texts:
That is my question:

How can I track the progress / read the output file of an ongoing calculation in GAMESS-LIBCCHEM from NVIDIA?

The steps I have followed are in:

https://www.nvidia.com/en-us/data-center/gpu-accelerated-applications/gamess/

In there, there is a command line:

nvidia-docker run -v $(pwd):/results --rm nvcr.io/hpc/gamess:17.09-r2-libcchem -c "cd /workspace/examples && rungms cc-h2co.inp"

But, that command line print an output file only when the calculation has finished.

I want to read the output while the calculation is running and I do not know how.

I am running it on my laptop: i7 + geforce 940m + 12 gb of ram


texts:
Does phloroglucinol respond to the

iodoform test?
cerric ammonium nitrate test?
2,4-DNP test?

I couldn't find any good sources that answer any of these.

I thought of this:

Tautomerism can "change" phloroglucinol to a 1,3,5-triketone,  which should respond to the iodoform test.
It is a phenol, so it should respond to the cerric ammonium nitrate test.
Again, the keto form should respond positively to the dinitrophenylhydrazine test.


texts:
Wood water obtained by running water through hardwood ashes has a high quantity of $\ce{K2CO3}$, historicaly this was called lye.  Yet soap recipes today seem to use $\ce{KOH}$ or $\ce{NaOH}$ as lye.
$\ce{KOH}$ is stronger than $\ce{K2CO3}$, so how would someone determine how much more $\ce{K2CO3}$ to substitute when $\ce{KOH}$ is called for in a recipe
I am using the method in the link to make lye, and the lye produced is mainly a combination of $\ce{K2CO3}$ and a little $\ce{Na2CO3}$, this should be sufficient to create soap
https://www.wikihow.com/Make-Lye


texts:
What is the hamiltonian for an atom with two electrons and a nuclear charge $Z$?

The Hamiltonian always takes the general form: $\hat H=\hat T + \hat V $

The kinetic energy of each of the electrons needs to be taken into account so: $\hat T=-\frac{\hbar^2}{2\mu}(\nabla_1^2+\nabla_2^2)$

The potential operator is where I am finding trouble. There are two terms for the attraction towards the nucleus - one for each electron: $-\frac{Ze^2}{4\pi\epsilon_0r_1}-\frac{Ze^2}{4\pi\epsilon_0r_2}$. However, the potential energy involved in the electron electron repulsion needs to be taken into account. My question is: are there two terms for this? To clarify do I need to calculate the increase in potential of electron 1 caused by electron 2 AND the increase in potential energy of electron 2 caused by the presence of electron 1? Or would adding: $\frac{e^2}{4\pi\epsilon_0r_{12}}$ take into account all of the potential energy involved in the electron electron interaction?


texts: This is a topic that I cannot find much information about. I would like to know what compounds are in the products formed from pyrolysis of canola oil. I found out by accident that when trying to ignite some used canola oil in an aluminum can without a cover, the oil had become a mix of black solids and black liquid. I have not tried heating the oil in a container that has no exposure to oxygen. I could probably get better results by limiting all exposure to oxygen. I recently tried this experiment again and the oil is slowly turning black and looking like crude oil. I did find one article on this subject that says there are alkenes in the oil. Does anyone have more information on this?


texts: Reduction half-reaction for the reduction of elemental oxygen

texts:
Write the reduction half-reaction for the reduction of elemental oxygen in the presence of water, producing hydroxide ions

This does not make sense to me - a half reaction (from what I understand) is when you have an "element + some number of electrons -> element charged" or "charged element -> element + some number of electrons"

Reaction:

$\ce{HOH + O -> 2OH}$

Oxidation States: They all seem to be neutral to me - but I may be missing something.

So, how is a half reaction being introduced into this and what would it look like? Also, how can i know which element/compound is reduced/oxidized and is the reducing agent/oxidizing agent?

I am really sorry if this seems simple but I am a chem noob and I was out for a month and my teacher is behind schedule so he is giving us worksheets without teaching and i do not understand a lot. Thank you for your time


texts: What is the mathematical reason behind the gradual increase in osmotic pressure?

texts:
Question:

  Arrange the following in increasing order of osmotic pressure, $0.1~\mathrm{M}$ cane sugar, $0.1~\mathrm{M}$ $\ce{NaCl}$ solution, $0.1~\mathrm{M}$ $\ce{H2SO4}$.

Solution: As the number of particles/effective concentration of  the solutions increase in the following order:

Cane sugar $(0.1~\mathrm{M})$ > $\ce{NaCl}$ $(0.2~\mathrm{M})$ > $\ce{H2SO4}$ $(0.3~\mathrm{M})$

So the osmotic pressure which is related to concentration by the relation $P=cRT$ varies as:

Cane sugar > $\ce{NaCl}$ > $\ce{H2SO4}$

Is the following reasoning correct?


texts: 1-bromo-2-fluorobenzene reaction with magnesium and furan

texts:
Why does bromofluorobenzene react with magnesium and furan to form a benzyne intermediate?

Does it have something to do with a Grignard being highly basic and a fluorine being electron withdrawing, thereby making elimination a likely pathway?

Then does a Diels-Alder type reaction commence, with furan acting as the diene and the benzyne acting as the dienophile?

How likely or favorable is this reaction in real life?


texts: Why is DMSO more polar than other solvents, yet it dissolves ionic compounds worse?

texts:
I'm working right now in the solvent importance in ionic character, and I noticed how a binary salt ($\ce{CuCl2}$) dissolved better in methanol than in dimethylsulfoxide, and in contrast, a coordination compound (Cu[salen]) dissolved better in DMSO that in the aforementioned solvent.

It doesn't make a lot of sense to me considering these properties I found:

DMSO:

Dipole moment: 3.96
Dielectric constant: 47

Methanol:

Dipole moment: 1.71
Dielectric constant: 33

I would have expected the binary salt to dissolve better in DMSO rather than Methanol, and the inverse in the coordination compound yet it didn't happen like that. Is there a intermolecular detail I'm not considering? An hydrophobic-hydrophilic portion in the structure? Thanks everyone.


texts: Why is this intermediate borane-hydroperoxide adduct unstable?

texts:
Boron has an empty p-orbital and is highly electron deficient because of an incomplete octet.

So shouldn't this intermediate be more stable than $\ce{BR3}$ (whose electron deficiency is only somewhat fulfilled through hyperconjugation) since boron's electron deficiency is satisfied by the increased negative charge (although the majority of negative charge is still on oxygen due to its high electronegativity).


texts: How to identify which of two given electrodes with corresponding solutions is reducing more?

texts:
For the sake of the question, let’s assume that you are provided with two labelled rods of the pure metals $\ce{A}$ and $\ce{B}$ and two unlabelled bottles containing $\pu{1.0 mol dm-3}$ aqueous solution of $\ce{A^m+}$ and  the other bottle containing $\pu{1.0 mol dm-3}$ aqueous solution of $\ce{B^n+}$.

I want to find out, which metal out of the given two is more reducing, and identify each solution that is given in the unlabelled bottles. What are the procedures that I should follow?

If I immerse $\ce{A}$ in a solution of  $\ce{A^m+}$, I guess  there will be no change. Because if I do so there would be an equilibrium prevail with the ions in the solution and the electrode, and I think this is true for $\ce{B}$ also.

But I don't know how to identify the one which gets reduced more, yet I know that the anode gets reduced. So I am confused about that.

I feel that the only clue I have is immersing $\ce{A}$ in  $\ce{B^n+}$ and vice versa for $\ce{B}$ also. But  really I don't know what  would happen if I do so.


texts: Which has a greater dominance: hydration enthalpy or lattice energy?

texts: When I was reading my notes I came up with a problem. I read that for the s block element salts, when checking the solubility, we consider the hydration enthalpy so we decide their stability in water. But then there is this exception: hydroxides don't follow this. They depend on lattice enthalpy for their stability. Which has a greater dominance and why? Is it the lattice energy or the hydration enthalpy? How can we differentiate them, and where to use these concepts for deciding stability? As in the case of hydroxides lattice energy plays a dominant role, not the hydration energy: why is it so?


texts:
I had a silver-looking coin (not valuable, don't worry) that was heavily covered in black. I thought it could be silver, so I cleaned it with the electrolysis method (salt + sodium bicarbonate solution; copper on the positive pole and the coin on the negative). This didn't really work, though it seemed to make the coin less black, so I realized the coin was not silver.

I found out it is a copper-nickel coin. Since then I tried immersion in vinegar + salt solution, which made it a bit cleaner, and scrubbing with sodium bicarbonate, which made it cleaner still. But I noticed that, though some parts are silvery, most of the coin has a slight redness as of copper. Is this the copper from the coin, or did I somehow manage to deposit copper on it? How can I make the coin silvery again?


texts: Is there a simple way to memorize/reason out the solubility rules?

texts:
Normally, to determine if a compound is soluble, I would just apply the solubility rules, which can be found here.

The problem is, these are not fun to memorize as there are often loads of exceptions for each ion. Also, they are easy to forget. Is there an alternative way to reason out if something is soluble or not?

I was thinking that lattice energy might be a factor in determining whether or not something is soluble or not because if the lattice energy is low, the ionic compound can easily break apart and form ions. Thus, if the charges are low, it should be soluble. However, this hypothesis doesn't really explain why fluoride and hydroxide salts are insoluble.


texts: What visual observations can confirm that a reactant is the limiting reagent?

texts:
I have this lab question for the lab called Copper Collection Stoichiometry, where we choose an amount of the limiting reagent (iron) for a reaction between copper (II) sulfate and iron. We are to dissolve copper (II) sulfate in water, making it blue, then add iron, and after filtrating, we should have copper left.

How do we know if iron was the limiting reagent in terms of the visual observations? We made it so that iron was the limiting reagent, but how do we know visually if it is?

I understand that in order for iron to be a limiting reagent, it should've reacted with the solution and all completely turned into copper after the experiment. However how do we know if all the iron actually turned into copper? There is no way that we can visually count every solid flake to make sure there's no iron. I also understand that if iron was the limiting reagent, then there should be still copper (II) sulfate left in the solution, as the reaction didn't completely occur. Is that the answer?


texts: Why is cyclopentadiene more acidic than dibenzocyclopentadiene although in the latter, the negative charge will be more distributed and consumed in resonance stabilization.?


texts: Is it the difference of energies of formation of the resonance hybrid and the average of the energy of formation of all the contributing structures? How would we even calculate the energy of a resonance contributer?


texts: Make pure phthalocyanines from phthalocyanine dyes

texts: We need a pure copper phthalocyanine for our experiments. Of course, we can buy it from Sigma Aldrich, but this means we'll have to wait a while. In local area we can buy only dyes which are about 98% purity, which is not enough. Is there any fast and easy method to purify it in lab?


texts: How does VSEPR theory explain the formation of different bond angles in PCl₅?

texts:
We know, that in the exited state, electrons of Phosphorus could go to higher states and form $\ce{dsp^3}$ hybridization. Therefore it will create five equal energy states of electrons. But my question is that, why are the angles of the bonds in $\ce{PCl5}$  90 and 120 degree instead of equally distributed? How does VSEPR theory explain the difference in the angles?

