If 1 gram of each of the following gases

Molar volume of a gas is volume occupied by 1 mole of gas at STP $(273.15$ $\mathrm{K}$ and 1 bar pressure) and is equal to $22700 \mathrm{~mL}$

$28 \mathrm{~g}$ of $\mathrm{CO}$ occupy volume $=22700 \mathrm{~mL}$

$\therefore 1 \mathrm{~g}$ of CO occupies volume $=\frac{22700}{28} \mathrm{~mL}$ at STP

Similarly,

$1 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{O}$ occupies volume $=\frac{22700}{18} \mathrm{~mL}$ at STP

$1 \mathrm{~g}$ of $\mathrm{CH}_{4}$ occupies volume $=\frac{22700}{16} \mathrm{~mL}$ at STP

$1 \mathrm{~g}$ of $\mathrm{NO}$ occupies volume $=\frac{22700}{30} \mathrm{~mL}$ at STP

(a) $\mathrm{CH}_{4}$ occupies greatest volume.

(b) NO occupies smallest volume.