## Chemistry (4th Edition)

$$K_c = \frac{[Products]}{[Reactants]}$$ Since there are 2 CO and 2 $CO_2$ in the balanced equation, both their concentrations are going to appear in the Kc expression to the power of 2. $$K_c = \frac{[CO_2]^2}{[CO]^2[O_2]}$$