Answer
The product mixture will have 4 molecules of $NH_3$ and 4 molecules of $N_2$.
Work Step by Step
1. Determine the balanced chemical reaction:
$$N_2 + H_2 \longrightarrow NH_3$$$$N_2 + 3H_2 \longrightarrow 2NH_3$$
2. Count the amount of reactants;
6 $N_2$
6 $H_2$
3. Identify the limiting reactant.
6 $N_2$ would produce 12 $NH_3$
6 $H_2$ would produce 4 $NH_3$
Thus, $H_2$ is the limiting reactant.
4. As we saw in the last step, 4 molecules of $NH_3$ will be produced, which will consume 2 $N_2$ molecules.
6 - 2 = 4
There will remain 4 $N_2$ molecules in the container.
