The aqueous solution of the following salts will be colored in the case of

Options

A. `Zn(NO_(3))_(2)`
B. `LiNO_(3)`
C. `Co(NO_(3))_(2)`
D. `Potash-alum`

Answer

To determine which of the given salts will produce a colored aqueous solution, we need to analyze the electronic configurations of the metal ions present in each salt. The presence of unpaired d-electrons in transition metal ions is responsible for the color in their solutions due to d-d transitions. Let's go through the salts one by one:

### Step-by-Step Solution:

1. **Analyze Zn(NO3)2:**
- The metal ion is Zn²⁺.
- Electronic configuration of Zn²⁺: Ar 3d¹⁰ 4s⁰.
- Since all the d-electrons are paired (10 paired electrons), there are no unpaired electrons.
- **Conclusion:** Zn(NO3)2 will not produce a colored solution.

2. **Analyze LiNO3:**
- The metal ion is Li⁺.
- Electronic configuration of Li⁺: He 2s⁰.
- There are no d-electrons in Li⁺, and thus no unpaired electrons.
- **Conclusion:** LiNO3 will not produce a colored solution.

3. **Analyze Co(NO3)2:**
- The metal ion is Co²⁺.
- Atomic number of Co is 27, so the electronic configuration is Ar 3d⁷ 4s².
- For Co²⁺, the configuration becomes: Ar 3d⁷ 4s⁰.
- In 3d⁷, there are 3 unpaired electrons (1 in each of three d-orbitals).
- **Conclusion:** Co(NO3)2 will produce a colored solution due to the presence of unpaired d-electrons.

4. **Analyze KAl(SO4)2·12H2O (Potash Alum):**
- The metal ions are K⁺ and Al³⁺.
- K⁺ has the configuration of Ar 4s⁰ (no d-electrons).
- Al³⁺ has the configuration of Ne 3s² 3p¹, which means it loses 3 electrons (2 from 3s and 1 from 3p), resulting in no d-electrons.
- **Conclusion:** Potash alum will not produce a colored solution as there are no unpaired d-electrons.

### Final Conclusion:
- The only salt that produces a colored aqueous solution is **Co(NO3)2**.