texts: What is the mass fraction of trichloroethene in the liquid phase using vapour pressure and mole fraction in gas phase?

texts:
Vapour-liquid equilibrium of a two-component ideal solution of trichloroethene ($\ce{C2HCl3}$) and trichloromethane ($\ce{CHCl3}$) is established at $\pu{25 °C}$. The mole fraction of $\ce{CHCl3}$ in the vapour phase is $0.73$. What is the mass fraction of $\ce{C2HCl3}$ in the liquid phase?  Round your answer to two significant figures.

The vapour pressures of trichloroethene and trichloromethane at $\pu{25 °C}$ are:

$$\begin{align}P_\text{vap}(\ce{C2HCl3}) &= \pu{73.0 mmHg}\\[0.5em]
P_\text{vap}(\ce{CHCl3}) &= \pu{199.1 mmHg}\end{align}$$

So, what I did was I found mole fraction of $\ce{C2HCl3}$ and then used the two mole fractions along with the vapour pressures to find the total pressure of the solution.

$$P_\text{vap}= \frac{0.73}{199.1}+\frac{0.27}{73} = \pu{165.053mmHg}$$

Then, from Raoult's Law I know that the mole fraction in liquid phase is equal to mole fraction in vapour phase, multiplied by vapour pressure, divided by total pressure. From that, I found the mole fraction of both things in liquid phase. I use the mole fraction to find mass of both, and then did mass of $\ce{C2HCl3}$ divided by the total mass that I calculated. I got an answer of

$\frac{15.68}{120}=0.13$ but it says that it's wrong. I'm not sure where I messed up?


texts: Why does 3-bromopropanoic acid have least pKb value when compared to 3-chloropropanoic acid, 3-fluropropanoic acid and fluoroacetic acid?

texts:
Shouldn't 3-bromopropanoic acid have the least pKb due to the reduced inductive effect and electronegativity, leaving the carboxylate anion with more electric charge on it?
Also, what will be the decreasing order of pKb?


texts: Is my bottle of "RooR"-brand glass cleaning liquid pure isopropyl alcohol or something else?

texts:
I have this exact bottle: https://www.grasscity.eu/media/catalog/product/cache/2b55fa971a29a7844993ad77b24950ac/i/m/img_3633_1_1.jpg
I originally purchased it to clean my vaporizer (I've since stopped doing that and thrown all the equipment away), and now I'm wondering if this liquid is "isopropyl alcohol", because I want to use it to clean video game cartridges' connectors/internals with cotton swabs.
The text is 100% in German, and does not mention "isopropyl" or "alcohol" anywhere. It has no ingredients listed anywhere. It's described as "biological glass cleaning". The store from which I bought it described it as "pure isopropyl alcohol", but who knows if they are lying/confused?
So, is this actually pure isopropyl alcohol? And can it thus safely be used for my cartridge/hardware cleaning purposes? Or is it some sort of weird proprietary mix which is only to be used for cleaning glass and causes horrible damage to anything else?
I'm surprised that they would not be legally required to have some sort of "list of ingredients". I thought that was definitely a law in Germany, like every other country I know of. And even if not a law, it seems reasonable to mention "isopropyl" or at least "alcohol" somewhere on the bottle. If it indeed is 100% pure isopropyl alcohol, you'd think they would want to brag about this and make a big deal of it.
It was very expensive.


texts: Color change of nitroglycerin. Potential hazard?

texts:
I recently nitrated around (~7mL) of glycerol through a process I have performed many times before. The nitroglycerin has been stored for ~3 weeks, and I noticed a drastic change in color from clear to an opaque dark green/blue.

I'm not sure exactly what occurred, but I am assuming some impurity in the final product was oxidized over the course of its storage. Most likely due to the fact that the container storing the fuming nitric acid I used for the nitration broke and the remaining acid was salvaged for this reaction.

Is there any chance the nitroglycerin could be unstable in its current state? I have not disturbed it and would like to dispose of it safely.


texts: Where do negative ions migrate from the salt bridge to which electrode in the voltaic cell?

texts:
In the voltaic cell with $\ce{Mg/Mg^2+}$ and $\ce{Ag+/Ag}$, I am not sure whether the ions move from the salt bride to the $\ce{Mg}$ cathode or the $\ce{Mg^2+}$ cathode. I distantly recall my teacher saying the cathode (in this case) is a metal, and so it can't be $\ce{Mg^2+}$? I am confused, and please help ASAP. Final is tomorrow.

Somewhat related question:
At the cathode during electrolysis, what is its charge and what type of reaction occurs?

Is the correct answer: positive charge, and reduction?


texts: Does Nitrogen dioxide change colour if we put it in a constant temperature of e.g. 100 kelvin?

texts: The changing of the colour of $\ce{NO2}$ is because of a change in temperature, resp. heating and cooling?


texts:
I'm familiar with the endo rule as well as the regioselectivity of the reaction. However, what I fail to understand is the stereoselectivity of the product in relation to the diene. For example, in the image below, which one is the correct product? I used to consider only 1 but I've seen several examples, in notes handed by my professor and some books, that provide only 2.

Also related, which one is accepted from the approachs below? I've seen only 1 being discussed but why should 2 be excluded? From what I've tried, they lead to different products while the orbital rules are not violated.

I've seen similar questions with no answers however. Also, books like Clayden's or March's do not point out something similar from what I've seen. The same goes for any website I've checked.


texts: Mechanism for synthesis of Meldrum's Acid

texts:
I have a little bit of problem trying to figure out the mechanism for the synthesis of Meldrum Acid. Meldrum acid is synthesis by a condensation reaction of acetone with malonic acid in acetic anhydride.

First, the carboxyl OH will be acetylated by acetic anhydride. But I can't figure out how the two ester bonds are being formed subsequently. I'm thinking that there's an acid-catalysed aldol condensation somewhere that results in the removing of water. Perhaps by attack of the enol (from acetone) to the acetylated carbon. But I'm not really sure about it either.

Any thoughts?


texts: When is it better to use coupled-cluster (CC) over configuration interaction (CI) calculations?

texts:
My experience with different theoretical methods in computational chemistry primarily comes from use and reading papers. My experience is that people almost always use CCSD instead of CISD if they wish to do calculations with single and double excitations.

My understanding is that truncated CI expansions suffer from not being size-extensive and also do not converge very quickly. I do not think coupled-cluster theories suffer in the same way.

Why, however, do people seem to prefer CCSD over CISD? What are the big advantages it has? Is any of it just a habit because CCSD(T) is the preferred method when possible, and so it's easier to make comparisons if these calculations come around in the future and can't be done in some current study?

Also, are there any systems for which it would definitely make more sense to choose a truncated configuration interaction calculation over a coupled-cluster method? Probably systems with some kind of low-lying excited state I would guess...

I'm not looking for a huge amount of math here, although that's totally fine. I would just be fine with the facts and any useful references.


texts: what are the cons of converting plastic to fuel

texts:
I have been trying to read how to fix plastic problems, there seems to be 3 outstanding solutions

Re-use
Recycle
Decompose to Fuel

Recycling is expensive, requires lots of water and the quality degrades on each recycle. I can partially understand why companies won't recycle

However I am unable to understand why would we not decompose to fuel. I have tried reading following articles:

Can plastic be used as fuel for vehicles?
https://www.power-technology.com/comment/plastic-to-fuel/
http://www.anthropocenemagazine.org/2019/02/new-technique-converts-plastic-waste-to-fuel/
http://www.deccanchronicle.com/science/science/180717/hyderabad-techie-recycles-plastics-into-fuel.html

It seems the primary way is Anhydrous pyrolysis requires no water, limited sorting and seems to convert 80% of plastic to fuel. I am unable to understand why would everybody not do this ? seems a viable solution and a profitable business


texts:
I stumbled across miscibility curves in the section Solubility of Liquids in Liquids (Organic Chemistry, by Wallwork and Grant) today. I'm not sure if my problem is with the way the content was laid out in the book or whether I'm not fully understanding the material, but I feel the book has dealt with the topic in a rather, obscure way.

I've taken snapshots of it and uploaded a portion of my text below.

What I want to know is if I interpreted the text (the bit about miscibility curves) correctly, which I seriously doubt.

Here's my interpretation:

This is the miscibility curve for phenol in water blah-blah-blah. All the points present in the area bound by the curve with the x-axis (concentration axis) are points of immiscibility. The curve itself represents the threshold of miscibility.

For example, at 20°C, phenol is soluble in water up till the concentration corresponding to point A on the curve. However, for phenol concentrations corresponding to points between A and B (lying on the line AB), the phenol-water mixture is immiscible and the phenol and water form separate layers. Although, at concentrations corresponding to point B (and beyond), the phenol is completely soluble. When for a constant temperature, the miscibility curve maps to two concentrations on the x-axis (eg; points A and B in the graph), which represent thresholds of miscibility at that temperature, the two mixtures (i.e- at A and B) are called conjugate pairs.

I labored for over two hours to come to the above conclusion, but when I saw the portion of the text which mentions that the liquids A and B exist together (at equilibrium) for the given temperature, I had to throw in the towel.

I have a very strong feeling that a large part of my 'interpretation' is horribly incorrect. If anyone's got the time, could you explain what the text actually means?


texts: Primary amine versus phosphoramidate reactivity with succinate esters

texts:
I have posted two reactions below. The top reaction is well known and occurs readily and near quantitatively (e.g. in protein modification), while the bottom reaction to my knowledge does not exist in the literature, but would be valuable to me. I would like to ask the experienced organic chemists out there if you think 2 and 4 will have similar reactivities with 1, or whether the phosphonate moeity will cause trouble or  reduce reactiveness (resonance stabilization or side reactions?).
Forgot to add it to the image, but I normally run the top reaction in dichloromethane at a little above 0 C, with N-hydroxysuccinimide produced as a by-product.

Note: I currently don't have the time/resources to test this, but plan to in the future if I think it will work.


texts: Determining Fluorescence Quantum Yield of C60 in Toluene

texts:
For my experiment, I am trying to determine the fluorescence quantum yield of C60-fullerene in toluene (at room temperature).  In order to do that, I need to have a standard sample with a valid and known fluorescence quantum yield. I have been looking for a standard sample with a known quantum yield in toluene, however, I am not sure of what to use.

Would it be better if I used a different solvent in determining the quantum yield and if so what solvent and standard should I use.


texts: What is the chemistry behind black colour of platinum black?

texts: Platinum is a silvery white metal and is highly unreactive then why it's powdered form "platinum black" is platinum metal but is black in colour. why would a metal such as platinum become black as a powder?


texts: What is wrong in this argument that dG must always be zero?

texts:
Under constant temperature and pressure, the change of the Gibbs free energy can be written as

$$\mathrm dG_\textrm{sys} = \mathrm dH_\mathrm{sys} - T\,\mathrm dS_\mathrm{sys}$$

And in the textbook that I have, when deriving this equation, they use the equation

$$\mathrm dS_\mathrm{univ} = \mathrm dS_\mathrm{sys} - \mathrm dH_\mathrm{sys}/T$$

I can understand to this step but the question occurs. Can't we write $\mathrm dS_\mathrm{sys}$ as $\mathrm dH_\mathrm{sys}/T$ also? If this T and the T that is used in the equation

$$\mathrm dS_\mathrm{univ} = \mathrm dS_\mathrm{sys} - \mathrm dH_\mathrm{sys}/T$$

are the same, than shouldn't $\mathrm dG$ always be zero? At which point am I wrong?


texts:
How to convert ethanal to 2-hydroxy-3 butenoic acid?

