Question

In which of the following equilibria, K_p and K_c are not equal?

Options

• \[\ce{CO_{(g)} + H2O_{(g)} <=> CO2_{(g)} + H2_{(g)}}\]

• \[\ce{2BrCl_{(g)} <=> Br2_{(g)} + Cl2_{(g)}}\]

• \[\ce{PCl5_{(g)} <=> PCl3_{(g)} + Cl2_{(g)}}\]

• \[\ce{H2_{(g)} + I2_{(g)} <=> 2HI_{(g)}}\]

Answer 1

\[\ce{PCl5_{(g)} <=> PCl3_{(g)} + Cl2_{(g)}}\]

Explanation:

K_p = K_c (RT)^Δn_g

If Δn_g = 0. Then K_p = K_c

(1) Δn_g = 2 − 2 = 0

(2) Δn_g = 2 − 2 = 0

(3) Δn_g = 2 − 1 = 1

(4) Δn_g =2 − 2 = 0

Hence, K_p and K_c are not equal in reaction (3).