Which pair will show common ion effect?

Options

A. `AgNO_(3) + KNO_(3)`
B. `NaCl + HCl`
C. `NH_(4)OH + NH_(4)Cl`
D. `BaCl_(2) + Ba(NO_(3))_(2)`

Explanation

To determine which pair will show the common ion effect, we need to understand the concept of the common ion effect and how it applies to different pairs of compounds. Here’s a step-by-step solution:

### Step 1: Understand the 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 from the salt shifts the equilibrium, affecting the dissociation of the weak acid or weak base.

### Step 2: Identify the Types of Compounds
- **Weak Acid + Salt of Strong Base**: This combination will show the common ion effect.
- **Weak Base + Salt of Strong Acid**: This combination will also show the common ion effect.
- **Strong Electrolytes**: These do not show the common ion effect as they completely dissociate in solution.

### Step 3: Analyze the Given Options
1. **AgNO3 and KNO3**: Both are strong electrolytes and will not show the common ion effect.
2. **NaCl and HCl**: NaCl is a neutral salt and HCl is a strong acid. This combination does not involve a weak acid or weak base, so it will not show the common ion effect.
3. **NH4OH and NH4Cl**: NH4OH is a weak base and NH4Cl is the salt of that weak base. The presence of NH4+ from NH4Cl will suppress the dissociation of NH4OH, thus showing the common ion effect.
4. **BaCl2 and Barium Nitrate**: Both are strong electrolytes and will not show the common ion effect.

### Step 4: Conclusion
The only pair that will show the common ion effect is **NH4OH and NH4Cl**.

### Final Answer
**NH4OH and NH4Cl** will show the common ion effect.

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