I tried crossed aldol condensation with formaldehyde followed by acid addition.After that how should I proceed ?


texts: I'm making a solution with linear poly(ethyleneimine) $\ce{[CH2CH2NH]_{n}}$.  The bottle indicates that the substance is hygroscopic and must be dealt with under inert gas.  Is this really necessary?  I don't currently have access to such a space - just the PEI and a balance.


texts:
Bit of a random one but I had an oven fire yesterday due to grease.  I decided to clean my over as a result but stupidly used baking POWDER rather than soda and wiped it off with vinegar.

Now I am really worried as I have a gas oven, and some of the baking powder has seeped through the holes at the bottom where the naked flame.  Do you have any idea whether this is dangerous?  Will the baking powder ignite or set fire? Or will it just burn off? I'm very worried about what will happen to the oven now.


texts: C-4 oxidation of octanoic acid to 4-oxooctanoic acid

texts:
I am leading a project in which I am attempting to synthesize 4-oxooctanoic acid in a (mostly) biological pathway.
Currently, I have reached a dead-end. I have a way to create octanoic acid through bacterial growth, I could not seem to find a way to proceed to the 4-oxo step with enzymes so I turned to chemistry.

Although this seems to be impossible due to the structure of octanoic acid. There appears to be no way to specifically target the fourth carbon to obtain the 4-oxooctanoic acid.

My question is: Am I correct in assuming that converting octanoic acid to 4-oxooctanoic acid is impossible (at least via simple oxidation)? Or would there be a better way to go about doing this?

Thanks in advance

PS: Here are pubchem links to the two structures involved.

https://pubchem.ncbi.nlm.nih.gov/compound/octanoic_acid#section=2D-Structure

https://pubchem.ncbi.nlm.nih.gov/compound/4-oxooctanoic_acid#section=Top


texts: Why is electronegativity increasing with oxidation state increase?

texts:
I may be a rudimentary fact or something really "not-that-hard-to-figure-out", but

  In inorganic chemistry it is common to consider a single value of the electronegativity to be valid for most "normal" situations. While this approach has the advantage of simplicity, it is clear that the electronegativity of an element is not an invariable atomic property and, in particular, increases with the oxidation state of the element. Wikipedia

Really? That means for example $\ce{C}$ in $\ce{CO3^{2-}}$ is more electronegative than a "bare" C atom? Why is that so?

Interestingly, I'm not able to find relevant info in the Net (and the wikipedia citation that should have hopefully got me results is behind a big bad paywall), so am leaving "reference-request" for the case of additional study.


texts: How does one find the probability of tunneling along a reaction coordinate computationally?

texts:
The idea for this question comes from Jan's comment over here. I realized I don't know how I would compute the probability of tunneling in the process of a reaction.

When I say "compute" I don't mean something rather trivial like finding the probability of a quantum harmonic oscillator being past the classical turning points which can just be done analytically.

For instance, if I were studying some reaction computationally (to estimate rate constants or something which depends on tunneling) and constructed a potential energy surface for a bond-breaking process, let's say the transfer of a hydrogen, how do I account for the possibility of tunneling through the barrier along this reaction coordinate?

I could speculate, but I imagine I would be wrong. How would one do this using common computational software and techniques?


texts: Why would this reaction occur? Won't it be unfavourable?

texts:
I was just reading about how Nitrogen and Oxygen combine to form Nitric oxide.

My question is, why would this reaction even occur? Isn't the valency of Nitrogen 3- and Oxygen 2-, and therefore this reaction seems to form a product that still hasn't achieved the octet electronic configuration.
Could I please have some help?
Thank you in advance.

Edit: Or even $\ce{N2O}$ or $\ce{NO2}$ for that matter?


texts: How large an energy difference in Hartree can be used to distinguish two different structures?

texts: For example, I use two different geometries of the same molecule to do optimisation in Gaussian, and the two resultant geometries look roughly the same. The energy difference between the two optimised geometries is only 0.0000001 a.u.. So can I view them as the same geometry? Or is the energy difference large enough to distinguish them? How large an energy difference is large enough for you to see two geometries as different geometries?


texts: How to calculate atmospheric composition

texts:
Okay, so I'm a novice in chemistry and am trying to figure something out.

Say that you want to turn carbon dioxide into oxygen using photosynthesis, given an infinite supply of water. Say that the atmosphere's volume is 100km^3 and has a pressure of 5kPa. The current composition of the atmosphere is 90% Carbon Dioxide, 5% Argon, 5% Nitrogen. You want to get the Oxygen in the atmosphere to the point that it's at 20% of the atmospheric composition. How would you calculate the atmospheric composition after you do that?

A step by step guide with just formulas would be fine, you don't necessarily have to solve this exact problem; I just need to figure out how you go about solving it. I'm only asking because when I tried doing the math and putting it back into a percent via # mols or their mass, I thought that in the end it should still have 5% Argon and 5% Nitrogen in the atmospheric composition since the chemical equation is only using the Carbon Dioxide in the air to make Oxygen.

Keep in mind when explaining it to me that I've only just completed my first semester of college chemistry, so make sure you tell me what each variable is!


texts: What is the difference between ΔG and ΔrG?

texts:
Consider the reaction

$$\ce{A -> B}$$

The reaction Gibbs free energy, $\Delta_\mathrm{r} G$ is given by the following equation
$$\Delta_\mathrm{r} G = \Delta_\mathrm{r} G^\circ + RT \ln Q$$

Now what is the difference between $\Delta G$ and $\Delta_\mathrm{r} G$ ?

Which one of the above represents $G_{\text{products}} - G_{\text{reactants}}$ ?

I read in my book $\Delta_\mathrm{r} G$ is the slope of $G$ plotted against the extent of reaction at different instants. And at equilibrium, it is zero. So can we say that it has value at a particular instant while $\Delta G$ is for a process ($\ce{A}$ to $\ce{B}$ in my question) i.e. is for a time interval?

Does $\Delta G$ for the above reaction represent change in Gibbs Energy when 1 mole of $\ce{A}$ reacts completely to form $1$ mole of $\ce{B}$ ?


texts:
I'm interested in the chemical synthesis of nucleoside phosphoramidites, but all the procedures I can find have "start with a protected nucleoside" as the first step. Searches for chemical synthesis of nucleosides all seem to find process that start with existing nucleobases, or in vivo processes, or speculative origin-of-life processes. Searching for chemical synthesis of nucleobases ONLY seems to find speculative origin-of-life processes.

What I'm looking for (just out of curiosity) are processes for chemical synthesis of nucleosides from a non-biological basis (not using pre-existing nucleobases) as used in typical commercial/industrial supply of nucleoside phosphoramidites. I'm starting to wonder if they even are chemically synthesized, or if they are instead harvested in some way, but it's hard to find a smoking gun that outright says it one way or the other without access to whitepapers anymore (no more university account).

Does anybody know?


texts: Valence bond theory and molecular orbital theory — how do they complement one another?

texts: Based on my readings, valence bond theory (VBT) and molecular orbital theory (MOT) tend to complement one another in explaining a molecule, but I don’t understand how VBT helps us explain the properties of a compound (other than bond angles). How does VBT complement MOT in aiding our understanding of molecules?


texts: How to rationalise the increasing bond length order in the carbonate ion, carbon monoxide, and carbon dioxide?

texts:
I am unable to rationalise the order of increasing bond length in $\ce{CO3^2-}$, $\ce{CO}$ and $\ce{CO2}$.
Having gone through the factors affecting bond length in two different books, my approach to the problem was:

$\ce{CO}$ has bond order 3 while carbonate and $\ce{CO2}$ have bond order 4 so
$\ce{CO}$ should have longest bond length.

$\ce{CO2}$ is sp hybridized while $\ce{CO3^2-}$ is sp2 hybridized.
Since carbonate has lesser s character and therefore it should have a greater
bond length than $\ce{CO2}$

Thus,
  $$\ce{CO2  <  CO3^2- < CO}$$

However, I am unsure about my method. What would be the best approach to determine the relative bond length order?


texts: Why is the reduction by sugars more efficient in basic solutions than in acidic ones?

texts:
Why is it said that reduction by sugars is much more efficient in basic media than in acidic media as in the following quote taken from Satyanaryana’s Biochemistry, 4th edition page 16?

  In the laboratory, many tests are employed to identify the reducing action of sugars. These include Benedict’s test, Fehling’s test, Barfoed’s test etc. The reduction is much more efficient in the alkaline medium than in the acidic medium. (sic emphasis)

Is it something to do with the reagents used because many of them are just basic solutions, but if the reagent happens to be an acidic solution then will be that statement valid?


texts: How to choose the correct name for calcium sulfate based on a calculations of the crystallisation water included?

texts:
I have a test review question which i really need help on. It states :

  A student heated a sample of the hydrate $\ce{CaSO4 * xH2O}$ in an evaporating dish over a bunsen burner to remove all the water and recorded the following data:

  Mass of empty evaporating dish: $\pu{19.73g}$
  Mass of evaporating dish + hydrate: $\pu{21.50g}$
  Mass of evaporating dish + anhydrous $\ce{CaSO4}$: $\pu{20.80g}$

  Determine A) the value of $x$ and B) the most likely name/formula of the hydrate.

I already figured out $x$ by getting the mass of water then simplifying the ratio of anhydrous to water.
But the second question which asks to name the formula of the hydrate really confused me. I would appreciate if anyone can guide me how to solve B.


texts: Is the adsorption of dissolved iodine onto activated carbon physical adsorption or chemical adsorption?

texts:
For an experiment, I am looking to see the effect of temperatures from 0–100 °C on the efficacy of activated carbon as an adsorbent. My adsorbate is iodine and I am confused as to whether the adsorption taking place below 100 °C is physical or chemical adsorption.

I have also read that physical adsorption decreases with an increase in temperature while chemical adsorption increases and then decreases with an increase in temperature. Additionally, I was wondering whether chemical adsorption takes place at all temperatures.


texts: Can baking soda or citric acid help clean a pot with burned-in milk rice?

texts:
The other day I was cooking milk rice and forgot about it so it burned a little on the bottom. This lower layer was very hard to clean. A lot of websites recommend boiling water in the pot with baking soda (Sodium bicarbonate) or citric acid to dissolve the burned residue and make it easier to clean the pot. I tried this but it did not help. I doubt there is even a chemical reaction between these reagents that would help in any way.

Is this another myth or is there scientific basis for given recommendation?


texts: How to calculate molarity of a solution by solving the percentage?

texts:
Molarity is number of moles per litre of solution and we calculate it by simply dividing moles by volume. But, if moles are not given and the w/w or w/v percentage is given then, how can we solve for the molarity?

