Colin McFaul
  • Member for 9 years, 7 months
  • Last seen more than 3 years ago
How do non-polar substances dissolve in non-polar solvents?
19 votes

I think @Ben Norris's answer is great, but I wanted to add one other reason that non-polar molecules will dissolve in non-polar solvents, even in the absence of interactions: entropy. If there are no ...

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Significant Figures Interpretation
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12 votes

This is part of the reason I really don't like the way we teach significant figures. What's really important isn't the number of digits you have, but rather the uncertainty in your measurements. I ...

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Fundamental forces behind covalent bonding
10 votes

Thinking about this like a physicist, there are four fundamental forces: the strong nuclear force, the weak nuclear force, the electromagnetic force, and gravity. The strong nuclear force holds the ...

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What type(s) of gloves are effective against DCM and acetone?
8 votes

I just did a bit of an experiment. My lab uses Kimberly Clark nitrile gloves, and we have a huge jug of acetone. First, I put a glove on my hand, and poured acetone all over it. My hand felt cold, but ...

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Temperature dependence in absorption spectroscopy
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8 votes

I am aware of one effect: doppler broadening. When the temperature increases, the speed distribution spreads out. That spreads out the distribution of the velocity component in the direction of your ...

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Why does oxygen not condense onto open dewers of liquid nitrogen?
7 votes

The boiling point of nitrogen is 77 K, and the boiling point of oxygen is 90 K, so oxygen is liquid when liquid nitrogen is around. Wikipedia repeats the warning you mentioned: Liquid nitrogen has ...

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Covalent Bond/Hydrogen Bond
7 votes

Covalent bonds are the bonds between the atoms within the same water molecule. Hydrogen bonds are the bonds between two water molecules. All molecules have covalent bonds, but only some molecules have ...

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standard reference for thermodynamic properties?
7 votes

I too usually refer to the CRC Handbook. Both of my copies (86th ed, 2005-06 and 46th ed, 1965-66) have a section on thermodynamic properties of materials. The CRC Handbook works for the most of the ...

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Molecular explanation of the Hofmeister Series
6 votes

A similar effect occurs in synthetic polymers. poly(N-isopropyl Acrylamide), (usually just p(NIPAM)) is a thermosensitive polymer. At room temperature, it dissolves easily in water. When you heat the ...

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Normalization of the wavefunction φ(x) = A
5 votes

Strictly speaking, both signs are valid solutions to the wave equation, so you probably should keep the $\pm$ in front of the wave function. If this is the only wave function you're working with, then ...

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What is the behavior of a Zwitterion during ion exchange chromatography?
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5 votes

I would expect it to depend on the pH of the mobile phase. The charge of your stationary phase and whether you want the azide to elute will determine what charge you want on the azide. Given that, you ...

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What legal guidelines exist for completeness of a Materials Safety Data Sheet?
5 votes

OSHA's FAQ says that chemicals that make up less than 1% (0.1% if it is a carcinogen) of a product do not need to be listed on the MSDS. So it looks like 3M could be in compliance if the oderants are ...

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Are refractive or density based Brix meters better for use with alcoholic drinks?
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4 votes

Once I got going, this turned out to be a lengthy answer. So here's the summary: the alcohol will introduce a significant error in both methods. The density measurement will probably be closer to the ...

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How to properly relate quantum mechanical energy to the classical world
3 votes

without resorting to recasing the results into a physical property such as velocity? The energy is a perfectly physical property. In fact, for many quantum mechanical systems, the energy is the ...

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Bent molecular geometry of water
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3 votes

Your understanding is correct. The usual explanation given in introductory classes is VESPR theory. The oxygen atom has four bond-like "things" coming out of it. Two of those are the covalent bonds ...

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Why are there quantised energy levels in the vibrational energy of a molecule?
3 votes

There is a general result in quantum mechanics that a bound system has quantized energy states. Atoms in a molecule are clearly bound to each other, so they have quantized energy states. More ...

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Recreational drugs by half life
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2 votes

Wikipedia reports biological half-lives for several recreational drugs I just tried (cocaine, THC, MDMA). In each case, I went to the page for the particular substance, and Wikipedia keeps an ...

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How can I control the oxygen in an erlenmeyer flask in a bioprocess?
2 votes

For clarity, I'm going to separate this into two parts: purging the oxygen from the flask, and filling the flask with a particular mixture of gas(es). It's the same idea in both cases, but the first ...

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Is there a liquid crystal or similar material that gets cloudy when an electric field is applied, but is otherwise clear?
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2 votes

I would expect this to exist. One major class of stimuli-responsive polymers is thermosensitive polymers. These have a sudden drop in solubility with an increase in temperature above a certain point. ...

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Why should I add lithium bromide to my GPC eluent?
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1 votes

The answer to my question appears to be in a 1977 paper by Nancy D Hann (DOI: 10.1002/pol.1977.170150604; full citation below). In it, she compares GPC of polyurethane in DMF with and without added ...

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