Practice question
Question
A solution contains 15 ppm of CHCl₃ by mass in water. What is its molality? (Molar mass: CHCl₃ = 119.5 g/mol)
Explanation
15 ppm = 15 g CHCl₃ in 10⁶ g water. Moles = 15/119.5 ≈ 0.1255 mol. Mass of solvent = 1000 kg. Molality = 0.1255/1000 ≈ 1.255 × 10⁻⁴ m.