The molar mass of NH3 is 17.03 g/mol. The molar mass of H2 is 2.0158 g/mol. In a particular reaction, 0.575 g of NH3 forms. What is the mass, in grams, of H2 that must have reacted, to the correct number of significant figures?

The balanced chemical reaction is:

N2 + 3H2 = 2NH3

We are given the amount of ammonia formed from the reaction. This is where we start our calculations.

0.575 g NH3 (1 mol NH3 / 17.03 g NH3) (3 mol H2 / 2 mol NH3) (2.02 g H2 / 1 mol H2) = 0.10 g H2