Talk:Molar mass

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molar mass

Molar mass is the mass of one mole of a chemical element or chemical compound. In SI, the unit is kg/mol. The molar mass can be obtained from the relative molecular mass (still often called erroneously molecular weight and abbreviated by MW) multiplying it by 0.001 kg/mol.

"What a tangled web we weave!"

The molecular weight of sugar is 342 and that means there are 342 grams per mole. Its that simple! Why confuse things so tremendously by introducing the obscure Dalton unit and molar mass versus molecular mass?? Wikipedia isn't meant to be read only by PhD physicists and chemists ... it is also meant to be read by us mere mortal masses. - mbeychok 20:50, 25 April 2006 (UTC)[reply]

Mass of a mole is called molar mass we can obtained it by molecular mass by miltiplying it by 0.001kg/mol. — Preceding unsigned comment added by 59.144.134.240 (talk • contribs) 12:24, 20 July 2006 (UTC)[reply]

The fact is that u, Da, g/mol, kg/mol are all used by physicists, protein mass spectrometrists, chemists, and SI-ists respectively. Tangled yes but we can't really sweep it under the rug. --Rifleman 82 17:06, 5 January 2007 (UTC)[reply]

molar versus molecular mass

Msg. to Nick Y: molar mass is the macroscopic mass of roughly 10²³ molecules, whereas molecular mass is the mass of one molecule. So, they differ in their units when their numeric values are (almost) equal, which is why I deleted usually. Both masses could be expressed in the same units (say kg), but then of course the numeric values would be different by a factor on the order of 10²³. I understand that you know all of this, but for clarity we should be careful about the formulation of these things.--P.wormer 11:36, 11 May 2007 (UTC)[reply]

I agree with you for the most part. The issue that I was trying to avoid, which is an idiotic one in my opinion, is that there really is no restriction on units and it is possible to use the same units. I.e. that the molar mass of water could be described as 108.396x10²³ u. Conversely molecular mass may be expressed as some very small number in g/mol. There is no reason to do such a thing but the units do not differ by definition and the insertion of a single word gets around the problem. While we are discussing things I do not see the need to discuss kg/mol in the context of the molar mass versus molecular mass section. I fully understand the need to discuss it in general. It is discussed directly above in the introductory section. If we stick to g/mol within this section for the sake of simplicity of addressing the issue at hand without saying that it must be this or that everything is simpler and clearer. e.g.

"The numeric values of molar mass and molecular mass are approximately equal, although they differ in their units, namely g/mol (chemistry) or kg/mol (SI and physics) for molar mass versus u for molecular mass. For most compounds (when using g/mol and u) the numeric values are not exactly equal but differ slightly."

Could be simply:

"When the molar mass and molecular mass are expressed in g/mol and u respectively they will almost always have similar but not identical numerical values."

--Nick Y. 18:15, 11 May 2007 (UTC)[reply]