When a solute dissolved in a solvent

A. Freezing pt incrases
B. Boiling pt increases
C. Vapor pressure increases
D. Concentration of the solvent
My answer is B.

If you are talking about a NON-VOLATILE SOLUTE you are right. It may or may not be true with a volatile solute and volatile solvent.

When a non-volatile solute dissolves in a volatile solvent, three things happen.
a. The vapor pressure of the solvent is lowered,
b. The boiling point of the solvent is raised,
c. The freezing point of the solvent is lowered.

The extent to which these three things happen depends SOLELY upon the number of dissolved particles.

Your answer is incorrect. When a solute dissolves in a solvent, it affects several properties of the solvent. One of these properties is the boiling point. However, it's worth noting that the boiling point can either increase or decrease depending on the nature of the solute and solvent.

To determine the correct answer, we need to consider the colligative properties of solutions. Colligative properties are properties that depend on the number of solute particles present in a solution, regardless of their chemical identity. The most significant colligative properties are freezing point depression, boiling point elevation, and vapor pressure lowering.

In the case of a solution, when a solute dissolves in a solvent:
A. The freezing point decreases: The presence of the solute particles disrupts the crystal lattice structure of the solvent, making it more difficult for it to freeze.
B. The boiling point increases: The solute particles occupy space in the solution, reducing the ability of the solvent molecules to escape into the gas phase, thus requiring a higher temperature to boil.
C. The vapor pressure decreases: The solute particles also hinder the evaporation of the solvent molecules, reducing the vapor pressure compared to pure solvent.
D. The concentration of the solvent remains the same: Concentration is not directly affected by dissolving a solute in a solvent.

Therefore, the correct answer is C. Vapor pressure decreases when a solute is dissolved in a solvent.