Answer to Question #133784 in General Chemistry for Rethabile Ndlovu

Question

At 700 K, Kc for the reaction H2(g) + I2(g) ⇌ 2HI(g) is 2.0 × 1019. What is Kc for HI(g) ⇌ 1/2H2(g) + 1/2I2(g)?

Answer 1

H₂(g) + I₂(g) ⇌ 2HI(g) (1)

HI(g) ⇌ 1/2H₂(g) + 1/2I₂(g) (2)

K_c(1) = [HI]² / [H₂][I₂]

K_c(2) = [H₂]^1/2[I₂]^1/2 / [HI]

Expressing K_c(2) by using K_c(1), we get

K_c(2) = (1/K_c(1))^1/2 = (1 / 2.0*10¹⁹)^1/2 = 2.2*10^-10

Answer: 2.2*10^-10