When `PCl_(5)` is heated, it dissociates into `PCl_(3)` and `Cl_(2)`. The vapour density of the gas mixture at `200^(@)C` and at `250^(@)C` is `70` and `58`, respectively. Find the degree dissociation at two temperatures.

Explanation

`PCl_(5)(g) hArr PCl_(3)(g)+Cl_(2)(g)`

Total moles `=1+x`. Using the result `=[(d_(0))/(d_(m))=(1+x)/(1)]d_(0)=` density of `PCl_(5)`
At `T=200^(@)C`
`rArr (d_(0))/(d_(m))=(V.D._(PCl_(5)))/(V.D._("Mix"))=(M_(0)//2)/(70)=(1+x)/(1)=(208.5//2)/(70)=1+x rArr x=0.49`
At `T=250^(@)C`
`(d_(0))/(d_(m))=(V.D._(PCl_(5)))/(V.D._("Mix"))=(M_(0)//2)/(58)=(1+x)/(1)=(208.5//2)/(58)=1+x rArr x=0.80`