Practice question

MCQ

Question

A solution contains 20 ppm of MgCl₂ by mass in water. What is its molality? (Molar mass: MgCl₂ = 95 g/mol)

Options

Choose one · Correct answer highlighted

2.0 × 10⁻⁴ m 2.5 × 10⁻⁴ m 2.105 × 10⁻⁴ m Correct 1.5 × 10⁻⁴ m

Explanation

20 ppm = 20 g MgCl₂ in 10⁶ g water. Moles = 20/95 ≈ 0.2105 mol. Mass of solvent = 1000 kg. Molality = 0.2105/1000 ≈ 2.105 × 10⁻⁴ m.

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