this may help you.
1. Calculate molecular mass of CuSO4•5H2O
2. Calculate molecular mass of ALL oxygen atoms in CuSO4•5H2O (which are 4 oxygen atoms in CuSO4 and 5 oxygen atoms in H2O so in total its 9 oxygen atoms, thus find molecular mass if 9 oxygen atoms)
3. Do mathematical cross multiplication
Molecular mass of CuSO4•5H2O - 1.67×10−2moles
molecular mass of 9 oxygen atoms - X moles
so
X= 1.67×10−2moles * molecular mass of 9 oxygen atoms / Molecular mass of CuSO4•5H2
and get the answer :3