For example, if we have 2 % w/v solution of $\ce{NaOH}$, how would we find its molarity? Do we solve by dividing 2 by 40 (molar mass of $\ce{NaOH}$)?


texts: Removing the hydrazine byproduct from the mitsunobu reaction

texts: Looking to remove the hydrazine byproduct left after the mitsunobu reaction. Using DIAD and polymer bound triphenyl phosphine. The reduced diad is coeluting with my product on silica. My thoughts for getting rid of it are trying an alumina column, acidic wash (I have an N-Boc so it can't be too acidic), or switching to a different azodicarboxylate.


texts: Is it possible to have three stable liquid phases in a binary mixture?

texts:
With this system, it would be possible to have three liquid phases and two liquid-liquid coexistence regions at various compositions. Similar behaviour is common for solids such as alloys, sometimes with even more stable phases.
I have been searching for a liquid mixture with this behaviour, but haven't found any. Are there any liquid binary mixtures which exhibit this behaviour, or is there any physical reason why this isn't possible? Does it have something to to with the higher disorder liquids have compared to solids?


texts: Is Coupling Reactions, Heck Reaction for example, different from Coupled Reactions like the production of Glucose 6-phosphate in living organism?


texts: What should be the pKa and IUPAC name of this compound?

texts: Note that this is not squaric acid as it has no double bond between the carbons holding the hydroxy groups.


texts: Why can oxygen have a coordination number of 3 in a complex between silver and SiO2?

texts:
I am running an MD simulation of silver with $\ce{SiO2}$. Initially, my silver atom is neutral and oxygen has a coordination of 2 with silicon having a coordination of 4. After the deposition of silver atoms, I find that the coordination of silver atoms ranges up to 12 and oxygen has coordination of 3 where a bond is formed with silver. Since $\ce{Ag-Si}$ bonds are not present, silicon's coordination number does not change.

I want to understand why oxygen is able to have a coordination number of 3 as with 2 bonds with silicon, the valency is already satisfied. I know silver forms a fcc-lattice where the coordination number is 12 but I want to get a more in depth detail of this change of coordination number. The basic physics behind it.


texts: Demonstrating decomposition of hydrogen peroxide using iron(III) nitrate catalyst

texts:
I need a way to prove/show that hydrogen peroxide was decomposed through use of catalyst.
I want to ensure that my catalyst: $\ce{Fe(NO3)3}$ or iron(III) nitrate is a catalyst, not a reactant/ consumed during the reaction.

$$\ce{2 H2O2 (aq) ->[Fe(NO3)3 (s)] 2 H2O (l) + O2 (g)}$$

When the reaction is happening, I will introduce a wooden glowing splint over the bubbling reaction and the wooden splint glowing brighter or reigniting will show that oxygen is being produced.

Question:

Now, how do I show that water is produced? Would I just boil the product I get after reaction (image above) and put cobalt chloride paper at the water vapour?

Also, if I were to use the orange solution above again as a catalyst (since it still contains iron(III) nitrate), would hydrogen peroxide decompose again? If so, is there a way to put iron(III) nitrate back to its solid state? or any way to reuse as catalyst?

Edit:
If it is easier to answer, it doesn't have to be with iron(III) nitrate. I have an option to use manganese dioxide, which is another catalyst that I can substitute for iron(III) nitrate. I think it should be OK since it does the exact same reaction.


texts: Effects of Ionizing a Radioactive Isotope

texts:
If you took your favorite radioactive isotope and ionized it using a strong electric field (or any other ionization method), thereby stripping it of an electron, what would happen when it decayed? For simplicity, assume this process takes place in a vacuum.

Would the resulting material also be ionized? (Main Question)

If the isotope decayed via beta decay, is there any chance the produced electron could take the place of the stripped electron?


texts:
I've been working on a project to absorb CO$_2$ from fossil fuel power plants.  I found these reactions:

$$\ce{2Li(s) + 2H2O(l) → 2 LiOH(aq) + H2(g)} \tag{1} $$

$$\ce{2 LiOH(s) + CO_2(g) → Li2CO_3(s) + H2O(l)} \tag{2}$$

The first one returns an aqueous solution of $\ce{LiOH}$, and the second one requires solid $\ce{LiOH}$. I was wondering if it's possible to use the aqueous solution in the second equation, or does it have to be solid?  Why?


texts:
If have read conflicting reports on the half-life of mercury in the brain. I would like to hear some estimates from this community.
I am also wondering how long chelation therapy would take to remove mercury from the brain.


texts: Why the DMM (multimeter) register negative resistance when measure a drop of hydrochloric acid

texts: I noticed that when I put the multimeter electrodes (in the ohmmeter mode) in a drop of hydrochloric acid with mild concentration (15%) the multimeter displays negative values. Can someone explain this behavior?


texts: How to perform NBO calculation to get Second Order Perturbation of Fock Matrix from unit to another of meatl complex?

texts: I am doing the NBO calculation of metal complexes but for some system I can fins in the output the Second Order Perturbation Theory Analysis of Fock Matrix in NBO Basis within different units and also from unit to another unit but for other system it treat the whole system as one unit and I cannot get the value from one unit to another (I mean from metal to ligand and vice versa)


texts: Ok, most people including me know that formal charge is just a book-keeping tool. I know how to calculate it, apply it to Lewis structures etc etc. But I am confused in its very basic definition which says - "Formal charge is the charge on an atom if the electronegativity differences are ignored" . If the electronegativity difference is ignored, then how can an atom have charge ? I know this is not a place to ask such a basic question , but still I am very confused about this miniscule definition.


texts: What makes alcohol a good conservation product?

texts: A common way of preserving food and organisms is immersion in alcohol. But what causes alcohol to preserve these items well?


texts:
For the precipitation reaction, I have to react $\ce{H2PtCl6}$ with $\ce{(NH4)2CO3}$ while maintaining the $\ce{pH}$ in the range of 7-8 at 60 °C. But the problem is Chloroplatinic acid is not precipitating. Instead, the acid evaporated by making holes in the aluminium foil which were not present before.
Can you please point out what I'm doing wrong?

Theoretical reaction:

$$\ce{(NH4)2CO3 (aq) + H2PtCl6 (aq) -> (NH4)2PtCl6 (s) + H2O (aq) + CO2 (g)}$$

PS: Aluminium foil was just used for proper heating


texts:
For the above question, here's what I'd thought:
1.  H+ ion from HCl protonates the oxygen
2. Chloride ion attacks the electrophilic carbon, opening the epoxide ring
3. So the final product formed is a chlorohydrin (which it really isn't)

Also, I didn't know what to do with methanol (guessing it just acts as the solvent, HOWEVER, the product contains a methoxy group)

Could someone please explain the mechanism to get to the actual product, and also highlight the mistake here?


texts: Curing of polyester resin that did not reach top exothermic temperature

texts:
When working with polyester resins for fiberglass or geloat, there are times where the thickness of the resin on the substrate is not sufficient to get a strong exothermic reaction and achieving a high temperature to "kick". I have been told in the industry to use artificial heat source to help it get to a high enough temperature for a good kick.

My question is: If you are working with a thin layer of resin or the ambient temperature is too low for the resin to kick on its own, and it was not artificially brought up to an appropriate temperature of say 250 degF and the resin stayed at a low ambient temperature of about 45 degF for several days before finally brought up to about 70 degrees, would the resin still cure eventually or will the overall cure be significantly compromised?

This type of scenario can happen a lot when doing minor gelcoat repair outdoors in colder climates.


texts: Mechanism for palladium-catalysed spirocyclisation of conjugated diene

texts:
I'm trying to work out the catalytic cycle for the following process:

I gather that the palladium will be reduced from Pd(II) to Pd(0) in the process and that the 1,4-benzoquinone is a redoxidant. However, I am not sure where the palladium would be initially inserted (possibly one of the double bonds?) and how the chlorine ends up on the final product.


texts: Why is it easier to determine the radius of inert/noble gases?

texts: My textbook says it is possible to determine the atomic radius of the inert gases like He, Ne, Ar etc because they roam freely and are incapable of forming bonds. However it is very difficult to find out the atomic radius of elements that are chemically active because the position of electron in an atom is uncertain (according to Heisenberg's principle I guess). I am just curious that the principle is true for the electrons of inert gases too, then why did they say it was possible for those gases but very difficult for the chemically active atoms?


texts: (Hydro)Carbon organic compounds with only 5 carbon atoms only and beyond

texts:
How many different organic structures (from the pure theoretical viewpoint) are there with carbon and hydrogen atoms and atoms without hydrogen can be made with 5 carbon atoms only? Is there any way to count them all using Polya enumeration theory for "n" (hydro)carbonatoms?
This is a follow up question from this Hydrocarbons with only 4 carbon atoms


texts:
My friend and I were debating about if Molarity is constant in a disolution if this one changes volume due to evaporation.
There was this problem that stated that 125 [mL] of sodyum chloride 0.122 [M] evaporates over time and final volume becomes 113 [mL]
I say Molarity keeps being constant, he says no because volume changes.
What do you think?


texts: Electrical and thermal conductivity of graphite

texts:
I was reading about carbon family where it was mentioned that electrical conductivity of graphite increases with temperature while thermal conductivity decreases.

However, I could not find a suitable explanation for that. According to me, electrical conductivity should decrease with rise in temperature as it happens in case of conductors.

Any help will be appreciated.


texts:
Why are trifluoromethyl diazirines so stable?
Trifluoromethyl diazirines stability is well documented, however I am yet to find an explanation of why...
Can it be homoaromatic or even aromatic?
2 pie e-, in a planar system? Even with the sp3 carbon, couldn't that make it homoaromatic?

Or is it just aided by the trifluoromethyl group withdrawing electrons from the strained ring?

Bonus points of you know the mechanism of Schmitz Diaziridine/diazirine synthesis.

Any resources or insight is greatly appreciated.

Thanks,
James


texts: How to rationalise the protonation of a compound with multiple double bonds?

texts: In the following reaction, why is the molecule protonated at the indicated carbon and not on one of the other double bonds?


texts: Why are some materials more flammable than others?

texts:
Wood and oil are flammable materials, but water isn't. Moreover, flames spread a lot faster in oil than in a piece of paper. What is the reason that it is so?

I also don't know why a small flame can spread out to a very big flame; what is the physical reason for it? I would like to know the molecular reasons in detail what makes fire so powerful.


texts: Why only structures corresponding to valleys on PES are taken into account?

texts:
I have had to ask this question again because it was marked as a duplicate but it wasn't. Here it goes..
Suppose we want to estimate $G_f^\circ$ of a molecule. If it has rotational conformers, right way to calculate $G$ should include a Boltzmann average of them.
We will do it as:
$$\large \langle G_f^\circ \rangle = \frac{\sum_{i}G_f(i)e^{-G_f(i)/k_BT}}{\sum_{i}e^{^{-G_f(i)/k_BT}}}$$
where the sum goes over the conformers.
Question:
Why $\langle G_f^\circ \rangle$ is estimated as the sum of $G_f(i)$ of only most stable conformers? (corresponding to minima on PES)
Example
Suppose the following rotational conformers:

Consider the $y-axis$ to be gibbs free energy, we would estimate $\langle G_f^\circ \rangle$ as the sum of structures corresponding to minima (ie 60º, 180º), but there are non-minimum structures around 180º with less energy than the minima in 60º. Why aren't them considered?
EDIT
Someone could argue that a conformer in 150º won't exist because there will be a driving force to 180º, but if we take the relative energies $\frac{G_f(150º)}{G_f(60º)}$ we get that 150º must have almost the same population as 60º. There might be some criteria I am missing or maybe a conceptual error.
Any edit will be welcome.


texts:
Which elements can be diatomic and why?

