As the solute dissolved into a liquid increases, the boiling point ____________.

As the solute dissolved into a liquid increases, the boiling point ____________.

• A. Decreases
• B. Increases
• C. Stays the same
• D. Fluctuates

Answer: (B)

When a nonvolatile solute is dissolved in a liquid, the boiling point rises. This happens because adding solute lowers the solvent’s vapor pressure—the dissolved particles interfere with the solvent molecules’ ability to escape into the gas phase. Boiling occurs when the vapor pressure of the liquid matches the external pressure, so you must heat the mixture to a higher temperature to reach that point. The bigger the amount of dissolved particles (higher molality and, for electrolytes, a larger van’t Hoff factor), the greater the boiling-point elevation. In formula terms, ΔTb = iKb m, so more particles or a larger i gives a larger increase.

When a nonvolatile solute is dissolved in a liquid, the boiling point rises. This happens because adding solute lowers the solvent’s vapor pressure—the dissolved particles interfere with the solvent molecules’ ability to escape into the gas phase. Boiling occurs when the vapor pressure of the liquid matches the external pressure, so you must heat the mixture to a higher temperature to reach that point. The bigger the amount of dissolved particles (higher molality and, for electrolytes, a larger van’t Hoff factor), the greater the boiling-point elevation. In formula terms, ΔTb = iKb m, so more particles or a larger i gives a larger increase.