Octane number of petrol (gasoline) can be increased by

Options

A. Aromatisation
B. Cracking
C. By adding anti-knocking agent
D. Nitration

Explanation

### Step-by-Step Solution:

1. **Understanding Octane Number**: The octane number is a measure of a fuel's ability to resist knocking during combustion. A higher octane number indicates better performance in engines, particularly in high-compression engines.

2. **Methods to Increase Octane Number**: There are several methods to increase the octane number of petrol (gasoline). The two primary methods mentioned are aromatization and cracking.

3. **Aromatization**:
- Aromatization is a process where straight-chain hydrocarbons (alkanes) are converted into aromatic hydrocarbons.
- Aromatic compounds generally have higher octane numbers compared to their straight-chain counterparts.
- This process involves the use of catalysts and typically occurs at high temperatures.

4. **Cracking**:
- Cracking is the process of breaking down larger hydrocarbon molecules into smaller, more useful ones.
- There are two main types of cracking: thermal cracking and catalytic cracking.
- Both processes can produce branched-chain hydrocarbons and aromatic compounds, which have higher octane ratings than straight-chain hydrocarbons.

5. **Conclusion**: Therefore, the octane number of petrol can be increased by both aromatization and cracking.

### Final Answer:
The octane number of petrol (gasoline) can be increased by methods such as aromatization and cracking.

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