What is the approximate mole fraction of urea in a 0.5 molal aqueous urea solution?
Advertisement
Answer and explanation
Correct answer: 0.0089
A 0.5 molal solution has 0.5 mol urea in 1 kg water. The water contains approximately 1000/18 = 55.5 mol. Total moles are therefore 55.5 + 0.5 = 56.0 mol. The mole fraction of urea is 0.5/56.0 = 0.00893, or about 0.0089. A value such as 0.5 would confuse molality with mole fraction.
Frequently asked questions
What is the correct answer to this question?
0.0089
Why is this the correct answer?
A 0.5 molal solution has 0.5 mol urea in 1 kg water. The water contains approximately 1000/18 = 55.5 mol. Total moles are therefore 55.5 + 0.5 = 56.0 mol. The mole fraction of urea is 0.5/56.0 = 0.00893, or about 0.0089. A value such as 0.5 would confuse molality with mole fraction.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Chapter 01: Solutions.
Advertisement