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

(a)`K_c=([PCl_3][Cl_2])/([PCl_5])`
(b)`K_c` (reverse) =`1/(8.3xx10^(-3))`=120.48
(c ) (i)No effect because `K_c` is constant at a given temperature
(ii) No effect
(iii) increases. Since reaction is endothermic, on increasing temperature, `k_f` will increase so that `K_c=k_f//k_b` will also increase.