Question

At 20°C, an aqueous solution that is 24.0% by mass in ammonium chloride has a density of 1.0674 g/mL. The formula weight of NH4Cl is 53.50 g/mol. The density of pure water at 20°C is 0.9982 g/mL. Calculate the concentration of the ammonium chloride solution in the units indicated below. SHOW ALL WORK including equations in symbols and dimensional analysis. Use the correct abbreviation for each concentration and units on all numbers. Final check each answer. Hint: assume a convenient mass of solution (like 100.0g).

Molarity (M):

Molality (m):

Mole fraction: Parts per million (by mass):

Answer 1

Let the mass of the solution = 100 gm

So, the mass of NH₄Cl = 24% of 100gm = 24 gm

Mass of water = 100gm – 24gm = 76 gm

Moles of NH₄Cl   

Moles of H₂O  

Density of solution = 1.0674 gm/mL

Volume of solution   

a) Molarity

b) Molality

c) Mole fraction =

d) ppm by mass =