Vapour density of PCl5 is 104.16 but when heated at 230o C its vapour density is reduced to 62. The degree of dissociation of PCl5 at this temperature will be:
Initial C 0 0
At eq.C(1−α) Cα Cα
Total moles at equilibrium =C(1−α)+Cα+Cα=C(1+α)
For a reaction at equilibrium, Vapour density is inversely proportional to the number of moles.
Totalmoles of eq.initial total moles=vapour density initialvapour density ateq.
∴, α=68 %