At `473 K`, equilibrium constant `K_(c )` for decomposition of phosphorus pentachloride, `PCl_(5)` is `8.3xx10^(-3)`. If decomposition is depicted as,
`PCl_(5)(g) hArr PCl_(3)(g)+Cl_(2)(g) Delta_(r)H^(Θ)=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.