To calculate the formula unit masses of compounds, we sum the atomic masses of the constituent atoms according to their respective formulas.

Given atomic masses:
– Zn = 65 u
– Na = 23 u
– K = 39 u
– C = 12 u
– O = 16 u

Formula Unit Mass Calculation:
1. ZnO (Zinc Oxide):
– Formula: ZnO
– Atomic mass of Zn = 65 u
– Atomic mass of O = 16 u
– Formula unit mass of ZnO = Atomic mass of Zn + Atomic mass of O
– Formula unit mass of ZnO = 65 u (Zn) + 16 u (O) = 81 u

2. Na₂O (Sodium Oxide):
– Formula: Na₂O
– Atomic mass of Na = 23 u
– Atomic mass of O = 16 u
– Formula unit mass of Na₂O = 2 × Atomic mass of Na + Atomic mass of O
– Formula unit mass of Na₂O = 2 × 23 u (Na) + 16 u (O) = 46 u + 16 u = 62 u

3. K₂CO₃ (Potassium Carbonate):
– Formula: K₂CO₃
– Atomic mass of K = 39 u
– Atomic mass of C = 12 u
– Atomic mass of O = 16 u
– Formula unit mass of K₂CO₃ = 2 × Atomic mass of K + Atomic mass of C + 3 × Atomic mass of O
– Formula unit mass of K₂CO₃ = 2 × 39 u (K) + 12 u (C) + 3 × 16 u (O) = 78 u + 12 u + 48 u = 138 u

Summary of Formula Unit Masses:
– ZnO (Zinc Oxide) = 81 u
– Na₂O (Sodium Oxide) = 62 u
– K₂CO₃ (Potassium Carbonate) = 138 u