The molecular mass of PCl5 is 208.32 but when heated to 230∘C, it is reduced to 124. The extent of dissociation of PCl5 at this tempearature will be
6.8%
46%
64%
68%
α=(M−Me)Me(y−1)=208.32−124124×(2−1)=0.68 y=2 for PCl5⇌PCl3+Cl2