a compound.


texts: Why is the boiling point of hydrogen sulfide higher than that of hydrogen chloride?

texts:
The boiling point of $\ce{H_2S}$ is higher than $\ce{HCl}$. Is this due to the greater number of hydrogen bond that $\ce{H_2S}$  can form compared to $\ce{HCl}$? I found this explanation for the comparison between $\ce{H_2O}$ and $\ce{HF}$ so I tried to use it here also, but I'm not even sure that the intermolecular forces among   $\ce{H_2S}$ and $\ce{HCl}$ molecules can be defined as "hydrogen bond" (which should occur only for  $\ce{F,O,N}$).

So how can the greater boiling point of  $\ce{H_2S}$ compare to $\ce{HCl}$ be explained?


texts: Help with iodine potassium-iodide / hydrogen peroxide reaction lab?

texts:
The setup: As part of my chemistry course, we're required to complete an in-home lab where we measure the reaction rate of an iodine potassium-iodide (IKI) solution with a hydrogen peroxide solution. We daisy-chain 2 Erlenmeyer flasks together with a system of rigid & flexible tubing, with a tube extending to an open graduated cylinder at the end. The chemical mixture is in the first flask, 200 mL of water is in the second flask, and about 10 mL of water is in the graduated cylinder. Here's how it all looks:

What's SUPPOSED to happen: once we mix the IKI/hydrogen peroxide solutions in Flask #1, we swirl this flask on and off for something like 20 minutes to start the reaction. The reaction should build up pressure (I think?), causing the water to be forced up a rigid tube in Flask #2 and over to the open cylinder. Note that the longer of the 2 rigid tubes in Flask #2 extends below the surface of the water. The water will then start to drip into the graduated cylinder and we measure the displacement, which will then give us a table of data points to determine the rate constant, rate order, and many cheerful facts (about the square of the hypotenuse...)
What's ACTUALLY happening: nothing. I've been swirling Flask #1 for over an hour, and not a single drop of water has been displaced into the graduated cylinder.
Question: any idea what might be going on? Would there be something wrong with the setup? All the flexible tubing fits pretty tightly over the rigid tubing, and the rubber stoppers on the flasks also fit pretty tightly. I don't know how to troubleshoot this, so any tips would be helpful!


texts: Electron affinity of nitrogen and exchange energy

texts:
When studying the effects of electron filling in chemistry, I was studying why energy is needed to add an electron to a nitrogen atom i.e. electron affinity.

Nitrogen already has an electron structure of $\ce{1s^2 2s^2 2p^3}$ and using my knowledge of exchange energy, the energy released as exchange energy is

$$\frac{3 \times 2}{2} = 3K $$

But adding an electron means there is 1 electron  $\ce{1s^2 2s^2 2p^4}$ with opposite spin to the rest of the other electrons so the total exchange energy is still

$$\frac{3 \times 2}{2} + \frac{1 \times 0}{2} = 3K $$

so why is it unfavourable i.e. endothermic for nitrogen to became a nitrogen anion $N^-$?


texts: How to determine the acidity or basicity of dissolved salts?

texts:
One kg of each substance below is dissolved in a bathtub full of water. Will it be acidic, basic, or neutral?
  $\ce{KNO2}$
  $\ce{HF}$
  $\ce{(CH3)3NHBr}$
  $\ce{HO-CH2-CH2-O-CH2-Cl}$

$\ce{KNO2}$, $\ce{K+}$ $\ce{NO2-}$ $\ce{K+}$ is inert and $\ce{NO2-}$ is the base of strong acid, so it should be basic overall.
$\ce{HF}$, $\ce{H+}$ $\ce{F-}$ $\ce{H+}$ is strong acid and $\ce{F-}$ is strong base so it should be neutral overall.
$\ce{(CH3)3NHBr}$, Molecule acts like a $\ce{H3NHBr}$ or $\ce{NH4+}$ $\ce{Br-}$ so $\ce{NH4+}$ is acidic $\ce{Br-}$ is neutral, so overall solution is acidic.
$\ce{HO-CH2-CH2-O-CH2-Cl}$, No idea.

Can someone please explain them, if they're wrong? Thank you.


texts: Why doesn't velocity enter into Heisenberg's Uncertainty Principle?

texts:
So I came across Heisenberg's uncertainty principle in my 11th grade book, and I'm not convinced. It says $\Delta x \Delta p \gt \frac{h}{4\pi}$. Okay, but how does velocity even matter to determine the path?

Now suppose we have, for the case of my argument, 100 exactly identical atoms of hydrogen. Now we find the positions of the lone electron in 100 different cases, and we can do it with 100% accuracy. Now, if we join the dots, won't we get the path of the electron? Why not? Please explain in simple words if you can.


texts: Which Oxygen atom in HCOOH (formic/methanoic acid) does Carbon donate its electrons to, to obtain a partial positive charge?

texts:
I was wondering if the Carbon atom in HCOOH (methanoic/formic acid) forms a positive partial charge by donating its electrons to both the Oxygen atoms, since they both possess a higher electronegativity value, or just one of them.

I was also curious about how the single bond and double bond between Carbon and the Oxygen atoms would affect the electron donation.


texts:
Looking around at various material compatibility charts, they seem quite divided on the compatibility of metallic mercury and polycarbonate. Some sources (here, here, or here) indicate that polycarbonate is resistant to any sort of degradation by mercury. However, other sources (here, here, or here) suggest the exact opposite, that polycarbonate and mercury are severely incompatible. Why the disagreement?
Few of these charts explain their methodology or sources, and I've yet to find anything describing the claimed reaction in any detail. Mercury isn't particularly rare in chemistry, many people recommend storing mercury in plastic containers for safety, and polycarbonate media bottles are available from several major labware manufacturers. Therefore, it seems unlikely that such a reaction wouldn't be documented  on the internet (apart from a few table entries).


texts: Health Risks Associated with Working in Chemistry Labs

texts: I've been working in a contaminants food quality lab for about 2 years now and was curious what the chronic health effects would be, should I be worried about cancer?


texts: How is mean square displacement defined in Brownian motion?

texts:
I am trying to calculate mean square displacement (MSD) of water in a simulation to calculate its diffusion coefficient. However I am little confused on its exact form. Can anyone please explain it in little detail?
My confusion is: from wikipedia first paragraph on MSD page

$$MSD = 1/T * \sum_\text{t=1}^\text{T} (x(t)-x_\text{0})^2$$

My understanding of it was that:

$$MSD =(x(0)-x_\text{0})^2/1 + \{(x(0)-x_\text{0})^2 + (x(1)-x_\text{0})^2\}/2 + \{(x(0)-x_\text{0})^2+(x(1)-x_\text{0})^2+(x(2)-x_\text{0})^2\}/3$$
... and so on

That is that each term in MSD is cumulative sum of all previous terms devided by time. However most of online programms that i saw (for example matlab programme at the last page of this link)
tries to calculate MSD as  just simple square of distance between initial position and position at time T. Can some one please explain if it is a cumulative sum of previous displacements or not.


texts: Thermodynamic stability of benzene derivatives

texts:
Q1. How can we comment on the thermodynamic stability of the following benzene derivatives?

Q2. What does thermodynamic stability mean, in general? What does it mean to compare the thermodynamic stability of more than compound?

Q3. How do we compare the thermodynamic stability of benzene derivatives? Is there a specific rule, or way to go about it? Would MOT (frost circles, to be specific) help?

I looked at the extent of resonance, and other such stabilizing phenomena/interactions. However, that only tells the extent of stabilisation of the compound due to those phenomena, not as a whole.

Edit: I wish to predict the order of stability using knowledge of chemistry, and not check enthalpy of formation data and then establish the order.


texts: What would explain urine that resists freezing?

texts: A frozen urine specimen is required for an organic acids lab test, but the urine refuses to freeze after 4 days in a regular freezer turned as low as it will go. What would explain this, and how cold might it need to be to freeze?


texts: The cutoff keeps defaulting to 0.05 in Jmol

texts:
I am using Jmol for previewing chemical structures. I need the isoSurface value to be 0.008 for 3d printing purposes.But, the cutoff for isosurface keeps defaulting to 0.05.

