Percent composition help??

Question

The question I am trying to answer is "What percentage of water is in the compound CuSO4 5H2O?" Now I know to get percentage I need to figure out Molar mass of H2O/Molar mass of CuSO4 5H2O and multiply by 100, but when I try to figure out the molar mass of water do I just get the MM of H20 or do I multiply water by the coefficient 5 because of the 5H20? Please help me..........I got the answer 14.04%, is that correct.

Answer 1

You must multiply Mm of water by 5, so:

Mm(CuSO4.5H2O) = 249.5 g/mol

Mm(H2O) = 18

percentage of water: 100*5*18/249.5 = 36.07%