Calculate the mass fraction of water in the crystalline hydrate of copper sulfate CuSO4; 5H2O

Given:
CuSO4 * 5H2O

Find:
ω (H2O) -?

1) Calculate the molar mass of CuSO4 * 5H2O:
M (CuSO4 * 5H2O) = Mr (CuSO4 * 5H2O) = Ar (Cu) * N (Cu) + Ar (S) * N (S) + Ar (O) * N (O) + Ar (H) * N (H) + Ar (O) * N (O) = 64 * 1 + 32 * 1 + 16 * 4 + 1 * 10 + 16 * 5 = 250 g / mol;
2) Calculate the molar mass of H2O:
M (H2O) = Mr (H2O) = Ar (H) * N (H) + Ar (O) * N (O) = 1 * 2 + 16 * 1 = 18 g / mol;
3) Calculate the mass fraction of H2O:
ω (H2O) = M (H2O) * N (H2O) * 100% / M (CuSO4 * 5H2O) = 18 * 5 * 100% / 250 = 36%.

Answer: Mass fraction of H2O is 36%.