Ncert Exercises & Solutions

If 1 g of each of the following gases are taken at STP, which of the gases will occupy (a) greatest volume and (b) smallest volume?

$CO, H_{2} O, {CH}_{4}, NO$

From Avogadro's law, we know that

Volume of 1 mole of the gas = gram molecular mass = 22.4 L at STP

Volume occupied by 28 g CO (1 mol CO) = 22.4 L at STP

(∴ Molar mass of CO = 12 + 16 = 28 g {mol}^{- 1})

∴

Volume occupied by 1 g CO

= \frac{22.4}{28} L at STP

Similarly, volume occupied by 1 g

H_{2} O = \frac{22.4}{18} L at STP

(∵ Molar mass of H_{2} O = (2 \times 1) + 16 = 18 g {mol}^{- 1})

Volume occupied by 1 g

{CH}_{4} = \frac{22.4}{16} L at STP

(∵ Molar mass of {CH}_{4} = 12 + (4 \times 1) = 16 g {mol}^{- 1})

Volume occupied by 1 g

NO = \frac{22.4}{30} L at STP

(∵ Molar mass of NO = 14 + 16 = 30 g {mol}^{- 1})

Thus, 1 g

{CH}_{4}

will occupy maximum volume while 1 g of NO will occupy minimum volume at STP.