How should I change it and can anyone also suggest why this keeps happening?


texts:
When we are titrating acid/base using ph meter we add distilled water to immerse the ph electrode.
Won't this affect the concentration of the acid/base: I mean isn't  this dillution.
Won't  this affect our calcultion of the concentration at the end.


texts:
My question is regarding $\ce{HCl}$. In my book it states that:

$$\ce{HCl (aq) -> H+ (aq) + Cl- (aq)}$$

I understand that when added to water the $\ce{H}$ leaves its electron to the $\ce{Cl}$ atom forming the $\ce{Cl-}$ and the $\ce{H}$ attaches to water to form the hydronium ion ($\ce{H3O+}$). Alltogether:

$$\ce{HCl + H2O -> H3O+ + Cl-}$$

Why does this dissociation actually occur scientifically? What causes the $\ce{H}$ to leave its electron behind to the $\ce{Cl}$ and form the hydronium ion? Why does water ($\ce{H2O}$) take the additional $\ce{H}$ ion? What is the general concept here in dissociation? Electronegativity?


texts: Xylan vs. Teflon for non-stick food pans?

texts:
I am looking at non-stick pans and some are Xylan® others, and most, are Teflon™.

What are the chemical differences?
What is better for cooking?
What is better for health safety?

I do know that Teflon can be consumed without a problem, as it is never degraded, but at very high temperatures the fumes are dangerous.


texts: My teacher told me that when we oxidise styrene with $\ce{KMnO4}$, it will stop at benzaldehyde. But I think that it will continue to go on till benzoic acid. Am I right?


texts: How do indicators work when they mixed with each other?

texts:
Methyl orange, bromothymol blue and phenolphthalein indicators were mixed together to form a solution.

Over what pH range would the solution be yellow?

I cannot understand the question. If two or more different indicators are mixed, do they still work as indicators? Because each their colours will blend with each other and result to formation of a new colour, how can we know what the color will be?


texts: I have a 8000 gallon water tank that has always had pristine clear water.   I have a brass float valve at the top input to the tank.  Someone put an aluminum ladder in the tank (15 ft deep tank) and after who knows how long, the ladder was encrusted with a white gooey powder and the water turned milky.  what happened?  Main question is IS the water safe to drink or how do I get rid of whatever is in there.


texts: What is the charge on the copper ion in antlerite?

texts:
Antlerite is $\ce{Cu3(SO4)(OH)4}$.

I'm trying to get the charge on the copper ion in this substance.  So far I have the mass of $1$ mole of antlerite, its percent oxygen content, and the number of individual hydroxide ions in a $\pu{955 mg}$ bead of the substance, if that information helps at all.

I need help to solve this question.


texts: Why is the silver nitrate chemical test more favorable than that of sodium iodide?

texts:
Two tests to determine the presence of alkyl chlorides are the silver nitrate in 1% ethanol and sodium iodide in 15% acetone tests.  These two tests both produce a precipitate when added to chloride ions (AgCl and NaCl respectively).

NaI in acetone must often be heated to 50ºC for several minutes to produce a visible precipitate.  In contrast, $ \ce{AgNO3} $ typically does not require heat and immediately produces a visible precipitate.

Why is the silver reaction so much more favorable than that of sodium?


texts: Investigating the displacement of a Se anion by a Sulphide anion

texts:
I am working with CdSe Quantum Dots suspended in hexane. I then tested the photoluminescence of my solution. Then I mixed my CdSe dots with a mixture of an organic conducting polymer which was dissolved in chloroform. I am attaching the structure of my polymer below.

My idea was to embed the dots in the polymer matrix. This would obviously quench the resultant luminescence of the dots because the excitons at the surface of the dots would be delocalized by the conducting matrix, but this should not result in a wavelength oriented shift of luminescence, but I am getting a shift. I am attaching the results of my photo-luminescence along with the structure of the polymer chain.

I suspect that the shift of the luminescence observed is due to an attempt by the S radical in the benzene ring of the polymer to displace the Se radical from my CdSe dots, or is there any other way that my dots could get chemically attacked by the polymer? And if so, is there any way to check it? Like a form of spectroscopy for instance?

The polymer to the left is PDMEET and the one to the right is PDMET. The shift in the luminescence image comes here.

.


texts: How can we define a non-spontaneous reaction?

texts:
Consider a reaction:$$\ce{$aA + bB$ <=> $cC + dD$}$$

The value of reaction quotient at a certain time $t$, $${Q_c = \frac{[C]^c[D]^d}{[A]^a[B]^b}}$$
where the concentrations $[A], [B], [C]$ and $[D]$ are at time $t$.

Let the reaction start initially at $t = 0$, with only reactants $i.e.$ $[A]$ and $[B]$ equal to say $1$ mol and $[C]$ and $[D]$ equal to $0$ mol. Hence, $$Q_c = 0$$

We know that the value of equilibrium constant $K_c$ must be such that, $$K_c > 0$$
Thus, $$Q_c < K_c$$
Which is the only condition for the advancement of reaction in forward direction. This condition does not consider the value of change in Gibbs energy $\Delta G$.

Now, considering the relation $$\Delta G = \Delta G^o + RT~\mathrm{ln}~Q_c$$
When $Q_c = 0+$ then $\mathrm{ln}~Q_c \to -\infty$, which means $\Delta G << 0$ and reaction is spontaneous in forward direction.

Hence, can it be concluded that every reaction is spontaneous in forward direction if it starts with only reactants?

If so, how can we define a non-spontaneous reaction?


texts: How to avoid oxidation of Si using a sub nanometer layer

texts: Does anyone know how and which material to use to protect a Si layer from Oxidation by a  small layer of thickness less than 1 nm ? (probably using atomic layer deposition)


texts: Dipole moment of ferrocene conformations

texts:
Which conformation of ferrocene has a zero dipole moment?

I thought that the answer should be the staggered conformation because it would have the cyclopentadienyl groups oriented away from each other. However, the answer given is the eclipsed form. I can’t understand why that happens.


texts: How is the hydration state of a chemical related to its adsorption of water?

texts:
I am trying to understand adsorption and hydration states better, and I was thinking about the different hydration states of calcium sulfate - anhydrous ($\ce{CaSO4}$), hemihydrate ($\ce{CaSO4*1/2H2O}$), or dihydrate ($\ce{CaSO4*2H2O}$).
I would assume that $\ce{CaSO4}$ and $\ce{CaSO4*1/2H2O}$ would adsorb more water than $\ce{CaSO4*2H2O}$, and I am suspecting that $\ce{CaSO4*2H2O}$ barely adsorbs any water at all since it is "saturated" in a way. But I cannot find any information on this. In fact, I can't seem to find any sources mentioning adsorption in the context of hydration, which is surprising to me - I would intuitively assume that these phenomenons are closely related.
I would therefore appreciate an explanation of the relation of adsorption and hydration. Basically, does a lower hydration state generally imply stronger adsorption? Is adsorption in fact the dominant process by which a chemical changes its hydration state? And how does desorption work for hydrated chemicals?


texts: Why is detergent better at cleaning than soap?

texts:
Soaps and detergent are both molecules that have a polar head and a long organic tail. In Soaps, the head is often a carboxylate ion $\ce{COO-}$ where as a detergent has a benzosulphonate $\ce{C6H11SO3-}$(or other) head:

I have often seen that detergents are 'stronger' than soaps. Why is this? It is given as the reason why we don't wash our skin with detergents. The only answer I could find is that detergents don't form insoluble salts with Mg and Ca (scum) but doesn't seem like it would have a large impact. So why are detergents stronger than soaps?


texts: What exactly happens when vegetable oil is partially hydrogenated?

texts:
My current assumption is that partial hydrogenation requires a polyunsaturated fat, because partial implies at least one but not all, which means there must be at least two double bonds in the fat, hence polyunsaturated, right?

Assuming that is correct:

My current understanding is that when you bubble hydrogen (using some heavy metal catalyst) through a vegetable oil, somehow this results in transforming polyunsaturated fats to unhealthy forms of unsaturated fats called trans fats.

What exactly is happening, here? I initially assumed that adding hydrogen to the fat would do little more than making double-bonded carbons into single bonds and then attaching two hydrogen atoms to the now-free valence electrons.

But apparently it also removes cis-kinks and makes them into straight trans-lines, which doesn't change the number of hydrogens but rather changes the shape.

So what's going on here exactly? What do we say partial hydrogenation is actually doing to the polyunsaturated fat?


texts:
I have some basic chemical measurement questions. I have to mix 3% of potassium sulfate with calcium sulfate as an accelerant. How do I calculate the 3%? Base it off 100%? Does this question make sense?

