Molecular mass of H₂ = 2 × Atomic mass of H
= 2 × 1 = 2u
Molecular mass of O₂ = 2 × Atomic mass of O
= 2 × 16 = 32u
Molecular mass of Cl₂ = 2 × Atomic mass of Cl
= 2 × 35.5 = 71u
Molecular mass of CO₂ = Atomic mass of C + 2 × Atomic mass of O
= 12 + 2 × 16 = 44u
Molecular mass of CH₄ = Atomic mass of C + 4 × Atomic mass of H
= 12 + 4 × 1 = 16u
Molecular mass of C₂H₆ = 2 × Atomic mass of C + 6 × Atomic mass of H
= 2 × 12 + 6 × 1 = 30u
Molecular mass of C₂H₄ = 2 × Atomic mass of C + 4 × Atomic mass of H
= 2 × 12 + 4 × 1 = 28u
Molecular mass of NH₃ = Atomic mass of N + 3 × Atomic mass of H
= 14 + 3 × 1 =17u
Molecular mass of CH₃OH Atomic mass of C+4 ×Atomic mass of H+Atomic mass of O
= 12 + 4 × 1 + 16 = 32u

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