Question

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

Answer 1

Formula unit mass of ZnO = Atomic mass of Zn + Atomic mass of O 

= 65 + 16 = 81 u 

Formula unit mass of Na₂O = 2 × Atomic mass of Na + Atomic mass of O 

= 2 × 23 + 16 = 62u 

Formula unit mass of K₂CO₃ 

= 2 × Atomic mass of K + Atomic mass of C + 3 × Atomic mass of O 

= 2 × 39 + 12 + 3 × 16 = 138u