An ideal solution is formed when its constituents:

Options

A. are converted into ideal gases
B. have zero volume change
C. have zero heat of mixing
D. both (2) and (3) are correct

Answer

To answer the question "An ideal solution is formed when its constituents:", we need to analyze the options provided and understand the characteristics of an ideal solution.

### Step-by-Step Solution:

1. **Understanding Ideal Solutions**:
- An ideal solution is one that obeys Raoult's law, which states that the partial vapor pressure of each component in the solution is equal to the vapor pressure of the pure component multiplied by its mole fraction in the solution.
- Ideal solutions are typically formed by mixing substances that have similar molecular structures and interactions.

2. **Analyzing the Options**:
- **Option A**: "are converted into ideal gas" - This is incorrect. Ideal solutions do not require their components to behave as ideal gases.
- **Option B**: "have zero volume change" - This is correct. In an ideal solution, the volume before and after mixing remains the same, meaning there is no volume change.
- **Option C**: "have zero heat of mixing" - This is also correct. The enthalpy change (heat of mixing) for an ideal solution is zero, indicating that no heat is absorbed or released during the mixing process.
- **Option D**: "both B and C are correct" - Since both B and C are correct, this option is also correct.

3. **Conclusion**:
- The correct answer is **Option D**, which states that an ideal solution is formed when its constituents have both zero volume change and zero heat of mixing.

### Final Answer:
An ideal solution is formed when its constituents have both zero volume change and zero heat of mixing (Option D).

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