Addition of `Hl` will significantly suppress solubility or dissociation or hydrolysis of which of the following ?

Options

A. `HF_(aq)`
B. `HBr_(aq)`
C. Saturated solution of sparingly solution of sparingly soluble salt `Pbl_(2)`
D. `HClO_(4(aq))`

Explanation

To solve the question regarding which substances' solubility, dissociation, or hydrolysis will be significantly suppressed by the addition of HI, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Nature of HI**:
- HI (hydroiodic acid) is a strong acid, meaning it dissociates completely in solution to produce H⁺ and I⁻ ions.

2. **Identify the Compounds**:
- The compounds given are HF (hydrofluoric acid), HBr (hydrobromic acid), PbI₂ (lead(II) iodide), and HClO₄ (perchloric acid).

3. **Analyze Each Compound**:
- **HF**: This is a weak acid that does not fully dissociate in solution. The addition of HI will increase the concentration of H⁺ ions, which will shift the equilibrium of HF dissociation back towards the reactants (HF), thus suppressing its dissociation.
- **HBr**: This is a strong acid, similar to HI. The presence of HI will not significantly affect the dissociation of HBr because both are strong acids and will fully dissociate.
- **PbI₂**: This is a sparingly soluble salt. The addition of I⁻ ions from HI will increase the concentration of the common ion (I⁻) in the solution, which will suppress the dissociation of PbI₂ according to the common ion effect.
- **HClO₄**: This is also a strong acid. The addition of HI will not affect its dissociation significantly, as both are strong acids.

4. **Conclusion**:
- The compounds whose solubility or dissociation will be significantly suppressed by the addition of HI are **HF** and **PbI₂**.

### Final Answer:
The correct options are **HF** and **PbI₂**.