Answer
The correct answer is (a) 120 mL
Work Step by Step
1. Find the excess/limiting reactants
$\frac{180 mL}{3} = 60 mL$
$\frac{60 mL}{1 } = 60 mL$
They have stoichiometric equivalence, so it does not matter which one we use to find the amount of product.
2.
$$\frac{180 mL \ H_2}{3} \times {2} = 120 \ mL \ NH_3$$
