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Why don't heavy and light gases separate in the atmosphere?

Everyone must have heard that balloons are filled with helium, and the fact associated with it that helium gas is light and light gases always go upward. There comes a question to mind: if the molar mass of $\ce{CO2}$ is greater than that of…
Vidyanshu Mishra
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Difference between Lindlar and Rosenmund catalysts

Is there any difference between the Lindlar and Rosenmund catalysts? I've checked around, and it seems the same compounds are used to make both. Is there a difference in their reactivities or are they essentially the same?
Black Jack 21
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Why are basis sets needed?

I am not sure whether this question is even reasonable, but here it goes. We are taught about the different types of basis sets (extended, minimal, double-zeta, plane wave), but I do not think it is clear as to why they are needed. After all, it is…
CoffeeIsLife
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How could I cause metal to rust rapidly?

I'm writing a novel set in the mid-nineteenth century. One of my characters needs to cause an iron padlock to rust rapidly, ideally within a matter of hours. The lock doesn't need to rust away completely - the goal is just to make it noisey and…
T.D. Smith
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Chirality of substituted adamantanes

Is this compound chiral? I can't tell where the chiral centres are because this polycyclic backbone is too confusing. I tried to draw a mirror image, but I got really confused and couldn't tell whether it was superimposable. And I don't have a…
orthocresol
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Why is H₂O V shaped?

We know that the molecule of H₂O is V-shaped. This is what makes it a dipole. But why is that? I mean, if the hydrogens have a partial positive charge, then they should try to get away from each other, until they are diametrically opposite to the…
Gerard
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Band gap of fullerenes

From what I have read about fullerenes, the lower fullerenes like $\ce{C60}$ or $\ce{C70}$ have higher bandgaps around 3.5 eV or such, while the higher fullerenes have much smaller bandgaps of the order of 0.5 eV. Initially I thought that this could…
ubuntu_noob
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Is there a formula to tell how many conformers of a molecule to generate?

Let's say we want to generate conformers of molecules (e.g., ligands for docking in a protein pocket). Is there a formula, like a function of the number of rotatable bonds, to decide how many conformers (maximum) to generate for a given molecule ?
Francois BERENGER
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How does alum improve the settling of particles to produce 'clean' water?

How does the addition of alum — potassium aluminium sulfate or $\ce{KAl(SO4)2}$ — help settle the dust particles in water? There was such a statement in my Year 9 textbook, and so I was wondering how exactly alum does it. Edit: I have posted an…
Yatharth Agarwal
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Structural representation of substituted benzene

Recently, I was watching a video about separating o-chlorotoluene and p-chlorotoluene from its solution. Following was a reaction demonstrated in the video: I was curious about the structure of chlorotoluene. In this, the chlorine substituent was…
Nilay Ghosh
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Why are full and half filled orbitals the most stable?

Why are degenerate orbitals (restricted to a single spin) less stable when neither fully filled nor completely empty? Why, in most molecules, are half-filled and fully-filled shells more stable than partially filled shells? I understand that…
Niels Kornerup
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Typography of Orbitals

For mhchem, I need to decide on a typographical representation of orbitals. Wikipedia tells me, there are atomic orbitals with letters s, p, d, f and g. In a later table, there is even h. Then, there are molecular orbitals with greek…
mhchem
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How to find a transition state for an electrophilic addition with Gaussian and map the reaction pathway?

I aim for two things with this post – on the one hand to produce a manual for other people to use, but also to verify what I obtained via searching, asking a more experienced user as well as receiving a reply from Gaussian support. I will assume…
DetlevCM
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What happens when you mix alum with soap?

I was handling alum one day and accidentally I touched toilet soap after that. They reacted with each other and formed a rubberlike sticky substance (like dried glue on palm). I am curious what was the chemical reaction and the substance which was…
Gaurav Adurkar
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Is the rate determining step the step with the largest Ea?

I've seen some controversy on this question while doing a brief search. For example, this SE answer quotes Wikipedia and says that the RDS is the step with the largest $E_a$. However, this UC Davis page says that In the potential energy profile,…
carbenoid
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