Molecular weight of H_{2} = 2 × 1 = 2 u

Molecular weight of O_{2} = 2 × 16 = 32 u

Molecular weight of Cl_{2} = 2 × 35.5 = 71 U

Molecular weight of CO_{2} = 12 + 2 × 16 = 44 u

Molecular weight of CH_{4} = 12 + 4 × 1 = 16 u

Molecular weight of C_{2}H_{6} = 2 × 12 + 6 × 1= 30 u

Molecular weight of C_{2}H_{4} = 2 × 12 + 4 × 1= 28 u

Molecular weight of NH_{3} = 14 + 3 × 1 = 17 u

Molecular weight of CH_{3}OH = 12 + 4 × 1 + 16 = 32 u