Why do the  five equal bonding pairs of electrons have a trigonal
 bipyramidal arrangement, with two different internal bond angles -
 120° in the plane and 90° between the plane and the axial atoms?


texts:
I was watching a TED-talk on artificial muscle, HASEL, where the inventor demos that an insulated oil in the presence of electric potential field gets displaced due to Maxwell stress inside oil.
Question: What are the chemical properties specifically of the oil that allows such contraction to occur? Can oil be replaced with other fluid of different chemical properties to amplify the contraction effect?


texts: Consider the following atomic model for Helium. Helium contains 2 electrons revolving in circular orbit around the nucleus,in such a way that there is minimum possible repulsion between them.Calculate the first ionisation energy of this Helium.Will there be any difference in the ionisation energies calculated and experimentally found?


texts: Kolbe's electrolysis of acetylenedicarboxylic acid

texts:
I have been wondering what this reaction would lead to?
The ethyne diradical can't dimerize because triple bonded cyclic structures don't form until 8 carbons. And even if it polymerizes I find no way to end it's chain. This could probably lead to the carbyne.

Is there any literature on this out there?


texts: How to calculate non-stoichiometric ratio

texts:
I'm reading a paper "Photocatalysis-mediated drug-free sustainable
cancer therapy using nanocatalyst." Here, the authors synthetise nanoplates of $\ce{SnS_{1.68}}$ with nanodots of $\ce{WO_{2.41}}$.
The authors said the valence state for $\ce{Sn}$ are $\ce{Sn^{4+}:Sn^{2+}} = 0.681:0.319$ so the non-stoichiometric ratio of $\ce{Sn:S}$ is $1:1.68$.
For the $\ce{WO_{2.41}}$ they said, valence state for $\ce{W}$ are $\ce{W^{6+}:W^{5+}:W^{4+}} = 0.307:0.216:0.477 $ so the non-stoichiometric ratio of $\ce{W:O}$ is $1:2.41$.
I would like to know where the 1.68 and 2.41 numbers come from.
Thanks in advance.


texts: Regioselectivity in Claisen condensation and aldol reaction

texts:
I'm having a hard time determining regio-selectivity in those two reactions.

At the image above I've drawn one example for each on of them. My question is how do we choose where the deprotonation will occur. My approach was that the base will deprotonate the substrate in order to produce the most stable enolate. In the Claisen condensation, A should be the main product since the -CH2- group is present thus corresponding the mechanism. For B there will be no acidic hydrogens so it is not favoured, or at least that's what I thought.

Moving to the aldol condensation I can't figure out which product will be the main. Theoretically in C, the enolate is more stable than that of D, but the final unsaturated ketone isn't more stable in D?

Either way, I can't comprehend how can we determine what enolate will be produced each time.


texts: Can metal oxides react with water to form a hydroxide, then that with HCl to make a salt?

texts:
Lets say I have a metal oxide and I put it in water, and it reacts. As far as I know, only metal oxides from group 1 and 2 react in water, making hydroxides.

Now here is my question: If I add HCl to the hydroxide, can I be sure that it will make a salt and water? Or are my previous assumptions wrong?

An example that works would be Sodium Oxide which reacted with water and then with HCl produces NaCl and water. Does it work the same way with all metals from this group though?


texts: What is the maximum covalency of oxygen?

texts: My text says it to be 4. I believe it's 2. Is there any compound where covalency of 4 is observed?


texts: Reaction of propylene oxide with ammonia or hydrazoic acid

texts:
I am supposed to identify the products A and B in the following scheme:

The three options I have been given are:

I think that since $\ce{HN3}$ is a stronger nucleophile than $\ce{NH3}$, B should form via an SN2 mechanism. So, cleavage should take place in such a way that $\ce{OH}$ group remains with the carbon attached to the $\ce{CH3}$ group. Hence I think option 1 is the answer, but I am not sure about it.


texts: Equilibrium Problem Involving Solids: Faulty?

texts:
I am convinced that this is a faulty problem:

$\ce{2 Cu + S -> Cu2S}$
For the reaction above, $\Delta H$, $\Delta S$, and $\Delta G$ are all negative. Which of the substances would predominate in an equilibrium mixture of copper, sulfur, and copper(I) sulfide at $298~\mathrm{K}$?  Explain how you drew your conclusions...

The problem as written does not include state symbols, but they are obviously all in the solid states. However, solids don't achieve equilibrium, at least as far as I know. Thus, how can one talk of an "equilibrium mixture" of solids?
Update:
How can I explain the fact that using the ubiquitous equation $\Delta G^{\circ} = -RT\ln K$, I do indeed get an equilibrium constant?


texts: How to prepare 2-bromobutane from 1-butanol?

texts: So my answer (g then b) was incorrect. I thought that the bulky strong base of b would do E2 on 2-bromobutane, making it but-1-ene, then just add $\ce{HBr}$. What is wrong with my way of thinking?


texts: I am trying to calculate PES for Molecular Oxygen and Atomic Nitrogen Exchange reaction. This is also known as Zeldowich reaction. I found that for  asingle reactions, there are many PES's which I believe are for different electronic configurations of the NO2 PES. I found that the multiplicity can be 2 or 4. Also I find different surface being named as A' and A" in the literature. I would like to what exactly are these and how can I compute these in Gaussian?


texts: Estimate the relative intensities of absorption given the split in energy levels

texts:
Estimate the relative intensities at $\pu{25 °C}$ of absorption originated in the ground state and the first excited state when the energy levels involved are separated by:
(a) $\pu{10000 cm^-1};$
(b) $\pu{1000 cm^-1};$
(c) $\pu{10 cm^-1}.$

Here, the given numbers are the wave numbers of the EM radiation.
I have a problem understanding the term “relative intensities”. What does it imply? My professor has told me to calculate it using the population of states using the formula:
$$\frac{N'}{N} = \exp\left(\frac{-\Delta E}{k_\mathrm B T}\right)$$
But my problem is that the term $N'/N$ is the ratio of the number of particles in excited state and the ground state. How does it relate to relative intensities?
I'm fairly new to spectroscopy so I might have used few terms in the wrong fashion.


texts: How to determine the magnetic character of heteroleptic complexes?

texts:
I was asked to find out the magnetic behavior (and essentially electronic configuration) of heteroleptic complexes using Valence Bond Theory and Crystal Field Theory.

But I am confused about how to do it. Especially in the ones which have both strong field and weak field ligands together; how am I to decide whether pairing of electrons will take place or not ?

For a more concrete example consider the complex $\ce{[Cr(NH3)_4Cl_2]^{+}}$


texts: In free radical substitution of propane with halogens, how do you know which carbon ends up with an unpaired electron after fission of C-H bond?

texts:
In free radical substitution of propane with a halogen (eg- chlorine), how do you know which carbon out of the three ends up with an unpaired electron after fission of C-H bond?

This image shows methane, so there is only one possibility since there is only one carbon, but what about alkanes like propane with multiple carbons? How do we know which carbon atom ends up with the unpaired electron and why?


texts: Are pi bond like like interactions possible when substituents in a compound are not directly connected?

texts:
identify the more acidic compound (and the answer is the III is more acidic than II ).

My reasoning: Consider II compound, we have oxygen attached to the carbon forming a sigma and a $\pi$ bond, this oxygen has two filled p orbitals. The oxygen in the ortho position to it (in II), also has two filled p orbitals. My theory is that as we have filled p orbitals, they can form a $\pi$ bond type interactions (*). After forming the two $\pi$ bonds, the compound is stable.
Now discussing III, applying the same idea as above, there is a larger distance for the  $\pi$ overlap and hence I think $\pi$ overlap is less stable compared to the case in II.
Hence, we can say that III is more acidic (**) than II, as the pi overlap of the p orbitals of the two oxygen atoms are farther and long in III, and II is more stable (less acidic) as the pi overlap is over a small distance.
I reached the correct answer but I am not sure if my reasoning for it is correct because I haven't seen directly similar explanations in textbooks, however, I felt this idea was hinted at.

*: Not a $ \pi$ bond in the strong sense of the word
**: Less stable


texts:
I have an application for a very thin, strong, electrical conductor that need to act as a (almost) frictionless support "rope". Typically materials like tungsten wire or platinum-iridium alloys have been used. I was wondering about carbon fiber. However, how could I bond it to a metal (brass?) support such that significant tension would not pull it free?

The kind of thickness would be around 100 microns, for a length of maybe 30mm supporting (in the middle) up to 20 grams as it bridges a gap of 20mm.


texts: Why is SN1 mechanism followed in diazo aromatic compounds' nucleophilic substitution?

texts:
There is considerable evidence that SN1 mechanism is followed in diazo aromatic compounds' nucleophilic substitution. I would like to know the reason for this and why is it preferred to SNAr mechanism even when the $\ce{N2+}$ could stabilize the carbanion-type intermediate through -I effect.

Does it have to do with the excellent leaving tendency of $\ce{N2+}$ but at the cost of formation of unstable phenyl cation?


texts: Which (carbonaceous) fuels produce more or less soot in a diffusion flame, and how to predict that?

texts:
From what I've read, the production of soot in a flame is still an open research topic. But some hydrocarbon fuels produce much more soot than others. Are there (simple) rules that tell which fuels produce more or less soot? Especially for aliphatics?

Some things that influence soot production that I am aware of:

The amount of oxygen available and if this is pre-mixed with the fuel. I want to limit this question to diffusion flames (non-pre-mixed) with plenty of air available.
According to Wikipedia, naphthalenes produce more soot than benzenes which produce more soot than aliphatics.
Longer carbon chains generally produce more soot than shorter carbon chains.

But now I read that ethanol and diethylene glycol produce less soot than methane, even though both contains two-carbon chains and methane only a single carbon atom. Does it apply in general that hydrocarbons with oxygen atoms produce less soot, or are these an exception? And are there more general rules to predict which fuels produce more or less soot, short of setting up a full chemical simulation?


texts: How do I calculate the isoelectric point of amino acids, each of which has more than two values of pKa?

texts:
For most amino acids, the $\mathrm{pI}$ is simply the arithmetic mean of the amino and carboxyl $\mathrm pK_\mathrm a$s. However, for tyrosine and cysteine, which have more than one $\mathrm pK_\mathrm a$ value, this rule of thumb doesn't apply.
I see that for tyrosine, it's the $\mathrm pK_\mathrm a$s of the carboxyl and amino groups that are averaged, but for cysteine it's those of the carboxyl group and the side chain.
I haven't been able to find an explanation of why this is the case, or what the reasoning behind the calculations is?


texts: Why is a buffer solution best when pH = pKa i.e. when A-/HA=1

texts:
Buffers work best when  $\mathrm{pH}$=$\mathrm{p}K_\mathrm{a}$

From the Henderson-Hasselbalch equation,

$\mathrm{pH}= \mathrm{p}K_\mathrm{a} + \log_{10}\left(\frac{[\ce{A-}]}{[\ce{HA}]}\right)$

If $\mathrm{pH}$=$\mathrm{p}K_\mathrm{a} \implies\log_{10} \ce{\frac{[A-]}{[HA]}} = 0 \implies \frac{[\ce{A-}]}{[\ce{HA}]}= 1$

But why does having $\frac{[\ce{A-}]}{[\ce{HA}]}= 1$  make it a good buffer solution?

When I look at a $\log_{10}$  graph, it looks like the further to the right $x$ i.e. $\ce{\frac{[A-]}{[HA]}}$ is, the less effect any change in $\ce{\frac{[A-]}{[HA]}}$ has on $\log_{10}\frac{[\ce{A-}]}{[\ce{HA}]}$ (and hence effect on $\mathrm{pH}$ as well).

So wouldn't this indicate that a good buffer would have a large $\log_{10} \ce{\frac{[A-]}{[HA]}}$ (as e.g. going from $\ce{\frac{[A-]}{[HA]}} = 10$   to $\ce{\frac{[A-]}{[HA]}}= 11$  will have a smaller change (0.04 in this example) in $\log_{10}\ce{\frac{[A-]}{[HA]}}$ than going from $v= 1/1$   to $\ce{\frac{[A-]}{[HA]}}= 2/1$) (0.3 in this example). Where both of these changes show addition of 1 M of base.

