For the reaction: H₂(g) + I₂(g) ⇌ 2HI(g), the value of equilibrium constant is 9.0. The degree of di — Chemical Equilibrium Chemistry Question

💡 Solution & Explanation

The equilibrium constant for the reverse dissociation reaction (2HI ⇌ H₂ + I₂) is K' = 1/9. If α is the degree of dissociation of HI, K' = (α/2)² / (1-α)² = α² / 4(1-α)². Setting this to 1/9 yields α / 2(1-α) = 1/3 => 3α = 2 - 2α => 5α = 2 => α = 0.4. Therefore, correct answer is C.