The limiting reagent is the reactant that is completely consumed first, thereby determining the maximum yield of product. The balanced equation (\text{N}_2 + 3\text{H}_2 \rightarrow 2\text{NH}_3) shows that 1 mol of (\text{N}_2) reacts with 3 mol of (\text{H}_2). Stoichiometric check: to consume 2 mol of (\text{N}_2), we need (2 \times 3 = 6) mol of (\text{H}_2). But only 3 mol of (\text{H}_2) is available, which is only enough to react with (3/3 = 1) mol of (\text{N}_2). Hence (\text{H}_2) is exhausted first and is the limiting reagent. (\text{N}_2) is incorrect because 1 mol of (\text{N}_2) remains unreacted after all (\text{H}_2) is consumed. (\text{NH}_3) is a product, not a reagent, so it cannot be the limiting reagent. Both cannot be limiting simultaneously in a standard stoichiometric scenario. This is a fundamental NCERT concept on limiting reagents in chemical reactions. Plausibility check: only (2 \times (3/6) = 1) mol (\text{N}_2) is consumed and (2 \times 1 = 2) mol (\text{NH}_3) is produced, confirming (\text{H}_2) is consumed first.