Consider the reaction between N2H4 and N2O4:
2N2H4(g)+N2O4(g)→3N2(g)+4H2O(g)
A reaction vessel initially contains 21.5 g N2H4 and 74.9 g of N2O4. Calculate the mass of N2H4 that will be in the reaction vessel once the reactants have reacted as much as possible. Assume 100 % yield.