How is oxygen prepared from air ?

Explanation

### Step-by-Step Solution:

1. **Understanding the Composition of Air**:
- Air is primarily composed of nitrogen (approximately 78%) and oxygen (approximately 21%), along with trace amounts of other gases.

2. **Liquefying Air**:
- The first step in preparing oxygen from air is to liquefy it. This is typically done by cooling the air to very low temperatures until it becomes a liquid.

...