Talk:Dimensional analysis

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Simple moles rather than "kg-mol"[edit]

Regarding section The factor-label method for converting units, I propose replacing references to "kg-mol" with plain "mol." According to article Mole (unit) linked in the very same section, "kg-mol" is an older term. It is a point of confusion that adds no value to the article. Furthermore, the very next section uses plain "mol" with the same meaning. If no one objects, I will change it in a couple of days.
Christopher Ursich (talk) 22:05, 19 December 2017 (UTC)

The mole commonly used in chemistry, if it needs disambiguation, is the gram mole (g-mol). The kg-mol is 1000 times bigger. It seems that the more commonly used name now is kilomole, following SI prefixing. Gah4 (talk) 00:23, 20 December 2017 (UTC)
You are correct; I missed that. If I were to make the change, I would need to adjust for that factor. That wouldn't be difficult, but I won't press the issue. I do still think, however, that it needlessly makes the content slightly more difficult. I have never encountered this curiously-derived term before, despite being a Chemistry major for a time. Thank you for your input.
Christopher Ursich (talk) 01:18, 21 December 2017 (UTC)
I used to work in a ChE lab, even though I wasn't ChE. In the US, ChE use pound-mole, and chemical reaction energies are in BTU/pound-mole. (Where others would use kcal/mole or eV.) I used to work on a curve fitting program for our lab, which would plot and fit absorption spectra. Previously, it did the x axis in kK (kilo keysers), but I added eV, kcal/mole and BTU/pound-mole, the latter mostly for fun, as I suspect it wasn't used. Gah4 (talk) 01:55, 21 December 2017 (UTC)

What is "kg/kgmol" supposed to be? kg/kg*mol, so mass/mass*mol = 1/mol? How could that be identical to kg/kmol (aka 1000g/1000mol = g/mol = mass/mol)? I can find such expression neither in the mole article nor Stoichiometry. Its does show up in one more article[1] but also with no further information given what this is supposed to be. If this is suppoed to be "kg/kg-mol" as stated in the mole article then it uses the wrong notation here... I will remove this unit and only state the "sometimes" used kg/kmol.

As a side not, this would be the molar mass of NO2 and not NOx, which obviously doesnt have a fixed molar mass. — Preceding unsigned comment added by Eheran (talkcontribs) 10:41, 8 January 2018 (UTC)

I believe that this modification is an improvement. Although we decided to not change the text in this way earlier, I see that the math portion really did need correction. The 'dot' character was being rendered to indicate multiplication of and , which "kgmol" is not.
Christopher Ursich (talk) 14:47, 8 January 2018 (UTC)
I have wondered about this. Yes, kg mole isn't kg times mole, but, conveniently, a kg mole is 1000 times the size of a gram mole. So, kg mole per kg should equal gram mole per gram. Funny units. Gah4 (talk) 15:17, 8 January 2018 (UTC)
Originally the 'mol' stood for molecule, and might be read as 1/dalton or 1/u. So a kilogram-mole is a number kg/u. Likewise, there was equiv (a mol of valance bonds, so 16 grams of oxygen = 1 g-mol O, or 2 g-equiv O.) A gram-ion was a charge of weight * electron-charge / dalton, so the faraday is a gram-ion, or a gram-mol of electrons. This is used in electroplating, etc. Wendy.krieger (talk) 11:52, 22 January 2018 (UTC)

Terence Tao article[edit]

The above is a bit complicated but might have stuff suitable for the article. The wiki article says "affine quantities" can be subtraced but not added. But I think the mathematical concept wanted is torsors, about which the wiki article is way too technical. The torsors talk page has some more useful links like this one. (talk) 10:07, 4 March 2018 (UTC)

fractional exponents[edit]

Why does the article say the exponents can be arbitrary rational numbers, rather than just integers? Could someone add an example? Thanks. (talk) 08:29, 18 March 2018 (UTC)