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I have seen many great physics questions in here, regarding material properties, atomic physics, physical chemistry and solid state physics. Case you don't as them on physics stack exchange. – Bernardo Kyotoku Dec 4 '10 at 9:07

Members of ACS or other professional organizations need to get the news about this SE! SE is very diverse, but these are great sources of specialists. – xenomancer Mar 17 '11 at 15:56

@Bernardo: There's a great deal of overlap between chemistry and other scientific disciplines, including physics, biology, and mathematics. – Bob Murphy Apr 7 '11 at 23:44

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79 Example Questions (10 closed)

active newest votes

up vote 23 down vote

added by Robert Harvey Jun 9 '10 at 22:36

up vote 22 down vote

added by Tobias Kienzler Jun 9 '10 at 9:52

e.g. methane, ethanol, ... – Tobias Kienzler Jun 9 '10 at 9:52

Very good question. You typically spend an aggregate of a few days on this in first-year university-level organic chemistry, and it's quite important if you're doing research. – Bob Murphy Dec 1 '10 at 4:28

This question is good in spirit but is extremely broad. – Nick T Jan 11 '11 at 18:16

The answer to such a question would be extremely long. It'd probably be more useful to narrow it down. – Borror0 Jan 16 '11 at 7:18

So, the general answer could be covered relatively briefly, but to discuss a specific piece of nomenclature would require a (potentially) more in depth answer. Answering this, specifically, for all compounds would be VERY long an tedious. – tryaria Mar 1 '11 at 23:29

show 1 more improvement suggestion

up vote 22 down vote

added by dthorpe Aug 13 '10 at 0:24

Sometimes, when someone mix two solvents, this effect happens. It doesn't happen only with water and ethanol, but with several other solvent mixtures (I can remember hexane/ethyl acetate, chloroform/methanol, and so on). – Cedric Mar 29 '11 at 23:09

up vote 21 down vote

added by googletorp Jun 9 '10 at 9:18

The only chemical reaction is the carbonic acid-to-carbon dioxide and water fizzy thing that would happen more slowly anyway. However, Mentos provide a fantastic nucleation surface which catalyzes that reaction. So a question of this is a great launchpad into issues around nucleation (important in many lab procedures), catalysis, surface chemistry, and a very interesting heterogeneous phase system involving solid phase (Mentos), liquid phase (coke), and vapor phase (bubbles). – Bob Murphy Dec 1 '10 at 4:36

up vote 21 down vote

added by Master Of Disaster Jun 10 '10 at 1:39

Has to do with electron shell configuration. Quantum dynamics and particle physics perhaps? – rightfold Aug 14 '10 at 17:40

Not particle physics, but certainly quantum dynamics. The orbital populations of electrons, and their interactions with the nucleus, determine the colors of gold and copper, as well as the high electrical conductivity of those plus silver. Not to mention other unusual properties like ferromagnetism in Fe/Co/Ni, and Hg being liquid at room temperature. – Bob Murphy Nov 30 '10 at 6:41

physics question. – Bernardo Kyotoku Dec 4 '10 at 8:25

@Bernardo: It's another question in the area of overlap between chemistry and physics. On the basis of quantum mechanics, it's possible to claim all chemistry questions are physics questions. – Bob Murphy Dec 13 '10 at 6:58

Our best knowledge of why this is so has to do with relativistic contraction of atomic orbitals. Quantum chemists like P. Pykköö have studied this problem. This firmly belongs in the "both physics and chemistry" camp. – AcidFlask Feb 21 '11 at 5:27

up vote 13 down vote

added by googletorp Jun 17 '10 at 10:53

	Just the average – rightfold Aug 14 '10 at 17:41
	@Time Machine: It's not quite that easy. In fact, you can wind up with some really wacky algebra. For instance, you can take a typical buffer solution at a given pH, and add a bunch of strong acid or base, and the pH will hardly budge. – Bob Murphy Jan 5 '11 at 5:23

up vote 11 down vote

added by KennyTM Jun 24 '10 at 19:09

Note: it's a kind of high-Tc superconductor. – KennyTM Jun 24 '10 at 19:10

up vote 7 down vote

added by oneat, edited by Beska Dec 1 '10 at 22:32

Very good chemistry question. The answer is yes, it's an extremely weak acid and a tiny fraction dissociates into a proton and an ethoxyl anion. The dissociation constant is low enough it can be ignored for most practical purposes. But you do need to be aware of it, because if you're doing a reaction that can be wrecked by proton catalysis, you might want to pick a different solvent. – Bob Murphy Dec 1 '10 at 4:59

up vote 7 down vote

added by Bob Murphy Nov 30 '10 at 17:34

up vote 7 down vote

added by oneat, edited by WikiSpeedia hang-around Dec 20 '10 at 16:08

up vote 6 down vote

added by googletorp Jun 10 '10 at 7:54

I'm so sorry I ran out of on-topic votes, because this is a wonderful chemistry question. – Bob Murphy Nov 30 '10 at 6:50

up vote 5 down vote

added by rlb.usa, edited by WikiSpeedia hang-around Dec 20 '10 at 16:19

119 isn't produced yet. – KennyTM Jun 11 '10 at 19:31

That's really a physics question. As you progress beyond uranium into the purely synthetic elements, the half-lives get progressively shorter and the elements harder to create. Past americium, you rapidly get to a place where you generate an atom at a time, and the half-life is way less than a second. So you can't really do any meaningful chemistry with those elements, and it's not really a good chemistry question per se. – Bob Murphy Nov 30 '10 at 6:56

I respectfully disagree that this is "really" a physics question. There are such people as nuclear chemists, and they do participate in nucleosynthesis research. Again, another "both physics and chemistry" question. – AcidFlask Feb 21 '11 at 5:31

I think this could be considered either a good chemistry or a physics question, for the reasons already stated. The periodic table is generally considered chemistry, but practically speaking there is very little done with the "chemistry" of an atom that exists for less than a second. As such, I don't think it's a good choice for one of the 10 defining questions. – tryaria Mar 1 '11 at 23:32

up vote 5 down vote

added by dthorpe Aug 13 '10 at 0:25

Thinking specifically of essence extraction and distillation: flavoring extracts (vanilla, orange, etc) are almost always alcohol based. – dthorpe Aug 13 '10 at 0:28

This deals with polarity, which is a fundamental topic in chemistry. – Bob Murphy Nov 30 '10 at 6:43

up vote 4 down vote

added by Tobias Kienzler Jun 9 '10 at 9:53

	Do you include physical chemistry or should this be asked on physics area51.stackexchange.com/proposals/1908/physics ? – Tobias Kienzler Jun 9 '10 at 9:53
	This question is a bit loose, would be better to ask a question like: which methods are used to calculate electron orbitals in atoms and molecules? – googletorp Jun 9 '10 at 9:56
	Quantum mechanics and physical chemistry belongs to this area. As long as the goal is to gain a better understanding of chemistry, how molecules react, placement of electrons etc, is within the subject. – googletorp Jun 9 '10 at 9:58
	quantum chemistry is definitely chemistry. – Stefano Borini Aug 13 '10 at 9:24
	The question as posed is susceptible to multiple interpretations, none of which are chemistry. For instance: 1. What is the cosmic reason orbitals exist? (Sort of a theology/philosophy question.) 2. Who discovered orbitals, and when and why did that happen? (A history-of-science question.) – Bob Murphy Dec 3 '10 at 6:24

show 6 more improvement suggestions

up vote 4 down vote

added by dthorpe Aug 13 '10 at 0:32

this is a question for popular natural science. The point of this SE is for advanced level chemistry. – Stefano Borini Aug 13 '10 at 9:23

@Stefano I agree. Here's a link: Popular Natural Sciences (disclaimer it's my referral link..) – Tobias Kienzler Aug 13 '10 at 10:19

So, the action of lipids as emulsifiers is popular natural science, but mentos in diet coke is advanced level chemistry? – dthorpe Aug 13 '10 at 22:35

Good question that has both simplistic and advanced explanations. – Radu Nov 4 '10 at 3:09

As a chemist, I agree there are both simplistic and advanced explanations. This question gets into issues like polarity, has quantum mechanical implications, relates to the biochemical construction of cell walls, lets one calculate the volume of a single surfactant molecule by experiment, has implications for a huge variety of industrial processes one might not suspect, and gets into notions like mordants. – Bob Murphy Nov 30 '10 at 6:31

up vote 4 down vote

added by Damien Oct 11 '10 at 8:11

I would love to get the answer as well, btw! – Damien Oct 11 '10 at 8:11

Good question, and no they're not. Absorption occurs when a substance enters the interior of something; adsorption occurs when a substance adheres to the surface of something. There are lots of interesting examples of both. – Bob Murphy Nov 30 '10 at 6:37

BTW, this is totally on-topic for chemistry. Zeolites are used in as catalysts in oil refining because they contain molecule-scale cages that ABsorb particular hydrocarbons and do things to them. On the other hand, you use finely divided platinum as a hydrogenation catalyst because it ADsorbs hydrogen in a way that makes it more reactive. You don't usually run into this much until upper-level undergraduate classes, but it can be really important if you're doing lab-based graduate research involving synthesis. – Bob Murphy Dec 16 '10 at 6:53

