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1500 questions
18
votes
4 answers
How much can the pH change through dilution?
Consider an acidic solution with Hydrogen ion concentration, $\ce{[H+]}$ of $10^{-5}\:\mathrm{M}$. Since $\:\mathrm{pH} = -\log \ce{[H+]}$ the $\:\mathrm{pH}$ of solution is $5$. Suppose we dilute solution 10 times with water. Now, $\ce{[H+]}$ is…
CrownedEagle
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18
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Why is a ketone more nucleophilic than an ester?
I guess the ester is a weaker nucleophile because it does have an additional oxygen atom, unlike the ketone, that is pulling electrons from the C-O double bond towards the carbon atom (this happens vice versa too of course with the ester oxygen).…
Jori
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18
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2 answers
Why is black-body radiation curve smooth without a sharp cutoff?
Planck's law is able to predict a graph that is consistent with experimental observation:
In essence, unlike Rayleigh-Jeans law that assumes equipartition theorem to hold (that each mode of motion shares equal energy at thermal equilibrium, so all…
TheLearner
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18
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3 answers
Why can radioactive contamination be spread by people?
So I am reading a book called "Voices from Chernobyl" where witnesses, nuclear plant workers, firefighters and other persons involved in the 1986 accident give testimony of their experiences.
The very first chapter goes along the lines of the wife…
Matias Barrios
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18
votes
2 answers
What is the "‡" symbol meaning in a reaction mechanism?
I was studying hydroboration from Clayden's Organic Chemistry [1, p. 1281] and the transition state had “‡” symbol in the upper right corner of the activated complex:
We know that this is not the whole story because of the stereochemistry.…
One-Eye-Triangle
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18
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2 answers
Why is potassium ferrocyanide considered safe for consumption, when it is just one reaction away from the highly toxic potassium cyanide?
According to this answer, heating potassium ferrocyanide will decompose it into potassium cyanide.
Now, potassium ferrocyanide is an approved anti-caking agent, and hence used in table salt, for example.
Table salt is often heated as part of…
HRJ
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18
votes
2 answers
Lewis Acidity and Bacteria
How does Lewis acidity correlate with bactericidal activity? I read on Wikipedia that the two are positively correlated but no explanation was given.
Does it have to do with the movement of electrons - i.e. a current? I'm guessing that having a…
Dissenter
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18
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3 answers
How do Precipitation Reactions behave in the Absence of Gravity?
How do precipitation reactions behave in the absence of gravity, say on the International Space Station (ISS)? I have seen water taking the shape of a sphere and not that of the container in space due to its surface tension. It takes a spherical…
Vishnu
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18
votes
6 answers
Is there a commercial liquid with refractive index greater than two?
I need a commercially available liquid with the following properties:
refractive index $n > 2$ at room temperature $(T \approx\pu{23 °C});$
transparent in visible region $(380$ to $\pu{700 nm});$
suitable for gap fillers in refractometers (gap…
Persian_Gulf
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18
votes
3 answers
Why is it considered acid rain with pH <5.6?
I recently read in a book that rain is considered acid rain if the pH falls below 5.6. However a substance is acidic when the pH is below 7; so why is the boundary for acid rain 5.6?
I was thinking pH between 5.6-7 would be too diluted to have an…
bobsburger
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18
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5 answers
Is it "common practice in Fourier transform spectroscopy to multiply the measured interferogram by an apodizing function"? If so, why?
The recent paper in Nature Independent confirmation of a methane spike on Mars and a source region east of Gale Crater is interesting and the basis is a reanalysis of 2013 data taken by a X spectrometer about the Mars Express spacecraft in orbit…
uhoh
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18
votes
1 answer
Why does depurination happen at a higher pH (or under less harsh conditions) than depyrimidation?
I've always wondered why the N-glycosidic bond, which connects the adenine or guanine purine bases to their sugars, was the easiest to cleave via acid hydrolysis, or why purines have the lowest ionization potentials? What is it about the rings /…
Deuterated
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18
votes
2 answers
Do non-classical carbanions exist?
There are some non-classical carbocations, such as the 2-norbornyl cation, in which the positive charge is heavily delocalised. Have non-classical carbanions also been discovered? I have not seen any non-classical carbanions in books. If there are…
Saheb Garain great chemist
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18
votes
3 answers
Why doesn't the boiling point of an aqueous solution depend on intermolecular attraction?
I understand that boiling point is a colligative property for aqueous solutions, and that it empirically depends on the mole fraction of the solute, rather than the identity of the solute. I understand the van't Hoff factor / ionic strength and why…
user5434
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18
votes
3 answers
What exactly happened when I added KOH to hydrogen peroxide?
I recently added a potassium hydroxide, $\ce{KOH}$, pellet to a small droplet of hydrogen peroxide (30 %), $\ce{H2O2}$. You could clearly see the potassium hydroxide dissolving in the droplet when instantaneously the solutions began to fizz strongly…
user2117