Ordinary white phosphorus ${\mathrm{P}}_4$ forms a vapour and dissociates into diatomic molecules at high temperature as : ${\mathrm{P}}_4\left(g\right)\rightleftharpoons 2{\mathrm{P}}_9\left(g\right)$
A sample of white phosphorous, when heated to $1000\mathrm{K}$, formed a mixture at equilibrium having a total pressure of $16 \mathrm{atm}$ and a density of $18.6$ $\mathrm{g}/\mathrm{litre}$. Use this information to evaluate ${\mathrm{K}}_{\mathrm{P}}$ for the above reaction [Use : $R=0.08$ atm-litre/K-mole]