Calculate the mass per cent of each element present in the molecule of calcium carbonate.

Molecular formula of calcium carbonate = CaCO₃

Molecular mass of CaCO₃ = 1 × Ca + 1 x C + 3 × 0

= 1 x 40 u + 1 x 12 u + 3 x 16 u

= 100 u

Gram molecular mass = 100 g/mol

1 mol of CaCO₃ = 100 g

(a) Mass % of Ca in CaCO₃ =( Mass of Ca / Molecular mass of CaCO₃) × 100

=( 40g / 100g ) x 100 = 40%

(b) Mass % of carbon in CaCO3 = (Mass of Carbon / Molecular mass of CaCO₃) x 100

= (12g / 100g) x 100 = 12%

(c) Mass % of oxygen in CaCO3 =( Mass of oxygen / Molecular mass of CaCO₃) x 100

= (48g / 100g) x 100 = 48%