The aqueous solution of the salt will be coloured in the case of

Options

A. `Zn(CO_3)_2`
B. `LiNO_3`
C. `Cl(NO_3)_2`
D. `CrCl_3`

Answer

To determine which salts will produce colored aqueous solutions, we need to analyze the electronic configurations of the metal ions in the salts. The presence of unpaired electrons in the d-orbitals is crucial for the coloration of these solutions.

### Step-by-Step Solution:

1. **Understanding the Requirement for Color**:
- A compound will exhibit color if it has unpaired electrons in its d-orbitals. This is because unpaired electrons can absorb visible light, leading to the appearance of color.

2. **Analyzing Each Option**:
- **Option A: Zinc (Zn)**:
- Zinc typically exists in the +2 oxidation state. Its electronic configuration is [Ar] 3d² 4s². In the +2 state, it loses two electrons from the 4s orbital, resulting in a configuration of 3d¹⁰.
- Since all d-orbitals are fully filled (3d¹⁰), there are no unpaired electrons. Therefore, zinc salts do not produce colored solutions.

- **Option B: Lithium (Li)**:
- Lithium is an alkali metal and does not have d-orbitals. Its electronic configuration is [He] 2s¹.
- Since it does not involve d-orbitals, lithium salts will not produce colored solutions.

- **Option C: Cobalt (Co)**:
- Cobalt can exist in various oxidation states, but in the +2 oxidation state, its electronic configuration is [Ar] 3d⁷.
- In the 3d⁷ configuration, there are 3 unpaired electrons. Thus, cobalt salts will produce colored solutions.

- **Option D: Chromium (Cr)**:
- Chromium in the +3 oxidation state has an electronic configuration of [Ar] 3d³.
- With 3 unpaired electrons in the 3d orbitals, chromium salts will also produce colored solutions.

3. **Conclusion**:
- The salts that will produce colored aqueous solutions are those containing cobalt and chromium, as both have unpaired electrons in their d-orbitals.

### Final Answer:
- The aqueous solution of the salt will be colored in the case of **Cobalt (Co)** and **Chromium (Cr)**.