Raoulttörvény

Raoults law, formulated by French chemist François-Marie Raoult in 1887, describes the vapor pressure of a solution. It states that the partial vapor pressure of each component in an ideal solution is directly proportional to the mole fraction of that component in the solution. Mathematically, this can be expressed as P_i = x_i * P_i°, where P_i is the partial vapor pressure of component i, x_i is its mole fraction, and P_i° is the vapor pressure of the pure component i at the same temperature.

This law is particularly applicable to ideal solutions, which are theoretical mixtures where the interactions between different molecules are similar to the interactions between identical molecules. In such solutions, the components do not exhibit any significant attractive or repulsive forces beyond those present in the pure substances. For non-ideal solutions, deviations from Raoult's law occur due to differing intermolecular forces between the solute and solvent.

When a non-volatile solute is dissolved in a solvent, Raoult's law predicts that the vapor pressure of the solution will be lower than that of the pure solvent. This reduction in vapor pressure is a colligative property, meaning it depends on the number of solute particles rather than their identity. This phenomenon is the basis for understanding boiling point elevation and freezing point depression, other colligative properties that are directly related to the decrease in vapor pressure.