Also, I need to measure out 5cc amounts of powder from a large bucket of powder. Is there a measuring cup for cubic centimeters?


texts: I am doing distillation using system of glassware including a flask and a glass joint. Recently I've faced a problem: the glass joint stuck in the flask. I tried to remove it but it broke and hurted my finger. I want to ask how to prevent this from happening again: can I use a paper masking tape or continue using grease? I am thinking to try the adhesive tape do you think it deserves trying?


texts: What is wrong with storing deionized water in glass containers?

texts: I have heard that in general storing deionized water in glass bottles is ill advised and that it is better to use plastic. Additionally this is especially important for water used in ICP. I have noticed that ICP standards (which use 1-2% nitric acid) all come in polyethylene bottles as well though the nitric acid used for rinsing (10%) is stored in a glass reservoir. Is there some reason that glass is unsuitable for ICP applications or is it another just economical to use plastic?


texts: These days I am working on a research project where I am supposed to run TLC for samples which are wax extracts from coconut butten nuts using chloroform as the solvent. All the samples have been concentrated to 10% from its original volume. I recently run a TLC for a sample using hexane(90%):diethyl ether(7.5%):acetic acid(1%) as the solvent system (this solvent system has been used to run similar wax extracts). But my TLC run resulted me very diffused streaks  having some curves towards both the sides  of the tlc plate. Can anyone tell me why this happens??


texts: Could an extremely strong reducing/oxidising agent attack nitrogen molecules?

texts: Could a very strong reducing agent like lithium aluminium hydride or a very strong oxidizing agent like manganese heptoxide react with $\ce{N2}$? Usually when people talk about reactive substances they emphasize either strong electron acceptors or donors. I am wondering if using such compounds could be employed in a brute force method of dissociating $\ce{N2}$ molecules. I know there exist industrial methods for that already, but i'm poking around to see if maybe there's a way to do it under atmospheric pressure without tailored molecules like enzymes or organometallic complexes.


texts: Is there an example of a closed shell molecule with a permanent ground state magnetic dipole?

texts:
It seems that molecules of point group C$_{n}$ and C$_{nh}$ can in principle support a permanent magnetic dipole moment (Barron, 2004). However, I cannot think of any closed shell molecules that physically have a magnetic dipole in the ground state.

Is this ever observed, and can you give an example of such a case?

Citation: Barron, Laurence D. Molecular light scattering and optical activity. Cambridge University Press, 2004.


texts: Ionisation Energy and Evidence of Subshells

texts:
In Chemistry Electron classes, I was told that first ionisation energy gives evidence of electron shells.

Now is this true due to the steep increase shown on a first ionisation graph when the previous shell is emptied, or am I wrong completely?

Thanks, Dave.


texts: Why is the polar-nonpolar electronegativity difference defined to be 0.4?

texts:
In introductory college chemistry, bonds between elements that have an electronegativity difference $\Delta EN > 0.4$ are generally consider to be polar (and thus have a dipole moment), while $\Delta EN < 0.4$ bonds are considered to be nonpolar. I think more advanced chemistry classes generally don't adhere strictly to this threshold, but I'm still curious if this 0.4 threshold has any meaning (or if it's just arbitrary).

For example, if there's an experiment plotting $\Delta EN$ vs. the intermolecular force strength, and there's a big jump on the graph at 0.4, that would be convincing evidence. Does anyone have an explanation along this line of reasoning?

(My question could also apply to the $\Delta EN > 1.7$ threshold for ionic vs. polar covalent. I saw a question on this before here, but I think it's worth further discussion.)


texts: Use of repeated numerical prefixes for substituents on methane

texts:
Take trichloromethane for example. Is its preferred IUPAC name:

  1,1,1-trichloromethane

or simply

  trichloromethane

And which is that rule in IUPAC that governs this naming? Thank you!


texts: Synthesis of 2-Phenylcyclopentanone from cyclopentanol

texts: My best try was to use aldol condensation after the reduction of the substrate(cyclopentanol) but that gives me a product with a methylphenyl substituent(2-Phenylcyclopentanone), nor a phenyl only.


texts: Predicting the products of reaction between ammonia and hydrogen peroxide

texts:
Like we do in organic chemistry is there any way to write the mechanism of the reaction between $\ce{NH_3}$ and $\ce{H_2O_2}$?

Can the products be predicted?


texts: Compressibility Factor Graph - Which gas attains a deeper minimum?

texts:
As in the given graph, how do I predict which curve among that of hydrogen, methane, and carbon dioxide attains a deeper absolute minimum? (greater deviation from Z=1). In fact, how do I make this comparison for any gases for that matter, and on what factors does this depend?

Is there any temperature dependence of the above?

If nothing can be said in general, I'd at least like to know how to make the comparison for ammonia and methane, as that has previously been asked in a contest years ago.

I'm looking for more of qualitative comparison, but all sorts of answers are welcome.


texts: Why do nitrile gloves turn yellow from sweaty hands?

texts:
When I take off my nitrile gloves after some hours in the lab, the inside of them has turned yellow. This happens especially in the regions around joints.

I suspect this is due to a reaction between some compounds in the sweat and the nitrile, but I couldn't find any definite answer online about what the responsible mechanism for this is.

What exactly is reacting and turning yellow?


texts:
Can hydrogen bonding occur if both O and H are in a ring having 6 members  however the ring is concave .
Example
3 hydroxycyclohexanone


texts: why do atoms need to be ionised in a mass spectrometer?

texts: why do atoms need to be ionized in a mass spectrometer? why can't you determine the mass of the atoms when they are not ionised? Also what is the mass-to-charge ratio


texts: Why are chelate complexes more stable than other complexes with unidentate ligands?

texts: I read that complex compounds with chelating ligands are thermodynamically more stable than complexes without them. Why would that be so?


texts: Determining identity of unknown compound with NMR data

texts:
I have the following IR spec, C NMR and H NMR data. The boiling points determined for the unknown compound were 116.8 and 119.1°C (two trials). Given the possible compounds, the unknown can be one of:
3-methyl-2-butanol
1-butanol
3-pentanol
2-pentanol
2-methyl-1-butanol. (These are based on boiling point)
I have eliminated some of these choices based on the number of different types of carbons (4, as shown on C NMR) but am not sure where the H of the OH is indicated in H NMR. There is no singlet present among the 3 groups of peaks, so where would it be?


texts: How to calculate the solubility product for PbS from galvanic potential?

texts:
Knowing that at 25 °C the following galvanic cell:
  $$\ce{Pb~|~Pb(NO_3)_2~1M~||~PbS~saturated~|~Pb}$$ shows an $\mathrm{EMF} =0.413~\mathrm{V}$, find the $K_\mathrm{sp}$ of $\ce{PbS}$.

My Approach
This is a concentration cell based on $\ce{Pb^2+}$. Since $\ce{Pb(NO3)2}$ dissociates completely, while $\ce{PbS}$ is a salt with a low solubility, the left semicell will be the cathode and the right one the anode.
So we have the following semireactions:
\begin{align}
 \ce{Pb^2+ + 2e- &-> Pb}  && \text{(cathode)} \\
 \ce{Pb  &-> Pb^2+ +2e- } && \text{(anode)}
\end{align}

And for the anode we also have $$\ce{PbS <=> Pb^2+ + S^2- }$$ where $\ce{[Pb^2+]} = \ce{[S^2- ]}= \sqrt{K_\mathrm{sp}}$.
So the semicell potentials are:
\begin{align}
E_\text{cathode} &= E^\circ\\
E_\text{anode}   &= E^\circ - \frac{0.059}{2} \log_{10}{[\ce{Pb^2+}]}\\
\end{align}

Thus:
$$0.413~\mathrm{V} = E_\text{cathode} - E_\text{anode} = \frac{0.059}{2} \log_{10}\ce{[Pb^2+]} \Rightarrow \ce{[Pb^2+]} = 10^{14} $$
And: $$K_\mathrm{sp} = \ce{[Pb^2+]}^2 = 10^{28}$$

I'm sure that I'm wrong for a sign but I don't understand where is the error.


texts:
My chemistry teacher once told me, that every atom should have at least as many neutrons as protons, to keep the electrons from crashing into the nucleus.

Protium, however, doesn't even have neutrons to begin with. How does this work? Or was my chemistry teacher wrong about this?


texts:
I’m trying to learn about ions. There is a slide with examples about combining cations with anions. It goes like this:

  $$\text{For} \ \ \ce{Al^3+} \ \ \text{ and } \ \ \ce{O^2-} \ \ \text{you get} \ \  \ce{Al2O3}$$

Wait what? So you have an atom of aluminum (in this case a cation because it loses three electrons) and an atom of oxygen (an anion since it receives two electrons). You combine them. Why do you now have TWO atoms of aluminum and THREE atoms of oxygen? Why does combining a cation and an anion suddenly spawn new atoms? And what happened to their charges?

