Which of the following pair of compounds is expected to exhibit same colour in aqueous solution?

Options

A. `FeCl_(3),CuCl_(2)`
B. `VOCl_(2),CuCl_(2)`
C. `CoCl_(2),FeCl_(2)`
D. `FeCl_(2),MnCl_(2)`

Explanation

To determine which pair of compounds is expected to exhibit the same color in aqueous solution, we need to analyze the electronic configurations of the transition metal ions in each pair and count their unpaired electrons. The presence of unpaired electrons is crucial because the color of transition metal complexes arises from d-d transitions, which occur when electrons are excited from lower to higher energy levels.

### Step-by-Step Solution:

1. **Identify the Compounds and Their Oxidation States**:
- The pairs given are:
1. FeCl3 and CuCl2
2. VOCl2 and CuCl2
3. CoCl2 and FeCl2
4. FeCl2 and MnCl2

2. **Determine the Electronic Configuration of Each Ion**:
- **FeCl3**: Iron (Fe) is in +3 oxidation state.
- Electronic configuration: [Ar] 3d5 4s0 (5 unpaired electrons)
- **CuCl2**: Copper (Cu) is in +2 oxidation state.
- Electronic configuration: [Ar] 3d9 4s0 (1 unpaired electron)

3. **Count Unpaired Electrons**:
- FeCl3 has 5 unpaired electrons.
- CuCl2 has 1 unpaired electron.
- **Conclusion**: They do not exhibit the same color.

4. **Next Pair: VOCl2 and CuCl2**:
- **VOCl2**: Vanadium (V) is in +4 oxidation state.
- Electronic configuration: [Ar] 3d1 4s0 (1 unpaired electron)
- **CuCl2**: As calculated earlier, has 1 unpaired electron.
- **Conclusion**: Both have 1 unpaired electron and will exhibit the same color.

5. **Next Pair: CoCl2 and FeCl2**:
- **CoCl2**: Cobalt (Co) is in +2 oxidation state.
- Electronic configuration: [Ar] 3d7 4s0 (3 unpaired electrons)
- **FeCl2**: Iron (Fe) is in +2 oxidation state.
- Electronic configuration: [Ar] 3d6 4s0 (4 unpaired electrons)
- **Conclusion**: They do not exhibit the same color.

6. **Final Pair: FeCl2 and MnCl2**:
- **FeCl2**: As calculated earlier, has 4 unpaired electrons.
- **MnCl2**: Manganese (Mn) is in +2 oxidation state.
- Electronic configuration: [Ar] 3d5 4s0 (5 unpaired electrons)
- **Conclusion**: They do not exhibit the same color.

### Final Answer:
The only pair of compounds that is expected to exhibit the same color in aqueous solution is **VOCl2 and CuCl2**.