Ammonia rapidly reacts with hydrogen chloride making ammoniu

Ammonia rapidly reacts with hydrogen chloride, making ammonium chloride. Calculate the number of grams of excess reactant when 4.06 g of NH3 reacts with 4.01 g of HCl.

Solution

The balanced equation is

NH3 + HCl -----> NH4Cl

number of moles of NH3 = 4.06 g / 17.031 g/mol = 0.238 mole

number of moles of HCl = 4.01 g / 36.46 g/mol = 0.110 mole

from the balanced equation we can say that

1 mole of HCl requires 1 mole of NH3 so

0.110 mole of HCl will require 0.110 mole of NH3

but we have 0.238 mole of NH3 which is in excess and NH3 is the limiting reactant

number of moles of excess reactant left = 0.238 - 0.110 = 0.128 mole

mass of 1 mole of NH3 = 17.031 g so

the mass of 0.128 mole of NH3 = 2.18 g

Therefore, the mass of NH3 produced would be 2.18 g