Iron and oxygen react to form iron(III) oxide; 4Fe(s)+3O2(g)-->2Fe2O3(s). Determine the limiting reactant in each of the following mixtures of reactants: a) 2.0 mol of Fe and 6.0 mol of O2. b) 5.0 mol of Fe and 4.0 mol of O2. c) 16.0 mol of Fe and 20.0 mol of O2.