Absolute alcohol can be prepared from rectified spirit by

Answer

To prepare absolute alcohol from rectified spirit, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Rectified Spirit**:
- Rectified spirit is a mixture that contains approximately 95.6% ethanol and 4.4% water. This mixture is known as an azeotropic mixture, which means it has a constant boiling point and cannot be separated by simple distillation.

**Hint**: Remember that an azeotropic mixture has a fixed composition and boiling point.

2. **Recognizing the Need for Absolute Alcohol**:
- Absolute alcohol is pure ethanol (100% ethanol) without any water content. To obtain absolute alcohol from rectified spirit, we need to remove the water.

**Hint**: Identify the difference between rectified spirit and absolute alcohol in terms of water content.

3. **Choosing the Right Method**:
- Among the options provided, we need to find a method that effectively removes water from the rectified spirit. The options include:
- Option 1: Removing water using concentrated sulfuric acid.
- Option 2: Removing water using phosphorous pentoxide.
- Option 3: Distilling over plenty of quicklime (calcium oxide).

**Hint**: Consider which method is most effective for dehydrating ethanol.

4. **Evaluating the Options**:
- **Option 1**: Concentrated sulfuric acid can dehydrate alcohols, but it can also lead to the formation of by-products and is not the most efficient for this purpose.
- **Option 2**: Phosphorous pentoxide (P2O5) is a strong dehydrating agent and can effectively remove water, but it is not commonly used in this context.
- **Option 3**: Quicklime (calcium oxide) is known to absorb water. When rectified spirit is distilled in the presence of quicklime, it absorbs the water, allowing for the separation of ethanol.

**Hint**: Think about the properties of quicklime and its ability to absorb moisture.

5. **Finalizing the Method**:
- The best method to prepare absolute alcohol from rectified spirit is by distilling the mixture in the presence of quicklime. This process removes water, allowing the ethanol to be collected in a purer form.

**Hint**: Remember that distillation with a dehydrating agent is a common laboratory technique for obtaining pure solvents.

6. **Conclusion**:
- Therefore, the correct answer is that absolute alcohol can be prepared from rectified spirit by distilling over plenty of quicklime (calcium oxide).

### Final Answer:
Absolute alcohol can be prepared from rectified spirit by distilling over plenty of quicklime (calcium oxide).