Question

Take the reaction: NH3 + O2 NO + H2O. In an experiment, 3.25 g of NH3 are allowed to react with 3.50 g of O2. Which reactant is the limiting reagent

Answer 1

The balanced chemical reaction is as follows:

2NH3 + 5/2O2 ----> 2NO + 3H2O

We are given the amount of the reactants to be used in the experiment. We use these values to determine the limiting reactant. We calculate as follows:

3.25 g NH3 ( 1 mol / 17.04 g ) = 0.191 mol NH3
3.50 g O2 ( 1 mol / 32 g ) = 0.109 mol O2

If we have 0.191 mol NH3, then to be able to react completely we need 0.23875 mol of O2. As we can see, O2 is not enough. Therefore O2 would be the limiting reactant since it is all being used up in the reaction.