Talk:Mole fraction

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dictionary definition?

I'm a bit confused here. The article appears to me to be a long-winded way of giving a dictionary definition, that the "mole fraction" of a component ("type of molecule") in a mixture is the proportion of molecules in the mixture to belong to it.

Is that correct? If so, can't we say so?

Appealing to moles appears to me to be a bit of a detour - for non-chemists, who are going to use this for theoretical rather than practical purposes, molecules are a more immediate concept. The mole fraction of X in Y is the probability that a molecule of Y, chosen at random, is actually X. The rest is pretty much obvious.

RandomP 10:30, 17 September 2006 (UTC)[reply]

It is mole fraction simply because solutions aren't always molecular. For the example given, there is no molecule of NaCl as it is an ionic compound. So we're not appealing to moles, rather the use of the mole is a more accurate usage. Yeah, that may be a bit much for the non-chemist maybe - so what? That said, the whole thing could be simplified and clarified as it is indeed one of the more simple concepts in chemical concentration. Vsmith 14:00, 17 September 2006 (UTC)[reply]

Thanks for the clarification! So it's more of a "particle fraction". Just out of curiousity, would a statement like "the mole fraction of hydrogen in water is 2/3" make sense to a chemist, make them wince, or both? (I.e. speaking of the numerical proportion of atoms in molecules rather than atoms/proper molecules/whatever compounds in a real solution)

"numerical proportion of X molecules in a solution Y" still strikes me as better terminology than "mole fraction", but changing chemical terminology is slightly beyond the scope of Wikipedia :-)

(Thanks for the cleanup edit, too!)

RandomP 16:25, 17 September 2006 (UTC)[reply]

Makes sense, although not usually stated that way. Chemical formulas are simply mole ratios of the constituent atoms or ions. The subscripts can be used to express a mole fraction. This can get complicated though - consider ammonium phosphate (NH₄)₃PO₄. Consider also alloys such as brass, in which two or more metals can exist in a range of proportions. Although usually expressed in terms of weight or mass percent, they can be described in terms of mole fractions for a particular alloy formulation - no molecules involved. Vsmith 17:04, 17 September 2006 (UTC)[reply]

This needs language that is easier to understand for someone taking Gen Chem for the first time, something non-mathematical, or "in plain english." This article plainly has me lost.

User: Komodo9mm: 2044pm, 30 Jan 2007