Aluminium metal is not acted upon by pure water as

Options

A. it is not a reactive metal
B. It is a light metal
C. it is protected by a film of aluminium oxide
D. Impurities in water are essential for the reaction to occur

Answer

### Step-by-Step Solution:

1. **Understanding the Reactivity of Aluminium**:
Aluminium is known to be a reactive metal. However, it does not react with pure water under normal conditions.

2. **Formation of Aluminium Oxide**:
When aluminium is exposed to air, it reacts with oxygen to form a thin layer of aluminium oxide (Al₂O₃) on its surface. This layer is very thin, approximately 4 nanometers thick.

3. **Role of Aluminium Oxide Layer**:
The aluminium oxide layer acts as a protective barrier. It prevents further oxidation of the underlying aluminium metal and inhibits its reaction with water. This phenomenon is known as passivation.

4. **Implications of Passivation**:
Due to the presence of the aluminium oxide layer, aluminium does not react with pure water. This layer effectively reduces the metal's reactivity, making it resistant to corrosion and wear.

5. **Evaluating the Options**:
- Option 1: "It is not a reactive metal." - Incorrect, as aluminium is reactive.
- Option 2: "It is a light metal." - Incorrect, as being light does not prevent reactivity.
- Option 3: "It is protected by a film of Aluminium Oxide." - Correct, as this explains why it does not react with water.
- Option 4: "Impurities in water are essential for the reaction to occur." - Incorrect, as pure water does not react due to the oxide layer.

6. **Conclusion**:
The correct answer is that aluminium is not acted upon by pure water because it is protected by a film of aluminium oxide.