Note: 2 similar questions where asked before: Why is buffer capacity at a maximum when the ratio of its components is 1? and Why does a buffer work best at the pH closest to its pKa?

The questions didn't show what exactly they didn't understand which I am attempting to do here. Also the answers were not useful as one said said the buffer is best when X (which I know), but not didn't explain why this is the case. The other questions answer provided a link which I read but was beyond me.


texts: What does the circle inscribed in a benzene ring represent?

texts:
I have seen benzene being depicted in two different ways:

For the right-hand structure, does the inscribed circle represent the movement of double bonds or electrons?


texts: How can enthalpy change of a system be negative while entropy change is positive?

texts:
$$\Delta G = \Delta H_\text{system}-T\Delta S_\text{system}$$

$$
\begin{array}{ccc}
\hline
\text{Sign of}~ΔH & \text{Sign of}~ΔS & \text{Spontaneity} \\
\hline
+ & + & \text{The reaction is spontaneous at high temperature} \\
+ & - & \text{The reaction is never spontaneous} \\
- & - & \text{The reaction is spontaneous at low temperature} \\
- & + & \text{The reaction is always spontaneous} \\
\hline
\end{array}
$$

When enthalpy change is negative, the reaction is exothermic, which means it releases energy into the surroundings. If the system is losing energy, shouldn’t the entropy of the system always decrease? I understand mathematically that $\mathrm{d}S = \mathrm{d}Q/T$, and if there is heat exchange, then entropy change can be positive.

But intuitively, if energy is taken away from the system, shouldn’t the entropy of that same system decrease? For some reason, I always thought that more energy means more entropy.


texts: Periodic table groups - which grouping is "right"?

texts:
In searching online, I've noticed there are a lot of different ways to group the elements of the periodic table.

Take mercury in the two tables linked below, for example:

http://i.telegraph.co.uk/multimedia/archive/02101/periodic_2101916b.jpg
http://www.sciencegeek.net/tables/PToE_basic.pdf

On the first table, it's explicitly outside of the transition metals. On the second table, it's included in the "transition metals" group.

Mercury is an example of this inconsistent classification, but in general, why is there no canonical grouping for all elements, across the periodic table? I see some tables mentioning "metalloids," but others not doing so. Or, sometimes elements are classified in entirely different groups altogether (like zinc, cadmium and mercury in the above-linked tables). Or, the lanthanides and actinides being included sometimes in the transition metals group, and sometimes not.

So which classification is right? Or rather, which one is the "most right"? Really: which one should I focus my efforts on remembering?


texts:
Sometimes I see 'alcohol free' written in big letters on toiletry bottles, such as on deodorants and shaving foams.

You would think that the toiletries bearing these words contain 100% no alcohol, but looking at the ingredients suggests otherwise - I still see alcohols in these products.

So does 'alcohol free' only refer to one type of alcohol not being present in the toiletry, such as a type of alcohol which causes irritation etc?


texts: POI is a bent molecule similar to water. How are the two molecules different it terms of bond angles and what causes this?

texts:
phosphorus oxyiodide ($\ce{POI}$) has the VSPER AXE formula of $\ce{AX2E}$ while water, $\ce{H2O}$ has the AXE code of $\ce{AX2E2}$. According to my work sheet $\ce{POI}$ should have a $120^\circ$ bond angle while $\ce{H2O}$ should have a bond angle of $104.5^\circ$.

Does this mean that due to the extra lone pair it creates less resistance resulting in a greater angle? Also, does it having three different elements in the equation do anything?


texts: Why does physisorption change to chemisorption at high temperatures?

texts:
I read in my textbook:

  In certain cases, physisorption changes to chemisorption as temperature is increased.

Could anyone explain why it is so? I know the basics of both physisorption and chemisorption, but I am unable to relate them to this statement.


texts: How much ascorbate to neutralize one liter of chlorinated tap water?

texts:
In Las Palmas de Gran Canaria, tap water is chlorinated. In an Internet forum, someone   claims that in 2008 the water had a chlorine concentration of 0,5 - 1mg/l. On the official site of Emalsa, the water provider, I couldn't find any information about chlorine concentration. I tried contacting them online, but the contact form is broken.

In another forum, I read that ascorbic acid (vitamin C) can be used to neutralize the chlorine: My taste buds say it works!

How much ascorbate/l do I need to neutralize the above amount of chlorine?


texts: Order of reactivity towards nucleophilic reagents considering alkyl halogenides, acyl halides and aromatic halogenides

texts: Considering alkyl halogenides (1°,2°,3°,4°), acyl halides, and aromatic halogenides and their combiations what is the order of reactivity towards nucleophilic reagents and why (considering inductive effect, mesomeric effect, etc.)? I know its a basic question that I could have searched for but I didn't find a source that compares all of the above.


texts: What transition metal ions form without oxidant in water pH 7?

texts: I am not sure how many transition metals will ionize without oxidants, where could I learn this?


texts: A question came in my test asking which of the compounds are not stored in glass. The answers were $\ce {HF, XeF6, XeF4, XeF2}$. I know about $\ce {HF} $ and $\ce {XeF6} $ but not about the other two. As far as I remember Xenon does not have any oxide or oxyfluoride in the +4 and +2 oxidation state. Thus I want to know if the given answers are correct and if so what are the reactions involved?


texts:
$\ce{CH2=CH-CH=CH-CH2-CH3}$

Is this hexa-1,3-diene or hex-1,3-diene?
And why?
When do you add an extra a and when do you not?


texts: How to obtain nitrogen using only homemade utilities?

texts: I am now constructing a RC plane. I would like to fill the tires of the landing gear with nitrogen to avoid combustion of oxygen during landing. I would therefore like to obtain a small amount of nitrogen using (only) home-made utilities. How can it be done?


texts: What is the correct structure for sulfur dioxide?

texts:
A question from the National Chemistry Olympiad (Germany-2008) goes as follows:

  Besides the composition of a substance the structure of its molecule or ion is of interest. To predict the structure you may use the electron repulsion theory
  (VSEPR).
  The following sulphur compounds are choosen as examples
  $\ce{SO2}$, $\ce{SO3(g)}$, $\ce{SOF2}$, $\ce{SO4^2-}$, $\ce{SF4}$, $\ce{SOF4}$, $\ce{SF6}$.

  b) Draw the structure of these species. Insert the free electron pairs of $\ce{S}$.
  Give the name of the geometrical shape of these compounds or ions.

I'm only interested in the structure of $\ce{SO2}$, that is represented in the answer sheet as $\ce{O=S-O}$ instead of the one I believe is the correct one $\ce{O=S=O}$.

What do you think?


texts: Why Fe(CO)5 exists, but Fe(NH3)5 doesn't?

texts:
Like in title: Why $\ce{Fe(CO)5}$ exists, but $\ce{Fe(NH3)5}$ doesn't?

Edit:

As Jan Dvorak pointed out, it may exist. If so: why is it so unstable?


texts: HDAC inhibitor and how it works on a cellular level

texts:
I have been working on a research project on the synthesis of a histone deacetylase inhibitor compound. I just realized that I am still a bit fuzzy on the how it works on a cellular level.

So, how does a histone deacetylase inhibitor work on a cellular level?


texts: Why is Acetic acid (pKa = 4.76) stronger than carbonic acid (pKa = 6.36)?

texts:
In order to try and understand this, I evaluated it via stability of conjugate bases. The acetate vs carbonate ion. The only difference is what's attached to the carboxyl group, the $\ce{-CH3}$ and the $\ce{-OH}$. Both anions seem to have equal resonance structures as I think resonance mainly only happens on the carboxyl group.

I think that because the methyl group is just larger than the hydroxyl group, it is able to better stabilize the negative charge on the molecule overall. But I also remember hearing that carbon can have a positive inductive effect, meaning it pushes electron density toward the carboxyl group, which would make it less stable.

I originally thought that carbonate would be more stable because the oxygen would pull the electron density toward itself, making the charge more evenly distributed.

If somebody could explain with diagrams I would appreciate it. I lost access to my software that did electron modeling functions for me.


texts: Are colligative properties applicable for volatile liquids and gases in liquid solvent? Why/Why not?

texts:
My teacher told me that the expressions for calculation of colligative properties like lowering in freezing point are only applicable if the solute is non volatile liquid or a solid. We cannot apply the formula for gases or volatile liquids. Is this true? If so then why/ why not?
I have not been able to come up with a satisfying reasoning explaining this statement. Also I have not been able to find evidence regarding this statement online. Although one of my books does say this without an explanation but I am not convinced.


texts:
Which route actually occurs? Is it really true that the carboxylic acid never forms under basic conditions?

Why not just form the -COOH and deprotonate it afterward?? Or is there a higher activation every barrier to the second route?

I understand that carboxylic acids don't stick around long in basic solutions but that doesn't necessarily mean they don't exist in basic solutions at all.


texts: Can someone explain clearly to me why some things are explosive?


texts: Gibbs energy derivative vs equilibrium for aqueous reaction

texts:
I am trying to find the Gibbs-energy equilibrium for the reaction $$\mathrm{A}+\mathrm{B}\rightleftharpoons\mathrm{C}.$$ According to most sources the equilibrium concentrations in an ideal solution should form a ratio $$\Delta G^0=-RT\ln\frac{[\mathrm{C}]}{[\mathrm{A}][\mathrm{B}]}.$$

I am having trouble seeing this when the stoichiometric coefficients on either side of the reaction are unequal, as in this example above.

The Gibbs energy for the solution should be $$G=n_A(\mu_A^0+RT\ln[\mathrm{A}])+n_B(\mu_B^0+RT\ln[\mathrm{B}])+n_C(\mu_C^0+RT\ln[\mathrm{C}]).$$

Assuming we started with a 1 L solution containing 1 mol of A and 1 mol of B, $\xi$ mol of each react to form $\xi$ mol of C, this equation should then be $$G=(1-\xi)(\mu_A^0+RT\ln(1-\xi))+(1-\xi)(\mu_B^0+RT\ln(1-\xi))+\xi(\mu_C^0+RT\ln\xi).$$

My understanding is that if the Gibbs free energy is at its minimum the reaction above will not be spontaneous in either direction and so the solution will be at equilibrium. The derivative of the above equation gives $$0=-(\mu_A^0+RT\ln(1-\xi))-RT-(\mu_B^0+RT\ln(1-\xi))-RT+(\mu_C^0+RT\ln\xi)+RT.$$

Some rearrangements result in $$\Delta G^0=-RT\ln\frac{[\mathrm{C}]}{[\mathrm{A}][\mathrm{B}]}+RT.$$

In other words, my expression is off by $\Delta nRT$. Having been unable to find any help on this matter on the internet, I feel I have either made some silly logical/mathematical mistake or have some fundamental misunderstanding. Please point out the error.


texts: Why does concentration of solutions of alkali metals in liquid ammonia change the magnetic properties?

texts:
In "NCERT Chemistry for Class XI - Volume II", in chapter "s-block elements", under the topic "Chemical Properties of alkali metals", it is given:

(vi) Solutions in liquid ammonia: The alkali metals dissolve in liquid ammonia giving deep blue solutions which are conducting in nature.
$$\ce{M + $(x + y)$ NH3 -> [M(NH3)_x]+ + [e(NH3)_y]- }$$
The blue colour of the solution is due to the ammoniated electron which absorbs energy in the visible region of light and thus imparts blue colour to the solution. The solutions are paramagnetic and on standing slowly liberate hydrogen resulting in the formation of amide.
$$\ce{M+(am) + e- + NH3(l) -> MNH2(am) + 1/2 H2(g)}$$
(where ‘am’ denotes solution in ammonia.) In concentrated solution, the blue colour changes to bronze colour and becomes diamagnetic.

