Which halogen acid has highest acidic strength (in water)?

Options

A. HCI
B. HF
C. HBO
D. HI

Explanation

To determine which halogen acid has the highest acidic strength in water, we will analyze the given halogen acids: HCl, HF, HBr, and HI.

### Step-by-Step Solution:

1. **Definition of Acid**:
- An acid is a substance that can donate H⁺ ions (protons) in a solution. The strength of an acid is determined by its ability to donate these protons.

2. **Dissociation in Water**:
- When halogen acids dissolve in water, they dissociate to form H⁺ ions and their respective anions:
- HCl → H⁺ + Cl⁻
- HF → H⁺ + F⁻
- HBr → H⁺ + Br⁻
- HI → H⁺ + I⁻

3. **Comparison of Bond Strength**:
- The strength of the acid is influenced by the bond strength between hydrogen and the halogen. As we move down the group in the periodic table (from F to I), the size of the halogen increases, leading to a weaker H-X bond.
- The bond dissociation enthalpy decreases as we go from HF to HI:
- HF has a strong bond due to the small size of fluorine.
- HCl has a weaker bond than HF.
- HBr has an even weaker bond than HCl.
- HI has the weakest bond among them.

4. **Conclusion on Acidity**:
- Since HI has the weakest bond, it can easily dissociate to release H⁺ ions compared to the other acids. Therefore, HI will have the highest acidic strength in water.

### Final Answer:
The halogen acid with the highest acidic strength in water is **HI**.

---