18 Apr
2011
18 Apr
'11
1:56 p.m.
I think the mole is defined from the number of
attons in a certain mass
of a certain isotope of an certain element (carbon 12 IIRC)
The mole is the amount of a substance which contains Avogadro's number=20
(6.0225 =D7 10^23 ) of atoms or molecules of the substance. Stated differently, it is the same amount of grammes
of the substance as=20
that element's molecular weight.
The definition says that it is the amount of a substance which contains=20
the same number of molecules of the substance as 12 grammes of=20
carbon-12, which is a way of expressing the number of molecules in such=20
I have an idea that the definition I came across specifies Carbon-12.
Since the atomic masses are not exact integer rations of each other (in
other words, an oxygen-16 atom is not exactly 4/3 of the mass of a
carbon-12 atom), I think you do have to specify the element you are using
here.
-tony