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# Calculate the molar mass of the following substances.(a) Ethyne, C$$_2$$H$$_2$$(b) Sulphur molecule, S$$_8$$(c) Phosphorus molecule, P$$_4$$ (Atomic mass of phosphorus =31)(d) Hydrochloric acid, HCl(e) Nitric acid, HNO$$_3$$

We know that molar mass of a substance is the sum of the atomic masses of all the elements.

(a) Molar mass of Ethyne C$$_2$$H$$_2$$
= 2 × Mass of C+2 × Mass of H
= (2 × 12) + (2 × 1) = 24 + 2
= 26g

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

(c) Molar mass of Phosphorus molecule, P4
= 4 × Mass of P = 4 × 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 × Mass of O = 1 + 14 + 3 × 16 = 63g