At a certain temperature, only 50% HI is dissociated into H 2 and I 2 at equilibrium. The equilibrium constant is :

Step-by-step solution

2 H I g ⇌ H 2 g + I 2 g Moles 1 - α α 2 α 2 Concentration 1 - α V α 2V α 2V K C = H 2 I 2 H I 2 = α 2V α 2V 1 - α V 2 ∴ α = 0.50 α 2 = 0.25 = α 2 4 1 - α 2 = 0 .50 × 0 .50 4 ×0.50 × 0 .50 = 1 4 K C = 0.25