Which of the following order is incorrect?

Options

A. HF gt HCL gt HBr gt HI - Acidic strength
B. Cl gt F gt Br gt - Electron affinity
C. `Cl_2 gt Br_2 gt F_2 gt I _2` - Bond dissociation energy
D. `F_2 gt CL_2 gt Br_2 gt I_2` - Oxidising power

Answer

To determine which of the given orders is incorrect, we need to analyze the properties of the substances mentioned in the question. The question involves the following concepts: acid strength, electron affinity, bond dissociation energy, and oxidation power.

### Step-by-Step Solution:

1. **Acid Strength Order**:
- Acid strength generally increases with increasing electronegativity of the atom bonded to hydrogen.
- The correct order of acid strength for the hydrogen halides (HX) is:
- HF < HCl < HBr < HI
- This means HF is the weakest acid and HI is the strongest.
- If the question provides a different order, that order is incorrect.

2. **Electron Affinity Order**:
- Electron affinity is the energy change when an electron is added to a neutral atom.
- Generally, electron affinity increases across a period and decreases down a group.
- However, fluorine has a lower electron affinity than chlorine due to its small size, leading to electron-electron repulsion.
- The correct order of electron affinity is:
- Cl > F > Br > I
- If a different order is provided, that order is incorrect.

3. **Bond Dissociation Energy Order**:
- Bond dissociation energy refers to the energy required to break a bond.
- As we move down the group in the halogens, the bond dissociation energy decreases due to the increase in atomic size.
- The correct order of bond dissociation energy is:
- F2 > Cl2 > Br2 > I2
- If the question provides a different order, that order is incorrect.

4. **Oxidizing Power Order**:
- The oxidizing power of an element is related to its ability to gain electrons.
- Fluorine is the most electronegative and has the highest tendency to gain electrons.
- The correct order of oxidizing power is:
- F2 > Cl2 > Br2 > I2
- If the question provides a different order, that order is incorrect.

### Conclusion:
After analyzing the four properties, if any of the provided orders in the question does not match the correct order derived from the concepts above, that order is incorrect. Based on the video transcript, the incorrect order is for acid strength.