`H_(2)Se` has higher boiling point than `H_(2)S`. This is best explained by

Options

A. Higher extent of hydrogen bonding in `H_(2)Se`
B. Higher polarity of `H_(2)S`
C. Higher polarity of `H_(2)Se`
D. Higher dispersion forces in `H_(2)Se` due to its higher molecular weight.

Answer

To determine why \( H_2Se \) has a higher boiling point than \( H_2S \), we can analyze the molecular properties and intermolecular forces involved.

### Step-by-Step Solution:

1. **Identify the Compounds**: We are comparing two compounds, \( H_2Se \) (Hydrogen selenide) and \( H_2S \) (Hydrogen sulfide).

2. **Understand Boiling Point**: The boiling point of a substance is influenced by the strength of intermolecular forces. Stronger intermolecular forces lead to higher boiling points.

3. **Types of Intermolecular Forces**: The primary types of intermolecular forces include hydrogen bonding, dipole-dipole interactions, and London dispersion forces. In this case, both \( H_2Se \) and \( H_2S \) are polar molecules, but their boiling points will be influenced significantly by London dispersion forces due to their molecular weights.

4. **Molecular Weights**:
- The molecular weight of \( H_2S \) is approximately 34 g/mol (2 for H and 32 for S).
- The molecular weight of \( H_2Se \) is approximately 81 g/mol (2 for H and 79 for Se).

5. **London Dispersion Forces**: These forces arise due to the temporary dipoles that occur when electrons move around the nucleus of an atom. The strength of London dispersion forces increases with increasing molecular weight because larger atoms have more electrons, which can create larger temporary dipoles.

6. **Comparison of London Dispersion Forces**: Since \( H_2Se \) has a higher molecular weight than \( H_2S \), it will also have stronger London dispersion forces. This is the primary reason for the higher boiling point of \( H_2Se \).

7. **Conclusion**: Therefore, the higher boiling point of \( H_2Se \) compared to \( H_2S \) can be best explained by the presence of higher London dispersion forces due to the greater molecular weight of \( H_2Se \).

### Final Answer:
The best explanation for why \( H_2Se \) has a higher boiling point than \( H_2S \) is that \( H_2Se \) has higher dispersion forces due to its higher molecular weight.