N2 (g) + 3H2 (g) <-> 2NH3 (g) is a reversible reaction. At equilibrium, a 0.5 L flask contains 0.25 moles of H2, 0.48 moles of N2, and 0.18 moles of NH3. What is the Key for this reaction? Answer choices: 2.4 x 10^-4 4.3 1.1 0.90