Question

A 25.1 molal concentration of ammonia (NH3) in water has a density of 0.982 g/ml. What are the mass percent, molarity and mole concentration of ammonia in this solution.

Answer 1

Molality of the solution = 25.1 molal

This means 25.1 moles of NH3 are present in 1000 g water.

Molar mass of NH3 = 17 g/mol

Mass of NH3 = 17 * 25.1 = 426.7 g

Total mass of the solution = 1000 + 426.7 = 1426.7 g

Mass percent of ammonia in the solution = 426.7 / 1426.7 * 100

= 29.91 %

Density of solution = 0.982 g/ml

Volume of solution = Mass / Density

= 1426.7 / 0.982

= 1452.85 mL

= 1.45 L

Molarity of solution = 25.1 / 1.45

= 17.3 M

Mole concentration of ammonia = Moles of ammonia / Volume of solution

25.1 / 1.45

= 17.3 M