N2 +O2 = 2NO has an equilibrium constant Keq of 0.10 mol/L @ 2000 degrees celcius. If the equilibrium concentration for NO is 0.40 mol/L and the equilibrium concentration for N2 is 0.80 mol/L, what is the equilibrium concentration of O2?

Write the Keq expression.

Substitute the equilibrium concentrations given. Solve for (O2). Post your work if you get stuck.