The correct group of halide ions which can be oxidised by oxygen in acidic medium is

Options

A. `I^(-)` only
B. `Br^(-)` and `I^(-)`
C. `Br^(-)` only
D. `Cl^(-1),Br^(-)` and `I^(-)`

Answer

To solve the question about which halide ions can be oxidized by oxygen in acidic medium, we need to analyze the oxidation states and the reactivity of the halide ions.

### Step-by-Step Solution:

1. **Identify the Halide Ions**: The common halide ions are fluoride (F⁻), chloride (Cl⁻), bromide (Br⁻), and iodide (I⁻).

2. **Understand the Oxidation Process**: In acidic medium, halide ions can be oxidized to their respective halogens. For example, iodide ions (I⁻) can be oxidized to iodine (I₂).

3. **Evaluate Oxidation Potentials**: The standard reduction potentials (E°) for the halide ions indicate their tendency to be oxidized. The relevant half-reactions are:
- I⁻ → I₂ + 2e⁻ (E° = +0.54 V)
- Br⁻ → Br₂ + 2e⁻ (E° = +1.07 V)
- Cl⁻ → Cl₂ + 2e⁻ (E° = +1.36 V)
- F⁻ → F₂ + 2e⁻ (E° = +2.87 V)

The more positive the E° value, the easier it is for the species to be reduced, which means the corresponding halide ion is less likely to be oxidized.

4. **Determine Which Halides Can Be Oxidized**:
- Iodide (I⁻) can be oxidized to iodine (I₂) in acidic medium.
- Chloride (Cl⁻) and bromide (Br⁻) are less likely to be oxidized because their oxidation potentials are higher, indicating they are more stable in their ionic form.

5. **Conclusion**: The only halide ion that can be oxidized by oxygen in acidic medium is iodide (I⁻). Therefore, the correct group of halide ions is I⁻.

### Final Answer:
The correct group of halide ions that can be oxidized by oxygen in acidic medium is **I⁻**.