In the last set of lines, it is given that in concentrated solution, the blue colour changes to bronze colour and the paramagnetic solution becomes diamagnetic.
How does the change in concentration affect the magnetic properties of the solution?
Wikipedia has nothing to offer to clarify my doubt.


texts:
What is the difference when following up ozonolysis with DMS (dimethyl sulfide), Zn/water, or just water? Or is there really no substantial difference at all?
In my textbook, the alkenes section uses DMS or Zn/water but then in the alkynes section it uses water with no explanation as to why that happens. My professor also uses them interchangeably, which gets confusing.


texts: What are inner core electrons and how do they influence chemical and physical properties?

texts:
There are six groups of p–block elements in the periodic
table numbering from 13 to 18. Boron, carbon, nitrogen,
oxygen, fluorine and helium head the groups. Their valence
shell electronic configuration is $\ce{ns^2 np^{1-6}}$(except for He).

  The inner core of the electronic configuration may,
  however, differ. The difference in inner core of elements
  greatly influences their physical properties (such as atomic
  and ionic radii, ionisation enthalpy, etc.) as well as chemical
  properties

The above lines are from my school's textbook.

How does inner core electron create such differences and and what are inner core electrons?


texts: I had my exam this week and one question asked whether $\ce{H2O2}$ was planar or not. I though that since the oxygen atoms are both sp³ hybridized and have two lone pairs each, the molecule should have a bent shape. I compared it $\ce{H2O}$ which also has the same shape and I knew was planar. But it turns out $\ce{H2O2}$ is not planar. Does anyone know the reason behind this?


texts: Thermodynamics effect of change of temperature on equilibrium

texts:
I'm studying thermodynamics and I don't understand, why, when we are asked which effect has a rise in temperature on the equilibrium constant of a reaction, we can't use the formula: $\Delta G= \Delta H-T \Delta S$, and say that if the reation is entropic, the change in free energy will more negative, therefore the reaction will be more spontaneous and the equilibrium shifts towards the products.

In my exercices books, it is said, that, according to le Chatelier's principle,the equilibrium will try to "fight" the new constraint and if it is exothermic,the equilibrium will shift towards the reactants, and if it is endothermic towards the products.

Le Chatelier's principle seems intuitive to me for the compression of a gas: when compressed, the molecules are now more narrow and they combine faster than they separate. But I don't see why it can be used in the raise of temperature.

Thank you in advance


texts: How do I calculate the normality of NaBrO3?

texts:
Find the mass of $\ce{NaBrO3}$ required to prepare $\pu{150 ml}$ of $\pu{0.75 N}$ solution based on the reaction
  $$\ce{BrO3- + 6 H+ + 6e- -> Br- + 3 H2O}$$

My analysis:

$\pu{150 ml}$ solution of $\pu{0.75 N}$ means $0.1125$ equivalents of $\ce{NaBrO3}$ are present in the solution. Since, according to the given equation, n-factor (of equivalence) of $\ce{NaBrO3}$ is $6$. So $0.1125$ equivalents means $0.01875$ moles of $\ce{NaBrO3}$. The molecular mass of $\ce{NaBrO3}$ is $151$. Thus, I get the mass as $\pu{2.83 g}$ approximately. Am I correct?

  Since the book says the answer should be $\pu{1.42 g}$


texts: Stability of 3d metal fluorides and iodides in different oxidation states

texts:
I read that the fluorides of 3d metals in lower oxidation states, e.g. $\ce{VF2}$, $\ce{TiF2}$, and $\ce{CuF}$ are thermodynamically unstable. For example, $\ce{CuF}$ disproportionates to $\ce{Cu + CuF2}$, as described on Wikipedia.

On the other hand, their iodides tend to be more stable (so, for example, $\ce{CuI}$ can be easily obtained from a redox reaction between $\ce{Cu^2+}$ and $\ce{I-}$). Why is this the case?


texts: Changes in conductivity of CuSO4 solution after NH3 solution is added

texts:
In my high school chemistry class we are writing a lab. Originally, I wanted to measure the rate of a ligand exchange reaction at different temperatures by measuring changes in conductivity. After some discussion, I came to the conclusion that there would be no change in conductivity and therefore I would not be able to use this method. Nonetheless, I decided to do the test the method; the results can be seen below:

This was quite a surprising result and so I decided to look at the reaction that occurs more closely. The full reaction is as follows:

Initially the solution consists of $\ce{[Cu(H2O)6]^{2+}_{(aq)}}$.

Once ammonia is added, the following reactions occur:

$$\ce{NH3_{(aq)} + H2O_{(l)} <=> OH- _{(aq)} + NH4+_{(aq)}}$$

$$\ce{Cu^{2+}_{(aq)}+ 2OH- _{(aq)} <=> Cu(OH)2 _{(s)}}$$

A continued addition of ammonia results in:

$$\ce{[Cu(H2O)6]^{2+}_{(aq)} + 4NH3 _{(aq)} <=> [Cu(NH3)4(H2O)2]^{2+} + 4H2O_{(l)}}$$

Looking at the reactions above which I obtained from here, I would assume that the conductivity increases due to the dissociation of water in the presence of ammonia to form ammonium and hydroxide ions. Is this assumption valid? Also, my experiment would like to use conductivity to measure how long it takes for the ligand exchange reaction to occur between the water ligands and ammonia ligands of copper. Would this be feasible, or would I only be measuring the rate at which ammonium and hydroxide is formed?

Note:
- The graph was obtained by using a conductivity sensor
- 25 ml of 35% ammonia solution was added to 25 ml of 0.5 mol $\ce{CuSO4}$ solution in this reaction.


texts: Is the hydrogen atom attached to the benzylic carbon in benzaldehyde acidic?

texts: If benzaldehyde loses hydrogen atom at the benzylic carbon, the negative charge will disperse into the benzene ring via resonance. So shouldn't the conjugate base formed be stable, implying that the hydrogen was acidic?


texts: Looking for a mechanism for the demercuration of organomercurial alcohol

texts:
I am teaching myself organic chemistry and am very frustrated that I cannot get a complete mechanism for the oxymercuration-reduction of an alkene to an alcohol. The reagents are an alkene, mercury(II)acetate, and water for the first step... the step I understand. It ends by forming organomercurial alcohol. This is then reacted in a second step with sodium borohydride in a solution of sodium hydroxide. I have searched for a mechanism for this step (specifically the reduction portion at the very end) but I cannot find one anywhere. The closest I have come to an answer is a source that says it probably had to do with radicals and inorganic chemistry. The products are an alcohol with the C-Hg(OAc) bond transplanted with a C-H bond, tetrahydroxyborate, reduced mercury (standard conditions), and OAc anion. Thanks any help is appreciated

Update:
I am attaching my attempt at a mechanism and would like someone to verify if it is the correct mechanism or tell me why it would not work. Thanks


texts:
From previous studies, I recalled in my lecture theatre today that lattice energy was the energy released when an ionic compounds is formed from individual atoms in the gaseous state. I thought this idea would follow through throughout my studies at university.

However, my lecturer this afternoon defined lattice energy as the following:

  • For an ionic solid the lattice energy is defined as the energy required to
  completely separate a mole of solid ionic compound into its gaseous ions

I thought this was my definition but in the reverse order.

Which one of us is correct, the lecturer or myself?


texts: Deriving the equation for reaction spontaneity

texts:
I'm trying to make sense of the derivation of the equation $$\Delta G = \Delta G^0_r + RT\ln(Q)$$

While searching for a derivation of this equation that made sense to me I came across a publication in the Journal of Chemical Education that suggests it is incorrectly applied if not completely wrong:

"Following this development, the paper investigates the source of the mathematical
and logical errors contained in textbooks ca. 1950 to the present that led to the
fallacious statements still present in most introductory chemistry textbooks and some
more advanced texts that the conditions for spontaneity are ΔG < 0 at constant T and
p and ΔA < 0 at constant T and V, whereas the corresponding conditions for
equilibrium are ΔG = 0 or ΔA = 0. This investigation shows the principal errors to be
(i) incorrect evaluation of definite integrals; (ii) failure to determine whether the
results of such integrations produce criteria for spontaneity and equilibrium that are
necessary conditions, sufficient conditions, both, or neither; and (iii) incorrect logical arguments related to equilibrium. (Spontaneity and Equilibrium III: A History of Misinformation)"

https://pubs.acs.org/doi/full/10.1021/ed500253e

Also, by the same author: https://pubs.acs.org/doi/10.1021/ed400453s

Here is the standard derivation:

For a given chemical reaction, let $v_i$ be the signed stoichiometric coefficient of reagent $i$ (That is, $v_i$ is negative for reactants and positive for products, with $|v_i| = $ the stoichiometric coefficient of reagent $i$).

Define the extent of the reaction, $\xi,$ as: $$\xi := \frac{n_i - n_{i,o}}{v_i} =  \frac{\Delta n_i}{v_i}$$

where $n_i$ and $n_{i,o}$ are the instantaneous number of moles and initial number of moles, (of reagent $i$) respectively. This quantity will have the same value regardless of which reagent is chosen to compute it and is therefore well-defined. It is effectively a measure of the reaction coordinate.

Note that: $$n_i = n_{i,o} + v_i\xi \to dn_i = v_i d \xi $$

$ \\ $
 $$dG = Vdp - SdT + \sum_i \mu_i dn_i \to \left(dG\right)_{P,T} = \sum_i \mu_i dn_i = \sum_i \mu_i v_i d \xi$$

In particular, $$\left( dG/d \xi \right)_{P,T} = \sum_i \mu_iv_i = \sum_i \left(\mu^o_i + RT\ln(a_i)\right)v_i = \sum_i \mu^o_iv_i + RT \sum_i \ln(a_i)v_i = \Delta G^o_r + RT \sum_i \ln(a_i^{v_i}) = \Delta G^o_r + RT \ln\left(\prod_i a_i^{v_i}\right) = \Delta G^o_r + RT \ln(Q)$$

In particular, $$\left( dG/d \xi \right)_{P,T} = \Delta G^o_r + RT \ln(Q)$$

I assert this is where it should stop. It tells you everything you need to know about the direction of spontaneity and the condition for equilibrium. For instance, the condition for equilibrium is that the free energy of the system is at a (local) minimum. To find the minimum of a differentiable function, you set its derivative equal to zero. Thus at equilibrium you have $Q = K$ and $dG/d \xi = 0$. Plugging this in gives $$K = e^{- \Delta G^o_r / RT}$$What I don't understand is how the left side gets equated with $\Delta G$. The left side is $\sum_i \mu_i v_i$. This is not the "instantaneous difference in free energy between the reactants and products". That would be $\sum_i \mu_i n_i$ (assuming such a notion even makes physical sense). I suppose you could call it $\Delta G_r$, but that perspective is confusing and would have no physical significance in the context of this equation (as you are viewing the reagents' concentrations as the variable that is moving as opposed to pressure or temperature).

I'm wondering if I am conceptually missing something?


texts: i need help with the fractional distillation method of a couple of substances at least more than two substances , just like air actually what am i looking for is that why do substances in air with a low boiling point like nitrogen reach higher the fractionating column even if it looks like that substances with higher boiling point will absorb more energy and thus eventually result in greater kinetic energy (at least to me). please help . heres how i came to know that nitrogen rises higher the fractionating column


texts: ICP-OES data treatment: correct for dilution and inweight, the units

texts:
Let's say the ICP-OES software gives me a concentration of 186,49 ppm (mg/L) of Mn. I diluted the acid digested sample to 14.2 mL. I weighed in 10.17 mg of the powder I analyzed. I need to calculate the actual concentration.

It is quite logical in my head what I need to do: multiply by diluted volume and divide by inweight. However, I don't understand my units.

