Which of the following compound are coloured due to charge transfer spectra ?

Options

A. `K_(2)Cr_(2)O_(7)`
B. `KMnO_(4)`
C. `AgBr`
D. `FeSO_(4)`

Answer

To determine which compounds are colored due to charge transfer spectra, we need to analyze each option based on the principles of charge transfer and d-d transitions.

### Step-by-Step Solution:

1. **Understanding Charge Transfer Spectra**:
Charge transfer spectra occur when there is a transfer of electric charge between two molecular entities. This transfer can lead to the absorption of light and thus the appearance of color in the compound.

2. **Analyzing the Options**:
- **Option 1: K2Cr2O7 (Potassium Dichromate)**:
- Chromium in K2Cr2O7 has an oxidation state of +6.
- The electronic configuration of Cr in this state is [Ar] 3d0 4s0, meaning there are no unpaired electrons.
- Since there are no unpaired electrons, d-d transitions cannot occur.
- However, the color arises due to charge transfer from oxygen to chromium, making K2Cr2O7 colored (orange).
- **Conclusion**: K2Cr2O7 is colored due to charge transfer spectra.

- **Option 2: KMnO4 (Potassium Permanganate)**:
- Manganese in KMnO4 has an oxidation state of +7.
- The electronic configuration of Mn in this state is [Ar] 3d0 4s0, indicating no unpaired electrons.
- Similar to K2Cr2O7, the color (purple) arises due to charge transfer from oxygen to manganese.
- **Conclusion**: KMnO4 is colored due to charge transfer spectra.

- **Option 3: AgBr (Silver Bromide)**:
- The color of AgBr is yellow, which arises from the polarization effect of the small Ag+ ion on the larger Br- ion.
- This color is not due to charge transfer spectra but rather due to the size difference and polarization.
- **Conclusion**: AgBr is not colored due to charge transfer spectra.

- **Option 4: FeSO4 (Iron(II) Sulfate)**:
- Iron in FeSO4 has an oxidation state of +2.
- The electronic configuration of Fe in this state is [Ar] 3d6 4s0, which means there are 4 unpaired electrons.
- The green color of FeSO4 arises from d-d transitions due to these unpaired electrons.
- **Conclusion**: FeSO4 is not colored due to charge transfer spectra.

3. **Final Answer**:
The compounds that are colored due to charge transfer spectra are:
- K2Cr2O7 (Potassium Dichromate)
- KMnO4 (Potassium Permanganate)

### Summary of Correct Answers:
- **K2Cr2O7**
- **KMnO4**