Which of the following is arranged in the increasing order of enthalpy of vaporization?

Options

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

Explanation

To solve the question regarding the increasing order of enthalpy of vaporization for the given substances (ammonia, phosphine, and arsenic hydride), we will follow these steps:

### Step-by-Step Solution:

1. **Understanding Enthalpy of Vaporization**:
- The enthalpy of vaporization (also known as latent heat of vaporization) is the amount of energy required to convert a unit quantity of a liquid into a gas at constant temperature and pressure.

2. **Identifying the Substances**:
- The substances we need to compare are:
- Ammonia (NH₃)
- Phosphine (PH₃)
- Arsenic Hydride (AsH₃)

3. **Analyzing Molecular Weights**:
- Determine the molecular weights of each substance:
- Ammonia (NH₃): 14 (N) + 3 (H) = 17 g/mol
- Phosphine (PH₃): 31 (P) + 3 (H) = 34 g/mol
- Arsenic Hydride (AsH₃): 75 (As) + 3 (H) = 78 g/mol

4. **Considering Molecular Weight and Enthalpy of Vaporization**:
- Generally, as molecular weight increases, the enthalpy of vaporization also increases because larger molecules require more energy to overcome intermolecular forces.
- However, ammonia has strong hydrogen bonding due to the presence of nitrogen, which is highly electronegative. This hydrogen bonding increases the enthalpy of vaporization for ammonia significantly compared to what would be expected based solely on molecular weight.

5. **Comparing the Substances**:
- Based on molecular weight alone, the order would be:
- Ammonia (17 g/mol) < Phosphine (34 g/mol) < Arsenic Hydride (78 g/mol)
- However, due to the strong hydrogen bonding in ammonia, its enthalpy of vaporization is greater than that of phosphine and arsenic hydride.

6. **Final Order**:
- Considering both molecular weight and the effect of hydrogen bonding, the correct increasing order of enthalpy of vaporization is:
- Phosphine < Arsenic Hydride < Ammonia

### Conclusion:
The increasing order of enthalpy of vaporization for the substances is:
**Phosphine < Arsenic Hydride < Ammonia**