Calculate the molar masses of the following substances:

(a) Ethyne, C₂H₂

(b) Sulphur molecule, S₈

(c) Phosphorus molecule, P₄

(d) Hydrochloric acid, HCl

(e) Nitric acid, HNO₃

The molar masses of all these substances will be equal to the respective molecular masses expressed in g/mol. Now:

(a) Molar mass of ethyne, C₂H₂ = Mass of C × 2 + Mass of H × 2

= 12 × 2 + 1 × 2

= 24 + 2

= 26 g/mol

(b) Molar mass of sulphur molecule, S₈ = Mass of S × 8

= 32 × 8

= 256 g/mol

(c) Molar mass of phosphorus molecule, P₄ = Mass of P × 4

= 31 × 4

= 124 g/mol

(d) Molar mass of hydrochloric acid, HCl = Mass of H + Mass of Cl

= 1 + 35.5

= 36.5 g/mol

(e) Molar mass of nitric acid, HNO₃ = Mass of H + Mass of N + Mass of O × 3

= 1 + 14 + 16 × 3

= 15 + 48

= 63 g/mol