When I multiply 186.49 mg/L with 0.0142 L, I get 22,648 mg. When I then divide this by 10.17 mg, I end up with 0.260. But this is unitless. How do I know what unit I have? I thought I converted the w/V concentration to w/w by this procedure, but the units does not follow.

Is it so, that I end up with a ratio (not sure what kind of ratio)? Then I think I understand. 0.26 would then represent 26 %, meaning my sample contains 26 % Mn. But how do I know that this is in w/w, and not w/V as I started with. I just don't get the units to add up.


texts: Would silica have the same effect as activated charcoal?

texts: Silica found in "do-not-eat" packets is a desiccant (I'm not sure about this); and so is activated charcoal. Would consuming it have the same effect if one were to have a stomach ache?


texts: Size consistency in computational chemisty methods

texts: I am looking for a clear answer that would explain what exactly size consistency is, why configuration interaction (CI) is not size consistent and how this leads to errors when using CI for large systems.


texts: Transition from ground state to excited state

texts:
I don't understand how to correctly find the term symbol of an excited state. I know that the first two permitted transitions for the Ne atom are 16.8eV and 19.8eV and I want to find the electronic configuration and the term symbol.

I assume that from the $2p$ orbital I'll have a transition to the $3s$ orbital (first excited state) and to the $4s$ orbital (second excited state). The selection rule $\Delta l=\pm1$ is obeyed. But what about the total angular momentum $j$? To find $j$ I have to know something about the spin $s$. Is it something about singlet and triplet states?


texts: Molecular Orbitals (only pi system) of Allyl system using group theory

texts:
I have just started reading group theory and their applications in the MO theory. I tried to get the equations of the pi molecular orbitals of allyl system using group theory, but I am stuck at the last part.

This is what I did so far—

Determined the point group of the allyl system to be $\ce{C_{2v}}$.
Used the 3 p orbitals as basis.
Found out the reducible representation. Reduction gives $\ce{A2 + 2B1}$

I am stuck at this point. I named the three p orbitals of C atoms as $\ce{\psi1, \psi2, \psi3}$. However, when I try to use the 'projection operator method' using the $\ce{\psi1}$ as generation vector, it gives me $\ce{\psi1 +\;\psi3}$ and $\ce{\psi1 - \psi3}$ (unnormalized). I don't know how to proceed.
 [image copied from Master Organic Chemistry webpage ]


texts: When I am studying magnetic properties in IB Chemistry, what particularly puzzles me is ferromagnetism. In my textbook, what accounts for paramagnetism in transition metals is unpaired electrons in their d orbitals. I suppose that ferromagnetism also comes from a particular electron configuration. I'm wondering why osmium isn't ferromagnetic, given that it is in the same group as iron, and has the same d-orbital configuration?


texts: Which atom goes in the middle of a lewis dot structure?

texts:
I've read online in multiple sites that the least electronegative atom goes in the middle with the exception of H, which always goes on the outside.

However, in the molecule NaCN, C is in the middle. Could anyone explain to me what is going on with this molecule?


texts: Why does cinnamaldehyde pass the ferric chloride test?

texts:
I was given some data to determine what the unknown compound was and figured out that it was cinnamaldehyde. After reviewing the classification test given to me by my professor, I was a bit confused as to why it would pass the ferric chloride test as well as pass a Lucas test but yet show no reaction.

Can someone explain to me why that is possible?

Also, in terms of solubility, why would cinnamaldehyde be soluble in sulfuric acid only and not both sulfuric acid and $\ce{NaHCO3}?$


texts: I know that optical activity means polarisation of light but what is so special in that that it changes the properties of the substances significantly


texts: What is the most appropriate (and easy-to-use) all-atoms force field for liquid electrolytes?

texts:
I need to simulate a salt diluted in a liquid electrolyte.
My experience is with LAMMPS, but so far I only had coarse grained toy models, and setting up the force field was straightforward.
Now I have a real molecule (>20 atoms), which I optimized quantum mechanically with MP2 and I have tried to run various tools to automatically get the parameters: VMD/topotool, ATB+moltemplate. Nothing really works and I need to tweak too many parameters by hand.
So I am wondering whether or not to use an all-atoms design MD software such as Amber or Gromacs. Which one would be the best candidate for my study case considering the physical system? which one is more easy to use when it comes to infer the force field from QM results?
Thank you
Marco


texts: Modelling planar ring molecules and their evolutions

texts:
This is the next step of my previous question.

I am trying to simulate a circular chain (ring) of molecules which are planar (two dimensional). What I do is take a planar unknot and embed it into a two dimensional lattice. Then I calculate energy of the unknot and try to evolve the unknot so that it reaches the canonical form. By definition it then has the minimum energy. To have a realistic definition of the energy I need to study real life planar unknots.

Can anyone please give me an example of the molecular chain which can stay as planar with it's minimum energy state is planar. A published study on the evolution of the geometry of the molecule will be highly helpful.


texts: Why does road salt reveal this bus's frame?

texts:
Our city sprays brine on the roads in the winter to prevent people from sliding around. It works but it makes it impossible to keep vehicles clean. One thing I've noticed is that the brine sticks to the city buses outlining the frame underneath the body panels, like so:

Doing some research, these buses are made out of stainless steel to prevent rusting.

Is there a chemical reason for this happening?


texts: What reaction is happening when a lithium polymer battery "is on fire"

texts:
When something goes wrong with a lithium polymer battery (as are commonly used to power electric models and robots), and it "catches fire", what is actually happening?

What gas or gasses are being released?

Here's a video of such an event.


texts: What occurs when stannous fluoride is combined with baking soda in the oral cavity?

texts:
I have googled this question in many forms over many months repeatedly.

For some background, when stannous fluoride is combined with water, it forms precipitates and/or oxidizes, rendering it less effective in the oral cavity.  Crest Pro-Health, as an example, adds a stabilizer, a gluconate, to maintain stability of the stannous fluoride. (If anyone can answer the question of how the gluconate stabilizes the stannous fluoride, that would be great too.)

My main question: What is the effect (via the chemical reactions) of combining a sodium bicarbonate/hydrogen peroxide solution with stannous fluoride in the oral cavity?  And how is that effect altered if hydrogen peroxide is not used?

According to me, the high pH of the baking soda neutralizes the acidity of the stannous fluoride, thus nullifying the effects of $\ce{SnF2}$. I also feel that the hydrogen peroxide oxidizes the stannous fluoride - and there may be some precipitates. But I am not sure.

I am asking these questions because I want to determine whether I can use a baking soda/peroxide toothpaste followed by an $\ce{SnF2}$/hexametaphosphate toothpaste.


texts: Why does diatomic oxygen have five filled molecular orbitals, but is considered to have two bonds?

texts:
So I'm taking an introductory chemical physics course and we are covering LCAO-MO.
We learn about the molecular orbitals that arise out of a combination of the two atoms atomic orbitals. This totally makes sense to me, but then we start learning about electron configurations and orbital diagrams. When we get to oxygen the textbook shows that oxygen has 8 electrons each, and when they combine they fill up the σ1s σ2s σ2pz π2px π2py bonding orbitals and the σ*1s σ*2s antibonding orbitals (with the π*2px π*2py antibonding orbitals each half filled). My question is:

Why does this result as a double bond?

I see it is partially addressed here: Molecular Orbital Theory and No. of bonds
But what they don't speak to is why there are two filled π2p bonding orbitals but only one pi bond. I understand how to calculate bond order but in my understanding thats our approach at reasoning out bond strength, it returns an integer value - it does not really tell me much about the actual bonds themselves. Is the pi bond that results some sort of hybrid between the π2px and π2py orbital? If there are two electrons each in the π2px and π2py orbitals, how does one electron in each of their respective antibonding orbitals play out in the formation of the bond?
Thank you ChemSE community!
*editted to further clarify I am aware of bond order calculations


texts: Is there any difference between balancing redox reactions in acidic and basic medium?

texts:
For balancing redox reactions in an acidic medium I follow this procedure:
1. Writing the half reaction
2. Balance the atoms other than $\ce{O}$ and $\ce{H}$
3. Balance the oxygen by adding water
4. Balance the hydrogen by adding protons
5. Make the number of electrons equal and add the half reaction.

Is there any difference if I change the medium if so what are the differences ?


texts: Creating small amounts of cellulosic ethanol from bamboo

texts:
I own a medium-sized farm and commercial aquaponics business in Pennsylvania. I try to make my business as green, sustainable, carbon-neutral and self-sufficient as possible.

As a way to cut out the need to buy expensive and/or fossil fuel derived fertilizers, I started composting my animal mortalities and  organic/green waste left over from our operation. But, in order to compost I needed a source of steady carbon for the composting process, so we planted around 60 acres of clumping moso-bamboo, 20 acres of "running" bamboo and bought a couple electric wood chippers to create our own carbon-negative sawdust replacement for creating our own "compost-tea" fertilizer on sight.

However, I found out that my yields of bamboo were so massive (we harvest the bamboo 2 to 3 times a year) that we're constantly trying to find new uses for it (turning it to feed for crickets, grasshoppers and grass carp which we use in turn to feed our tilapia and prawns, occasionally feeding it to our alpacas and gasification power during the winter months).

We added a "combined heat and power" 145 KW gasification + Waste Heat Recovery micro-steam turbine power generation system to make up for the loss of daylight and efficiency from our solar PV system during the winter months. And two years later we still have way too much excess bamboo.

So while looking up other ways to utilize it and I found out about Chinese researchers creating a "cost-effective" cellulose ethanol from it. So I decided to Google around if there are any pre-existing procedures or methods to create ethanol from bamboo but I'm pretty much getting squat.

So my questions are:

What's the basic process of creating fuel ethanol from bamboo? Do you know of any books or resources that describe this in more detail? If not, would there be any special procedures/material/equipment needed to create ethanol from it?
Would it be worth the capital investment of buying all the stuff required to produce only about around 3000-4500 gallons of a year? I was told that under form 5110.74, a small producer of ethanol can only produce 10,000 proof-gallons of it, which apparently translates to just over 5000 gallons of fuel or something.

I really don't want to have to sell my excess bamboo to flooring and paper companies that are likely still using environmentally detrimental ways to process and ship its derivative products because it would go against my desire to help protect the environment. But I also don't want to invest into a "money pit" that I will never see any ROI on (I'd rather just use it to expand my operation by hiring new employees, branching out into land-based Marine shrimp and seaweed farming, lithium-ion energy storage, etc).


texts: Can thionyl bromide produce alkyl bromides?

texts: Thionyl chloride ($\ce{SOCl2}$) is used with alcohols to produce alkyl chlorides. Similarly, can thionyl bromide ($\ce{SOBr2}$) be used with alcohols to produce alkyl bromides?


texts: Calculation of rupture force in a covalent bond

texts:
Is there any way to theoretically or mathematically calculate the rupture force of a covalent bond?
One of the articles I saw said that it is the maximum derivative of the potential energy curve. Is this true?


texts:
How can one calculate pKa values from first principle calculations, static or dynamics?

I have encountered some works using CPMD where people try to find pKa values from -(i) constrained Molecular Dynamics (MD) and (ii) metadynamics. These are somewhat more intricate ways, I believe. Is there any other simpler ways (theoretical/computational)? Can not we do it from simple MD?
Please suggest some references as well, if possible.

