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 = 28g 

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

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

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

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