The volume occupied by the molecules contained in $4.5 \mathrm{kg}$ water at STP, if the intermolecular forces vanish away is

Molecular mass of water is $18 \mathrm{g} {\mathrm{mol}}^{-1}$

Therefore, number of moles in $4.5 \mathrm{kg}$ of water will be,

$n=\frac{4500}{18}=250$

Volume occupied by one mole of gas at STP is $22.4$ Litre

Therefore, volume occupied by $250 \mathrm{mol}$ of water will be

$V=22.4\times {10}^{-3}\times 250$

$\Rightarrow V=5.6 {\mathrm{m}}^3$