Why is it desirable to use unleaded petrol in vehicles fitted with catalytic converters?

Explanation

### Step-by-Step Solution:

1. **Understanding Catalytic Converters**:
- Catalytic converters are devices in vehicles that convert harmful pollutants from the engine exhaust into less harmful emissions. They primarily target pollutants like carbon monoxide (CO) and nitrogen oxides (NO).

2. **Role of Catalysts**:
- The catalytic converter contains precious metals such as platinum (Pt) and palladium (Pd) that act as catalysts. These metals facilitate the chemical reactions that convert harmful gases into less harmful substances like carbon dioxide (CO2) and nitrogen (N2).

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