The addition of HCl will not supress the ionisation of

Options

A. `CH_3COOH`
B. `C_6H_5COOH`
C. `H_2S`
D. `H_2SO_4`

Answer

To solve the question "The addition of HCl will not suppress the ionization of which compound?", we will analyze each option based on the concept of the common ion effect and the nature of the acids involved.

### Step-by-Step Solution:

1. **Understand the Common Ion Effect**:
- The common ion effect states that the addition of an ion that is common to two solutes will suppress the ionization of a weak electrolyte. This occurs because the equilibrium shifts to the left, reducing the concentration of ions produced by the weak electrolyte.

2. **Identify the Compounds**:
- The compounds given are:
- CH3COOH (acetic acid)
- C6H5COOH (benzoic acid)
- H2S (hydrogen sulfide)
- H2SO4 (sulfuric acid)

3. **Determine the Nature of Each Compound**:
- **CH3COOH (Acetic Acid)**: This is a weak acid that partially ionizes in solution:
\[ \text{CH}_3\text{COOH} \rightleftharpoons \text{CH}_3\text{COO}^- + \text{H}^+ \]
- **C6H5COOH (Benzoic Acid)**: This is also a weak acid and behaves similarly to acetic acid:
\[ \text{C}_6\text{H}_5\text{COOH} \rightleftharpoons \text{C}_6\text{H}_5\text{COO}^- + \text{H}^+ \]
- **H2S (Hydrogen Sulfide)**: This is another weak acid:
\[ \text{H}_2\text{S} \rightleftharpoons 2\text{H}^+ + \text{S}^{2-} \]
- **H2SO4 (Sulfuric Acid)**: This is a strong acid that ionizes completely:
\[ \text{H}_2\text{SO}_4 \rightarrow 2\text{H}^+ + \text{SO}_4^{2-} \]

4. **Analyze the Effect of Adding HCl**:
- When HCl is added to a solution, it dissociates completely to produce H⁺ ions:
\[ \text{HCl} \rightarrow \text{H}^+ + \text{Cl}^- \]
- The addition of H⁺ ions will shift the equilibrium of weak acids (CH3COOH, C6H5COOH, H2S) to the left, suppressing their ionization due to the common ion effect.

5. **Conclusion**:
- Since H2SO4 ionizes completely and does not establish an equilibrium (it is a strong acid), the addition of HCl will not suppress its ionization. Therefore, the answer to the question is:
- **H2SO4** (option 4).

### Final Answer:
The addition of HCl will not suppress the ionization of **H2SO4**.