At room temperature the equilibrium constant Kc for the reaction: 2NO(g)=N2(g)+O2(g) is 1.4x10^30. In the atmosphere at room temp. the concentration of nitrogen gas is 0.33 mol/L and the concentration of oxygen gas is about 25% that value. Calculate the equilibrium concentration of nitrogen monoxide in the atmosphere.

Answer 1

initial:
NO = 0
N2 = 0.33
O2 = 0.33 x 0.25 = ??

change:
NO = 2x
N2 = -x
O2 = -x

equilibrium:
NO = 2x
N2 = 0.33-x = 0.33 since x is so small.
O2 = 0.0825-x = 0.0825 same reason.

Substitute into Kc expression and solve for x.
Post your work if you get stuck.