Motivation

Hydrogen, Nitrogen, Oxygen and the Halogens tend to be thermodynamically stable as a diatomic molecule at room temperature, and are usually labelled as diatomic nonmetals. (Although I am unsure about Astatine). These are the ones you learn in school and I am fine with their reasoning. I want to know about other elements in particular.

Looking at the rest of the non-metals: Carbon, Phosphorus and Sulfur have diatomic molecules in gaseous states. All with a common theme of being heated at very high temperatures.

This leaves us with diatomic Selenium which I could not find anything on.

Further notes

Diatomicity doesn't seem to be just a non-metal thing:

Lithium forms diatomic molecules and all diatomic alkali metals are claimed to be stable in gaseous states. Found from this question.
Silicon has been reported to have a diatomic molecule similar in structure to carbon.
Tungsten, Chromium, Uranium and Molybdenum are claimed to be diatomic with a sextuple bond.
Supposedly Noble gases can form dimer molecules but if these are considered diatomic is debatable.


texts: How do people know HCN smells like almonds?

texts:
I was told by my chemistry teacher that $\ce{HCN}$ smells like almonds. She then went on to tell a story about how some of her students tried to play a prank on her by pouring almond extract down the drain to make her think that they had inadvertently created $\ce{HCN}$ gas. She said that she knew that it wasn't $\ce{HCN}$ because if she had smelled the almond scent, then she would have already been dead.

I never asked her, but how do people know $\ce{HCN}$ smells like almonds if they would die before they knew what it smells like?


texts:
What is the melting point of egg yolk?
Well, generally, when we break an egg, the yolk is in liquid state. After we pour it on a pan, the egg starts to cook and it hardens. My question is, can an egg melt/boil ?
What are the conditions to be imposed?


texts: Why does the addition of heavy water cause OH and NH peaks in NMR spectra to disappear?

texts:
When $\ce{D2O}$ is added to a sample, the OH and NH peaks in a $\ce{^1H}$ NMR spectrum disappear. This is the basis of (for example) the $\ce{D2O}$ shake test, and is also the reason why peptide/protein NMR is commonly run using $90\%~\ce{H2O}/10\%~\ce{D2O}$  as a solvent (or else the NH peaks would be unobservable).
What causes them to disappear from the spectrum?


texts: Difference between reversible and irreversible processes

texts:
On a quiz, I was asked for the difference between reversible and irreversible processes.

I said:

For a reversible process, you can change direction at any time without disturbing equilibrium.
For an irreversible process, the macroscopic variables may not always be defined.

I was given 1/4 point for this answer. I asked the professor what the issue is with the answer, and she could not articulate a clear reason, and eventually said she'll re-think it.

Do you see a problem with my answer? If so, please explain.


texts: Why catalyst does not alter the entropy of a reaction?

texts: In my textbook it is written that "Catalyst does not alter the entropy of a reaction". But why? There is literally no explanation given in my textbook as to why this is true. Could you please explain why this is true? I mean if a catalyst speeds up or slows down a reaction so shouldn't it affect the entropy of a reaction? I am really confused. Please explain. Would greatly appreciate it!


texts: Nucleophilic addition - Propanal vs Benzaldehyde

texts:
According to my school textbook, carbon atom of the carbonyl group benzaldehyde is less electrophilic than that of propanal because polarity of the carbonyl group is reduced in benzaldehyde due to resonance.

I can't understand how. If I draw the resonating structures, the oxygen atom takes the delocalised electron and not the carbon atom. So, resonance shouldn't affect the electrophilicity of the carbon atom. Moreover, benzene being a -I group, induces a partial positive charge on the carbon.

What is the correct reason?


texts:
I would like to create a copper mirror on a plate of sandblasted glass.

I know that a reaction exists:

$$\ce{CuSO4 + N2H2 -> Cu + N2 + H2SO4}$$

I know that such a plate of copper is very weak. Therefore, I would like to use sandblasted or laser etched glass.

My question(s) are:

Would laser etched glass be sufficient to retain the deposition? I.e. if I plate a complete glass slide, part of which is etched, and part of which is smooth – can I safely wipe off the smooth part from deposited copper, while the etched part provides a good adhesion to the deposited layer?
Is there a way to replace the hydrazine? I read that fructose could work – but is not reliable. I also know that $\ce{Zn}$ and $\ce{P}$ also work as reducing agents. But they work at an elevated temperature. Is it possible that we can do this at room temperature with an easily available, less poisonous or explosive (possibly from the drug store or the hardware store) agent?


texts: In an E1 reaction, I understand that the base reacts with the hydrogen of the carbon which is next to the positive charged carbon of the cation (of an haloalkane), because this hydrogen is supposed to be acidic. Why is that? And again, in an E2 reaction, why is the hydrogen that is attacked by the base, acidic? I am not sure how the polarity of the halogen affects the situtation.


texts: Why aren't methanal and ethanal also ketones?

texts: Why aren't the aldehydes methanal/formaldehyde and ethanal/acetaldehyde also ketones? Ketones are defined by replacing any H - C - H in an alkane with C=O, which is true for both of these: methanal replaces two hydrogen atoms in methane with C=O, while ethanal does it with ethane.


texts: Calculate Ethanol content after heating for N minutes

texts:
Does there exist a formula I can use to calculate alcohol content of a solution after heating it for some time?

I have the following use-case:
I am making a pecan pie. I have a thick sugary solution. I am not sure how much the makeup of the solution matters. Just assume its more viscous than water. I add 75 ml of 40%v  alcohol and I heat it at a temperature high enough to cause boiling for 20 minutes. How much alcohol remains at the end of 20 mins.

Obviously there are a lot of variables here that would make it impossible to give a precise answer. I would be interested in an answer that solves an "easier" version of this problem, for example: having 1 liter of water, adding to it 100ml of 100%v alcohol (Ethanol), boiled for 100 minutes, how much alcohol is left?

How quickly does alcohol boil off? Is it dependent on is concentration within a solution? is there a formula for that?


texts:
What makes sea salt coarser than other salt?
I have tried checking online but no one seems to discuss this. It seems that the grain of sea salt is larger, but I don't understand since the salt is dissolved in the sea water so how does it become coarse.


texts: How does O-benzoyl-N-methylhydroxylamine hydrochloride oxidise this ketone?

texts: How does the mechanism of this reaction with BzONHMe work? Can part of it act as a base and abstract the alpha proton? Would be great if someone could help me!


texts: What is the explanation of the structure of H2XeO4?

texts:
Using the obsolete VSEPR theory I had a hard time predicting the structure of $\ce{H2XeO4}$. So I looked it up. I found the molecule via chemapps.stolaf.edu:

It looks weird to me. I can't explain the molecular structure. Can anyone explain it using more sophisticated theories like molecular orbital theory (MOT)?
I don't know much MOT, yet.


texts: Calculating total volume mixing NaCl and water

texts:
I'm (as a non chemist) trying to calculate the the volume of a NaCl solution. The problem is that I know the volume of water prior to mixing in NaCl, but I want to know the volume of the solution after.

If my little research is correct, I need to use partial molar volumes of NaCl to estimate the volume change in response to adding NaCl. I found a value of $\pu{16.61 cm3/mol}$ for NaCl (and some other literature values being similar). The initial volume of water is 12 liter, and the added mass of NaCl is 1000 g, or 17.11 moles. This results then in $\pu{284 cm3}$ increase in volume, and a total volume of 12.284 liter.

My question is to what degree the partial molar volumes are dependent on the concentration in the solution and the temperature of the solution? I would like to do these estimations of total volume for a range of temperatures from 2 degrees C to 30 degrees C, and with variable amount of NaCl concentrations. I was not able to find information on whether NaCl partial molar volumes are dependent on these factors, but it seems other aqueous mixtures are.

Thanks!


texts:
In the reaction of combustion of gunpowder,

  Sulfur is used to speed up the reaction and acts like a catalyst in that it increases the rate of reaction. However, unlike a catalyst, it is used up in the reaction.

I understand that transition metals are often used as catalysts but why can sulfur act like a catalyst?


texts:
In a practice examination that I'm using to study for my upcoming midterm, one of the questions asks to choose three elements from a row of the periodic table and to give the order of the increasing oxidation half cell potential of the neutral element. Is it correct to assume that a more electronegative element would have the lowest half cell oxidation potential? Because it would be the most resistant to losing its electrons?

Would a correct sequence (highest oxidation half cell potential to lowest) be B, C, N because as the sequence goes from left to right it becomes increasingly electronegative and therefore less likely to be oxidized?


texts: Which mutated enzymes act as better drugs than their non-mutated form?

texts:
Is there an enzyme which is used as a drug (let it be called version $A$) and a mutated version of it ($M$), where the activity of $M$ was found to be higher than $A$?

Any references on such a case would be greatly acknowledged.


texts: Using table salt as a way to limit humidity in an unoccupied house

texts:
We own a static caravan in the UK (Snowdonia region, so rainy and wet all year round, moderately cold winters) and we leave it unoccupied during Winter (Oct-Feb).

We were advised of an apparently common practice among caravan owners which is to leave open boxes of table salt in each room, under the premise that they will capture moisture in the air and lock it away chemically in order to reduce the risk of moisture related decay in the building's structure.

I was skeptical that this would work but in the interests of science I did it anyway last winter.  I took 7 plastic ice-cream tubs and put roughly 1 kilogram of domestic table salt into each and put one in each room of the home (two in the largest room - the kitchen/living room space).

I (stupidly) never took photos of this phenomenon but I have attempted to illustrate my findings...

Fig. B is complete speculation on my part as I did not return to the home during Winter to observe it.  However in Spring when I returned, all of the tubs had experienced a change in their appearance.

All the tubs were now dry again, presumably down to evaporation due to increasing weather temperatures.  And therefore releasing all that moisture back into the building again!

Three of the tubs were largely unchanged with some noticable "caking" together of the salt into crumbly, grainy lumps which returned to normal looking salt grains when crushed.

The most profound change from the remaining tubs was as you see in Fig. C of the diagram.

The salt had actually accumulated on the walls of the tub as a fine sediment.  This suggests that water had accumulated in large amounts in the tub and had in fact risen higher than the original depth of the dry salt grains!  I'd estimate that the tub would have had to accumulate about 0.5kg of water in order for the water/salt solution to reach the depth indicated by the dry sediment.

The salt had solidified into a single, large mass.  The volume seemed to have increased noticeably but the density had also decreased accordingly, so the salt had basically expanded in it's container and solidified.  It was crumbly and brittle and some of it had been reduced to a very fine sediment.

The home is a single storey, about 12m x 4.5m x 2.5m in volume.

