Final answer:
The mass of ammonium chloride needed to prepare a 500.0 mL (0.5000 L) of a 0.198 M solution can be found by multiplying the number of moles (calculated from molarity and volume) by the molar mass of NH4Cl, resulting in 5.30 grams.
Step-by-step explanation:
To determine the mass of ammonium chloride in a 500.0 mL (or 0.5000 L) of a 0.198 M solution, we must use the formula for molarity (M), which is the number of moles of solute divided by the volume of the solution in liters:
M = moles of solute / liters of solution
The molar mass of NH4Cl is 53.50 g/mol. To find the mass, we convert moles to grams using the molar mass:
Calculate the number of moles of NH4Cl using the molarity and volume of the solution:
Moles of NH4Cl = 0.198 moles/L × 0.5000 L = 0.099 moles
Convert the moles to mass:
Mass of NH4Cl = moles × molar mass = 0.099 moles × 53.50 g/mol = 5.30 g
Therefore, the mass of ammonium chloride needed is 5.30 grams.