We’re given the following balanced reaction:
6 Na(s) + N2(g) → 2 Na3N(s)
Part A: We’re being asked to calculate the mass of sodium nitride, Na3N, that will be formed in the reaction of 80.0 g Na and 20.0 g N2.
Notice that we are given the mass of both reactants: this means we need to determine the limiting reactant, which is the reactant that forms the less amount of product.
This is because once the limiting reactant is all used up, the reaction can no longer proceed and make more products.
This means the limiting reactant determines the maximum mass of the product formed.