Explain qno.60 Ans(2):


60. 'a' moles of PCl₅ are heated in a closed container till equilibrium is established 
PCl₅(g) $\rightleftharpoons$PCl_​3(g) +Cl₂ (g)
at a pressure of P atm. If 'b' moles of PCl₅  dissociate at equilibrium, then 
$$\begin{gathered} \left(1\right) \frac{\mathrm{a}}{\mathrm{b}}=\frac{{\mathrm{K}}_{\mathrm{P}}}{{\mathrm{K}}_{\mathrm{P}}+\mathrm{P}} \left(2\right) \frac{\mathrm{a}}{\mathrm{b}}={\left(\frac{{\mathrm{K}}_{\mathrm{P}}+\mathrm{P}}{{\mathrm{K}}_{\mathrm{P}}}\right)}^{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.} \\ \left(3\right) \frac{\mathrm{a}}{\mathrm{b}}={\left[\frac{{\mathrm{K}}_{\mathrm{P}}}{{\mathrm{K}}_{\mathrm{P}}+\mathrm{P}}\right]}^{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.} \left(4\right) \frac{\mathrm{a}}{\mathrm{b}}=\left[\frac{{\mathrm{K}}_{\mathrm{P}}}{\mathrm{P}}\right] \end{gathered}$$