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 I ` - 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 order is incorrect among the given options, we will analyze the properties of the compounds and elements provided: H2O, HBr, HCl, and HF.

### Step 1: Analyze the properties of the compounds
1. **Bond Dissociation Energy**: This is the energy required to break a bond in a molecule. Generally, for hydrogen halides (HX), the bond dissociation energy decreases as we move down the group in the periodic table (HCl > HBr > HI) due to the increasing size of the halogen atoms, which weakens the H-X bond.

2. **Electron Affinity**: This refers to the energy change when an electron is added to a neutral atom. For halogens, the electron affinity generally increases as we move up the group (F > Cl > Br > I) due to the smaller atomic size and higher electronegativity of fluorine.

3. **Oxidizing Power**: In the halogen group, the oxidizing power decreases down the group (F2 > Cl2 > Br2 > I2) because the ability to gain electrons decreases with increasing atomic size.

### Step 2: Evaluate the given compounds
- **H2O**: Water has a strong hydrogen bond due to the high electronegativity of oxygen.
- **HF**: Hydrofluoric acid is known for its high bond dissociation energy due to the strong H-F bond.
- **HCl**: Hydrochloric acid has a weaker bond compared to HF.
- **HBr**: Hydrobromic acid has an even weaker bond than HCl.

### Step 3: Identify the incorrect order
- The bond dissociation energy order for the hydrogen halides is generally accepted as:
- HCl > HBr > HI > HF (incorrect because HF has a very strong bond).
- The electron affinity order for halogens is:
- F > Cl > Br > I (correct).
- The oxidizing power order for halogens is:
- F2 > Cl2 > Br2 > I2 (correct).

### Conclusion
Based on the analysis, the incorrect order is the bond dissociation energy of the hydrogen halides, particularly because HF has a very strong bond compared to HCl and HBr.

### Final Answer
The incorrect order is: **HCl > HBr > HI > HF**.