In a solution the mole fraction of solute is 0.25. If molar mass of solute is 60 and solvent is water what is the approximate mass percent of solute?
Answer and explanation
Correct answer: 52.6 percent
Mole fraction is based on the ratio of solute moles to total moles. Assume 1 mol total solution: solute = 0.25 mol and water = 0.75 mol. Solute mass = 0.25 × 60 = 15 g; water mass = 0.75 × 18 = 13.5 g. Total mass = 28.5 g. Therefore mass percent = (15/28.5) × 100 ≈ 52.6%, so option C is correct. Treating mole fraction as mass fraction would incorrectly suggest 25%.
Frequently asked questions
What is the correct answer to this question?
52.6 percent
Why is this the correct answer?
Mole fraction is based on the ratio of solute moles to total moles. Assume 1 mol total solution: solute = 0.25 mol and water = 0.75 mol. Solute mass = 0.25 × 60 = 15 g; water mass = 0.75 × 18 = 13.5 g. Total mass = 28.5 g. Therefore mass percent = (15/28.5) × 100 ≈ 52.6%, so option C is correct. Treating mole fraction as mass fraction would incorrectly suggest 25%.
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.
