Question

Which of the following does not show positive deviation from Raoult's law?
(A) Phenol-aniline
(B) Ethanol-acetone
(C) Acetone-carbon disulphide
(D) Methanol-water

Answer 1

Hint: Raoult's law was termed because of François-Marie Raoult, a French pharmacist who discovered, while conducting an experiment, that when chemicals were combined in a solution, the solution's vapour pressure reduced concurrently. Raoult's law, which was developed in 1887, is also known as the law of thermodynamics.

Complete Step by Step Solution:
Let’s discuss the positive and negative deviations one by one.
When the attractions between A-B are lower than the attraction average in the purest section of the mixture, there is a positive deviation from Raoult's law and the vapour pressure observed is larger than expected. For example, a combination of acetone and ethanol indicates a positive divergence from Rault's equation.

Negative divergence from the law of raoult indicates that when both liquids are combined, the total vapour pressure of the initial liquid is larger than the total vapour pressure of the solution. As an example, consider Nitric and Water Solution.

In the given question, we need to find out which of these given options does not show the positive deviation. Negative deviations from Raoult's law occur when the intermolecular attractive interactions between A-A and B-B are weaker than those between A-B, resulting in a drop in vapour pressure and negative deviations. A combination of aniline and phenol is an example of this kind.
Therefore, As a result, option A is right.

Note: In order to answer these problems, we must first grasp Raoult's law. In addition, we should have a clear understanding of the positive and negative deviations from Raoult's law.