Question

When common salt is dissolved in water –

• A. Melting point of the solution increases
• B. Boiling point of the solution increases
• C. Boiling point of the solution decreases
• D. Both melting point and boiling point decreases

Answer 1

The correct option is B

Boiling point of the solution increases

In vapor pressure terms, a liquid boils at the temperature when its vapor pressure equals the surrounding pressure. For the solvent, the presence of the solute decreases its vapor pressure by dilution. A non-volatile solute has a vapor pressure of zero, so the vapor pressure of the solution is less than the vapor pressure of the solvent. Thus, a higher temperature is needed for the vapor pressure to reach the surrounding pressure, and the boiling point is elevated.