The boiling points at atmospheric pressure of `HF, H_(2)S, NH_(3)` can be arranged in the following order :

Options

A. `HF gt NH_(3) gt H_(2)S`
B. `HF gt H_(2)S gt NH_(3)`
C. `HF lt H_(2)S lt NH_(3)`
D. `HF lt NH_(3) lt H_(2)S`

Answer

To determine the boiling points of HF (hydrogen fluoride), H₂S (hydrogen sulfide), and NH₃ (ammonia), we need to analyze the intermolecular forces present in each compound. Here's a step-by-step solution:

### Step 1: Identify the Intermolecular Forces
- **HF (Hydrogen Fluoride)**: HF exhibits strong hydrogen bonding due to the highly electronegative fluorine atom. This results in significant intermolecular attractions.
- **NH₃ (Ammonia)**: NH₃ also exhibits hydrogen bonding, but the electronegativity of nitrogen is less than that of fluorine, making the hydrogen bonds in NH₃ weaker than those in HF.
- **H₂S (Hydrogen Sulfide)**: H₂S has weaker dipole-dipole interactions and London dispersion forces since sulfur is less electronegative than both nitrogen and fluorine. It does not exhibit hydrogen bonding.

### Step 2: Compare the Strength of Intermolecular Forces
- **HF** has the strongest intermolecular forces due to strong hydrogen bonding.
- **NH₃** has moderate intermolecular forces due to hydrogen bonding, but weaker than HF.
- **H₂S** has the weakest intermolecular forces as it lacks hydrogen bonding.

### Step 3: Determine the Boiling Points
- The boiling point is directly related to the strength of the intermolecular forces. Therefore, we can arrange the compounds based on their boiling points:
- **HF** has the highest boiling point due to strong hydrogen bonding.
- **NH₃** has a lower boiling point than HF but higher than H₂S due to its hydrogen bonding.
- **H₂S** has the lowest boiling point as it lacks hydrogen bonding.

### Final Order of Boiling Points
Thus, the boiling points can be arranged in the following order:
1. **HF** (highest boiling point)
2. **NH₃**
3. **H₂S** (lowest boiling point)

### Conclusion
The correct order of boiling points at atmospheric pressure is:
**HF > NH₃ > H₂S**

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