Weight Fraction of Atoms

The mass fraction of atoms in a molecule can be also obtained from the abundance generating function. For this purpose, we modify the abundance generating functions somewhat. We show this for carbon  

So here we have replaced the dummy parameter r by t t c in the case of the abundance generating function for carbon and f by t t o in the case of the abundance generating function for oxygen. 

For carbon monoxide, the abundance generating function expands to 

Inspection of Eq. (12.15) reveals that the exponent of the dummy parameter t informs about the total mass number and the exponents of c and o inform about the particular isotopes constituting the group. 

In practice, it is more efficient to calculate the averages from the atoms, to store them and to add the individual averages of the atoms that are constituting a molecule together. 

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