Which of following does not show common ion effect ?

Options

A. ` HCN + KCN `
B. `HCI+NH_4 CI`
C. `CH_5 COOH +CH_3 COONa`
D. none of these

Answer

To solve the question "Which of the following does not show common ion effect?", we need to analyze each option provided in the question based on the conditions that lead to the common ion effect.

### Step-by-Step Solution:

1. **Understanding Common Ion Effect**:
The common ion effect occurs when a weak acid or weak base is in equilibrium with its salt. The presence of a common ion shifts the equilibrium, affecting solubility and ion concentration.

2. **Conditions for Common Ion Effect**:
- A strong acid with its salt formed from a weak base.
- A weak acid with its salt formed from a strong base.

3. **Analyzing Each Option**:
- **Option A: HCN + KCN**
- HCN is a weak acid, and KCN is the salt formed from HCN and KOH (a strong base).
- This follows the second condition for common ion effect.

- **Option B: HCl + NH4Cl**
- HCl is a strong acid, and NH4Cl is the salt formed from NH4OH (a weak base) and HCl.
- This follows the first condition for common ion effect.

- **Option C: CH3COOH + CH3COONa**
- CH3COOH (acetic acid) is a weak acid, and CH3COONa is the salt formed from acetic acid and NaOH (a strong base).
- This follows the second condition for common ion effect.

- **Option D: None of these**
- This option suggests that none of the previous options show the common ion effect.

4. **Conclusion**:
Since options A, B, and C all demonstrate conditions that lead to the common ion effect, the correct answer is **Option D**: None of these.

### Final Answer:
**Option D: None of these**