Question

For the reaction H2(g) + 12(g) = 2HI(g), Kc = 50.2 at 445°C. If
[H2] = [12] = [HI] = 1.75 x 10-3 Mat 445°C, which of the
following is true based on the above?

Answer 1

Qc < Kc, the reaction proceeds from left to right to reach equilibrium

Further explanation

Given

K = 50.2 at 445°C

[H2] = [I2] = [HI] = 1.75 × 10⁻³ M At 445ºC

Reaction

H2(g) + I2(g) ⇔2HI(g)

Required

Qc

Solution

Qc for the reaction

$\tt Qc=\dfrac{[HI]^2}{[I_2][H_2]}\\\\Qc=\dfrac{(1.75.10^{-3})^2}{1.75.10^{-3}\times 1.75\.10^{-3}}=1$  

Qc < Kc ⇒ reaction from left(reactants) to right (products) (the reaction will shift on the right) until it reaches equilibrium (Qc = Kc)