Question

Calculate the formula unit masses of ZnO, Na₂O, K₂CO₃ given atomic masses of Zn = 65u, Na = 23u, K = 39u, C = 12u and O = 16u.

Answer 1

i) ZnO
(Atomic mass of Zn) + (Atomic mass of O)
= 65 + 16 = 81u.
ii) Na₂O
(2 × Atomic mass of Na) + (Atomic mass of O)
= 2 × 23 + 1 × 16
= 46 + 16
= 62u.
iii) K₂CO₃
(2 × Atomic mass of K)+ (Atomic mass of C) + (3 × Atomic mass of oxygen)
= 2 × 39 + 12 × 1 + 16 × 3
= 78 + 12 + 48
= 138u.