A binary solution of two volatile liquids and denote the two components as 1 and 2. When taken in a closed vessel, both the components would evaporate and eventually an equilibrium would be established between vapour phase and the liquid phase. Let the total vapour pressure at this stage be p_total and p₁ and p₂ be the partial vapour pressures of the two components 1 and 2 respectively. These partial pressures are related to the mole fractions x₁ and x₂ of the two components 1 and 2 respectively. The French chemist, Francois Marte Raoult (1886) gave the quantitative relationship between them. The relationship is known as the Raoult’s law which 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.

Which will show negative deviation from Raoult's law?

ΔV_mix < 0

The correctanswer is 2: \( \Delta V_{\text{mix}} < 0 \)

When a solution deviates negatively from Raoult's law, it means that the observed behavior of the solution is different from what would be expected based on the ideal behavior described by Raoult's law. Negative deviation occurs when the interactions between unlike molecules are stronger than those predicted by Raoult's law. This leads to a decrease in the vapor pressure of the solution compared to what would be expected from the individual vapor pressures of the pure components.

One of the key indicators of negative deviation is a decrease in volume upon mixing. This means that the molecules in the mixture pack more closely together than expected. The negative value of \( \Delta V_{\text{mix}} \) indicates that the volume of the mixture is less than the sum of the individual volumes of the pure components.

Now, let's address the options:

1. \( \Delta V_{\text{mix}} > 0 \): This statement is not correct for negative deviation. Negative deviation is associated with a decrease in volume, so \( \Delta V_{\text{mix}} \) should be less than 0.

2. \( \Delta V_{\text{mix}} < 0 \): This statement is correct. Negative deviation is indeed associated with a decrease in volume upon mixing, and \( \Delta V_{\text{mix}} \) is less than 0.

3. \( \Delta V_{\text{mix}} \geq 0 \): This statement is broader than necessary. Negative deviation specifically implies \( \Delta V_{\text{mix}} < 0 \).

4. \( \Delta V_{\text{mix}} \leq 0 \): This statement is broader than necessary. Negative deviation specifically implies \( \Delta V_{\text{mix}} < 0 \).

Therefore, the correct answer is option 2: \( \Delta V_{\text{mix}} < 0 \). This indicates that a solution with negative deviation from Raoult's law experiences a decrease in volume upon mixing due to stronger-than-expected interactions between unlike molecules.