Mark the strongest acid

Options

A. HF
B. HCl
C. HBr
D. Hl

Explanation

To determine the strongest acid among HF, HCl, HBr, and HI, we need to analyze the strength of these acids based on their molecular structure and the bond strength of the hydrogen-halogen bond.

### Step-by-Step Solution:

1. **Identify the Acids**: The acids we are comparing are:
- HF (Hydrofluoric acid)
- HCl (Hydrochloric acid)
- HBr (Hydrobromic acid)
- HI (Hydroiodic acid)

2. **Understand Acid Strength**: The strength of an acid is determined by its ability to donate a proton (H⁺) in solution. The easier it is for the acid to dissociate and release H⁺, the stronger the acid.

3. **Analyze Bond Strength**: The bond strength between hydrogen and the halogen affects the acid's strength. As we move down the group in the periodic table from fluorine to iodine, the bond strength decreases:
- HF has a very strong H-F bond.
- HCl has a weaker H-Cl bond than HF.
- HBr has an even weaker H-Br bond.
- HI has the weakest H-I bond.

4. **Dissociation of Acids**: The weaker the bond, the easier it is for the acid to dissociate:
- HF → H⁺ + F⁻ (strong bond, weak acid)
- HCl → H⁺ + Cl⁻ (weaker bond, stronger acid than HF)
- HBr → H⁺ + Br⁻ (weaker bond than HCl, stronger acid than HCl)
- HI → H⁺ + I⁻ (weakest bond, strongest acid)

5. **Conclusion**: Based on the bond strengths and the ability to dissociate, HI (Hydroiodic acid) is the strongest acid among the given options.

### Final Answer:
The strongest acid among HF, HCl, HBr, and HI is **HI (Hydroiodic acid)**.