Question

Calculate the molar mass of the following substances:

(a) Ethyne, C₂H₂

(b) Sulphur molecule, S₈

(c) Phosphorus molecule, P₄ (atomic mass of phosphorus = 31)

(d) Hydrochloric acid, HCl

(e) Nitric acid, HNO₃

Answer 1

(a) Molar mass of ethyne, C₂H₂ = 2 × 12 + 2 × 1 = 26 g

(b) Molar mass of sulphur molecule, S₈ = 8 × 32 = 256 g

(c) Molar mass of phosphorus molecule, P₄ = 4 × 31 = 124 g

(d) Molar mass of hydrochloric acid, HCl = 1 + 35.5 = 36.5 g

(e) Molar mass of nitric acid, HNO₃ = 1 + 14 + 3 × 16 = 63 g