A 0.067 mol sample of formaldehyde vapor, CH₂O, was placed in a heated 500 mL vessel and some of it decomposed. The reaction is CH₂O(g) ⇌ H₂(g) + CO(g). At equilibrium, the CH₂O(g) concentration was 0.034 mol L⁻¹. Calculate the value of Kc for this reaction.