Thanks in advance.


texts: What do numbers in parenthesis after elements respresent?

texts:
I have seen elements with a number in parentheses after them in literature, but cannot find what it means. What does the number in parentheses after an element represent, such as in W(100) or Mo(110)?

https://aip.scitation.org/doi/abs/10.1063/1.1727919
https://www.sciencedirect.com/science/article/pii/0039602880900886


texts: Determining absolute configuration when the lowest priority group is not facing backwards

texts:
I have learnt that the absolute configuration of a chiral centre can be labelled as (R) or (S) according to the Cahn–Ingold–Prelog rules, when the hydrogen (or other lowest priority group) is facing backwards, i.e. going into into the page, and the remaining groups decrease in priority clockwise or anticlockwise respectively. On the other hand, if the hydrogen is coming out of the page (i.e. as a wedge) we swap our answer from (R) to (S) or vice versa (to get the hydrogen going into the page).
But what do we do when the hydrogen is flat and not a wedge or dash, as is the case here?

The priorities are

Chlorine atom
Carbon chain on left (propyl group)
Carbon chain on right (methyl group)

This gives an anticlockwise or (S) configuration. But the answer is given as clockwise or (R) configuration.
Why is this the case? The hydrogen isn't coming out of the page. Is there something else that has to be done when the hydrogen is flat or in the plane of the page?  If I visualise it rotating to bring the H to the back, I still end up with an (S) configuration.


texts: Why are there as many molecular orbitals as atomic orbitals?

texts: So molecular orbitals are represented as a weighted sum over atomic orbitals. Of course I reckon that the total sum of the weights per atomic orbital has to equal 1, when summed over all molecular orbitals. But why then should n atomic orbitals results in exactly n molecular orbitals? Is there a fundamental reason for this I am not seeing?


texts: Does nitrogen pressure in tyres fluctuate to much a lower degree than air with changes in temperature?

texts:
This is my first question in this site. I am referring to this question.The linked question what is the advantage of filling nitrogen in bike tubes over air and I got some answers such as:

The biggest advantage to filling your tires with Nitrogen is consistency.
Air pressure fluctuates based on temperature, whereas Nitrogen fluctuates to a much much lower degree

and

Nitrogen changes pressure with temperature slightly less than water does

But I want to know the reason. Please help me understand this scientifically.


texts:
Why do carbon dioxide and sodium hydroxide not form sodium oxide and carbonic acid?

$\ce{CO2 + 2NaOH -> Na2O + H2CO3}$

as opposed to:

$\ce{CO2 + 2NaOH -> Na2CO3 + H2O}$

This is in the context of fractional distillation of liquified air, before which carbon dioxide must be removed using sodium hydroxide.


texts:
A racemate consists of 50 % $d$ and 50 % $l$ forms of an optically active compound. But how can someone ensure exact 50% quantity comparing molecule by molecule? There will always be some difference in number of molecules in both forms of optically active compounds. Is this sufficient for the mixture to rotate the plane polarised light in clockwise or anticlockwise direction?

According to wikipedia "Racemization can be achieved by simply mixing equal quantities of two pure enantiomers."


texts: I'm pretty sure this doesn't follow Le Chatelier's Principle

texts:
The likelihood is that I'm misunderstanding what's going on here.

Consider the reaction $\ce{A <=> B}$, where $K_\mathrm{c}=1$.

Initially, the system at equilibrium, where $[\ce A]=\pu{1M}$ and $[\ce B]=\pu{1M}$.
The system is then disturbed to increase $[\ce A]$ by $\pu{1M}$. Instantaneously, $[\ce A]=\pu{2M}$ and $[\ce{B}]=\pu{1M}$. Le Chatelier's principle suggests that the equilibrium position moves to the right to minimise the increase in $[\ce A]$.
The system then returns to equilibrium, such that $[\ce A]=\pu{1.5M}$ and $[\ce{B}]=\pu{1.5M}$.

Clearly, the relative amounts of $[\ce A]$ and $[\ce B]$ have not changed, so the equilibrium position has not changed, which is in direct contradiction with Le Chatelier's principle.

I think my misunderstanding may lie in one of the following:

My definition of equilibrium position (the relative amounts of reactants and products at equilibrium).
Between which numbers the equilibrium position is considered to move, let me elaborate on this: the relative amount of $[\ce A]$ and $[\ce B]$ have not changed between 1 and 3 ($1/1=1.5/1.5$), but they have changed between 2 and 3 ($1/2\ne 1.5/1.5$), so I see how the equilibrium position could be said to have moved right from step 2 to step 3 as the amount of B increases and the amount of A decreases.


texts: How is the Born-Lande equation modified when the structure is not NaCl?

texts:
Often the Born-Lande equation is quoted (alongwith the calculation of the Madelung constant and Born exponent) with reference to rock-salt structure. But what if we take some other crystal, like rutile $\textrm{TiO}_2$. The Coulomb interaction energy for a reference $\text{Ti(IV)}$ ion is now:
$$
U_{E} = \frac {e^2}{4π\epsilon_0} \sum_{\text{all surrounding ions}} \left( \frac {16}{r_{\text{Ti}^{4+}}} -  \frac {8}{r_{\text{O}^{2-}}} \right)
$$
I'm unable to figure out how does one get the Born-Lande equation using this expression for the electrostatic energy, that for the Pauli repulsion remaining as it is (that is, $U_P = \sum A/r_k^n$). If it were a rock-salt structure, we would say, lattice energy is,
$$
U_{\text{lattice}} = \sum_{\text{entire lattice}} \left( U_E + U_P \right)
$$
And after a little mathematical manipulation we would get,
$$
U_{\text{lattice}} = -\frac{N_A Mz^2e^2}{4πR_0\epsilon_0} \left(1 - \frac1n\right)
$$
However this doesn't seem proper for the case of rutile (and other cases too, like perovskite). Any suggestions are welcome.


texts: Acetic acid odor while testing CO2 sensor; can it be easily removed, is there a better way?

texts:
A friend asked me to help test a hobby-quality $\ce{CO2}$ sensor MG-811 (updated link). It uses a solid electrolyte and should provide a sensitivity of something like -40 mV per decade. I though I'd just use a small amount of acetic acid + baking soda to make roughly 4,000 ppm in a large container, and compare to "fresh air" which should be roughly 400 ppm, or at least within the 350 to 600 ppm range, as a very rough initial test.

But then I noticed/remembered (duh!) that the acid smells quite strong. Are these simply molecules of $\ce{CH3COOH}$ that are evaporating, or are they bringing along molecules of water in some kind of cluster?

I realized that they could potentially contaminate the sensor, so I'd like to know what I'm up against in terms of removing them from the gas before immersing the sensor.

I've tried to look up the vapor pressure of acetic acid, and it seems to be quite large, about 10 Torr at 20C. See for example here and here. So I'm thinking of using some kind of ad-hoc cold-trap to try to remove it. Might there be another way to do this without using special laboratory equipment? Would passing the gas over dry $\ce{NaHCO3}$ or a solution of it help to "getter" the remaining acetic acid vapor?

Or, is there a better way to produce a controlled amount of $\ce{CO2}$ to begin with?


texts: Confusion on when to use mass of entire solution when performing q=mc∆T

texts:
I hope you are having a good day.

I am studying for the AP Chemistry exam in May 2020. While studying, I encountered a doubt.

In Problem 1 (the question on the top), the educator saw that the problem was referring to the solution as a whole (the problem states ∆Hsoln), and used 100 g + 10 g = 110g grams for the mass in Q = mc∆T and then, on the next part, did ∆H = -Q/n to find the enthalpy of solution.

However, in Problem 2 (the question on the bottom), the educator uses the total mass of the solution (200 grams) even if the problem refers to the reaction (the problem states ∆Hrxn) and not the solution. When I saw the question, I thought I had to convert the 1 mol Ag+ and 1 mol Na+ to grams, and add those masses for (m) in Q=mc∆T since the problem referred to the reaction and not the solution.

As a result, I am confused as to when exactly I should use the mass of the entire solution instead of the mass of the reactants in my Q = mc∆T and ∆H = ±Q/n calculations.

Thanks so much!!! :)


texts: How can I know the colour change of this reaction?

texts:
After you react rotundone ($\ce{C_{15}H_{22}O}$) with water it loses all of the double bonds (except the carboxylic bond, $\ce{C=O}$) and gets two of the functional group $\ce{-OH}$ (alcohol). Two compounds are formed, one (A) where both the alcohol groups are tertiary and another (B) where one is tertiary and the other is primary.

I'm asked to state and explain the colour change of both A and B when they react separately with acidified potassium dichromate(VI) solution.

Now I can see that compound A would have no colour change because the $\ce{-OH}$ groups are tertiary so the potassium dichromate won't react or oxidise them.
I can also see that there will be a colour change on compound B because one of the $\ce{-OH}$ groups is primary, so the potassium dichromate will oxidise and react with it.

Here's my problem:

I'm expected to know that when compound B reacts, it changes from orange to green. How would I know that rotundone is orange in the first place? And what makes it go green?
I know that I'm expected to use intuition as we definitely aren't required to know the colour of rotundone.


texts: How to determine the chemical state of a reactant or product in a chemical equation?

texts:
I am asked this question:

Write a balanced equation, including state symbols, for this reaction:
$\ce{calcium + hydrochloric acid -> calcium chloride + hydrogen}$

I answered this:

$\ce{Ca(s) + 2HCl(aq) -> CaCl2(s) + H2}$

This was the correct answer:

$\ce{Ca(s) + 2HCl(aq) -> CaCl2(aq) + H2}$

I thought that the $\ce{CaCl2}$ was a solid precipitate (ppt.) instead of aqueous(aq).
Here are the known chemical states:

solid(s)
liquid(l)
gas(g)
aqueous solution(aq)

Is there any method to work out the chemical state of a reactant or product in a chemical equation, if I know the chemical states of all of the other reactants?


texts: Can a reaction happen if a product change phase under reaction conditions?

texts:
Suppose we have the reaction :
$$\ce{A(s) + B(s) <=> C(g)}$$
The equilibrium constant will be equal to $e^{-\frac{Δ_rG}{RT}}$ and it varies with temperature. Suppose that $\ce{A}$ and $\ce{B}$ come into contact at temperature $T$ and pressure $p$ where the phase diagram for $\ce{C}$ at these conditions correspond to liquid phase. Will the reaction take place at all? I mean if it takes place but all the gas that is produced is converted into liquid then the reaction quotient will be zero at all times. But shouldn't at some time the reaction reach equilibrium with $K=p^{eq}_{c}$? Are equilibrium constants meaningfull only if the conditions allow for the compounds to be in the physical state that the chemical equation indicates?
After reading the comments I felt that I should add some details. If the reaction is happening in a closed vessel then we can combine the reactions ($1$), ($2$) to get ($3$):
\begin{align}
\ce{A(s) + B(s) &<=> C(g)} & (1)\\
\ce{C(g) &<=> C(l)}          & (2)\\
\ce{A(s) + B(s) &<=> C(l)} & (3)
\end{align}
What if the reaction takes place at open vessel so that all gas turns into liquid?


texts:
Rarely does the literature describe the synthesis of esters from amides. I understand that amides are a relatively unreactive functional group but they can easily be hydrolysed to give carboxylic acids under basic or acid conditions. Why can't they be converted to methyl esters under similar conditions using methanol in place of water?

Surely the mechanism would be identical to hydrolysis? Additionally, the pKa of water is very similar to methanol so I cannot justify it on the basis of nucleophilicity/basicity. The only thing I can think of is steric hindrance but methanol isn't that bulky compared to water.


texts:
A sample of $\pu{1.42 g}$ of helium and an unweighted quantity of oxygen gas are mixed in a flask at room temperature. The partial pressure of helium in the flask is $\pu{42.5 torr}$, and partial pressure of oxygen gas is $\pu{158 torr}$. What is the mass of the oxygen in the container?

