What is the approximate molality of a 36.5 percent by mass hydrochloric acid solution?
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Answer and explanation
Correct answer: 15.75 mol kg−1
Use 100 g solution. It contains 36.5 g HCl and 63.5 g water. HCl moles = 36.5/36.5 = 1 mol, while solvent mass is 63.5 g = 0.0635 kg. Therefore molality = 1/0.0635 = 15.748 mol kg−1, approximately 15.75 mol kg−1. Molality uses water mass, not total solution mass or volume.
Frequently asked questions
What is the correct answer to this question?
15.75 mol kg−1
Why is this the correct answer?
Use 100 g solution. It contains 36.5 g HCl and 63.5 g water. HCl moles = 36.5/36.5 = 1 mol, while solvent mass is 63.5 g = 0.0635 kg. Therefore molality = 1/0.0635 = 15.748 mol kg−1, approximately 15.75 mol kg−1. Molality uses water mass, not total solution mass or volume.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Chapter 01: Solutions.
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