In which of the following compounds H-bond exist?I.HF II.`NH_3` III.`H_2O` IV.HI

Options

A. I and II
B. III and IV
C. I,II,III
D. I,III and IV

Answer

To determine in which of the given compounds hydrogen bonds exist, we need to analyze each compound individually.

### Step-by-Step Solution:

1. **Understanding Hydrogen Bonding**:
Hydrogen bonding occurs when a hydrogen atom is covalently bonded to a highly electronegative atom (like N, O, or F) and is attracted to another electronegative atom in a different molecule or within the same molecule.

2. **Analyzing Each Compound**:
- **I. HF (Hydrogen Fluoride)**:
- In HF, hydrogen is bonded to fluorine, which is highly electronegative. Therefore, HF can form hydrogen bonds.

- **II. NH3 (Ammonia)**:
- In NH3, hydrogen is bonded to nitrogen, which is also electronegative. Thus, NH3 can form hydrogen bonds.

- **III. H2O (Water)**:
- In H2O, hydrogen is bonded to oxygen, which is highly electronegative. Water can form hydrogen bonds, and it is known for its strong hydrogen bonding capabilities.

- **IV. HI (Hydrogen Iodide)**:
- In HI, hydrogen is bonded to iodine. Although iodine is somewhat electronegative, it is not as electronegative as N, O, or F. Therefore, HI does not typically form hydrogen bonds.

3. **Conclusion**:
The compounds that can form hydrogen bonds are:
- HF
- NH3
- H2O

The compound that does not form hydrogen bonds is:
- HI

### Final Answer:
Hydrogen bonds exist in the following compounds: **I. HF, II. NH3, III. H2O**. Hydrogen bonds do not exist in **IV. HI**.

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