As volume is not stated, I assume it's constant, and temperature is a constant too. Therefore, from the ideal gas law

$$\frac{p}{n} = \frac{RT}{V}$$

For helium and oxygen gas, the above formula is applicable, and the mass of oxygen can be determined:

\begin{align}
\frac{\pu{0.5592 atm}}{1.42/4.0026} &= \frac{\pu{0.20789 atm}}{m(\ce{O2})/31.99} \\
\to m(\ce{O2}) &= \pu{4.22 g}
\end{align}

This is my attempt on finding the mass. However, I believe it's not right. Why is that the case?


texts: 19F MAS NMR chemical shift tensor and the crystal structure

texts:
$\ce{^{19}F}$ MAS NMR is measured on fluorine-doped $\ce{TiO2}$. $\ce{F}$ is to substitute $\ce{O}$ and the crystal structure is anatase, which has a tetragonal crystal system with a space group $\ce{I 41/a m d S(141)}$. Using the observed isotropic chemical shift value, a chemical shift anisotropy (CSA) analysis is carried out using Simpson and gives a uniaxial chemical shift tensor ($\ce{δ11 = δ22 ≠ δ33, etha = 0}$). This result dictates a three-fold symmetry at the fluorine site. In anatase with a tetragonal system, however, the oxygen ions occupy position 8e with a point group of ${mm}$ and no three-fold axis.

How can the uniaxial chemical shift tensor, indicating three-fold symmetry, correlate to the crystal structure of anatase which does not possess any three-fold axis?


texts: What is the stability order of the carbocation and carboanion?

texts:
So I came up with examples as below:

1
2

Now I am confused about the +I and -I effect in these structures since to my knowledge it can only be applied when there is a substituent (I might be wrong). I understand the role of resonance but do not get how to apply the +I and -I effect in these so I need help. I have basic knowledge about the substituents which give +I and -I effect but still can't get it.


texts: Electronic effects of substituents in the benzyne mechanism

texts:
On the topic of nucleophilic aromatic substitution (S$_N$Ar) reactions, the benzyne mechanism is discussed. When considering the position of substitution, electronic and steric factors are mentioned. When considering electronic factors, effects of substituents on the ring are viewed rather differently, compared to how they are viewed in the conventional electrophilic aromatic substitution reaction.

Pg. 525 from Organic Chemistry (2nd ed.) shows the following diagram:

In the discussion of the benzyne mechanism, conventionally electron-donating groups are said to not be able to exert their donating effects and are even viewed as electron-withdrawing via the inductive effect. However, I cannot see why they behave in this way. Why is their donating effect no longer significant? Certainly, their p orbitals are still in conjugation with the rest of the $\pi$ system right?

However, if their electron-donating effects were more important, then we would observe ortho and para attack by the nucleophile, so as to generate the negative charge at the meta position, which is apparently not the case as experimentally observed.

Reference

Clayden, J., Greeves, N., & Warren, S. (2012). Organic Chemistry (2nd ed.). New York : Oxford University Press Inc


texts:
Why do sodium halides react so differently with sulfuric acid?
\begin{align}
  \ce{NaF + H2SO4 &-> NaHSO4 + HF}
    \tag{1a}\label{NaF}\\
  \ce{NaCl + H2SO4 &-> NaHSO4 + HCl}
    \tag{1b}\label{NaCl}\\
  \ce{2 NaBr + H2SO4 + 2H+ &-> Br2 + SO2 + 2H2O + 2Na+}
    \tag2\label{NaBr}\\
  \ce{8 NaI + H2SO4 + 8H+ &-> 4 I2 + H2S + 4 H2O + 8Na+}
    \tag3\label{NaI}
\end{align}

Conventional explanation: $\ce{NaI}$ is a strong enough reducing agent to reduce the sulfur, and $\ce{NaBr}$ is a little less strong, so sulfur is not reduced as much. Equivalently, $\ce{H2SO4}$ is not as strong an oxidising agent to reduce $\ce{NaF}$ and $\ce{NaCl}$.

My ensuing question: Why is reaction \eqref{NaI} more favourable than \eqref{NaBr} and $(\ref{NaF},\ref{NaCl})$ for sodium iodide, so that it reacts with sulfuric acid like it does. What factors are involved: what is more stable, for instance, (or there is lower Gibbs free energy or something else) about reducing sulfur as much as possible (as $\ce{NaI}$ 'chooses' \eqref{NaI} over $(\ref{NaF},\ref{NaCl},\ref{NaBr})$?

Ditto for sodium bromide. I understand why \eqref{NaI} is impossible, but why is \eqref{NaBr} chosen over $(\ref{NaF},\ref{NaCl})$?


texts: Nomenclature of MnO4^-: is it an oxyanion?

texts:
Having a real pain with nomenclature. Look at this substance:

$$\ce{MnO4-}$$

So, do we have an anion of manganese and oxygen, or is that just an anion of oxygen? Anyway, my book says that $\ce{MnO4-}$ is "permanganate".

Since it ends with "-ate", it seems my book thinks $\ce{MnO4-}$ is an oxyanion (because those are the ones that end with things like "-ate" and "-ite").

However, it was my understanding that an oxyanion is when you have oxygen and a non-metal. But manganese is a metal! What is going on here then?

And not just that. Let's assume that $\ce{MnO4-}$ is indeed an oxyanion called permanganate. From what I've learned, if you remove one oxygen atom (getting  $\ce{MnO3-}$), it should become just manganate, right? But, according to my book, manganate is $\ce{MnO2-}$. It had to lose two oxygen atoms and not one to become manganate. Why?


texts: What happens when 3-(2-chlorophenyl)propanenitrile is treated with sodium amide?

texts: I'm having some trouble figuring out what happens in the above reaction. Based on the strongly basic conditions I think that a benzyne mechanism should be operative, but I'm not sure what else should happen, or whether the nitrile is involved in the reaction. What is the product and how is it obtained?


texts: How does liquid gallium interact with a gold leaf

texts:
I would like to know what happens when gold leaf comes into contact with liquid gallium. Will the gold dissolve into (alloy with) the gallium, wet the gallium or have no reaction with gallium?
The reason I am asking this question is to figure out if I could gild some gold leaf onto a base metal (that is compatible with gallium) and use the gallium as an 'adhesive' between the gold and base metal. I am planning on using this as a gold plated cathode in electrolysis experiments.


texts: A problem regarding solubility and concentration

texts:
A solution is $\pu{0.10 M}$ $\ce{Ba(NO3)2}$ and $\pu{0.10 M}$ $\ce{Sr(NO3)2}$. If solid $\ce{Na2CrO4}$ is added to the solution, what is the $\ce{[Ba+]}$ when $\ce{SrCrO4}$ begins to precipitate?  $\mathrm{K_{sp}}=\pu{1.2 \times 10^{-10}} \text{ for } \ce{BaCrO4}$
$\mathrm{K_{sp}}=\pu{3.5 \times 10^{-5}} \text{ for } \ce{SrCrO4}$

The solution given in my textbook is:

$\mathrm{K_{sp1}}=\ce{[Sr^2+][CrO4^2-]}$ $$\ce{[CrO4^2-]}=\frac{3.5\times 10^{-5}}{0.1}=3.5\times 10^{-4} \pu{M}\tag{1}$$ $\mathrm{K_{sp2}}=\ce{[Ba^2+][CrO4^2-]}$ $\ce{[CrO4^2-]_{total}}\approx\ce{[CrO4^2-]}\text{ from } \ce{SrCrO4}$ $$\ce{[Ba^2+}]=\frac{1.2\times 10^{-10}}{3.5\times 10^{-4}}=3.4\times 10^{-7}\pu{M}$$

First of all, in equation $(1)$ why did they put $\ce{[Sr^2+]}$ same as the initial concentration (before the addition of $\ce{Na2CrO4}$)? When $\ce{Na2CrO4}$ is added,  $\ce{[Sr^2+]}$ will react with $\ce{CrO4^2-}$ (obtained from $\ce{Na2CrO4}$) to form precipitate. The concentration of $\ce{[Sr^2+]}$ will undoubtedly change until the equilibrium is established.
This given solution is totally confusing, I would appreciate if you could tell me the proper way of solving this problem. I tried this on my own, but after calculating the concentration of $\ce{CrO4^2-}$, I couldn't make sense out of this question.


texts: Determining the equation of state when given thermodynamic relations

texts:
Empirical observations of a thermodynamic system have shown that:

  $$\begin{align}C_{\mathrm m,V} &\neq C_{\mathrm m,V}(T) \\[6pt]
\left(\frac{\partial U}{\partial V_\mathrm m}\right)_{T} &= f(V_\mathrm m) \\[6pt]
\left(\frac{\partial U}{\partial p}\right)_{V} &= g(V_\mathrm m) \end{align}$$

  where $f$ and $g$ are functions of the molar volume, $V_\mathrm m$. Determine the state equation.

How can I solve this problem?


texts: Absorption spectrum of Hydrogen molecule in UV region 200 nm - 300 nm (not Atomic Hydrogen)

texts: Can somebody provide Absorption spectrum of Hydrogen molecule? I have searched days for absorption spectrum of Hydrogen molecule in 200 nm - 300 nm UV region and All I got is absorption spectrum of atomic hydrogen. I do find little about absorption spectrum of hydrogen molecule in the region 90 nm to 180 nm in some astrophysics research papers.


texts:
I came across a term "millamolecule" to represent macrocycles with a molecular weight between 500 and 1,000 daltons. Google Scholar show several resources which use this term e.g., Google Scholar Results

What could be origin of this term or is it just a buzzword invented by pharma companies?


texts: Why are alkali hydrides strong reducing agents?

texts: My book says that alkali hydrides are strong reducing agents. It also says that this is especially true at high temperatures? Is there any particular reason behind it?


texts: Isolation of codeine phosphate from Tylenol 2

texts:
So here is my question. This may be controversial for some, but I would like to tell you it is purely speculative and has no bearing on anything I would actually do.

If one has in their hands a bottle of Tylenol 2 (codeine phosphate, caffeine, & acetaminophen). Each pill containing 8 mg codeine phosphate, 15 mg caffeine, & 300 mg of acetaminophen within each capsule (I am unsure of the ratio or weights of any binders with the capsule). If someone wanted to isolate the codeine phosphate and remove all of the APAP and caffeine in the process what would you do? I personally have a theory, but it is untested:

Cold extraction of APAP from codeine phosphate/caffiene in water mixture.
Filtration of Cold Extraction mixture. (removing ALL APAP from mixture).
Dissolving of organic compound (caffeine) from water/codeine phosphate mixture with dichloromethane reagent.
Utilize a separation funnel to remove dichloromethane from $\ce{H2O}$ mixture.
Utilize a chemistry hotplate with the new mixture to reduce the amount of water to zero ($0$) using controlled evaporation. Maintaining $\pu{32^\circ C}$ or different temperature?
Harvest pure codeine phosphate from bottom of evaporated flask and weight using proper scale for highest precision when weighting the final product.

Is this a good method or is there something more effective, simpler etc.? remember this is all done with products that are affordable to the average person, not prime lab equipment. Just basic chemical stuff for the most part.

I would like to make another comment noting my lack of chemistry knowledge, so please no unnecessary comments pointing that out.


texts: Reaction between copper II sulfate and ammonium

texts:
The reaction between hexaaquacopper(II) and ammonium reacts as follows

$$\ce{[Cu(H2O)6]^2+ + 4NH3 -> [Cu(NH3)4(H2O)2]^2+ + 4H2O}$$

Apparently it's known from physical measurements that the hexaamine complex $\ce{[Cu(NH3)6]^2+}$ is not formed? Why is this?

Edit: This isn't a homework question by the way, I'm genuinely curious seeing as the hexaamine complex is formed when ammonium is reacted with complex cobalt ions.


texts:
Over dinner, some vegan friends of mine discussing plans to open a 5 star organic restaurant inside the cabin of an airbus A380.

