Which of the following hydrides has the least boiling point ?

Options

A. `H_(2)S`
B. `H_(2)O`
C. `H_(2)Se`
D. `H_(2)Te`

Explanation

To determine which hydride has the least boiling point among the hydrides of the oxygen family (H2O, H2S, H2Se, H2Te), we can follow these steps:

### Step 1: Identify the Hydrides
The hydrides we are considering are:
- H2O (Water)
- H2S (Hydrogen sulfide)
- H2Se (Hydrogen selenide)
- H2Te (Hydrogen telluride)

### Step 2: Understand the Trends in Boiling Points
Boiling points of hydrides in the same group can be influenced by several factors:
1. **Molecular Weight**: Generally, as the molecular weight increases, the boiling point increases due to stronger Van der Waals forces.
2. **Hydrogen Bonding**: Molecules capable of hydrogen bonding (like H2O) will have higher boiling points compared to those that do not exhibit hydrogen bonding.

### Step 3: Analyze Each Hydride
- **H2O**: Exhibits strong hydrogen bonding due to the high electronegativity of oxygen, resulting in a high boiling point.
- **H2S**: Does not exhibit hydrogen bonding as strongly as water, leading to a lower boiling point than H2O.
- **H2Se**: Has a higher molecular weight than H2S but still does not form hydrogen bonds, resulting in a boiling point higher than H2S but lower than H2O.
- **H2Te**: Similar to H2Se, it has a higher molecular weight and a lower boiling point than H2Se.

### Step 4: Compare the Boiling Points
Based on the above analysis:
- H2O has the highest boiling point due to hydrogen bonding.
- H2S has a lower boiling point than H2O but higher than H2Se and H2Te.
- H2Se has a higher boiling point than H2S but lower than H2Te.
- H2Te has the highest molecular weight but the weakest intermolecular forces among these hydrides.

### Conclusion
The hydride with the least boiling point is **H2S**.

### Final Answer
**H2S (Hydrogen sulfide) has the least boiling point among the given hydrides.**

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