Question

At 473 K, equilibrium constant Kc for decomposition of phosphorus pentachloride, PCl₅ is 8.3 ×10^–3 . If decomposition is depicted as, 

PCl_{5 (g)} ⇌ PCl_3(g) + Cl_2(g) Δ_rH⁰ = 124.0 kJ mol^–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 

(i) more PCl₅ is added 

(ii) pressure is increased 

(iii) the temperature is increased ? 

Answer 1

(a) K_c=[PCl₃] [Cl₂] / [PCl₅]

(b) 120.48 

(c) (i) equilibrium will shift on RHS. 

(ii) equilibrium will shift on LHS. 

(iii) equilibrium will shift on RHS.