Exactly what I thought too! But they raised an interesting point: apparently the taste of certain foods changes depending on the altitude you consume it at.

I looked into it a little and discovered lots of interesting facts about Heston Blumenthal cooking salmon and whatnot for astronauts, but not must hard-chemistry behind why our sense of taste depletes the higher in the atmosphere we go.

So what causes such a taste discrepancy? Is it compounds within the food that "lose" their flavour, or it just our perception of taste that changes?


texts: How do I round a calculation involving both addition/subtraction and multiplication/division to the correct number of significant figures?

texts:
I'm just learning about significant figures (sig figs) in my chemistry class, and I'm confused about the rules. An example to my problem: if I had the following expression:
$$\left ( \frac{2.378 - 1.2}{1.03} \right )$$
I've thought of 2 ways to approach this. Which one is correct (or is neither correct)?

Approach 1:

Round each intermediate operation as you go. This is what my textbook does for its examples, but it itself suggests "Approach 2" below. I'm just listing this approach here as an option since addition/subtraction and multiplication/division have their own rules for rounding (hence, maybe do intermediate-operation rounding).

1) Round the subtraction part.

$$\left ( \frac{1.2}{1.03} \right )$$

2) Do the division and round.

$$1.2\,\,\, (2\ \mathrm{sig\ figs})$$

Approach 2:

In actual practice, the book says:

  In a series of calculations, carry the extra digits through to the final result, THEN round.

I think it means this:

1) Do the subtraction, but keep the *exact* number while noting that the rounded number was supposed to have 2 sig figs.

$$\left ( \frac{1.178}{1.03} \right )$$

2) Do the division with the exact number and the denominator, and since this step produces the final result, NOW you round, rounding to 2 sig figs per the note in Step 1.

$$1.1\,\,\,(\text{2 sig figs})$$

The problem here is that these two approaches produce 2 different results. So, to repeat, which one is correct (or is it neither)? The textbook doesn't provide an example like this. I found two different websites, but they too conflict with each other.

http://www.occc.edu/kmbailey/chem1115tutorials/Sig_Fig_and_Math_Answers.htm
(From the solution to problem #3, I should use "Approach 1".)

http://fabice.com/misc/significant_figures.html
(It quotes, "In a composed operation, intermediate results are not rounded." So that means I should use "Approach 2?".)

Compared to the other questions on this forum, this question seems silly, but I find the concept of sig figs important if I want to understand chemistry at all.


texts:
I have a question that reads:

  $\ce{H3A}$ is a tribasic acid. The three deprotonations can be written as

  $\ce{H3A <=>[pKa1 = 2.9] H2A- <=>[pKa2 = 4.2] HA^{2-} <=>[pKa3 = 5.2] A^{3-}}$

  What is the predominant species in a 0.10M solution of $\ce{H3A}$ at pH 5?

  a) $\ce{H3A}$

  b) $\ce{H2A-}$

  c) $\ce{HA^{2-}}$

  d) $\ce{A^{3-}}$

I worked this out as

$\ce{Ka1 = \frac{[H+][H2A-]}{[H3A]}}, \ce{Ka2 = \frac{[H+][HA^{2-}]}{[H2A-]}}, \ce{Ka3 = \frac{[H+][A^{3-}]}{[HA^{2-}]}}$

At pH 5, $\ce{[H+] = 10^{-5}M}$

So,

$\ce{[H+] = 10^{-5} = Ka1\frac{[H2A-]}{[H3A]} = 10^{-2.9} \frac{[H2A-]}{[H3A]}}\ce{\implies \frac{[H2A-]}{[H3A]} = 10^{2.1} }$

and similarly,

$\ce{\frac{[HA2-]}{[H2A-]} = 10^{0.8}}$

$\ce{\frac{[A^{3-}]}{[HA^{2-}]} = 10^{-0.2}}$

Since $\ce{[HA^{2-}] > [H3A], [HA^{2-}]>[H2A-] and [A^{3-}]<[HA^{2-}]}$, the predominant species is $\ce{HA^{2-}}$, so c).

This is the correct answer according to the solutions, but I'm not sure if my logic is correct, or if there's an easier way to arrive at the same conclusion (it's significant working out for a MCQ).


texts: Would an aqueous solution of Zn(2+) develop a positive charge if solid zinc was dipped into it?

texts:
Say you have a beaker containing $\pu{1M}$ solution of $\ce{ZnSO4}$. The solution will be electrically neutral because there will be an equal number of cations and anions. If you then put a zinc electrode into the solution, will some of the solid zinc reduce to give the solution a slightly positive net charge(because of the excess zinc ions)? Or will there be an equilibrium between the oxidation and reduction of zinc that would keep the solution electrically neutral?

Will the answer be any different in the case of copper-zinc galvanic cell with no salt-bridge? Will the electrolytic solution in the zinc half-cell of a copper-zinc galvanic cell with no salt-bridge develop a positive charge? The scenario is the same as the one in the previous passage except now the zinc electrode will be connected to a copper electrode.

For some context, I was trying to understand why the electrolytic solution in a galvanic cell needs to be electrically neutral in order for the electrodes to develop a non-zero potential difference.


texts: Producing sulphur dioxide for using in a reaction

texts:
I am doing an investigatory project on studying the coloured reactions of d-block and f-block elements. I have included two reactions that require sulphur dioxide as a part of my study.

$$\ce{5SO2 + 2KMnSO4(purple) + 2H2O -> 2H2SO4 + 2MnSO4(pale pink) + K2SO4}$$
$$\ce{SO2 + K2Cr2O7(orange) + 3H2SO4 -> K2SO4 + Cr2(SO4)3(green) + 3H2O}$$

Now, my problem is I need an effective method to produce sulphur dioxide to be able to use for these in a school laboratory environment. I thought of using ferrous sulphate which on heating gives $\ce{SO2}$,
$$\ce{2FeSO4 ->[{$\Delta$}] Fe2O3 + SO2 + SO3}$$
But this reaction also produces $\ce{SO3}$. Will that screw with any of the above reactions? Also, are all the above reactions feasible in a school laboratory? Do suggest if there are better methods and how I can make it to react with the other reactants.


texts: Why is gasoline consisting of heavily branched alkanes better fuel than gasoline consisting of more linear alkanes?

texts:
As far as I know, the reason isooctane is better than octane in gasoline engines is because the octane is more prone to ignition by pressure. This makes it ignite when it is not supposed to, which damages the engine.
Isooctane, however, is somehow less prone to this. Why is that? Why is isooctane "more resistant to the potential of ignition incited by pressure"? How are the higher number of ligands involved in this?


texts: How do we recognise a Hybridised Sp3 orbital?

texts: As far as i know the sp3 orbital is a combination of orbitals. But how do we know if we have a hybridised orbital or not?


texts: What are we seeing in this AC salt-water copper-wire experiment?

texts:
There's a highly watched video on YouTube by "ElectroBoom" on the effects of passing AC (not DC) current through salt water. The water gets cloudy and at the end of the video we can see one of the copper wires has been eaten away by the process.

Is there really "a reaction of the copper with the salt in water" as the author of the video claims? Or is it a pure physical process where the copper "boils off" the wire?


texts: What do typical results from inductively coupled plasma mass spectrometry (ICP-MS) look like, and how do I interpret them?

texts:
I have a degree in chemical engineering and remember having seen a inductively coupled plasma mass spectrometer (ICP-MS) during the laboratory part of a chemistry course I took while at university, but it is many years ago. Now I would like to know what a typical output from a ICP-MS looks like and how I interpret the results.

There is no picture at the wikipedia page but some frequency domain like plots can be found with a Google search and I understand the Fourier transform and how it is used in number theory.

Are the ICP-MS results anything like the spectrum from the Fourier transform of some signal?


texts: steam distillation vs fractional distillation

texts:
I am a high school student and I am a little confused in the techniques used to purify organic compounds, for e.g we study in steam distillation we reduce the external pressure on the compound to be purify by passing steam over it, which reduces its boiling point
1)first of all, how is that possible? In first look I thought that the external pressure on that compound should be increased because now not only air, steam is will also exert pressure over it.
2)Ok, if I assume that it will decrease then also ,why do we use this? if we have to reduce the external pressure like this, I think  we can do this in fractional distillation also by taking mixture of water and water immiscible compound then here also the boiling point should decrease isn't it?


texts: Does a wavefunction have to be an eigenfunction of an operator in order to obtain an expectation value?

texts: I am reviewing an intro quantum chemistry book and I came across the line "If $\hat{A}$ corresponds to a physical property of the system, whether or not $\psi$ is an eigenfunction of $\hat{A}$, the average value of that property is given by the expectation value of the operator." Doesn't $\psi$ have to be an eigenfunction of the operator in order to obtain an expectation value?


texts: I know that oxidanes are oxygen chains and rings. For example trioxidane is $\ce{HO-O-OH}$. I can see this turning into $\ce{O2}$ and $\ce{H2O}$ like hydrogen peroxide does. Since the double bonds in $\ce{O2}$ are strong do oxygen compounds without nitrogen ever explode?


texts: Why is lead's first ionisation enthalpy greater than that of tin?

texts:
Using Slater's rule, I found that both lead and tin's $Z_\mathrm{eff}$ for 6p and 5p electrons equal. However, the ionisation energy is different. Is comparing ionisation enthalpy on the basis of $Z_\mathrm{eff}$ not correct?

Also, I found Clementi-Raimondi Effective Nuclear Charge which probably explains the trend, but why is this different to Slater's rule?


texts: Is this a violation of Equipartition theorem?

texts:
My book has a question asking to calculate average kinetic energy of the molecules in 8g of methane.

By the Equipartition theorem, I calculated that energy:
1. per molecule per degree of freedom = $(1/2)kT$ (by definition)
2. per molecule = $3kT$ (since methane is polyatomic => 6 degrees of freedom*)
3. per mole = $3RT$
4. for 8g methane ($=0.5$ moles) = $1.5\cdot RT$

But the answer stated by my book is $0.75\cdot RT$  - just half of what mine is.

This is not the only question where values have mismatched. I have started losing faith from Equipartition theorem.

Question:

  What did I get wrong?

SUMMARY+UPDATE: Final conclusion reached is that while total kinetic energy is indeed the one Equipartition theorem gives (and so it's correct! :D) but the textbook assumes the molecule to be at at very low temperatures (although this is NOT mentioned) implying the rotational and vibrational energies are NOT counted.

*=>my textbook says so. I understand that there's a lot of complex things in this topic, but let's please assume it is 6 as my book says.


texts:
This was one of the question that was given in the school exam.

But what I am expecting is that $\ce{Cu+}$  attains a $d^{10}$ configuration by losing one electron from s-subshell. Since it has fully filled d-orbital, it should be stable. But it is found that it is unstable and tends to disproportionate in aqueous medium or with moist air to form $\ce{Cu^2+}$ where  $\ce{Cu^2+}$ has incompletely filled d-orbital ($\ce{d^9}$ configuration) . For example:

$$\ce{Cu2O(s) + H2SO4(aq) -> Cu(s) + CuSO4(aq) + H2O(l)}$$

$$\ce{Cu2O(s) + 2H+(aq) -> Cu(s) + Cu^2+(aq) + H2O(l)}$$

Oxidation number changes: $\ce{2Cu(I) -> Cu(0) + Cu(II)}$

(source)

Why is this so?


texts: Whats the effect of pressure on water electrolysis of sea water with increase in depth?

texts: I’m currently working on an underwater robot and was hoping to use the gas bubbles produced by water electrolysis for buoyancy control. The operating depths range from 200–1000 m.