What is the approximate mass percent of urea in a 0.5 molal aqueous urea solution?
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Answer and explanation
Correct answer: 2.91 percent
Use 1 kg water as the basis because molality is 0.5 mol kg−1. The solution contains 0.5 mol urea. With molar mass about 60 g mol−1, urea mass is 30 g. Total solution mass is 1000 + 30 = 1030 g. Therefore mass percent = (30/1030) × 100 = 2.91% approximately. The denominator must be total solution mass.
Frequently asked questions
What is the correct answer to this question?
2.91 percent
Why is this the correct answer?
Use 1 kg water as the basis because molality is 0.5 mol kg−1. The solution contains 0.5 mol urea. With molar mass about 60 g mol−1, urea mass is 30 g. Total solution mass is 1000 + 30 = 1030 g. Therefore mass percent = (30/1030) × 100 = 2.91% approximately. The denominator must be total solution mass.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Chapter 01: Solutions.
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