The next example is this:

  $$\text{For} \ \ \ce{Ca^2+} \ \ \text{ and } \ \ \ce{Br-} \ \ \text{you get} \ \  \ce{CaBr2}$$

Alright. I see a pattern. For some reason, if the charge of an atom is positive or negative, such number will define the number of atoms for the other element. So since calcium has $2{+}$, there would be two bromine. And since bromine has $-1$ there will be one calcium. I don’t get why, though.

And a third example,

  $$\text{For} \ \ \ce{Na+} \ \ \text{ and } \ \ \ce{CO3^2-} \ \ \text{you get} \ \  \ce{Na2CO3}$$

Ok so this is a bit weird since there are now three elements involved.

But according to the pattern, since sodium has charge $+1$, there should be just one $\ce{CO3}$ molecule. And since $\ce{CO3^2-}$ has a charge of $-2$, there should be two of sodium.

Great, I suppose it’s an useful pattern, but my questions are:

Why? Why does losing/gaining an electron cause the other element to gain/lose atoms?
Does this pattern apply only when you combine a cation with an anion? What if it is the other way around? (An anion with a cation, or does it make no sense at all?)
After combining a cation with an anion, do both atoms lose their charge? Observe how the results no longer have $+$ or $-$ superscripts.


texts:
Copper(II) ions are blue and chromate(VI) ions are yellow therefore copper(II) chromate(VI) would turn out to be green because it's a mixture of blue and yellow.

In the same way, silver ions are colourless while chromate ions are yellow. So shouldn't silver chromate be yellow as well?


texts: Parameter effects on kinetics of esterification for bio-diesel production

texts:
I want to discuss the effect of parameters on the kinetics of esterification for bio-diesel production. In esterification process, temperature effect and molar ration are two important parameters. During conversion of oliec acid with methanol to bio-diesel, temperature contributes more than molar ratio ( happen before 70 to 80 % conversion to bio-diesel). But after 70 to 80% conversion molar ratio contribute more than temperature.

My question is why this happens. Why the contribution of temperature and molar ratio reverse after 70 to 80% conversion to bio-diesel?


texts: Partial pressure of water in a submerged balloon

texts:
A balloon is half filled with water at sea level ($P = \pu{1 atm}$, $T = \pu{298K}$) such that the partial pressure of water is $\pu{24 mmHg}$.  It is then submerged to a point where $P = \pu{2 atm}, T = \pu{298K}$.  What will be the vapor pressure of water at that point?

My first instinct is to find the mole fraction of water in the balloon.  Using Dalton's law,

$P_{total} = P_{\ce{H2O}} + P_{\mathrm{atm}} = 24 + 760 = \pu{784 mmHg}$

$P_{\ce{H2O}} = X_{\ce{H2O}}\,P_{total}$

Solving for $X_{\ce{H2O}}$, I get $24/784$.  Then I use that to find the new partial pressure at the new depth, $(24/784)\cdot 1520$.  But the answer seems to be that the partial pressure of water remains constant. Can someone explain why the partial pressure will be constant?


texts: With molecular formula, how do I know if it linear or one element surrounded by other elements?

texts:
If I was given a molecular formula (i.e, PoOBr2), how do I know if the Lewis structure is linear (4 in-a-row, basically a straight line) OR it is an element surrounded by other 3 elements?

I know the answer for this is Po in the central and surrounded by other elements.


texts:
Consider as solution of pure water at $\pu{25 ^\circ{}C}$ with a $K_{\mathrm{w}} =  10^{-14}$.
If we are to add an acid to the mix we would observe an increase in hydronium and an equal decrease in hydroxide content.
Yet, I fail to see how the hydroxide ion concentration can decrease with an increase in hydronium concentration.
Lets add $\ce{HCl}$ to our solution: $$\ce{HCl + H2O -> Cl- + H3O+}$$
Concentration $[\ce{H3O+}]$ increases,  concentration $[\ce{OH-}]$ decreases in order to fulfill the $K_{\mathrm{w}}$ constant of $10^{-14}$.
Through what reaction exactly then will the hydroxide content decrease (by turning into water I assume)? Where does $\ce{OH-}$ gets an $\ce{H+}$ from? Not from $\ce{H3O+}$, I assume seeing that every molecule of a strong acid is said to turn into an hydronium ion 1:1.
Please enlighten me.


texts: Why is a double bond given priority over substituents during IUPAC nomenclature?

texts:
My book names this compound as 6-ethyl-5-methylcyclohex-2-en-1-one.
I have learnt that after numbering the principal functional group which is ketone in this case, we have to treat all other groups as substituents and therefore I think the name should be 2-ethyl-3-methylcyclohex-5-en-1-one.
Why should the double bond be given priority?


texts: What means can be used to distinguish different sorts of plastic?

texts:
So, different sorts of plastic usually have different marks on them (the resin identification code, like 1/PET for polyethylene terephthalate etc). However, sometimes one can encounter a piece of plastic (or film; it can be even non-plastic like cellophane) without identification code or whatever sign. What ways to distinguish plastic types can you propose?

It is desirable that these methods can be applied without lab hood and chemical hazard when applied to ordinary types of plastic (at least PET, HDPE, PVC, LDPE, PS, PP, cellophane) unless there's a simple way to eliminate some variants which would cause hazard (like "don't use this for white non-transparent plastics and that otherwise). Ideally this shouldn't require reagents which are hard to accuire but if you have some ideas, throw them anyway.


texts: How do you determine which non-metal is written first in a covalent compound? This has been a confusion for me for quite some time.


texts: Is it possible to identify the source of a protein hydrolysate

texts:
I have a powder which only declares to be "Protein Hydrolysate"
Meaning that the all the protein has been broken down.

We've tried to identify the source of the powder with DNA research. But no usable DNA (parts) where found.

Is there a way to identify the source of this powder? (ie. chicken, pork, cow, shark, dolphins or unicorns)

For clarification, we failed to find any DNA in the powder. so we're looking for alternative ways to analyse it.


texts: Determine surface area of heat exchange tube

texts:
A heat exchanger is used to cool down a stream of $\pu{20 kg s-1}$ of water from $\pu{80 °C}$ to $\pu{60 °C}$. The cooling water enters at a rate of $\pu{12 kg s-1}$ and $\ce{20 °C}$. The overall heat transfer coefficient is $\pu{2 kW m-2 K-1}$ and the heat capacity of water is $\pu{4.183 kJ kg-1 K-1}$

Calculate the surface area.

I am stuck on what the last step of the calculations should be.
I began with calculating the outlet temperature for the cooling stream using that $q$ is constant, I set IN = OUT:
$$m_hC_pΔT_\mathrm{in} = m_cC_pΔT_\mathrm{out}\label{eq:1}\tag{1}$$
From $\eqref{eq:1}$ I got that $T_\mathrm{2out} = \pu{53 °C}$
Then I calculated the logarithmic temperature difference, which I got to be
$ΔT_\mathrm{ln} = \pu{-33.075 °C}$.
After this I am confused as to how I can get the surface area of the tube.
Edit
I did a heat balance, IN - OUT = 0:
$$(m_hC_pΔT_\mathrm{in} + m_cC_pΔT_\mathrm{in}) - (m_hC_pΔT_\mathrm{out} + m_cC_pΔT_\mathrm{out}) = 0$$
simplified into:
$$m_hC_pΔT_\mathrm{in} - m_hC_pΔT_\mathrm{out} - UAΔT_\mathrm{ln} = 0$$
However when I try to solve for A I get a negative value, which isn't correct.


texts: Concentration of minor products in the nitration of nitrobenzene

texts:
I was baffled by the concentration of minor products in the nitration of nitrobenzene.

This is the picture from Solomon Frhyle's book, page $695$:

Since nitro is electron withdrawing and meta directing, the high concentration of meta isomer is justified. However, I had predicted the order to be $m>p>o$ because both nitro groups are electron withdrawing and if they are close together they will cause destabilisation by increasing charge density at adjacent places. On the other hand in the para isomer, the nitro groups are far away so development of partial positivity at opposite ends shouldn't be a big problem.

Could someone explain why the para isomer is less in concentration and how my reasoning is incorrect?


texts: According to the law of equivalence, the number of equivalents of each reactant and product in a reaction are equal. Why is this the case?


texts: Does davis safety lamp detect explosive gases in ship compartments?

texts:
I feel managers at Bangladesh ship breaking yard are not properly caring for safety of workers. Many workers die in explosions while salvaging metal.  documentary available  on YouTube by National Geographic Channel.
My question is does Davis safety lamp work in compartments  of a ship since it detects explosive gases in coal mines.


texts: How does concentration affect The Position Of Equilibrium?

texts:
I was taught that
when the concentration of the reactants is greater than the concentration of products then the position of equilibrium is shifted towards the left.

