A 1.000 L vessel is filled with 2.000 moles of N2, 1.000 mole of H2, and 2.000 moles of NH3. When the reaction N2(g) + 3 H2(g) ?? 2 NH3(g) comes to equilibrium, it is observed that the concentration of H2 is 2.15 moles/L. What is the numerical value of the equilibrium con- stant Kc?