It is found that in 11.2L at $0^{0}C$ and 1 atm, of any gaseous compound of ‘X’, there is never less than 15.5 gm of ‘X’. It is also found that 11.2 L of vapours of ‘X’ at $0^{o}C$and 1 atm, weighs 62 gm. The atomicity of ‘X’ is:

11.2L at $0^{o}C$ and 1 atm of compound $\Rightarrow \frac{1}{2}\text{mole}$ ‘X’ is always $\ge 15.5g$

$\therefore$In 1 mole, of compound of ‘X’ $\ge 31g$

$\therefore$ Atmoic weight of ‘X’=31

( $\because$ in one mole of compound of any element there should always be 1 mole of atoms of that element)

Also 11.2L of vapour of ‘X’ weighs $\Rightarrow 62g$

$(At{0}^{o}C,1atm)\left(\frac{1}{2}\text{mole}\right)$

$\therefore$Molecular weight of ‘X’ =124

Atomicity of ‘X’ $=\frac{124}{31}=4$