molarity is defined as the number of moles of solute in volume of 1 L solution.
The molarity of solution to be prepared is 4.5 M
the volume of solution to be prepared is 1 L
therefore number of moles in 1 L - 4.5 mol
mass of NH₄Cl required - 4.5 mol x 53.5 g/mol = 240.8 g
A mass of 240.8 g of NH₄Cl is required to make a solution of 4.5 M