My questions then:

Is this a valid technique for capturing excess moisture over Winter?
Are my observations and presumptions reasonable...  Is Fig. B what really happened?
What is the chemistry / physics process that caused the salt to be transformed from Fig. A to Fig. C?
How many times did the tubs cycle between states B and C?  Was it a single cycle that lasted all of winter, or a daily cycle following ambient weather temperatures?  I could not tell just by looking at C on the last day of the experiment.


texts: What is the product of the titration of potassium permanganate and iron(II) sulfate?

texts: I recently did an experiment at school, where I had to titrate KMnO4 with FeSO4. The solution was colourless, then turned yellowish until the end point was reached and it turned pink in one drop. After letting it sit for a while, the pink tinge disappeared. Can someone please explain what happened and show the products and this mysterious observation? Thanks


texts:
If $\ce{NaCl}$ is such a strongly bonded ionic compound, why it does it disassociate so readily in $\ce{H2O}$? One would think that because of the very strong ionic bond it would not disassociate it all. Further, why do other compounds like $\ce{AgCl}$ or $\ce{HF}$ not disassociate as readily even though they also have strong bonds?

Although others have marked this as duplicate, I prefer the wording of this question as it explicitly refers to NaCl has having a strong bond (which includes the search term I used to find this website). I have been writing a manuscript in which I have been attempting to answer this question (among others). The real answer becomes a bit complicated, but I will try to give a short answer.

It is my opinion that thermodynamic data is not always properly understood. The first thing we should understand is that the same thermodynamic change in energy should result whether the reaction were to take place in the gas phase (Born-Haber cycle) or in solution. This is a principle of conservation of energy, Hess's Law. In the Born-Haber Cycle, the sum of the energies for vaporization, ionization, and lattice energies are determined. If a hypothetical solution phase Born-Haber calculation were to be performed, the same amount of energy would exchange, except for the solvation energy, which is small. That is what the poster was asking.

If you were to think about the conditions of a solution phase Born-Haber cycle, then you would take the elements and convert them directly to solvent separated ions. What this should tell you is that you have just calculated the solution phase energy of a redox reaction of sodium and chlorine to give sodium and chloride ions. This bypasses the implication of sodium chloride having a strong affinity for its ions. Yes, it would take a lot of energy to separate sodium and chloride ions in the gas phase. That is why the lattice energy is so large, but if we did the reaction in solution, we will not have a gas phase lattice energy component in our calculations. Of course this seems plausible as the solution phases of HCl and NaOH are ionic. This is consistent with our expected properties of HCl to act as an acid (chloride having a low affinity for cations) and NaOH to act as a base (sodium having a low affinity for electrons). The sum is we should not expect NaCl to have a strong affinity (not none) for the ions of the opposite charge.

By the way, I think you will also find a good correlation of heterolytic solution phase bond strength with bond length (actually, ion gap). This is different from the homolytic bond energies you may find reported in many tables, including the poster's question, "Why does NaCl dissolve in H2O despite its strong ionic bond?"

PW


texts:
We have drinking water with the following values:

Calcium mg/l 62.7
Magnesium mg/l 10.3
total hardness 7.) dH 11.1
Total hardness 7) mmol/l CaCO3 1,99
Carbonate hardness °dH 8.5
Hydrogen ion concentration (pH-value) - 7,8

To use the water for my plants, I reduce the pH with phosphoric acid to 6.8 PH.
If I now want to find out how many calcium and magnesium ions are in the water, do I only need to read out the amount of calcium / magnesium that are listed or must the calcium from the total hardness / carbonate hardness be added too, since it was present in the form of CaCO3 / Ca(HCO3)2 and not as ions before I brought the pH Down.


texts: Conversion from a PPB value to µg/m3 of Isobutylene

texts:
I have a quite simple problem, found a lot of information about it, but I am not sure anymore if I do my calculations right.

I own a sensor, which reports measurements in isobutylene units as PPB. So if I understand this right, the measurement would be the number of isobutylene molecules per one billion (x/1'000'000'000).

Therefore to convert this value into the more common µg/m3 unit, I would just use this formula:

$$ \text{Concentration}\ \frac{µg}{m3} = \frac{\text{Concentration}\ \text{PPB}\times\text{Molecular Mass}\ \frac{g}{mol}}{\text{MolarVolume}\ l} $$

Therefore to convert 400 PPM of isobutylene, with a molecular mass of 56.106 g/mol or 0.0005879 g/l, in the molar volume of a gas at STP with 22.4 l, the calculation would be:

$$ \frac{400\times56.106}{22.4} = 1001.9 \frac{µg}{m^3} $$

This seemed very high to me, and the Range of the sensor is 0-1056 PPM.

Is this the correct formula for the conversion?


texts: Is the Friedel-Crafts alkylation of benzene with cyclopropenyl chloride feasible?

texts:
Is the Friedel-Crafts alkylation of benzene with cyclopropenyl chloride according to the following scheme feasible?

Would the attack of the benzene towards the cycopropylium take place?
I am wondering about this, as the cyclopropyl carbocation is aromatic, which  implies that it is highly stable.
If it reacts with the benzene ring, it would lose the aromatic stabilisation, thus rendering it comparatively less stable.


texts: How could mass increase when sulfuric acid is added to calcium carbonate?

texts:
Context: I was doing an experiment in class that investigates the rate of mass loss over time when $\pu{20 mL}$ of sulfuric acid is added to $\pu{5g}$ of calcium carbonate. I did the experiment 3 times, each experiment involves mixing four, $\pu{20 mL}$ different concentration of sulfuric acid ($\pu{0.5 M}$, $\pu{1.0 M}$, $\pu{1.5 M}$, and $\pu{2.0 M}$) into $\pu{5g}$ of calcium carbonate.

Hypothesis: If concentration increase, the rate of mass loss should increase too

Result: Everything went out just fine, however, in each of the 3 experiments, when I add the $\pu{2.0 M}$ sulfuric acid to the calcium carbonate, the mass INCREASES (mass still loss overtime).

Could anybody please explain how could this be happening? As they react, carbon dioxide is produced and there should only be a mass loss. Also, this only occurs with the $\pu{2.0 M}$ sulfuric acid, the other concentrations work out just fine.

Could the electronic scale wasnt working properly? but this only happened with $\pu{2.0 M}$ acid.


texts: Can I make a mirror on PET plastic using Tollen's reaction?

texts:
I want to make a very shiny surface, like a mirror. I tried to use chrome paint but it's barely shiny. It's more like gray even though I bought one of the most expensive chrome looking paint.

I know mirrors can be produced using Tollen's reagent on glass (seen some demonstrations on YouTube).

But glass is quite expensive for what I want - I would like to make the mirror on plastic - more specifically on PET - the same material that a normal Coca Cola bottle is made from. I have big sheets of this PET material and I intend to transform them into mirrors.

Will silver deposit on the PET as it does on glass?

I need to order the ingredients online, then wait for it a couple of days - also because they are quite large quantities, it will end up being quite expensive. So, before making a mistake, I thought to ask here.

Could I use a Tollen's reaction to make a mirror on plastic?


texts: So I was doing a Gizmo for my Science class and I came across this question: "Why do phase changes occur?" I could not find anything about it in my resources. Does anybody here know the answer?


texts: How are the 4 molecules of O2 bonded in the O8 molecule at low temperature and high pressure to form a rectangular box structure?

texts:
1. List item
The discovers of O8 admitted to not knowing nor understanding the bonding in O8 at very low temperatures and high pressure. They concluded that O8 was a retangular box, not a cube & that this allotrope of oxygen was composed of 4 normal O2 molecules...


texts:
I came across the following problem in my book:

Now my confusion is how will cyclohexene be obtained? I read that primary alcohols dehydrate by E2 mechanism because of formation of a primary carbocation. Further I read in Solomons organic chemistry that rearrangement in Primary alcohols occur due to the reversibility of the reaction:

So I tried to figure out the mechanism:

So I am unable to find how cyclohexene will be obtained. For ring expansion to take place there must be positive charge on the alpha carbon but in E2 mechanism there is no possibility of carbocation formation


texts: What is the difference between Dielectric and Capacitive Polarizable Continuum Model?

texts:
I have good background knowledge on Quantum Chemistry calculations but my knowledge on Solvation Models is not that amazing.

Many times I read a paper that uses TD-DFT, they also assign some solvent to their calculations. Some papers use Dielectric-PCM and some others use Capacitive-PCM. I know that D-PCM assumes the solvent as Dielectric media and C-PCM assumes as Capacitive Field and I have some very basic knowledge on them but what I can not understand is when we use which?

For example what is the criteria for selecting DPCM or CPCM for Methanol solvent?


texts: Writing Topology file for Ligand for Gromacs

texts:
Is there any tutorial for how to manually write the topology file for any Ligand file(PDB for mol2)? There are so many sites which provides it like ProDrug or ATB but no where the actual process is written. Can anyone explain the process?

PS: I am actually not sure this question belong to which SO.


texts: Why cotton and wool clothes shrink after washing them?

texts:
I want to take measures to avoid my clothes shrinking in the washing machine and in manual washing. I read here if the water is hot that contributes more the shrinking.

The Wikipedia article is kind of as they say in Wikipedia, a "stub" (too short) and doesn't explain the reasons very scientifically.


texts: What products do 4-nitrobenzaldehyde and 3-nitrobenzaldehyde give in a crossed Cannizzaro reaction and why?

texts:
What are the products of  reaction of 4-nitrobenzaldehyde with 3-nitrobenzaldehyde in the presence of $\ce{NaOH}$ when they show Cannizzaro reaction?

To my understanding, 4-nitrobenzaldehyde has more electrophilic carbonyl because the nitro group is an electron withdrawing group and at para position it exerts a very strong mesomeric effect, so it should form the carboxylic acid. To my surprise, I was told that it's the other way around.

Can someone explain me why this is true?


texts: At what pressure is the triple point of ethane?

texts: Depending on source there are two givens for the triple point of ethane: 0.8 Pa or 1.1 Pa. Only one of them can be correct, which one is?


texts: How do I determine the number and order of ligand orbitals?

texts:
I am trying to create interaction diagrams for transition metal species by reducing the representations for both $\sigma$ and $\pi$ ligand orbital sets and mixing them with the metal orbitals. The order of metal orbitals is obvious because I know I have my 5 degenerate $n\text{d}$ orbitals, then my $(n+1)\text{s}$ orbital, which is higher in energy due to its principal quantum number, then my $(n+1)\text{p}$ orbital, which is higher in energy due to penetration (it's a p orbital); and the number of metal orbitals is apparent because my character table lists the each representation's matching function, so I can tell $\mathrm{A}_{1g}$ will have s-symmetry and $\mathrm{E}_g$ will match my $\mathrm{d}_{x^2-y^2}$ and my $\mathrm{d}_{z^2}$ orbitals, for example.

I don't see exactly how I should do the same for my ligand orbitals, though. For example, I know that my ligand $\pi$ orbital irreducible representation is $\Gamma_{\pi} = \mathrm{T}_{1g} + \mathrm{T}_{2g} + \mathrm{T}_{1u} + \mathrm{T}_{2u}$, and I know from my table's matching function list that there will be three $\mathrm{T}_{1u}$ $(x,y,z)$ and three $\mathrm{T}_{2g}$ $(xy, xz, yz)$ orbitals, but I don't know how to identify that there are also three $\mathrm{T}_{1g}$ and $\mathrm{T}_{2u}$ orbitals, since my character table doesn't list the matching functions for those representations.