However when I used La'Chateliers Principle then we know that if you increase the concentration of reactants then the system wants to revert that change a hence produce a higher concentration of products (and subsequently a lower concentration of reactants) but wouldn't this then mean that the equilibrium would shift to the right?


texts: I'd like to better understand radiocarbon dating, however, I do not know what resources I must use in this regard. Could someone walk me through the process of radiocarbon dating with a few examples? (I'm already well-versed with the basics of nuclear chemistry).


texts: What should be the oxidation state of oxygen in HOF (hypofluorous acid)?

texts:
What should be the oxidation state of oxygen in $\ce{HOF}$ (hypofluorous acid)?

Sources on the internet have confused me. Most state its oxidation state to be 0, while the others state that it is -2 (considering the oxidation state of fluorine to be +1, which is a bit surprising for me as it's the most electronegative element in the periodic table)

Source stating the oxidation state to be -2:

  J. Chem. Educ. 1972, 49 (4), 299:
  The two possibilities brought forth in the Note are (1) assign hydrogen +1, oxygen -2, and fluorine +1 or (2) assign H +1, oxy- gen 0, and fluorine -1. On the grounds that $\ce{HOF}$ is a powerful oxidizing agent, the conclusion reached in the Note is that (1) should be favored.

Other sources stating the oxidation state to be 0:

Yahoo Answers!
Answers.com


texts:
So I was reading through my textbook on deviations from an ideal gas, and they had plotted a curve of experimental PV/nRT against the pressure.

They talk a lot about why the volume is really smaller than what the ideal gas predicts, and so on, and thats why as the pressure increases, the deviation from the ideal gas law increases. They further accredit the imbalances to IMFs, and how when the molecules are in closer contact, they tend to form stronger and more IMFs. This all makes sense. This would imply that as the pressure increases or as the temperature decreases, the deviation from the ideal gas would be increasingly over 1. However, when looking at the curve they present, it isn't a clear direct path from no deviation to much deviation. For example, when looking at Methane, CH4, at 200 atm it has a certain negative magnitude, yet at 400 atm, it is back to acting like a ideal gas.

What causes this section of the curve[P=0 to P=400] of Methane that doesn't follow the general trend of increasing pressure --> more deviation from ideal gas?


texts:
Why is o-halophenol more acidic than m-halophenol?

My thoughts: m-halophenol has only the -I effect which favors acidity while o-halophenol (which has greater -I) but also has +r which should reduce the effect caused by -I.


texts: Can someone draw what the missing structure is? I can't find it.


texts: Change in temperature if salt is dissolved in water with different initial temperatures

texts:
I will mix a salt with room-temperature water and 8 degree Celsius water. Then I will compare the heat of solution with each other.

Does the initial temperature of the water affect how much the heat of solution and change in temperature will be?


texts:
Problem
Problem 3, concept check 8.2 from Campbell Biology [1, p. 150]:

Some partygoers wear glow-in-the-dark necklaces that start glowing once they are “activated” by snapping the necklace. This allows two chemicals to react and emit light in the form of chemiluminescence. Is the reaction exergonic or endergonic? Explain.

Answer
Answer key [1, p. A-8]:

The reaction is exergonic because it releases energy—in this case, in the form of light. (This is a nonbiological version of the bioluminescence seen in Figure 8.1.)

From [1, p. 143]:

Figure 8.1 The green glowing spots on the outside of this Brazilian termite mound are larvae of the click beetle, Pyrophorus nyctophanus. These larvae convert the energy stored in organic molecules to light, a process called bioluminescence, which attracts termites that the larvae eat. Bioluminescence and other metabolic activities in a cell are energy transformations that are subject to physical laws.

Question
The answer is an exergonic reaction. What I understand of an exergonic reaction is that not only does it have a negative $ΔG,$ it releases energy. In this case, the energy released is light energy.
My original answer endergonic reaction as for the problem given, to “activate” the necklace, doesn’t it require energy from partygoers to snap the necklace? Is the $ΔG$ value for the light being released much less than the $ΔG$ value of the energy being used to snap the necklace?
Reference

Urry, L. A.; Cain, M. L.; Wasserman, S. A.; Minorsky, P. V.; Orr, R. B.; Campbell, N. A. Campbell Biology, 12th ed.; Pearson: New York, NY, 2020. ISBN 978-0-13-518874-3.


texts: Finding Pressure of M in a Charge Exchange

texts:
Ar (RE = 15.5 eV) is the reagent gas in a charge exchange experiment. If Ar+ reacts with anisole with a rate constant of 2.26x10-10cm3 molecules-1/s-1 and 65% of the Ar ions react in 25 milliseconds, what is the PRESSURE of anisole if the temperature of the ion source is 25 C? The IE of anisole is 7.78eV.

Not exactly what to do here. I know that -Hrxn=RE-IE, meaning that -Hrxn=7.72eV. Converting this would be -Hrxn=749.21kJ/mol. How would you go about using the rest of the information given along with this -Hrxn to find the pressure?


texts: Why do the electrons, arising from the oxidation of the anode, flow through an external circuit? Why does it not just flow through the electrolyte and reduce the cathode? Why do the electrons give the wire preference?


texts: Does the bond dissociation enthalpy vary with temperature?

texts:
The $\ce{H-H}$ bond enthalpy is $436 \mathrm{kJ/mol}$:

$$\ce{H2 (g) -> 2H (g)} \qquad \Delta H = +436 \mathrm{kJ/mol}$$

Does this only apply at the standard temperature of $298 \text{K}$, i.e. would the bond enthalpy vary if I decrease or increase the temperature?

And is it practically just so that, for a temperature $T$, as long as you pump the bond enthalpy’s worth of kilojoules into the substance, it will be atomized?


texts: How to determine if a complex has a crystal field stabilization energy of zero?

texts:
I have encountered with the following question:

  The complex having zero crystal field stabilisation energy is:

  (A) $\ce{[Mn(H_2O)6]^3+}$ (B) $\ce{[Fe(H_2O)6]^3+}$ (C) $\ce{[Co(H_2O)6]^2+}$ (D) $\ce{[Co(H_2O)6]^3+}$

Zero crystal field stabilisation energy will be the case when the metal has either $d^{10}$ configuration or $d^5$ configuration with every orbital having one electron. For Iron($\ce{Fe^3+}$) the d orbital is half filled. Now the problem is, water is in the middle of the spectrochemical series, i.e. it is moderately strong ligand. So, how to decide whether the d orbital will have the 'every orbital half filled' condition or not ?


texts:
When it's cold outside, some household water-based products (liquid soaps, wet wipes) become cold to the touch as well. Since these products are used directly on the skin, their coldness may cause discomfort to the user (especially babies and the elderly).

I am wondering if there is any convenient way to warm these products at least to room temperature of 23-25°C to reduce the discomfort. I am guessing the main obstacle is water's relatively high specific capacity (at 15°C, it is approximately 4.19 J/g∙°C, according to this table, taken from this blog entry), which may also be influenced by other ingredients of the soap, but I'm not sure in which direction...

As a possible solution, I thought of putting hot water in some vessel and submerging the soap container in it. I haven't tried it yet, but I wonder how hot should the water be and how much water do I need (i.e. how deep should the container be submerged), when taking into account the volume of soap and the plastic container itself.

And there's still the issue of the wipes, which can't be submerged in water...

Repeating the question: Is there any convenient way to warm water-based products to room temperature at home?


texts: Which steps are most critical in driving glycolysis foward?

texts:
I'm assuming that the non-reversible steps (1,3,10 on the chart below) in glycolysis are the most critical in driving it forward, but I have a feeling it might be something else.  If so, why are they the most critical?

I've been using this chart as a reference.

The second half of my question is how mass-action ratio (Q) affects these reactions.


texts: How to determine which combination of substances will give a buffered solution given target pH and Kb of each substances

texts:
What combination of substances will give a buffered solution that has a pH of 5.05? (Assume each pair of substances is dissolved in 5.0 L of water.) (Kb for NH3 = $1.8 × 10^{–5}$; Kb for C5H5N = $1.7 × 10^{–9}$)

  a)1.0 mole NH3 and 1.5 mole NH4Cl

  b)1.5 mole NH3 and 1.0 mole NH4Cl

  c)1.0 mole C5H5N and 1.5 mole C5H5NHCl

  d)1.5 mole C5H5N and 1.0 mole C5H5NHCl

According to my text book it is choice C but I do not understand why and here was my thought process:

For starters I change the $K_b$ into $K_a$ to get : $5.6*10^{-10}$ for Ammonia and for the other I got: $5.9*10^{-6}$

It seems to me that this has to do with the Henderson Hasselbach Equation so I set up the following:

$5.05=5.9*10^{-6}+log{\frac{Base}{acid}}$

$5.05=5.9*10^{-10}+log{\frac{Base}{acid}}$

because I already have two substances.

