The equilibrium constant only depends on the units of concentration in reaction b) COCl₂(g) ⇔ CO(g) + Cl₂(g). Therefore, b) COCl₂(g) ⇔ CO(g) + Cl₂(g) is correct .
The equilibrium constant depends on the units of concentration when the change in the stoichiometric coefficients of the reactants and products is not equal.
This is because the units of concentration are raised to the power of these stoichiometric coefficients in the expression for the equilibrium constant.
Let's analyze each reaction:
a) CO(g) + H₂O(g) ⇔ CO₂(g) + H₂(g)
The stoichiometric coefficients are all 1, so the change in these coefficients is 0 (1 - 1 + 1 - 1 = 0).
Therefore, the equilibrium constant does not depend on the units of concentration.
b) COCl₂(g) ⇔ CO(g) + Cl₂(g)
The stoichiometric coefficients change from 1 to 1 and 2, respectively (1 - 1 + 2 = 2).
Therefore, the equilibrium constant will have concentration raised to the power of 2, causing it to depend on the units of concentration.
c) NO(g) ⇔ 1/2N₂(g) + 1/2O₂(g)
The stoichiometric coefficient changes from 1 to 1/2 and 1/2, respectively (1 - 1/2 - 1/2 = 0).
Therefore, the equilibrium constant does not depend on the units of concentration.