Also; my understanding of how to decide on the ligand orbitals' relative energy levels is dubious. Yves Jean's Molecular Orbitals of Transition Metal Complexes says "one must analyze the bonding or antibonding character" (p. 43), but I am not getting it right every time. Can anyone give me some tips?


texts: Why does protic solvent suggest E1 mechanism rather than E2?

texts: If I understood correctly, having a protic solvent increases chance of E1 mechanism. But I can not rationalize this because carbocation intermediate is a positively charged molecule, and by surrounding that with a lot more positive protons will make the whole system in an unstable state. Hence it should make it less likely for E1 to occur. Is my understanding wrong or did I miss some important fact?


texts: hydroxychloroquine (HCQ) Synthesis: Which mechanism?

texts:
Draw the product of the following reaction and provide an explanation for this reaction knowing that $\mathrm{ROH}$ or $\mathrm{RNH_2}$ +  $\mathrm{PhCl}$ do not react at all.

I have no doubt that the answer is hydroxychloroquine (HCQ), but how would it be formed if the reaction:
$\mathrm{RNH_2}$ +  $\mathrm{PhCl}$
does not happen? Or, is the question hinting that the reaction takes the $\mathrm{S_N1}$ pathway where the phenylcation gets formed? If so, why does the Cl atom para to the nitrogen leave more readily than the other Chloride?


texts: Could Na+ ions in water used with a humidifier cause dust everywhere?

texts:
We have very dry air in our small family house.

So we bought a humidifier ( https://www.klarstein.com/All-products/Monaco-Digital-Ultrasound-Humidifier-White.html )

But here comes the issue: the tap water is very hard and this causes that dust is everywhere.. due to the humidifier + hard tap water.. like everywhere, even the notebooks fan are full of the white dust, overheating, brutal.

So we need to buy a "water-softener" ex.: "BlueSoft S30 SVR34" ( http://euro-clear.eu/uploads/content/catalog/EC_residential_product_catalog.pdf )

But: I can read that this "water-softener" device "replaces the Ca++ and Mg++ to Na+ ions"

The big question to chemistry: if the water will have many "Na+ ions" and not "Ca++ and Mg++" ions, would it solve the "dust" issue? So we will won't have any more white dust everywhere, if the humidifier is turned on?

We already asked the vendor, but they are not sure that this will solve the issue.


texts: Order of filling electrons in Jahn-Teller energy diagram

texts:
When filling electrons in atomic or molecular orbitals we fill first the lower energy orbitals and then the higher, according to Pauli and Hund's rule. But this seem not to be the case when considering metal complexes. According to Wikipedia

For example why the $d_{xy}$ orbital in the $d^4$ high spin is not fully occupied? Is the pairing energy that changes the order of filling the orbitals?


texts: Which acids are created by the combination of a gas and water?  I know that carbonic acid is created by combining carbon dioxide and water, but are there others?  Is there a specific name for this kind of acid?


texts: Why is Fmoc base-labile and Moz acid-labile?

texts:
I'm learning about the Zuckermann approach to combinatorial chemistry in my MedChem lecture. My textbook claims that the Fmoc protecting group is base-labile while the Moz protecting groups is acid-labile. Please see image below.

Both protecting groups have the same exact structure that is bonded to the amine (methoxycarbonyl) so should be equally reactive to either an acid or a base. How come this isn't true?

In other words, why  does hydroxide succesfully attack the carbonyl to liberate the amine in Fmoc, but not in Moz. Conversely, why does hydronium protonate the amine to create a good leaving group for the resultant water molecule to attack Moz and kick it (the amine) off, but Fmoc is not open to this pathway? (NOTE: These are my assumptions for how the mechanisms work. They could be (and most likely are) wrong.)


texts: What is the importance of using a pKa value instead of a pKb value when describing drug chemistry?

texts: Why do we only consider the $\mathrm{p}K_\text{a}$ value of a drug regardless of whether it is an acid or base? Why do we not use the $\mathrm{p}K_\text{b}$ value?


texts: How to get equation of state from fugacity

texts:
Given that the fugacity of a substance is $f=Pe^{bT}$, how do I obtain the equation of state of the substance?
This is my approach, but I have not made good headway:
$$RT d (\ln f) = VdP \\
d(\ln f) = \frac{V}{RT} dP \\
bdT = \left( \frac{V}{RT} - \frac{1}{P}\right)dP$$
But what next? I see that
$$\left( \frac{V}{RT} - \frac{1}{P}\right)dP = \frac{(Z-1)}{P}dP$$
But I don't see how I can reduce this further.
My end goal is to find derivatives of pressure wrt temperature keeping volume constant. How do I go about this problem?


texts: Can fungi metabolize pluronic polyol f127?

texts: I am looking for a gelling agent that can be used in place of agar, where its carbon must not be bioavailable for fungi. I have read about pluronic polyol f127 as substitute for agar. Can fungi metabolize carbon from this polymer?


texts:
Methionine and cysteine are the principal sulfur-containing amino acids, and
oxidation of cysteine and methionine residues had been well studied. How come NOT all proteins carry Methionine and/or Cysteine are under Redox Control?


texts: Can a spectrometer be used to figure out spice ratios in a sauce?

texts:
There is a really good sauce that a local restaurant makes. I have had trouble recreating it, but have gotten somewhat close. I had the following idea:

I could take an "image" of the sauce's color spectrum under good light using a USB spectrometer, and compare it to the spectrum of my home made version. I could then slowly tweak the ingredients and resample the color spectrum of the home made sauce until it started converging and eventually matched the restaurant's.

What could prevent this from working well?
Could this realistically outperform taste testing?


texts:
Here is a question from my practice problems:

I know that the answer is A, but I don't know why.  Is it because A has the most moles of gas on the left? thanks


texts: What's an "amagat"? How is it different from the Loschmidt Number?

texts:
At class, we were (briefly) taught about the Loschmidt Number/Constant ($n_0$), which isn't really different from the Wikipedia definition,

The Loschmidt constant or Loschmidt's number (symbol: $n_0$) is the number of particles (atoms or molecules) of an ideal gas in a given volume (the number density).

Furthermore, it says,

It is usually quoted at standard temperature and pressure, the 2010 CODATA recommended value is  per cubic metre at $0 °C$ and 1 atm.

 (Yes, I know STP is currently defined at 1 bar pressure, and not 1 atm. Since this isn't my main question, I'm bringing it up here: Is the Wikipedia definition of the Loschmidt number inaccurate? Should it be defined at 1 bar, instead?)
Reading on, I saw,

Being a measure of number density, the Loschmidt constant is used to define the amagat, a practical unit of number density for gases and other substances:
1 amagat = $n_0$ = $2.686 7805(24)$ x $\mathrm{10^{25}}$ per cubic meter,
such that the Loschmidt constant is exactly 1 amagat.

To begin with, I've never heard of an "amagat" [<--- I mean the unit, not the law named after the same person]. Yes, this may be the result of my shortcomings as a high-schooler with limited (almost pitiful, really) exposure to physical chemistry...but what bugs me more, is that I still can't wrap my head around it even now.
Including the Wikipedia definition for the amagat before I continue,

An amagat is a practical unit of number density. Although it can be applied to any substance at any conditions, it is defined as the number of ideal gas molecules per unit volume at 1 atm and 0 °C.

We already have the good ol' Loschmidt Number...so why introduce another term/unit that is (seemingly) defined the same way, has the same value and carries the same (SI) units?
Besides, what's with the "...practical unit of number density." bit?


texts: Cell potential for redox titration of iron(II) with cerium(IV)

texts:
Calculate $E_\mathrm{cell}$ for an electrochemical cell consisting of SCE and a platinum wire indicator electrode dipped in a titration vessel containing $\pu{25 ml}$ $(\pu{0.01 M})$ solution of $\ce{Fe^2+}$ ions after addition of $\ce{Ce^4+}$ solution of concentration $\pu{0.01 M}$ of
A) $\pu{5 ml}$
B) $\pu{25 ml}$
C) $\pu{50 ml}$
SCE is attached to the negative terminal of voltmeter. Given data:
$$
\begin{align}
E^\circ(\ce{Fe^2+/Fe^3+}) &= \pu{0.77 V} \\
E^\circ(\ce{Ce^4+/Ce^3+}) &= \pu{1.61 V}\\
E(\text{SCE}) &= \pu{-0.24 V}
\end{align}
$$

I tried doing this, but one thing I don't get over with is that isn't iron ions and cerium ions both oxidising and reducing? Why is there another electrode? Please clarify as much as possible.


texts: I'm working on a project where I have to understand the concept of topological isomer. I found a review or two containing the idea but I couldn't find a book or a detailed description of what a topological isomer is. I would like a suggestion for a book, article or other resource that gives me a clear definition (Wikipedia doesn't do a good job either). Or I would like someone to give me a clear description of what a topological isomer is.


texts: After reading a number of explanations about it after googling, I'm a bit confused on this. Some explanations are doing it using a solution density, others aren't, though most are. On one site it's showing different densities for a solution of a compound at different w/w% values. I'm now very lost as to how you convert from a w/w% to molarity. Can someone clarify?


texts:
From "Smarter than a 5th Grader":

  What is the simplest structural unit of an element or compound?

  molecule,
  atom,
  neutron,
  proton

For covalent compounds, the answer would definitely be molecule. But I'm unclear as to how to show that the answer for ionic compounds or elements is "molecule".

For example, https://sites.google.com/site/rccchem2a/chapter-4-chemical-bonding-the-i states that ionic compounds: "Do not have molecules as basic structural unit. Instead extended array of positively and negatively charged particles called ions." Is the term 'structural unit' defined across Science as only for covalent compounds?


texts: Why does the solubility of LiCl increase with temperature if the dissolution is exothermic?

texts:
In an answer to another question, the following data on the solubility of $\ce{LiCl}$ at different temperatures is presented.

This suggests that dissolving LiCl is endothermic (according to the van't Hoff relationship).  However, the enthalpy of dissolution has been measured and extrapolated to infinite dilution, and it is negative (the value given in one of the comments is $\Delta H = \pu{-37 kJ/mol}$, reference).

What is the reason for this discrepancy? Is it because $\ce{LiCl}$ is so soluble that there is some non-ideality effect? Maybe dissolving the first couple of molecules of $\ce{LiCl}$ is endothermic, but then when you dissolve more it becomes exothermic? Or is the activity of $\ce{LiCl}$ at increasing temperatures actually decreasing even though the concentration is increasing? Or is the van't Hoff relationship not a general one?

There is another question ($\ce{NaOH}$ solubility with temperature) which claims that Le Chatelier's principle sometimes does not apply, but it does not mention van't Hoff (and the answer might be incomplete).


texts: How to index molecules in computer programs?

texts:
Is there a standard way how can the index over a molecular structure be kept in the computer?

A molecule is a graph, where nodes have labels (chemical element type), and edges are chemical bonds.

There is SMILES representation that determines the molecular structure, but SMILES representation isn't unique.

One can take the set of all possible SMILES representations for one molecule, sort them alphanumerically, and pick the first element. This would be a unique string that is in one-to-one relationship with a molecule, and would satisfy my request.

