Which is the correct order of decreasing boiling point of azeotropic mixtures `X-H_(2)O`?

Options

A. `HI gt HBr gt HF gt HCl`
B. `HI gt HCl gt HBr gt HF`
C. `HF gt HCl gt HBr gt HI`
D. `HCl gt HF gt HBr gt HI`

Answer

To determine the correct order of decreasing boiling points of azeotropic mixtures of the form X-H₂O, we need to analyze the components of the mixtures based on their molecular characteristics and intermolecular forces.

### Step-by-Step Solution:

1. **Understanding Azeotropic Mixtures**:
- Azeotropic mixtures are binary liquid mixtures that boil at a constant temperature and have the same composition in both liquid and vapor phases. The boiling point of these mixtures is influenced by the nature of the components involved.

2. **Factors Affecting Boiling Point**:
- The boiling point of a substance is primarily influenced by the strength of intermolecular forces. Stronger intermolecular forces lead to higher boiling points.
- The size of the molecules and their polarities also play a crucial role. Generally, larger molecules with higher molecular weights exhibit higher boiling points due to increased van der Waals forces.

3. **Analyzing the Given Compounds**:
- The compounds in consideration are H₂O, HI, HBr, HCl, and HF.
- **HI** has the largest molecular size and mass, leading to the highest boiling point.
- **HCl** is a polar molecule and has a higher boiling point than HBr due to its stronger intermolecular forces despite HBr being larger in size.
- **HBr** has a lower boiling point than HCl but is higher than HF.
- **HF** has hydrogen bonding, which is strong but its overall molecular weight is lower than that of HBr and HCl.

4. **Boiling Points of Each Compound**:
- HI: 127 °C
- HCl: 110 °C
- HBr: 106 °C
- HF: 19.9 °C

5. **Determining the Order**:
- Based on the boiling points and the analysis of intermolecular forces, we can establish the order of decreasing boiling points:
- HI > HCl > HBr > HF

### Final Order:
The correct order of decreasing boiling points of the azeotropic mixtures X-H₂O is:
**HI > HCl > HBr > HF**