A portion of 1 molal solution containing 1 kg solvent is mixed with a portion of 2 molal solution containing 0.5 kg solvent. What is the final molality?
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Answer and explanation
Correct answer: 1.33 mol kg⁻¹
Molality is moles of solute divided by kilograms of solvent. The first portion contains 1 × 1 = 1 mol solute, while the second contains 2 × 0.5 = 1 mol. Thus, total solute is 2 mol and total solvent is 1 + 0.5 = 1.5 kg. Final molality is 2/1.5 = 1.33 mol kg⁻¹. The solvent masses, not solution masses, are added.
Frequently asked questions
What is the correct answer to this question?
1.33 mol kg⁻¹
Why is this the correct answer?
Molality is moles of solute divided by kilograms of solvent. The first portion contains 1 × 1 = 1 mol solute, while the second contains 2 × 0.5 = 1 mol. Thus, total solute is 2 mol and total solvent is 1 + 0.5 = 1.5 kg. Final molality is 2/1.5 = 1.33 mol kg⁻¹. The solvent masses, not solution masses, are added.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Chapter 01: Solutions.
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