But is there a standard way how to have a value that is in one-to-one relationship with a molecule that can be used as an index in the database that has many molecules in it?

By extension, how to efficiently search a set of molecules and, given a particular molecule, find a set of the closest structural matches? What characteristics of the molecules should be memorized that would allow such search to be efficient?


texts:
I am trying to understand the different behaviors of sugar syrups when it comes to candy making. Specifically, maple syrup vs molasses.
In making maple candy, pure maple syrup is heated to soft ball stage, which is 235F or about 113C. It is then cooled without stirring to 175F (79.5C), then beaten until it becomes opaque and thick, indicating sugar crystals have begun forming. When it cools to room temp, it has a somewhat fudgy consistency and is fairly brittle. If you do the same process with molasses, you get a sort of proto-taffy. In fact, you can pull it, and it will incorporate air, but doesn't quite reach taffy consistency (taffy typically also includes a fat and an emulsifier, and is also cooked just above soft ball stage to 244F so this is probably why).
I've been able to find some resources on the differences in chemical composition. This paper: https://doi.org/10.1016/0963-9969(96)00000-2 tested 80 maple syrup samples and determined the average syrup was 68% +/- 4% sucrose, with less than 1% each fructose and glucose. In contrast, the Encyclopedia of Food Sciences and Nutrition (Second Edition) available at https://www.sciencedirect.com/topics/neuroscience/molasses lists molasses as 30-40% sucrose, 4-9% glucose, and 5-12% fructose. Since glucose syrup is added to other candies (including taffy, ice cream base, and fondant) to prevent crystallization, I assume the higher level of glucose is what's preventing the molasses from forming crystals and making a candy similar to maple candy?
Maple syrup also has a significantly higher water percentage, 32% on average compared to molasses at 17-25%, so the cooking process to bring maple syrup to temp is longer than it is to bring molasses to temp. Additionally, maple syrup is mildly acidic, with malic acid being the largest contributor. Is it true that with a mild acid the cooking temperature is not high enough to hydrolyze the sucrose to glucose and fructose?
What ultimately drives the crystallization process? If, for example, you added a significant measure of table sugar to molasses to bring the total sucrose percentage up to 75%, and then cooked it as with maple syrup, could you reasonably expect it to crystallize into a solid candy? Would it have to be a higher percentage because of the glucose present? Or is the higher native glucose level an insurmountable issue in terms of the chemistry?
ETA: Is there a food-safe reaction that can be done in a home kitchen to synthesize the glucose and fructose in molasses to sucrose?
(a final note, I have tested this with 3/4 cup of molasses to 2/3 cup sugar, and again got something closer to a very soft and sticky taffy. It is possible that this was simply not enough sugar, and that it needs to be portioned by mass not volume.)
Any insight is appreciated, thank you!


texts: Describing evaporation without entropy -- what about Helmholtz?

texts:
I have in mind a rigid, impervious, heat-insulating vessel containing a monatomic liquid and vacuum. The vessel has an insulating forcefield inside, exactly at the surface of the liquid. It can be toggled.

Step 1: The liquid is in thermal equilibrium. The field is switched off for a very short, predetermined time. Some portion of the molecules at the surface exceed some threshold of kinetic energy, enough to escape into the vacuum.

Step 2: Now the liquid is no longer in thermal equilibrium because some of its fastest molecules have escaped. The same can be said for the vapor, except it lacks slow ones. We wait until both regain equilibrium -- they will do so separately because of the forcefield -- and then turn the field back on.

We return to step 1. This time there is some condensation as well as evaporation.

We repeat steps 1 and 2 again and again. At each iteration we can always predict the proportion of liquid that will evaporate, and the proportion of vapor that will condense, based purely on the temperatures of the liquid and vapor, the volume of the liquid, the pressure of the vapor, and the length of time the field is off. We can do this without considering changes in entropy.

But the Helmholtz energy is what determines the direction of this process, and its calculation requires knowledge of the change in entropy.

So is there a problem with my model?


texts: What are the limitations of the Hendersson-Hasselbalch equation?

texts:
Our instructor told us that prior to the equivalence point, the $\mathrm{pH}$ of a solution is dependent on the HH equation. However, when I tried practicing for polyprotic acid titration, I came upon this problem that does not make any sense at all. When I'm using the HH equation, the $\mathrm{pH}$ I get is lower than the initial $\mathrm{pH},$ which is illogical.

The problem goes likes this:

  What is the $\mathrm{pH}$ of the solution of $\pu{25 mL}$ $\pu{0.100 M}$ of $\ce{H2SO3}$ $(K_\mathrm{a1} = \pu{1.23e-2},$ $K_\mathrm{a2} = \pu{6.6e-8})$ when $\pu{5 mL}$ of standardized $\pu{0.1000 M}$ of $\ce{NaOH}$ is added?

The initial $\mathrm{pH}$ that I've calculated is $1.53,$ but every time I try to use HH for the computation of the first $\pu{5 mL}$ increment of titration, the $\mathrm{pH}$ is lower than the $\mathrm{pH}$ of the initial conditions.


texts: Why do aromatic compounds have an upfield shift upon coordination to metals?

texts:
Why do aromatic compounds have an upfield shift upon coordination to metals e.g. ferrocene? The 1H NMR shows a single environment at ~4.1 ppm. This is in contrast to the usual aromatic shift of between 6-9 ppm. At the moment, I have the following rationale, although I am not convinced about 2/3:

1) Coordination of the aromatic group to the Fe essentially localises the double bonds, as Fe will backbond into the aromatic $\pi$*-orbitals.

2) Bonding of the aromatic group to the Fe will disrupt the ring current which would also cause an upfield shift. However, there seem to be several papers online which suggest the presence of ring currents even in sandwich complexes?

3) There are 6 $\pi$-electrons for only 5 carbons in Cp, therefore there are essentially 1.2 $\pi$-electrons per Cp carbon whereas there is 1 $\pi$-electron for each carbon in Cp. Therefore Cp is more shielded than benzene naturally and will have a lower shift.


texts: Why does thallium form TlF and TlF3 but aluminium only forms AlF3?

texts: Does this have something to do with the inert pair effect?


texts: Why are lyophillic sols uncharged and lyophobic sols charged?

texts:
Gums, resins, glue, gelatin starch are uncharged and lyophillic where as metal sulphides and hydroxides are charged and lyophobic.

Right after studying o-chem this seemed quite contradictory as polar solvents are supposed to dissolve polar solutes and non polar solvents non polar solutes.

Why does this not work for sols, why are polar/charged compounds lyophobic but uncharged lyophillic?


texts:
$$\left(\frac{\partial U}{\partial V}\right)_{\!T}$$

I know that this partial derivative is equal to zero for an ideal gas, but how do I determine that? Do I need to use the fundamental thermodynamic relations?


texts: How do we predict the order of melting points of group 1 and group 2 halides?

texts:
I get really confused by this:

The order of melting points of group 2 chlorides is: $$\ce{BaCl2 > SrCl2 > CaCl2 > MgCl2 > BeCl2}$$ This is completely understandable by Fajan's Rules.

But, the order for group 1 halides is: $$\ce{NaCl > KCl > RbCl > CsCl > FrCl > LiCl}$$

This is what I don't get! Considering Fajan's Rules, $\ce{NaCl}$ is the most covalent, least cationic size, so shouldn"t it have the lowest melting point?


texts: Energy and time considerations in chemical reactions

texts:
I'm working on hydrothermal decomposition of organic matter at high temperature and pressure (400 bar). The reactions are too complex and numerous to model individually, but proceed in a similar fashion at different temperatures.  If the reaction proceeds to the same point in 1 minute at 300degC and 1 day at 100degC, is there any way to use this information to estimate the amount of 'energy' required to do the work?  I know this is a strange question, but I want to see if the same decomposition is achieved using electrochemical energy in an ion trap. I'm not sure how I'm going to be able to compare the systems in terms of energy applied. I am quite sure that the hydrothermal decomposition depends on the force of the bonds being broken, as does the electrochemical decomposition...
Am I going down the wrong rabbit hole to calculate the specific energy of the water at this temperature?  How would time come into the equation then?


texts: How do dibromopyrazolones undergo base-promoted decomposition?

texts: I was not sure but seeing the base as NaOH I used the fact that it will take most acidic hydrogen that is N-H and electron pair will come over it and it will resonate from two sides. I could make upto this intermediate but next I am not really sure the ring will break up and give the product as option D.


texts: Why does 9-fluorenone dissolve in hexane?

texts:
I know like dissolves like, but I am still unclear.  9-fluorenone has a polar $\ce{C—O}$ bond.

Is it because 9-fluorenone can only form London forces with other 9-fluorenone molecules and hexane can break these forces?


texts: GAMESS and Gaussian : what is the maximum efficient number of supported nodes?

texts:
I have looked at GAMESS and Gaussian manuals but can not find the maximum number of efficient nodes. As I tried GAMESS on our supercomputer, I can add as many CPUs as I want but it really does not Improve the calculation time and efficacy . On the other hand just adding maximum number of CPUs is just waste of CPU-Hour time and resources.

Is there any criteria for selection of best number of CPUs for optimum resource usage ?


texts: Finding out the number of atoms in the sun.

texts:
This is the question from the text book:

This is what I did, since it worked with all the previous questions (similar to this).

$$
\frac{\frac{4}{3}\pi(7*10^8)^3*1.4}{1.008} * 6.022*10^{23}
$$

This equals $1.2 *10^{51}$, but the answer is $1.2*10^{57}$

What have I done wrong? Thank you in advance.


texts: What is the name of the glyoxal radical after removing two hydrogen atoms?

texts:
What is the name of the radical that results from removing two hydrogen atoms from glyoxal ($\ce{CHO-CHO}$)? It has a roughly this structure: $$\ce{O=C^.-C^.=O}$$

It is an important intermediate in heterogeneous electrocatalysis (for instance, J. Phys. Chem. Lett. 2015, 6, 11, 2032-2037). For simplicity, in most articles it is called "carbon monoxide dimer". However, it should have a systematic name like other crucial intermediates like $\ce{-CHO}$ (formyl) or $\ce{-OCH3}$ (methoxy).

Please note that the answer is probably not ethenedione, which is the hypotetic dimer of carbon monoxide in gas phase.


texts: How do I extract cyanide from apple seeds?

texts: I'm working on a crime story about cyanide poisoning from apple seeds. I just would like to have an idea of what processes and extraction techniques might be involved in getting cyanide from the seeds. The character is supposed to have access to a high school chemistry lab; so I was thinking equipment and tools that can be found in a typical HS lab. I prefer a detailed answer, step by step, if possible. If not then just generalized terminologies would work.


texts: How to convert pCO2 (uatm) in seawater to grams

texts:
I have seawater pCO2 measurements, and I need to convert them from uatm to moles or grams for around a 50m depth integration.
I know the solubility coefficient and temperature among other data.

For example, I have:

445.87uatm seawater pCO2
2.77*10-5  (mol atm-1 m-3) solubility coefficient
50 m Hypothetical integration depth
12 (carbon to mole conversion)

The air-sea flux equation is F=delta pCO2 (atm) * solubility (mol atm-1 m-3)  * gas transfer velocity (m / yr)
Which gives an answer in mol / m2 / year.

