A solution has molality 2. If the mass of solvent is 250 g what are the moles of solute?
Answer and explanation
Correct answer: 0.50 mol
Molality is defined as moles of solute per kilogram of solvent, not per kilogram of solution. Convert the solvent mass: 250 g = 0.250 kg. Using moles of solute = molality × mass of solvent in kg gives n = 2 mol kg⁻¹ × 0.250 kg = 0.50 mol. Therefore option B is correct; using 250 directly would ignore the required kilogram conversion.
Frequently asked questions
What is the correct answer to this question?
0.50 mol
Why is this the correct answer?
Molality is defined as moles of solute per kilogram of solvent, not per kilogram of solution. Convert the solvent mass: 250 g = 0.250 kg. Using moles of solute = molality × mass of solvent in kg gives n = 2 mol kg⁻¹ × 0.250 kg = 0.50 mol. Therefore option B is correct; using 250 directly would ignore the required kilogram conversion.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Some Basic Concepts of Chemistry. Topic: Mole concept and molar mass.
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