Amu vs g/mol

[Skarl]

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If 1 mol of a compound contains 96g of mass, why can we not conversely say that 96 amu of that compound contains 1 mol of that compound? This is a UWorld Gen Chem question but with quantities changed and the compound omitted to focus on the general concept and avoid copyright.

 

[AdaptPrep]

Hi, Skarl--

1 amu is 1.67 x 10^-24 g. That is the reciprocal of Avogadro's number (6.022 x 10^23). In other words, 1 amu = 1 / (6.022 x 10^23). Therefore, if 1 mole of a compound has a mass of 96 grams, 1 MOLECULE of that compound has a mass of 96 amu.

It might be easier to think of it as "amu per molecule" and "grams per mole". Of course, you can always calculate grams per molecule by using either conversion factor.

Good luck!