10.0 mol of ammonia gas is injected into a 4.0 L container. At equilibrium, 1.2 mol of nitrogen gas is found in the container. The number of moles of ammonia gas left in the container must be which of the following? N2(g) + 3H2(g) ⇌ 2NH3(g)
A. 8.8 mol
B. 2.4 mol
C. 7.6 mol
D. 6.4 mol
E. 9.2 mol