forráspontemelkedést

Forráspontemelkedés is a colligative property of solutions. It describes the phenomenon where the boiling point of a pure solvent is increased when a non-volatile solute is dissolved in it. This effect is proportional to the molality of the solute. The greater the concentration of solute particles, the higher the boiling point of the solution.

The increase in boiling point, often denoted as $\Delta T_b$, can be calculated using the formula $\Delta T_b = K_b \cdot m \cdot i$, where $K_b$ is the ebullioscopic constant of the solvent, $m$ is the molality of the solution, and $i$ is the van't Hoff factor, which accounts for the number of particles the solute dissociates into in the solution. For non-electrolytes, $i$ is typically 1.

This property arises from the reduced vapor pressure of the solution compared to the pure solvent. The solute molecules occupy some of the surface area of the liquid, hindering the escape of solvent molecules into the gas phase. Consequently, a higher temperature is required to reach a vapor pressure equal to the external atmospheric pressure, which is the definition of the boiling point.

Forráspontemelkedés has practical applications, such as the use of antifreeze in car radiators. Ethylene glycol, the solute, lowers the freezing point and raises the boiling point of water, preventing the radiator fluid from freezing in cold weather and boiling over in hot weather. Another example is the addition of salt to water when cooking pasta, which slightly increases the boiling point of the water.