At 473K, equilibrium constant K_c for decomposition of phosphorus pentachloride, PCl_5 is 8.3 xx10^(-3). If decomposition is depicted as, PCl_(5(g))hArr PCl_(3(g)) + Cl_(2(g)) ,Delta_r H^ө=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 ?

At 473K, equilibrium constant K_c for decomposition of phosphorus pent

1.	At 473K, equilibrium constant K_c for decomposition of phosphorus pentachloride, PCl_5 is 8.3 xx10^(-3). If decomposition is depicted as, PCl_(5(g))hArr PCl_(3(g)) + Cl_(2(g)) ,Delta_r H^ө=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 ?
Answer» Solution :(a)`K_c` for REACTION : `K_c=([PCl_3][Cl_2])/([PCl_5])` (b)`K._c` for reverse reaction =`1/(K_c " FORWARD reaction")` `therefore K._c= 1/(8.3xx10^(-3))`=120.48 (C) Effecton `K_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 increases.