To calculate the total volume of carbon in grams, can I use:
pCO2 (uatm) * 1 000 000 (atm) * solubility  (mol atm-1 m-3) * integration depth (m) * 12 (to convert to grams). And then if I had a time component, divide by the number of days to get (g/m2/day).

This gives:

(445.87*1 000 000)*2.77e-5*50*12 =  7410359.39 (gC / m2)  or 7410.36 kgC/m2.

Is this correct? Is the integration depth a valid assumption in replacing gas transfer velocity?
Is using the solubility the correct way to calculate this mass using Henrys' Law?
Can you point me in any resources to check these calculations?

Thanks very much.


texts: What would you call the polymerised sheet-like polymer arising from Fittig reaction of 1,3,5-trichlorobenzene?

texts:
If we dip a sample of chloroalkane in an ethereal solution, radicals form at the sites where chlorines are attached, which subsequently pair with other radicals.

Now, consider 1,3,5-trichlorobenzene:

If I attempted to perform a Wurtz-Fittig reaction with this, I suspect the product would be a two dimensional polymerised product. I drew a portion of it:

This polymer is quite interesting. Has this been observed before? Does it have a name?

While looking for the name of this molecule is my primary concern, it would be great if I could also get some information about its properties. This polymer looks like a "hollow" version of graphene, so I believe this would have some properties of graphene, although quite lighter. I think this could conduct electricity, due to conjugated $\pi$ systems of benzene rings. I also believe it would be quite porous, and probably allow small molecules like $\ce{H2O}$ to pass through.


texts: Solubility of n-butanol and n-butanamine

texts: I ran across something saying that n-butanamine is miscible in water while butanol is only partially soluble. Is this correct? Can anyone offer an explanation? I would have guessed that the decreased polarity of the amine relative to the alcohol would have resulted in lower solubility for n-butanamine.


texts: Stability between benzyl free radical and tertiary free radical

texts:
My teacher told me that the hyperconjugation of 9 alpha hydrogen domintes over resonance (for a carbocation )and so the stability of a tertiary carbocation is more than benzyl carbocations due to exceptional hyperconjugation .

I was convinced to the fact and started applying to the questions but then i got stuck and was confused when i saw the stability order of the following groups of free radical .
According to me the order told by my teacher for carbocation should still be valid for free radical .but in the following picture benzyl free radical is ahead of tertiary free radical in terms of stability.


texts:
I want to brew beer using helium instead of $\ce{CO2}$.

Most beers use about 2.5 grams of $\ce{CO2}$ per litre except stout like Guinness which uses nitrogen as it allows bubbles for much longer hence a frothy head on the stout.

So, perhaps a blend of helium and nitrogen would work? Helium is more soluble and if used in place of $\ce{CO2}$, as soon as the seal broke on a can it would escape rendering the cartoon voice idea useless.

How much helium can I squeeze into a litre of beer with or without compounding it to get the chipmunk voice?


texts: Is glass an amorphous solid or supercooled liquid?

texts:
I have been informed that glass is a super-cooled liquid and is also considered to be an amorphous solid.

Can it be both and, if not, what category does it fall into?


texts:
We take 10mL of $H_2SO_4$ with a $96\%$ of mass and density $1.84g/cm^3$, and we add it into a flask that has $0.5L$ of capacity, filled up to half of the flask with distilled water. We shake the mixture and we add in more distilled water up to the level of $0.5L$. Find the molarity and molality.

$\mathbf{Attempt. }$ My problem comes up when trying to find molality, I've found molarity like this (and this meets with the book's solution):
Let $M$ be molarity, defined as $M=\frac{n_s}{V_{T}}$ where $n_s$ is the number of moles of the solute and $V_T$ the total volume of the mixture. As we know $V_s=0.01L$ and $d_s=1.84g/cm^3=1.84g/mL=1840g/L$. We can find the mass $m_s$: $$m_s=d_s\cdot V_s=18.4g$$ and then find the moles of the solute $n_s=18.4g\cdot\frac{1 mole\ H_2SO_4}{98g\ H_2SO_4}\approx 0.188 moles \ H_2SO_4$ and then the $V_T=0.5L$ so $$M=\frac{0.188moles}{0.5}\approx 0.38M$$ and this part agrees with my book now, the issue is with molality.
$\mathbf{Doubt/The\ part\ where\ I'm\ stuck.} $ With molality, which I'll denote $m$, defined as $m=\frac{n_s}{m_{solvent}(kg)}$, where $m_{solvent}$ is the mass of the solvent in kg. Okay well, I attempted this and it gave me $245.2m$ while the book's answer is $0.37m$. My attempt:
We know $n_s$, and $m_{solvent}=m_{mixture}-m_{solute}$, and from the percentage given of the solute $96\%$, we also know that $0.96m_{mixture}=m_{solute}\implies m_{mixture}=\frac{m_{solute}}{0.96}$, and we finally plug that in the previous equation: $m_{solvent}=\frac{m_{solute}}{0.96}-m_{solute}$, plugging $m_s=18.4g$ we get $m_{solvent}=0.767g$. Converting to kg, we get $m_{solvent}=0.000767kg$. And finally plugging into the molality: $$m=\frac{0.188moles}{0.000767kg}\approx 245.11m$$ where I have gone wrong so that it does not meet with my book's solution?


texts: An iodine ion is the larger of the two, but why if they have the same amount of electrons? Also, $\ce{Li}$ is larger than $\ce{Li+}$, don't more electrons mean larger radius?


texts: Calculating KC Given Equilibrium Concentrations

texts:
Ex. N2O4(g) 2NO2(g)
• If you place 0.0350 mol N2O4 in 1 L flask at
equilibrium, what is KC?
• [N2O4]eq = 0.0292 M
• [NO2]eq = 0.0116 M

i want to know from where this coming

• [N2O4]eq = 0.0292 M

• [NO2]eq = 0.0116 M


texts: How does selenium protect against mercury poisoning?

texts:
I have read that it is not essential to avoid fish with mercury in them if they also have a correspondingly high level of selenium because mercury poisoning is primarily primarily the result of mercury disabling selenium based antioxidants.

How does selenium intake protect against mercury poisoning?  Can enough selenium counteract the effects of high mercury intake and does it matter what kind of exposure took place (breathing vapors etc)?


texts:
Does anyone know how one could extract Silica $\ce{SiO2}$ from a one or more of the following compounds in either ground or powder forms?

Plagioclase: $\ce{Ca2Al2Si2O8}$
Pyroxene: $\ce{(Ca,Mg,Fe)2Si2O6}$
Olivine: $\ce{(Mg,Fe)2SiO4}$

Ideally the process would only involve energy and mechanical processes rather than adding many other chemicals.


texts: Determining ratio of competing fragmentation processes in mass spectrometry

texts:
In a photoionization experiment, three photons of wavelength 266 nm were absorbed by a neutral molecule of 6-methyl-2-heptanone. If the kinetic energy of the electron removed during ionization is 1.4 eV, what is the ratio of the simple cleavage to the rearrangement produced fragment ions? The following plot describes the fragmentation of the molecular ion of 6-methyl-2-heptanone. The IE of this compound is 9.10 eV.

My intuition would just be to use the value of 9.10 eV provided in order to look at the rates of cleavage to rearrangement in order to determine ratios. I'm not sure how the 1.4 eV and the 266 nm photons come into play.


texts:
Cinnabar($\ce{HgS}$)  is one of the most common ores of mercury.
Why does it not exist at $\ce{HgO}$ or some other such compound?
Is there any reason for why it is so prevalent?
Does it react less with other compounds, or maybe due to some solid structure of HgS having some characteristic property giving it more stability?
I'm seeking an explanation without the mention of free energy, because it doesn't properly explain the phenomenon for me. I understand that cinnabar is abundant in the crust, and my question is why is $\ce{HgS}$ so common?


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So during school today, I am running an electrolysis experiment with water and sodium bicarbonate copper leads on both the anode and cathode.  I am noticing the usual $\ce{NaO}$ on the anode, and $\ce{H2C2}$ on the cathode.  However, on the anode, the copper is obviously oxidizing, and changing the hue of the water to a bright green-blue.  How can this be calculated into the chemical equation?

Also, is this equation correct?

$$\ce{H2O + NaC2 + energy  ->  NaO + H2C2}$$

(with the order of anode then cathode)

Yes, I am aware that this is the best possible situation, but in general, is this what is supposed to be happening?


texts: Negative coefficients for DIIS in SCF procedure

texts:
I am trying to implement the direct inversion of the iterative subspace (DIIS) algorithm in my simple HF program. After some problems it now seems to work. I can calculate the correct energies in roughly the same number of steps as in the literature.
My problem is that when generating the Fock matrix from previous Fock matrices I sometimes have negative expansion coefficients. This leads to expansion coefficients for the newest Fock matrix larger than one. The coefficient still sum to one.
Did anyone else encounter this problem?


texts:
Can 2-methylpropan-2-ol be converted into methyl ketone the action of $\ce{I2}$ in the presence of alkali base and thus give iodoform test?

Answer given to this question is that it can't give iodoform test. Please could someone confirm this with an explaination.


texts: Beer's Law: Are the graphs of concentration/time and absorbance/time supposed to look very similar?

texts: For my lab, I'm trying to figure out if the reaction between NaOH and crystal violet is a zeroth, first, or second reaction. My slope is 5.714*10^4 and y-intercept 0.008016. In logger pro, after finishing collecting my absorbance/time of NaOH and crystal violet, I tried getting the concentration of crystal violet by using that equation. When graphed, it looks exactly the same as my original graph, just on different numbers. I'm confused by this because when I've tried graphing ln(concentration) and 1/concentration, the graph returned no straight lines. I'm wondering if I'm doing something wrong.


texts: During the Iodoform reaction of acetone why does the second iodine addition happen on the carbon that already has undergone substitution instead of the other carbon?


texts: What is the meaning of cmmol in chemistry?

texts: I came across a unit called $\text{cmmol dm}^{-3}$ in buffer solutions. What does this unit mean?


texts:
I'm studying the model of a particle in a linear box when we have a chain of unsaturated carbons. I have a chain with 3 bonds and 4 atoms of carbon.
I'm applying the expression
$\lambda = \frac{8cmL^2}{ n^2 h}$
(instead of n I'm calculating the variation of n) where $c$ and $m$ are the light speed and the mass of the electron, respectively and $L$ is the length of the box ($=(3+1) \times d_\ce{CC}$, where $d_\ce{CC}=\pu{1.41E-10 m}~$ is the carbon-carbon distance), and I assume the transition with less energy is $3^2-2^2$.
I calculated 210 nm and the correct answer should be 207 nm. Am I taking an incorrect approach?


texts: What is the right color of calcium copper titanate?

texts:
I'm browsing Alibaba for calcium copper titanium oxide $\ce{CaCu3Ti4O12}$ (CCTO) and I find it variety of colors: pure brown, pale brown, reddish brown or grayish dark brown. Wikipedia does not tell the right color either.

What is the right color for CCTO?

All of these below are sold as CCTO on Alibaba. Can it be that they have different color but are equally valid products?