What is the approximate mole fraction of acid in a 36.5% by mass hydrochloric acid solution?
Answer and explanation
Correct answer: 0.221
Take 100 g of solution. It contains 36.5 g HCl, equal to 36.5/36.5 = 1 mol, and 63.5 g water, equal to 63.5/18 ≈ 3.528 mol. Total moles are 1 + 3.528 = 4.528 mol. Therefore, the HCl mole fraction is 1/4.528 ≈ 0.221, so B is correct. The value 0.365 is the mass fraction, not the mole fraction, and 0.635 is the water mass fraction.
Frequently asked questions
What is the correct answer to this question?
0.221
Why is this the correct answer?
Take 100 g of solution. It contains 36.5 g HCl, equal to 36.5/36.5 = 1 mol, and 63.5 g water, equal to 63.5/18 ≈ 3.528 mol. Total moles are 1 + 3.528 = 4.528 mol. Therefore, the HCl mole fraction is 1/4.528 ≈ 0.221, so B is correct. The value 0.365 is the mass fraction, not the mole fraction, and 0.635 is the water mass fraction.
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.
