Which of the hydrogen halides forms salts like `KHX_2` (where X is a halogen atom)

Options

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

Explanation

To determine which hydrogen halide forms salts like `KHX2` (where X is a halogen atom), we can analyze the properties of each hydrogen halide given in the options: HF, HCl, HBr, and HI.

### Step-by-Step Solution:

1. **Understanding the Question**: We need to identify which hydrogen halide can form a salt with the formula `KHX2`. Here, `K` represents potassium, and `X` represents a halogen atom.

2. **Analyzing the Halides**:
- **HF (Hydrogen Fluoride)**: Fluorine is the most electronegative element. When HF dissociates, it can form HF2^- ions in the presence of potassium ions (K+), leading to the formation of KHF2.
- **HCl (Hydrogen Chloride)**: Chlorine is less electronegative than fluorine. HCl does not typically form a salt of the type KHCl2 because it does not have the same strong hydrogen bonding capability as HF.
- **HBr (Hydrogen Bromide)**: Similar to HCl, HBr does not form a salt of the type KHBr2 for the same reasons.
- **HI (Hydrogen Iodide)**: Iodine is even less electronegative than bromine and chlorine, and HI does not form a salt of the type KHI2.

3. **Conclusion**: The only hydrogen halide that can form a salt of the type `KHX2` is HF, due to its ability to form strong hydrogen bonds and the presence of the highly electronegative fluorine atom.

### Final Answer:
The hydrogen halide that forms salts like `KHX2` is **HF (Hydrogen Fluoride)**.