The boiling points of the following hydrides follow the order of

Options

A. `NH_3 gt AsH_3 gt PH_3 gt SbH_3`
B. `SbH_3 gt AsH_3 gt PH_3 gt NH_3`
C. `SbH_3 gt NH_3 gt AsH_3 gt PH_3`
D. `NH_3 gt PH_3 gt AsH_3 gt SbH_3`

Explanation

To determine the order of boiling points for the given hydrides (NH3, PH3, AsH3, SbH3, BiH3), we can analyze the factors that influence boiling points, such as molecular weight and intermolecular forces.

### Step-by-Step Solution:

1. **Identify the Hydrides**: The hydrides we are considering are:
- NH3 (Ammonia)
- PH3 (Phosphine)
- AsH3 (Arsine)
- SbH3 (Stibine)
- BiH3 (Bismuthine)

2. **Consider Molecular Weight**: As we move down the group in the periodic table, the molecular weight of the hydrides increases:
- NH3: Molecular weight = 17 g/mol
- PH3: Molecular weight = 34 g/mol
- AsH3: Molecular weight = 77 g/mol
- SbH3: Molecular weight = 124 g/mol
- BiH3: Molecular weight = 209 g/mol

3. **Intermolecular Forces**: The boiling point of a substance is influenced by the strength of intermolecular forces. Hydrogen bonding is a significant factor:
- NH3 exhibits strong hydrogen bonding due to the presence of nitrogen, which leads to a higher boiling point than expected based solely on molecular weight.
- The other hydrides (PH3, AsH3, SbH3, BiH3) primarily exhibit Van der Waals forces, which are weaker than hydrogen bonds.

4. **Order of Boiling Points**: Taking into account both molecular weight and the presence of hydrogen bonding:
- NH3 has the highest boiling point due to hydrogen bonding.
- Following NH3, the boiling points will increase with molecular weight:
- SbH3 (124 g/mol) > AsH3 (77 g/mol) > PH3 (34 g/mol) > BiH3 (209 g/mol).
- However, BiH3 has a lower boiling point than expected due to its larger size and weaker Van der Waals forces.

5. **Final Order**: The final order of boiling points from highest to lowest is:
- NH3 > SbH3 > AsH3 > PH3 > BiH3

### Conclusion:
The order of boiling points for the hydrides is:
**NH3 > SbH3 > AsH3 > PH3 > BiH3**