Question

What is the equilibrium constant expression for the reaction below?
H2 (g) + I2 (g) → 2 HI(g)

Answer 1

Further explanation

Given

Reaction

H₂ (g) + I₂ (g) → 2HI(g)

Required

The equilibrium constant

Solution

The equilibrium constant is the value of the product in the equilibrium state of the substance in the right (product) divided by the substance in the left (reactant) with the exponents of each reaction coefficient

The equilibrium constant for reaction  

pA + qB ⇒ mC + nD  

$\large {\boxed {\bold {K ~ = ~ \frac {[C] ^ m [D] ^ n} {[A] ^ p [B] ^ q}}}}$

So for the above reaction :

$\tt K=\dfrac{[HI]^2}{[H_2][I_2]}$