But from here I feel like that wasn't the best route I should take because I got stuck right here and would like some assistance.


texts:
Why do vinylic carbocations generally not undergo hydride rearrangement from neighbouring sp3 carbon to get more stability?

According to me, a rearrangement would lead to an allylic carbocation, which is more stable than vinylic, hence the rearrangement should be favorable.


texts:
(E)-stilbene may be separated by crystallization from (Z)-stilbene and the side product of the Wittig reaction, triphenylphospine oxide (TPPO), by using absolute ethanol. My question is why? (E)-stilbene and (Z)-stilbene are isomers of each other, why (and how) do they differ in polarity? If both are of low polarity, why is (Z)-stilbene soluble in ethanol, but not (E)-stilbene? Also why is (Z)-stilbene the more polar isomer of the two and has a lower $R_f$ value in TLC?
An initial reasoning of mine was that (Z)-stilbene were more hindered than the (E)-isomer, and thus less stable. Yet, this doesn't make sense to me.


texts: Why do we not include water in equilibrium expression calculations? And can you go into detail on why pure liquids and solids have a constant concentration as well, please and Thanks.


texts: Can two metals combine to form a compound?

texts: what I mean is can a metal react with another metal to form a compound? non-metals react with each other and form compounds with covalent bonds can the same happen with metals.


texts: Why is a LCAO necessary within Hartree Fock?

texts:
As I understand it, the electronic Schrödinger equation cannot be solved for polyelectronic systems. To circumvent this problem in the Hartree-Fock method, it is assumed that the polyelectronic wavefunction can be written as a combination of single-electron, molecular orbitals. To satisfy the anti-symmetry requirement, this combination takes the form of a Slater determinant.

What is the value of then going on to express these molecular orbitals as a linear combination of atomic orbitals? Would a Hamiltonian written to describe a single electron in the molecular environment (a molecular orbital) not lead to an analytically solvable Schrödinger equation?


texts: Does any chirality-dependent inorganic chemical reaction exist?

texts:
In the particle physics, there are non mirror-symmetric reactions.

In the organic chemistry, particularly in complex proteins, there are reactions producing only a single chirality of molecules.

But what is in the intermediate regime? Does any inorganic chemical reaction exist with an asymmetric chirality behavior?

I suspect, maybe it would be possible with highly asymmetric electron clouds, probably with a significant EM octopole moment.


texts:
The energetics of the mechanism of saponification were previously under debate, but I will admit, I misrepresented a point.

Here is the revised mechanism of saponification proposed by someone other than myself. It is the one on top.

The previously suggested mechanism is in the middle.

The textbook mechanism is the bottom one.

Now, it does seem that if the mechanism were concerted then proton abstraction would be much more plausible from a thermodynamic standpoint. If the second mechanism were akin to scaling Mt. Everest, then the first one looks to me to be more like climbing the rock wall at the gym.

We start with the same reactant - an ester - but in the second mechanism we are going through a dianion intermediate. In the first mechanism however we are simply going through a concerted transition state en route to the stable carboxylate.

So, again, I ask - which is (kinetically) correct?


texts: How does the diffusion coefficient of a species affect the limiting current for a RDE voltammagram?

texts: And how do I find the diffusion coefficient from a Levich plot?


texts: Any substance too poisonous to measure an LD50?

texts:
A recent question on poisons was answered in part by bringing up the concept of $\pu{LD_{50}}$ and animal testing and so on; none of that was new to me, but it did bring to mind a question I don’t know the answer to:

Has there ever been a substance that scientists have actively tried to determine $\pu{LD_{50}}$ for, and could not because they were unable to determine a dosage low enough to kill “just” half of the subjects?

Please note that this question is not restricted, strictly, to any technical definition of “poison.” Rather, answers must meet these requirements:

There must be research (considering that I am looking for something that might be a negative result and those do not get published as much as they should be, I won’t demand peer-reviewed publication, but the goal should have been to attempt peer-review publication if it had worked out—effectively, I mean serious work), and
that research must use the term “$\pu{LD_{50}}$” to characterize the substance.

Basically, I don’t want to get into debates about what is, or is not, a poison here. If a researcher is willing to call something $\pu{LD_{50}}$, then I am willing to accept it as a “poison” for the purposes of this question.

I also don’t want speculation, or for a user here to characterize something as $\pu{LD_{50}}$ when the underlying research doesn’t call it that. It is not enough to say, for example, “well I’m sure even a single atom of antimatter inside your body would be pretty bad,” you need to cite a particular researcher who has performed experiments with the goal of determining what they themselves called $\pu{LD_{50}}$ for that substance.

I suspect the answer is no, but I have no idea how to research something like this.


texts: What is an example of a very low temperature endothermic reaction?

texts:
Shakashiri describes the reaction of solid Ammonium Thiocyanate and solid Barium Hydroxide Octahydrate resulting in an endothermic reaction leading to subzero temperatures. I've performed this experiment and measured temperature as low as about $-10\ ^\circ\text{C}$.

Are there known chemical reactions that can lead to even lower temperatures?


texts: Effect of reduction potential on particle size of chemically precipitated silver particles

texts: Is there no mathematical relationship between redox potential and particle size saying that an $X$ potential should yield a $Y$ particle size? Right now its general that large redox potential results in smaller particles, but I want to know if, for example, for silver particles I use $\ce{AgNO3}$ with glucose reducing agent and say the redox potential is $\pu{0.33V}$, what the ballpark for the particle size should be based on that potential (assuming $\mathrm{pH}$ does not change)?


texts: How can I free base cystamine dihydrochloride?

texts:
I am using cystamine (free based) to conjugate to a phosphate group on an oligonucleotide. I tried several keyword searches on Google for neutralizing the dihydrochloride at the ends of the cystamine. But, I am unable to find a protocol. I had once found a procedure for the process, but I did not reference it and hence I am unable to find it again.

The procedure I followed was:

Dissolve the cystamine.2HCl in water.
Transfer to a separation funnel and add chloroform.
To this add 1N NaOH.
After shaking vigorously collect the chloroform layer which contains the cystamine.
Repeat extraction couple of times using more chloroform.
Pool fractions - dry with anhyd. MgSO4 - transfer to an RBF.
Evaporate on a RotaVap
Dry on schlenk line and store in an inert environment at 4 deg. C.

However, the extraction was not very efficient. Can anyone refer a protocol for the same?

Thanks a lot for your help!!!!


texts: Why can't Ethene Carbocation do Hyperconjugaion?

texts:
Question
I was studying Hyperconjugation and taught that Hyperconjugation is like Resonance of Sigma bonds ( C-H ) when any other Carbocation or alkene or alkyne carbon influences it (sigma bonds C-H). This happens only when the p orbital of that Carbocation, alkene, or Alkyne is parallel to the Sigma bond ( C-H ) so this can't happen on direct carbon neighbors of sigma bond carbon ( C-H ) which are sp hybridized because Carbocation would be far in geometry from the ( C-H ) bond of the neighbor but why can't this happen Alkene? It's hard to specify this in text so I uploaded an image for help.
What I tried? (You can skip this)

Of course, I first Googled it but since this is hard to describe in text so I didn't find useful
results. So I used different methods suggested by Google to smart search and also used methods such
as emphasizing words by quoting them and then only putting words of preference in them and still the
results weren't quite useful.

Then I asked several students but their answers were quite scattered and weren't mostly based on
logic. Upto this time only it was already 2 Hr's on it.

I searched this in some books where Hyperconjugation is mentioned but they were not specifically
describing this topic.

