Among the following , select the pair that does not form an ideal solution

Options

A. Carbon tetrachloride and Silicon tetrachloride
B. Chlorobenzene and Bromobenzene
C. Chloroform and Carbon tetrachloride
D. Benzene and toluene

Answer

To determine which pair does not form an ideal solution, we need to analyze the interactions between the molecules in each pair and see if they obey Raoult's law. An ideal solution is formed when the interactions between the molecules of the different components are similar to the interactions between the molecules of each component.

### Step-by-Step Solution:

1. **Understand Ideal Solutions**:
- An ideal solution is one where the enthalpy of mixing is zero and the solution obeys Raoult's law. This occurs when the intermolecular forces between the components are similar.
- Raoult's law states that the partial vapor pressure of each component in a solution is equal to the vapor pressure of the pure component multiplied by its mole fraction in the solution.

2. **Analyze Each Pair**:
- **Option 1: Carbon Tetrachloride (CCl₄) and Silicon Tetrachloride (SiCl₄)**:
- Both compounds contain chlorine and are similar in structure. They have similar intermolecular forces (both are non-polar).
- **Conclusion**: This pair forms an ideal solution.

- **Option 2: Chlorobenzene (C₆H₅Cl) and Bromobenzene (C₆H₅Br)**:
- Both compounds are aromatic and have similar structures, differing only in the halogen atom (Cl vs. Br). Their intermolecular forces are similar.
- **Conclusion**: This pair forms an ideal solution.

- **Option 3: Chloroform (CHCl₃) and Carbon Tetrachloride (CCl₄)**:
- Chloroform is a polar molecule (due to the presence of hydrogen) and exhibits dipole-dipole interactions. Carbon tetrachloride is non-polar and exhibits London dispersion forces.
- The difference in polarity leads to different intermolecular forces.
- **Conclusion**: This pair does not form an ideal solution.

- **Option 4: Benzene (C₆H₆) and Toluene (C₆H₅CH₃)**:
- Both compounds are non-polar hydrocarbons and have similar structures. Their intermolecular forces are similar.
- **Conclusion**: This pair forms an ideal solution.

3. **Final Answer**:
- The pair that does not form an ideal solution is **Option 3: Chloroform (CHCl₃) and Carbon Tetrachloride (CCl₄)**.