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

Solution:

Listed below is the molar mass of the following substances:

(a) Molar mass of Ethyne C₂H₂= 2 x Mass of C+2 x Mass of H = (2×12)+(2×1)=24+2=26g

(b) Molar mass of Sulphur molecule S₈ = 8 x Mass of S = 8 x 32 = 256g

(c) Molar mass of Phosphorus molecule, P₄ = 4 x Mass of P = 4 x 31 = 124g

(d) Molar mass of Hydrochloric acid, HCl = Mass of H+ Mass of Cl = 1+35.5 = 36.5g

(e) Molar mass of Nitric acid, HNO₃ =Mass of H+ Mass of Nitrogen + 3 x Mass of O = 1 + 14+

3×16 = 63g