______ states that for a solution of volatile liquids, the partial vapour pressure of each component of the solution is directly proportional to its mole fraction present in solution.

Raoult’s law

The correct answer is option 2. Raoult’s law.

Raoult's law describes the behavior of ideal solutions, particularly those involving volatile liquids. It states that the partial vapor pressure of each component in a solution is directly proportional to its mole fraction in that solution, assuming ideal behavior. Mathematically, Raoult's law can be expressed as follows:

\[ P_i = x_i \cdot P_{i}^{\text{pure}} \]

where:
\( P_i \) is the partial vapor pressure of component \(i\) in the solution,
\( x_i \) is the mole fraction of component \(i\) in the solution,
\( P_{i}^{\text{pure}} \) is the vapor pressure of pure component \(i\) (i.e., the vapor pressure of the pure substance when it is not in a mixture).

This law is applicable when the interactions between molecules of different components in the mixture are similar to those between molecules of the same component. In other words, it assumes that the intermolecular forces between different molecules are comparable.

Raoult's law is particularly valid for ideal solutions, which are mixtures that follow the behavior predicted by the law. It is essential to note that deviations from Raoult's law can occur in real solutions, especially when there are significant interactions or deviations from ideal behavior among the components.