At 473 K, equilibrium constant Kc for decomposition of phosphorus pentachloride, PCl5 is $$8.3 \times 10^{-3}$$. If decomposition is depicted as,

$$PCl_{5}(g) ⇌ PCl_{3}(g)+Cl_{2}(g)$$

rH° = 124.0 kJmol–1

(a) Write an expression for Kc for the reaction.

(b) What is the value of Kc for the reverse reaction at the same temperature?

(c) What would be the effect on Kc if

(ii) pressure is increased?

(iii) The temperature is increased?

Asked by Abhisek | 1 year ago |  77

##### Solution :-

(a) $$K_{c}=\dfrac{[PCl_{3}(g)][Cl_{2}(g)]}{[PCl_{3}(g)]}$$

(b) Value of Kc for the reverse reaction at the same temperature is:

$$K_{c}^{‘} = \dfrac{1}{K_{c}}\\ \\$$

$$=\dfrac{1}{8.3 \times 10^{-3}}$$

$$= 1.2048 \times 10^{2}\\ \\$$

$$=120.48$$

(c)

(i) Kc would remain the same because in this case, the temperature remains the same.

(ii) Kc is constant at a constant temperature. Thus, in this case, Kc would not change.

(iii) In an endothermic reaction, the value of Kc increases with an increase in temperature. Since the given reaction in an endothermic reaction, the value of Kc will increase if the temperature is increased.

Answered by Pragya Singh | 1 year ago

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