what is the loss in the mass when 1.25 g of blue copper(II) sulphate crystals is heated and decomposed to anhydrous copper (II) sulphate?

Molar mass of anhydrous CuSO₄ = (63.5 + 32.1 + 16.0×4) g/mol = 159.6 g/mol
Molar mass of H₂O = (1.0×2 + 16.0) g/mol = 18.0 g/mol
Molar mass of blue CuSO₄•5H₂O crystals = (159.6 + 18.0×5) = 249.6 g/mol

Equation for the decomposition of blue copper(II) sulphate crystals :
CuSO₄•5H₂O(s) → CuSO₄(s) + 5H₂O(g)
Mole ratio CuSO₄•5H₂O : H₂O = 1 : 5

No. of moles of CuSO₄•5H₂O decomposed = (1.25 g) / (249.6 g/mol) = 1.25/249.6 mol
No. of moles of H₂O vapour given off = (1.25/249.6 mol) × 5
Mass of H₂O vapour given off = (1.25/249.6 mol) × 5 × (18.0 g/mol) = 0.45 g

Loss in mass on heating = 0.45 g