Consider the following four liquids :
1.Water : highly polar, `H-`bonging 2. Hexanol : slightly polar, some `H-`bonding
3.Chloroform : slightly polar, `no H-`bonding 4. Octane : non-polar , no `H-`bonding
Which pair of liquids is immiscible ?
The solutions of water and octance are immiscible. Why?

Answer

To determine which pairs of liquids are immiscible, we need to analyze the polarity and hydrogen bonding characteristics of each liquid.

### Step-by-Step Solution:

1. **Identify the Polarity and Hydrogen Bonding of Each Liquid:**
- **Water:** Highly polar, capable of hydrogen bonding.
- **Hexanol:** Slightly polar, capable of some hydrogen bonding.
- **Chloroform:** Slightly polar, no hydrogen bonding.
- **Octane:** Non-polar, no hydrogen bonding.

2. **Apply the Principle of "Like Dissolves Like":**
- Polar liquids tend to mix well with other polar liquids.
- Non-polar liquids tend to mix well with other non-polar liquids.
- Polar and non-polar liquids do not mix well (immiscible).

3. **Evaluate Possible Pairs:**
- **Water and Hexanol:** Water is highly polar, hexanol is slightly polar. They may have some miscibility due to hydrogen bonding, but it will be limited.
- **Water and Chloroform:** Water is highly polar, chloroform is slightly polar. They are likely to be immiscible due to the lack of significant hydrogen bonding.
- **Water and Octane:** Water is highly polar, octane is non-polar. They are immiscible.
- **Hexanol and Chloroform:** Both are slightly polar but have no hydrogen bonding. They may be somewhat miscible, but not completely.
- **Hexanol and Octane:** Hexanol is slightly polar, octane is non-polar. They are likely to be immiscible.
- **Chloroform and Octane:** Chloroform is slightly polar, octane is non-polar. They are likely to be immiscible.

4. **Conclusion on Immiscibility:**
- The pairs that are immiscible are:
- Water and Octane
- Water and Chloroform
- Hexanol and Octane
- Chloroform and Octane

5. **Why are Water and Octane Immiscible?**
- Water is highly polar, while octane is non-polar. According to the principle of "like dissolves like," these two liquids do not mix well, leading to immiscibility.

### Final Answer:
The pair of liquids that is immiscible is **Water and Octane**. They are immiscible because water is highly polar and octane is non-polar.