If the molality of a dilute solution is doubled, what happens to the elevation of boiling point?

The correct option is It doubles.

Explanation

The elevation of boiling point (ΔT_b) is a colligative property, meaning it depends on the number of solute particles in a given amount of solvent rather than the nature of the solute. For dilute solutions, the elevation in boiling point is directly proportional to the molal concentration (molality) of the solution.

Analysis

The relationship between the elevation of boiling point and molality is expressed by the equation:

ΔT_b = K_b × m

Where:

• ΔT_b is the elevation in boiling point.
• K_b is the molal boiling point elevation constant (Ebullioscopic constant), which is specific to the solvent.
• m is the molality of the solution.

Since ΔT_b is linearly proportional to m, if the molality is doubled (becomes 2m), the elevation of boiling point also doubles.

Key Takeaway: In dilute solutions, colligative properties such as boiling point elevation exhibit a linear relationship with the molality of the solute.