33
QuizMultiple Choice

N/A — Exam

Question 33 • Chemistry

Which statement explains why an increase in molality increases the boiling point of a solution?

Answer
A
The addition of solute increases the solvent’s ability to boil.
B
The addition of solute increases the solvent’s vapor pressure. A higher temperature must then be applied to overcome the change.
C
The solute’s molecules repel the solvent’s molecules, giving them higher binding energy and hence the need for higher temperature.
D
The addition of solute decreases the solvent’s vapor pressure. A higher temperature must then be applied to overcome the change.

Explanation

Adding more dissolved solute lowers the solvent’s vapor pressure. A liquid boils when its vapor pressure equals the surrounding pressure, so the solution must be heated to a higher temperature to reach that point. Thus, increasing molality raises the boiling point because the solute decreases the solvent’s vapor pressure.

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