The `HF_(2)^(Θ)` ion solid state and liquid `HF` but not in the dilute aqueous solution
Energy of H-bond is maximum in .

Options

A. `F-H---O`
B. `F-H---F`
C. `O-H---O`
D. `O-H---F`

Explanation

To solve the question regarding the energy of hydrogen bonds in different states of HF2^- ion and liquid HF, we need to analyze the factors affecting hydrogen bond strength and energy.

### Step-by-Step Solution:

1. **Understanding Hydrogen Bonds**:
- Hydrogen bonds occur when hydrogen is covalently bonded to a highly electronegative atom (like fluorine, oxygen, or nitrogen) and is attracted to another electronegative atom.

**Hint**: Remember that hydrogen bonds are stronger when hydrogen is bonded to more electronegative atoms.

2. **Identifying the Context**:
- The question mentions the HF2^- ion in solid state and liquid HF but not in dilute aqueous solution. This indicates that we need to consider the environments where hydrogen bonding is significant.

**Hint**: Consider the states of matter and how they influence molecular interactions.

3. **Comparing Environments**:
- In the solid state of HF2^- and in liquid HF, hydrogen bonds can form effectively due to the proximity of molecules and the presence of fluorine, which is highly electronegative.
- In dilute aqueous solutions, the presence of water molecules can disrupt hydrogen bonding due to competition for hydrogen bonding sites.

**Hint**: Think about how the presence of other molecules (like water) can interfere with hydrogen bonding.

4. **Evaluating Bond Strength**:
- The strength of hydrogen bonds is influenced by the electronegativity of the atoms involved. Fluorine is the most electronegative element, which means hydrogen bonds involving fluorine will have the highest energy.
- Therefore, in both solid HF2^- and liquid HF, the hydrogen bonds formed are strong due to the involvement of fluorine.

**Hint**: Recall that the more electronegative the atom bonded to hydrogen, the stronger the hydrogen bond.

5. **Conclusion**:
- The energy of hydrogen bonds is maximum in the solid state of HF2^- and liquid HF because they involve hydrogen bonded to fluorine, which is highly electronegative. In contrast, in dilute aqueous solutions, the hydrogen bonds are weaker due to interference from water molecules.

**Final Answer**: The energy of hydrogen bond is maximum in solid HF2^- and liquid HF.