More volatile hydride is

Options

A. `PH_(3)`
B. `NH_(3)`
C. `BiH_(3)`
D. `AsH_(3)`

Answer

To determine which hydride is more volatile among PH3, NH3, BiH3, and AsH3, we need to analyze the boiling points and molecular weights of these compounds. Here's a step-by-step solution:

### Step 1: Understand Volatility
Volatility refers to how readily a substance vaporizes. A more volatile substance has a lower boiling point.

### Step 2: List the Hydrides and Their Molecular Weights
- **NH3 (Ammonia)**: Molecular weight = 17 g/mol
- **PH3 (Phosphine)**: Molecular weight = 34 g/mol
- **AsH3 (Arsine)**: Molecular weight = 77 g/mol
- **BiH3 (Bismuthine)**: Molecular weight = 209 g/mol

### Step 3: Analyze Boiling Points
The boiling points of these hydrides generally increase with increasing molecular weight. However, NH3 has strong intermolecular hydrogen bonding, which significantly raises its boiling point compared to what would be expected from its molecular weight alone.

- **NH3**: High boiling point due to hydrogen bonding.
- **PH3**: Lower boiling point compared to NH3, as it does not exhibit hydrogen bonding.
- **AsH3**: Higher boiling point than PH3 but lower than NH3.
- **BiH3**: Highest boiling point due to the largest molecular weight.

### Step 4: Compare Boiling Points
- **NH3**: High boiling point due to hydrogen bonding.
- **PH3**: Lower boiling point (most volatile).
- **AsH3**: Moderate boiling point.
- **BiH3**: Highest boiling point.

### Step 5: Conclusion
Since PH3 has the lowest boiling point among the listed hydrides, it is the most volatile hydride.

### Final Answer
**PH3 (Phosphine) is the most volatile hydride.**

---