@Bob we have adsorption and absorption in our textbooks for chemistry. How is this off-topic? – Qyuubi Feb 12 '11 at 12:48

@QH7: I don't know - I wasn't the person who voted that it was off-topic. In my experience as a professional chemist, this is so on-topic, it's off the charts. :-) – Bob Murphy Feb 13 '11 at 22:02

up vote 4 down vote

added by Svante Oct 24 '10 at 16:57

up vote 4 down vote

added by Qyuubi Feb 12 '11 at 12:52

	I would really like to know the answer to this one. – Qyuubi Feb 12 '11 at 12:53
	@QH7 They can have different optical properties (don't know the underlying physics), but in biological systems it's almost always because the enzymes will only fit particular orientations. – Nick T Feb 15 '11 at 4:15

up vote 3 down vote

added by Robert Harvey Jun 9 '10 at 22:37

	A better question would be how orbitals explain the structure of a molecule. – googletorp Jun 10 '10 at 7:56
	@googletorp: If you know enough to ask the question that precisely, do you really need an answer? – Robert Harvey Jun 22 '10 at 23:37
	@Robert Harvey These questions is not about getting an answer on something you don't know, but defining the Q&A site to be. – googletorp Jun 23 '10 at 5:53
	Oh, wow. Where do you want to start on this one? After eight years of university chemistry, I could probably natter for weeks continuously about this topic. – Bob Murphy Nov 30 '10 at 6:45

up vote 3 down vote

added by Master Of Disaster Jun 10 '10 at 1:41

closed as off topic by KennyTM, Tobias Kienzler, Vortico, Douglas S. Stones, googletorp Jun 23 '10 at 5:54

This question does not relate to the topic of the proposal.
It was closed as part of an automated migration of off-topic to close votes on September 29, 2011.

	Off topic — same reason as area51.stackexchange.com/proposals/4964/chemistry/…. – KennyTM Jun 10 '10 at 10:11
	I disagree - the accuracy of carbon dating is entirely in the field of analytical chemistry - albeit generally analyzed in geochemistry. Although radioactive decay is a question in physics, it is the chemistry involved here that makes the answer interesting. – tryaria Mar 1 '11 at 23:12

up vote 3 down vote

added by Gordon Gustafson Dec 4 '10 at 0:58

up vote 3 down vote

added by Gordon Gustafson Dec 4 '10 at 1:00

Ay caramba, that's such a great question I just transferred one of my on-topic votes, and another one I could talk about continuously for weeks. – Bob Murphy Dec 13 '10 at 6:34

up vote 3 down vote

added by Radu Feb 7 '11 at 18:38

Here goes: Freewares: ACD/ChemSketch freeware, DrawIt (former ChemWin), Symyx Draw (formely ISIS/Draw) for Windows; Open-source: bkchem (python-based, cross-platform), ghemical (GNOME) and xdrawchem (the latter two for Linux); and Jmol and Marvin Sketch (Java) – Cedric Mar 29 '11 at 23:12

up vote 3 down vote

added by AcidFlask Feb 21 '11 at 6:17

up vote 2 down vote

added by googletorp Jun 9 '10 at 9:16

Very good chemistry question which deals with things like polarity and hydrogen bonding; there are also implications for things like the chemical structure of cell walls. – Bob Murphy Jan 15 '11 at 22:47

up vote 2 down vote

added by rlb.usa Jun 10 '10 at 16:27

I'd think fire is rather physically. But Physical Chemistry might cover it, too – Tobias Kienzler Jun 11 '10 at 7:24

The simplistic answer is rapid oxidation, but the details are extremely complex, vary a lot among combustibles, and are not fully understood. – Bob Murphy Nov 30 '10 at 6:50

up vote 2 down vote

added by dthorpe Aug 5 '10 at 23:41

That was on the Science Channel program "How It's Made" a week or two ago. I was surprised at how much of the refining is done with just mechanical processing. – Bob Murphy Dec 13 '10 at 6:27

up vote 2 down vote

added by visitor93746, edited by WikiSpeedia hang-around Dec 20 '10 at 16:15

Why would this be considered off-topic? I'm starting to study chemistry and this is a real question I have - what other topic does this fall into if not Chemistry? – visitor93746 Oct 3 '10 at 19:51

It's a good question, but it's answered in the Wikipedia article's IUPAC definition. It's a ratio of mass-to-mass, and the units cancel out. – Bob Murphy Dec 1 '10 at 4:38

up vote 2 down vote

added by visitor93746 Sep 21 '10 at 20:09

Good physical chemistry question. – Bob Murphy Nov 30 '10 at 6:44

up vote 2 down vote

added by shellholic Nov 22 '10 at 17:16

Where this question is more a physics question, it's a step in the typical path to spectroscopy. (spectroscopic theory is very physics-like) – shellholic Nov 22 '10 at 17:18

