Bond dissociation energies of HF, HCl, HBr follow the order

Options

A. `HCI gt HBr gt HF`
B. `HF gt HBr gt HCI`
C. `HF gt HCIgt HBr`
D. `HBr gt HCI gt HF`

Answer

To determine the order of bond dissociation energies of HF, HCl, and HBr, we will analyze the factors affecting bond strength and dissociation energy.

### Step-by-Step Solution:

1. **Understanding Bond Dissociation Energy**:
Bond dissociation energy is the energy required to break a bond between two atoms in a molecule. Higher bond dissociation energy indicates a stronger bond.

2. **Identify the Halogen Group**:
HF (hydrogen fluoride), HCl (hydrogen chloride), and HBr (hydrogen bromide) are all compounds formed between hydrogen and halogens (Group VIIA elements). The halogens in order of increasing atomic size are: Fluorine (F), Chlorine (Cl), and Bromine (Br).

3. **Consider Atomic Size**:
As we move down the group from fluorine to bromine, the atomic size increases. Larger atomic size generally leads to longer bond lengths, which typically results in weaker bonds. Therefore, we can expect the bond strengths to decrease from HF to HCl to HBr.

4. **Analyze Electronegativity**:
Electronegativity is the ability of an atom to attract electrons. Fluorine is the most electronegative element, followed by chlorine and then bromine. Higher electronegativity in HF leads to a stronger bond due to the greater attraction between the hydrogen and fluorine atoms.

5. **Evaluate Hydrogen Bonding in HF**:
HF exhibits strong hydrogen bonding due to the high electronegativity of fluorine. This additional interaction contributes to a higher bond dissociation energy compared to HCl and HBr, which do not exhibit hydrogen bonding to the same extent.

6. **Conclusion**:
Based on the above factors, we can conclude that the bond dissociation energies follow this order:
\[ \text{Bond Dissociation Energy Order: } HF > HCl > HBr \]
Therefore, the correct answer is that HF has the highest bond dissociation energy, followed by HCl, and then HBr.

### Final Answer:
The order of bond dissociation energies is:
\[ \text{HF} > \text{HCl} > \text{HBr} \]