Image


texts:
I have performed a Gaussian16 calculation to explore the size-consistency problem for the CISD and CCSD methods. The system I am studying is the water dimer and the results are not what I expected at first. I have computed the energy of the dimer for both models (single point calculation) where the two monomers are 100 Å away and the energy of the and the energy of the monomer.
I wanted to compute the difference between those energies for both methods as two times the energy of the monomer and the energy of the dimer. If a method is size-consistent, the difference should be zero. These are my results:
$$
\begin{array}{lrr}
\hline
\text{Quantity}  & \text{CCSD} & \text{CISD} \\
\hline
\text{Monomer energy}/\pu{Ha}  & -75.012  & -75.012  \\
\text{Dimer energy}/\pu{Ha}    & -150.030 & -150.026 \\
\text{Abs. difference}/\pu{Ha} & 0.004    & 0.002    \\
\hline
\end{array}
$$
I have been reading many articles and papers and what I expected is that CISD is not size consistent for a system of more than two electrons while CCSD is size-consistent.
However, the value of the difference is larger in the case of CCSD, what makes me think that it is telling me that CCSD is less size-consistent for my problem than CISD. Am I wrong? What do these values mean?


texts: How does hydrogen gas build up in hot water lines?

texts:
Recently I was reading through the owner's manual of a washing machine; notably, the warnings in the front of the booklet. One warning stood out to me; it said that if the hot water in your house has not been run in a few weeks $\ce{H2}$ can build up in your lines. The warning of course stated that this can only occur under certain circumstances so I'm assuming it is quite rare.

Okay, so my question is, under what conditions does hydrogen gas build up in a hot water line?


texts: Is it necessary that filling up orbitals start from spin-up orientation only? And also, is it mandatory to fill the electrons with one kind of spin or they can be filled with spin up and spin down(as shown in the photofor clarifying my doubt)


texts: Is there any formula that can be used to find loss of mass due to binding forces in atomic and sub atomic particles?

texts: Atomic weight of Br-79 is 79.641 if you add the masses of protons and neutrons. However, in periodic table, it is less than the value given here. How is the difference arrived at for all the elements listed in the periodic table?


texts: Can I make aluminium monostearate $(\ce{C18H37AlO4};$ $\pu{344.472 g mol-1})$ by reaction between stearic acid $(\ce{C18H36O2};$ $\pu{284.484 g mol-1})$ and aluminium hydroxide $(\ce{Al(OH)3};$ $\pu{78.00 g mol-1})$ or by adding more aluminium hydroxide in aluminium tristearate?


texts: Generating density matrix of a wavefunction from common quantum chemistry software

texts: I am looking for density matrixes for a couple of closed shell and open-shell systems, and I wonder if there is a trivial way to make e.g.  Gaussian just generate an output for me. I may be wrong but most quantum chemistry software seems to generate the density matrix when checking SCF convergence, so it would make sense if there were an option to save it.


texts:
I do not understand how we obtain the product in option one.
According to Free radical stability order tertiary carbon radical is more stable than secondary carbon radical which is more stable than primary carbon radical. So hydrogen selectivity should also follow the same order. Then why is it that we get option(1) instead of option (2).
I’m only in high school so please try to keep it simple.


texts: How can I test if a spirit (tequila) has oxidised?

texts:
Is there a way to test if tequila has oxidised and if so the level of oxidisation?
It would be best if this could be done without a control sample, but the most important thing is if I can do this with 'household' equipment  - although I do have access to a hydrometer.


texts: How far does the delocalisation (resonance) effects for substituents extend for a conjugated system?

texts:
Let's say we have a conjugated system like this one:

Now, the delocalisation of the benzene electrons with the nitrate system means that the ortho, and para positions on the immediate benzene ring would be more electron deficient than the meta position. This effect will be seen in 1H NMR and 13C NMR signals for the protons or carbons on the ortho/para/meta position. Also, the electrophilic substitution on those positions will be affected.

Now as I understand, the resonance effects of the $\ce{-NO2}$ group is due to the overlap of N 2p orbitals with the benzene ring p orbitals, which skews the sizes of molecular orbitals, and makes certain carbons more electron-deficient than others.

However, are resonance effects independent of distances over which they act? I am not sure if distance would have any role on the skewing of the molecular orbitals.

Does the distant benzene ring, and the double bond in between also show the resonance effects from the nitro group on the first ring? If so, is it as strong, or is it weaker? Can this be seen in NMR spectra? or the reactivity of the distant benzene ring?


texts: What is the softening temperature of styrofoam?

texts:
Does anybody know the softening temperature of styrofoam (expanded polystyrene)?

By styrofoam I mean the solid made of expanded polystyrene balls used in packaging.


texts:
Someone I know mixed the liquid forms of Iron Out and CLR (Calcium, Lime, & Rust Remover) together to clean out a plastic bathtub.

I have the SDS sheets for each:

https://images-na.ssl-images-amazon.com/images/I/61Dkhh0JXRL.pdf - CLR
https://summitbrands.com/wp-content/uploads/2018/03/Iron-OUT-liquid-English-GHS-Rev-01-29-18.pdf - Iron Out

The bathroom smells terrible, has produced a cough in the person using it, and now my eye burns a little from very brief contact. I was wondering what kind of gas (if any) was created when these two chemical cleaners were mixed?


texts: Why do all atomic masses have decimals if there are some elements that don't have isotopes?

texts: I understand that the way to calculate the atomic mass is to obtain a weighted average of the masses of all the isotopes of an element. I also understand that there are about 26 elements that are monoisotopic. If the reason the atomic masses have decimals is because of this weighted average, then it should follow that the monoisotopic elements should have a whole-number mass. Therefore, why do all the atomic masses have decimals?


texts: Proof of buffers inability to maintain exact same pH

texts:
I was wondering if the following is a legitimate proof of the statement above. Assume we have

HA -> A- + H+

where [HA] + [A-] is our buffer.

If we add a small amount of H+ one of two things will happen:

1) The H+ will not react with A- ...thereby raising the pH so we are done.

2) The H+ will react with A- ...converting to [HA]

looking at the HH equation we know that

pH = pKa + log(ratio)

since ratio_before != ratio_after

pH_after = pKa + log(ratio_after) and pH_before = pKa + log(ratio_before)

so therefore

pH_after - log(ratio_after) = pH_before -log(ratio_before)

Now assume pH_after == pH_before.... we get -log(ratio_after) = -log(ratio_before) which is a contradiction of above, so pH_after != pH_before.

What are your thoughts?


texts: How are the molar mass and molecular mass of any compound numerically the same?

texts:
This observation is really annoying me, and the internet isn't providing me with any solid answers. Either their definitions of molar mass completely differ, or they don't stick to their own definition while actually calculating the molar mass of a certain element or compound.

Now, according to Wikipedia,

  The molar mass M is a physical property defined as the mass of a given
  substance (chemical element or chemical compound) divided by the
  amount of substance.

and it's unit is

  g/mol

My understanding of this is that we're calculating the total mass of all the atoms(or molecules) present in 1 mole of that element(or compund). This means that we would have to take the atomic mass of that element and multiply it by the number of atoms present in 1 mole of that element, which is 6.022 × 10^23 atoms.

So for example, the relative molecular mass of water is 18.02 u, and it's almost the same as the molar mass of water, which is 18.015 g/mol.

So my question is, how is 18.02 u × (6.022 × 10^23) = 18.015 g/mol?


texts: How does radiation facilitate the formation of tetravalent iron?

texts:
In reading the article abstract What Oxidation State of Iron Determines the Amethyst Colour?, the author states that in regards to the gemstone amethyst, from clear quartz:

  The crystal was transformed into violet amethyst by gamma-irradiation. The change in colour was accompanied by changes in the Mössbauer spectrum that can be interpreted as the conversion of trivalent iron into the tetravalent state: $\ce{Fe^{3+}→Fe^{4+}}$

How does gamma radiation facilitate the conversion of oxidation state of iron, from $\ce{Fe^{3+}}$ to $\ce{Fe^{4+}}$?


texts: Confusion about the oxidation state of copper in copper cyanide re-dissolved with excess cyanide

texts:
$\ce{CuSO4}$ when reacts with $\ce{KCN}$ forms $\ce{CuCN}$ while it is insoluble in $\ce{H2O}$. It is soluble in excess of $\ce{KCN}$ due to the formation of the following complex:
a) $\ce{K2[Cu(CN)4]}$
b) $\ce{K3[Cu(CN)4]}$
c) $\ce{CuCN2}$
d) none

Answer given is b) but we know that $\ce{Cu^2+}$ is more stable hence anwser should be a), shouldn’t it?


texts: Why is neodymium the most paramagnetic lanthanide?

texts:
My textbook says that paramagnetism rises to a maximum in neodymium.

I don't understand how gadolinium has 8 unpaired electrons, whereas neodymium has only 4. Shouldn't paramagnetism be higher  in gadolinium?

