the equation for the reaction is as follows;
NH₃ + HCl --> NH4Cl
one of the 2 reactants have been added in excess, to find out which reactant is in excess we need to find the number of moles of each reactant
NH₃ moles reacted - 6.01 g / 17 g/mol
= 0.35 mol
HCl moles reacted = 4.91 g / 36.5 g/mol
= 0.13 mol
the stoichiometry of NH₃ : HCl = 1:1
therefore the number of moles reacted should be equal, however NH₃ there are more moles than HCl which means that NH₃ has reacted in excess
the number of NH₃ moles that would have reacted = 0.13 mol
The mass of NH₃ reacted = 0.13 mol * 17 g/mol
= 2.21 g
the excess amount of reactant is = 6.01 g - 2.21 g
= 3.8 g
the answer is 3.8 g
