In the reaction C(s) + CO2(g) ⇋ 2CO(g) the following amounts of substances were formed in 0.2 litre flask at equilibrium: C = 0.1 mole, CO = 0.05 mole and CO2=0.1 mole, CO = 0.05 mole and CO2=0.06 mole. The equilibrium constant is