Ncert Exercises & Solutions

1.1 Calculate the molar mass of the following:

(i) $H_{2} O$ (ii) ${CO}_{2}$ (iii) ${CH}_{4}$

(i) $H_{2} O$ :

The molecular mass of water, $H_{2} O$

= (2 × Atomic mass of hydrogen) + (1 × Atomic mass of oxygen)
= [2(1.0084) + 1(16.00 u)
= 18.02 u

(ii) ${CO}_{2}$ :

The molecular mass of carbon dioxide, ${CO}_{2}$
= (1 × Atomic mass of carbon) + (2 × Atomic mass of oxygen)
= [1(12.011 u) + 2 (16.00 u)]

= 44.01 u

(iii) ${CH}_{4}$ :

The molecular mass of methane, ${CH}_{4}$
= (1 × Atomic mass of carbon) + (4 × Atomic mass of hydrogen)
= [1(12.011 u) + 4 (1.008 u)]

= 16.043 u