Step 1: Understanding the Concept:
A solution that obeys Raoult's law strictly over the entire range of concentration is called an ideal solution. In an ideal solution, the intermolecular attractive forces between the solute and solvent molecules (A-B interaction) are nearly equal to those between the pure components (A-A and B-B interactions).
Step 2: Key Formula or Approach:
Identify the nature of intermolecular forces in each mixture. Mixtures of structurally similar and non-polar compounds typically form ideal solutions.
Step 3: Detailed Explanation:
Let's analyze the given liquid mixtures:
- (A) Chloroform + acetone: They form strong hydrogen bonds between them (\(\text{Cl}_3\text{C-H}\) ... \(\text{O=C(CH}_3\text{)}_2\)), making A-B interactions stronger than A-A or B-B. This leads to a negative deviation from Raoult's law.
- (B) Carbon disulfide + acetone: Dipole-dipole interactions between acetone molecules are broken by the non-polar \(\text{CS}_2\) molecules. Thus, A-B interactions are weaker, leading to a positive deviation.
- (C) Benzene + toluene: Both are structurally similar, non-polar aromatic hydrocarbons. The intermolecular forces in pure benzene, pure toluene, and the mixture are almost identical (weak van der Waals forces). Therefore, it behaves as an ideal solution and obeys Raoult's law.
- (D) Ethanol + acetone: Ethanol molecules are strongly hydrogen-bonded. Addition of acetone breaks some of these bonds, making A-B interactions weaker than A-A. This results in a positive deviation.
Step 4: Final Answer:
The mixture of Benzene and Toluene forms an ideal solution.