To determine the limiting reactant, we need to compare the moles of each reactant to their stoichiometric coefficients in the balanced chemical equation. The balanced equation for the reaction between nitrogen gas (N2) and hydrogen gas (H2) to form ammonia (NH3) is:
N2(g) + 3H2(g) -> 2NH3(g)
From the equation, we can see that the stoichiometric ratio between N2 and H2 is 1:3. This means that for every 1 mole of N2, we need 3 moles of H2 to react completely.
Given that there are 3 moles of N2 and 6 moles of H2, let's calculate the moles of H2 needed to react with 3 moles of N2:
Moles of H2 needed = 3 moles of N2 × (3 moles of H2 / 1 mole of N2) = 9 moles of H2
Since we only have 6 moles of H2 available, which is less than the 9 moles required, the limiting reactant is H2 (hydrogen gas). This means that N2 is in excess, and some of it will remain unreacted after the reaction is complete.