Calculate the formulae masses of the following compounds:
(i) Sodium oxide, Na2O
(ii) Aluminium oxide, Al2O3
(Given: Atomic masses: Na = 23 u; O = 16 u; Al = 27 u)
(a) Molecular mass of Na2O = (2 x Na) + (1 x O) = (2 x 23) + (1 x 16) = 62u
(b) Molecular Mass of Al2O3 = (2 x Al) + (3 x O) = (2 x 27) + (3 x 16) = 102u