How many grams of hydrogen gas are needed to completely react with excess nitrogen to produce 26.7 grams of ammonia (NH3)? N2 + H2 → NH3

4.74 g H2

Explanation:

First, balance your reaction:

N2 + 3H2 --> 2NH3

Now convert 26.7 g NH3 to moles NH3 by dividing by its molar mass (17.031 g/mol). Then multiply by the mole ratio of 3 mol H2 for every 2 mol NH3 to get moles of H2. Finally multiply by the molar mass of H2 (2.016 g/mol) to get grams of H2.

26.7 g NH3 • (1 mol NH3 / 17.031 g NH3) • (3 mol H2 / 2 mol NH3) • (2.016 g H2 / 1 mol H2) = 4.74 g H2