In which of the following, hydrogen bond is the strongest ?

Options

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

Explanation

To determine which of the following has the strongest hydrogen bond, we need to analyze the electronegativity of the atoms involved in the hydrogen bonding. Hydrogen bonds occur when hydrogen is covalently bonded to a highly electronegative atom, such as fluorine, oxygen, or nitrogen.

### Step-by-Step Solution:

1. **Identify the Elements Involved**:
- Look at the options provided. Identify the elements that are involved in hydrogen bonding in each option. Common elements that form hydrogen bonds include fluorine (F), oxygen (O), and nitrogen (N).

2. **Understand Electronegativity**:
- Recall that electronegativity is a measure of an atom's ability to attract and hold onto electrons. The more electronegative an atom, the stronger the hydrogen bond it can form when bonded to hydrogen.

3. **Compare Electronegativity Values**:
- Fluorine (F) is the most electronegative element, followed by oxygen (O) and then nitrogen (N). The electronegativity values are approximately:
- Fluorine (F): 4.0
- Oxygen (O): 3.5
- Nitrogen (N): 3.0
- Chlorine (Cl): 3.0

4. **Analyze the Options**:
- If the options include compounds like HF (hydrogen fluoride), H2O (water), and NH3 (ammonia), we can compare their hydrogen bonds:
- HF has a hydrogen bond between H and F.
- H2O has hydrogen bonds between H and O.
- NH3 has hydrogen bonds between H and N.

5. **Determine the Strength of Hydrogen Bonds**:
- Since HF involves hydrogen bonding with fluorine, which has the highest electronegativity, HF will have the strongest hydrogen bond.
- H2O has strong hydrogen bonds due to the presence of oxygen, but they are weaker than those in HF.
- NH3 has the weakest hydrogen bonds among these options because nitrogen is less electronegative than both fluorine and oxygen.

6. **Conclusion**:
- Based on the analysis, the strongest hydrogen bond is found in HF (hydrogen fluoride).

### Final Answer:
The strongest hydrogen bond is in HF (hydrogen fluoride).