Has this got anything to do with the magnetic moment associated with orbital angular momentum?


texts: Can carbon subnitride be used as a fuel with similar properties to gasoline?

texts: I am trying to figure out if Dicyanoacetylene, aka carbon subnitride, aka $\ce{C4N2}$, can have a similar reaction with air as gasoline, or if it only creates a lot of heat but not much expansion?  As I understand it, the thing that makes gasoline useful is that when it combusts, the product has a much lower density than the reactants, causing a huge expansion to reduce pressure (which drives pistons in an engine).  Does $\ce{C4N2}$ have a similar effect, or does it have only comparatively negligible expansion compared to gasoline and simply generates more heat? Or might it produce a similar expansion or more than gasoline?


texts: Reaction Pathways: What to do when IRC geometries are relaxed (optimized) and the energy changes significantly

texts:
The Story:

Reaction pathways can be difficult things to deal with using electronic structure methods.  Intrinsic reaction coordinates (IRCs) can be determined a number of ways (a discussion of these methods lie way outside the scope of this post).  Suffice to say, the reaction pathway is an 'energy' pathway of reaction, connecting reactants and products, usually through some intermediate and/or transition state (TS).

For the purposes of this question, imagine implementing some sort of IRC technique which begins with a previously resolved transition state (Figure 1).  The computation follows the reaction coordinate in both the forward and reverse directions from the TS energetically downhill until it reaches a (for the sake of simplicity) a minimum energy point with features which satisfy the method used.  In general, the structure and energy of this final IRC geometry should be very representative of the structure which is connected to the TS via the pathway determined.  If you were to optimize this final geometry, you should get good agreement between the optimized structure and the IRC configuration.

Now consider this scenario.  An optimization was performed on the IRC resolved structure B and the energy relaxation was significant and the structure significantly changed, giving rise to a new (and lower) energy.  One could no longer (within the formalism of IRC methods) say that the optimized structure B lies on the reaction pathway, and therefore is not a representative configuration at point B on the reaction pathway associated with the TS.

The Question:

Does anyone know of an example in the literature where this type of behavior occurs?  How does one 'deal' with a situation like this?

Other Information:

Let us assume the following:

That this scenario occurs with a few IRC procedures (not just one).
That the IRC computations were given a ridiculously large amount of
cycles and steps
That various stepsizes were sampled in parallel IRC jobs with no
significant difference in the results

(I will add more as I think of them)

Potentially Helpful Imagery

Imagine two somewhat complex molecules coming together to form a single covalent bond.  You run an IRC from the TS (which describes the bond formation) in the reverse direction and the intermolecular separation begins to increase.  This separation continues to increase until the IRC job terminates properly.  Now imagine running an optimization on these two (slightly complex) molecules which are separated by maybe 4.0 Å.  Obviously these molecules are going to interact because they are not infinitely separated.  You observe the (slightly complex) molecules moving toward each other during the optimization procedure (rotating, twisting, gyrating along the way) until you now have a minimum energy structure which is much lower in energy than the resulting IRC computation.  These two molecules interact via intermolecular interactions (no covalent bonds are formed between the molecules).  This optimized structure is analogous to a reactant complex (as opposed to separated reactants) and has an energy a few kcal mol$^{-1}$ lower than the corresponding IRC geometry.  How on earth does this fit in to the reaction pathway?


texts:
I carried out an experiment and it goes like this:

2-bromoethanol + dihydropyran (DHP) ---> 2-(2-bromoethoxy)oxane

Acidic ion exchange resin was added alongside as a source of H+ ions (catalyst).

If, instead of using acidic ion exchange resin, a conventional acid such as p-toluenesulfonic acid was used as a catalyst. How can it be removed from the product?

I thought of using a weak base, but would there be any side products formed?


texts:
My question as stated above, is how Volume a state function? As described by the  definition of a state function, that it is independent of the path adopted to bring about a change in it, how can volume be one, wouldn't volume change differently if we brought about a change in it by say increasing/decreasing temperature rather than say pressure?

Thanks

PS:Please explain in simple terms, as i am beginner in thermodynamics.

Thanks again.


texts: Rate of reaction and dependence on concentrations

texts:
Consider the decomposition of ozone as follows

(fast)
$$\ce{O3  <=> O2 + O}$$

(slow)
$$\ce{O + O3  -> O2 }$$

The question comes here if the concentration of $\ce{O2}$ is increased , then comment on the rate of the reaction.

increases
decreases
constant
cannot be predicted

My try: I have a confusion that the rate law is not given so we cannot tell about the actual dependence of the rate on the concentration of $\ce{O2}$, I know that the rate law will depend upon the slow step as it is the rate determining step. Answer given is 2) decreases , can we apply Le Chatelier's principle here? Increase in $\ce{O2}$ , backward reaction so less rate?


texts:
In a chemistry olympiad I had this morning, there was a question on the acidity of polysulfanes. Specifically, it asked candidates to explain the increasing acidity of polysulfanes as the number of sulfur atoms in the polysulfane increases. The standard answer would involve usage of the concepts of inductive effects of electronegative elements. However, I thought perhaps, there was more to it. Thus, in addition to writing about the increasing stabilisation of the $\ce {HS_x^-}$ conjugate base via stronger inductive effects as $x$ inceases, I also wrote an additional point about the increasing stabilisation coming from the increased ability of the anionic sulfur atom in $\ce {HS_x^-}$ to accept a hydrogen bond from the other terminal $\ce {H-S}$ as $x$ increases.

I was thinking that as the number of sulfur atoms in the chain increases, the chain becomes more "flexible" and thus, the ease of hydrogen bond formation increases. Of course, this will mean that the acidity would increase up to a certain point, where the ease of hydrogen bond formation no longer increases. After consultation with various general inorganic chemistry textbooks, I was not able to find a reason explaining this trend in acidity.

Firstly, I would like to ask if anyone knows the correct explanation. Secondly, I would like to ask if my proposal is plausible.


texts: Why does hard water have to pass through the cation exchange resin first followed by the anion exchange resin? Why can't it be the other way around?


texts:
If we add an impurity atom (doping) to the crystalline struture of another material and take the XRD of the doped material what kind of peak shift can we expect. For the better description of my question i have added an image below

In the image black bold line ($2\theta $) is the standard XRD peak of a material; blue ($2\theta ^{L}$) and green ($2\theta ^{R}$) dotted lines are the peak shift caused due to the doping of impurity atom. Can you tell me if there is any relationship between dopent size and peak shift (right/left dotted lines).


texts: Is one syn aldol product preferentially formed over the other?

texts:
In Carruthers' Modern Methods of Organic Synthesis, the following aldol reactions of two (Z)-enolates with benzaldehyde are shown:

The two transition states shown seem to be different, and lead to different stereochemistry in the product (the first product has both Me and OH pointing away from the plane, whereas the second has both pointing out of the plane).

Is this significant, and if it is, how can we predict which TS is used for which problem specifically?


texts: I had a fairly simple question regarding supersaturation and crystallization. When a supersaturated solution is crystallized, is all of the solute crystallized or just the excess solute (such that the solution remains saturated)? After crystallization, would you expect to find some quantity of the solute still dissolved?


texts:
https://youtu.be/iHBz77E625o

In this video there are pieces of matboard that are soaked in water saturated with NaCl. The pennies themselves are made of zinc and copper. With the electrical energy from the zinc and copper would the chloride let go of its electron and the sodium gain back its electron producing a Na Cl battery within a Zn Cu battery?

Would the water in the process separate into hydrogen and oxygen through electrolysis? If so since hydrogen is very flammable would a combustion reaction occur in the air giving you water again?


texts: Stability of dialkyl substituted alkenes

texts:
The stability order of alkyl substituted alkenes with respect to heat of hydrogenation was given as
$$\ce{R_2C=CH2} > \ce{RHC=CHR}~(\textit{trans}) > \ce{RHC=CHR}~(\textit{cis}).$$
While I understand that trans alkene is generally more stable than cis, I don't understand why $\ce{R_2C=CH2}$ is the most stable. Shouldn't there be repulsion between the bulky alkyl groups which leads to decrease in stability?


texts: Hydrogen peroxide: catalyst changes colour during peroxide decomposition

texts:
When adding iron(III) chloride to hydrogen peroxide, the hydrogen peroxide decomposes.

Iron(III) chloride is a catalyst.

But when it is first added, it changes its colour to dark brown, then near the end it turns to orange.

  Why does the colour change?

I heard that it has to do something with reaction intermediate. Correct?

It is seen on: iron(III) chloride

Also, the colour changes when different catalyst is used like iron(III) nitrate and potassium iodide potassium iodide, iron(III) nitrate