If it is a physics question why don't ask in a physics forum – Bernardo Kyotoku Dec 4 '10 at 8:40

Sigh. This question was covered in detail in two quantum chemistry courses I took, one as an undergraduate and one while working on my doctorate. Both texts had the word "Chemistry" in the title and not "Physics". Maybe I should go to the physics forum and respond to every question with, "That's really mathematics," which on a fundamental level is all physics really is. – Bob Murphy Dec 14 '10 at 0:01

up vote 2 down vote

added by Bob Murphy Nov 30 '10 at 17:38

up vote 2 down vote

added by avakar Dec 16 '10 at 16:21

Excellent chemistry question. What's your other electrode made of? The electrolyte solution has become saturated with whatever-it-is sulfate, and as you keep pumping electricity through, you keep putting more whatever-it-is sulfate into the electrolyte, so it's precipitating out. – Bob Murphy Dec 19 '10 at 3:07

@Bob, thanks :) Both electrodes are copper; the sulfuric acid is being turned to copper sulfate. Beyond the fact that the amount of copper sulfate increases, is it possible that with sulfuric acid vanishing, the pH of the solution increases, decreasing the solubility of the copper sulfate? – avakar Dec 19 '10 at 22:16

Hmm. That sounds fishy. You're basically schlepping copper from one copper electrode to the other; there should be no pH change. However, you could also simply be dissolving your copper electrodes by a redox reaction which would generate hydrogen gas from the protons dissociated from the sulfuric acid as a by-product, and you'd get copper sulfate precipitate. Do you see bubbles? (Don't light any matches... :-) – Bob Murphy Dec 23 '10 at 6:09

up vote 2 down vote

added by annemphillip Jan 23 '11 at 22:59

An excellent question. I'm not sure people know the answer to this yet. – AcidFlask Feb 21 '11 at 5:37

Actually, it's pretty simple. Gases are miscible, so as each nitrogen bubble passes through the water, some of the oxygen dissolved in the water migrates into the bubble. As you keep bubbling more nitrogen through, you remove more and more of the dissolved oxygen. It's really the same as if you mixed up salt and sand, and ran water through the mixture: you'd "de-salt" the sand. – Bob Murphy Apr 7 '11 at 23:54

up vote 2 down vote

added by Radu Feb 6 '11 at 16:10

Wow, what a great organic chemistry question, with quantum mechanical implications! – Bob Murphy Apr 7 '11 at 23:58

up vote 2 down vote

added by Qyuubi Feb 12 '11 at 13:02

Great question, and the answer differs based on the type of bond. For instance, chlorine is sigma-withdrawing but pi-donating, and the reasons for the difference are quite interesting. – Bob Murphy Feb 13 '11 at 22:07

up vote 2 down vote

added by Robin, edited by WikiSpeedia hang-around Feb 22 '11 at 6:39

	It's a simple measurement to do. I'm sure Google know this as well. – M'vy Mar 1 '11 at 17:16
	An on-topic question would be "What is pH?" – tryaria Mar 1 '11 at 23:23
	I know what is pH but I dont know the pH value for coke and pepsi. – Robin Mar 2 '11 at 4:06
	Off-topic. To expand on what googletorp said elsewhere, I don't think we want this site to become an encyclopedia of physical constants people could easily find using a search engine. – Bob Murphy Mar 30 '11 at 4:14

up vote 2 down vote

added by Robin, edited by WikiSpeedia hang-around Feb 22 '11 at 6:38

How about HSO4-? :P – Radu Feb 19 '11 at 20:08

up vote 1 down vote

added by dthorpe, edited by WikiSpeedia hang-around Dec 20 '10 at 16:17

Interesting question with a very long answer. – Bob Murphy Dec 1 '10 at 6:02

Such questions would have many variable depending on what one has at one's place. Many reasons might be practical problems not pertaining to chemistry as such. – Qyuubi Feb 12 '11 at 12:41

up vote 1 down vote

added by rightfold Aug 14 '10 at 17:37

I don't think that this question is specific enough. – Radu Nov 4 '10 at 13:33

Actually, it's a very serious question in physical organic chemistry. P.D. Bartlett did some quite striking work around this during the 1930s at Harvard, using substituted benzoic acids, that's still widely cited, and forms the basis for modern structure-activity relationship theory which is fundamental to areas like pharmaceutical design. However, the answer wouldn't be short. :-) – Bob Murphy Nov 30 '10 at 7:01