How do I determine the equilibrium concentration given Kc and the concentrations of component gases?
For a reaction in the form $\ce{ \mathit{a}\,A + \mathit{b}\,B &lt;=&gt; \mathit{c}\,C}$, the quilibrium constant $K_c$ is given by

$$K_c = \frac{[C]^c}{[A]^a[B]^b}$$

You might want to check yours.