Question

(i) What is molar mass?
(ii) Calculate the molar mass of the following substances:
C₂H₂, HCl, HNO₃

Answer 1

(i) Mass of 1 mole of a substance is equal to its molar mass.
(ii) C₂H₂= 2 ✕ molar mass of carbon + 2✕molar mass of hydrogen
= 2 ✕ 12 g + 2 ✕ 1g
= 26 g
HCl = 1 ✕ molar mass of hydrogen + 1 ✕ molar mass of chlorine
= 1 ✕ 1 g + 1 ✕ 35.5 g
= 36.5 g
HNO₃ = 1 ✕ molar mass of hydrogen + 1 ✕ molar mass of nitrogen + 3 ✕ molar mass of oxygen
= 1 ✕ 1 g + 1 ✕ 14 g + 3 ✕ 16 g
= 63 g