At `473 K`, equilibrium constant `K_(c)` for decomposition of phosphorus pentachloride, `PCl_(5)` is `8.3 xx 10^(-3)` . If decomposition is depicted as,
`PCl_(5)(g) hArr Pcl_(3)(g) + Cl_(2) , Delta_(r)H^(ɵ) = 124.0 kJ "mol"^(-1)`
a) write an expression for `K_(c)` for the reaction.
b) what is the value of `K_(c)` for the reverse reaction at the same temperature ?
c) what would be the effect on `K_(c)` if (i) more `PCl_(5)` is added (ii) pressure is increased (iii) the temperature is increased ?

Explanation

`K_(c )=([PCl_(3)(g)][Cl_(2)(g)])/([PCl_(5)(g)])`
b. `K'=1/K_(c )=1/(8.3xx10^(-3))=120.48`
c. i. No effect as `K_(c )` is constant at constant temperature.
ii. No effect
iii. As given reaction is endothermic, on increasing the temperature, `k_(f)` will increase. As `K_(c )=K_(f)/K_(b), K_(c )` will increase with increase of temperature.