2.56 g of  ${\mathrm{S}}_8\left(\mathrm{s}\right)$ is taken which vapourises and when equilibrium gets established between ${\mathrm{S}}_8\left(\mathrm{s}\right)$ and S(g) then the vapours were found to occupy 960 ml at $1 \mathrm{atm}$ and 273 K. The fraction of S8 (s) undissociated s given by: