2.0 g of pure calcium was quantitatively converted to 2.8 g of its oxide. Calculate the atomic weight of calcium.

Reaction  Ca+12O2⟶CaO Equivalent of Ca = Equivalent of CaO. ∴  Wt. of Ca Wt. of CaO= Eq. wt. of Ca Eq. wt. of CaO              …(1)Let Eq. wt. of Ca = E ; Eq. wt. of CaO = Eq. wt. of Ca+ Eq. wt. of oxygen=E+ At. wt. of oxygen, 16 Valency of oxygen; 2=E+8 Substituting the values in equation (1), we get, 22.8=EE+8;2E+16=2.8E0.8E=16. Hence E=160.8=20.At. wt. of Ca = Eq. wt. of Ca × Valency of calcium = 20 × 2 = 40