Photocatalysis is useful in breakdown of

Options

A. Acids and alkalies
B. Chemicals containing heavy metals
C. Toxic chemicals
D. All the above

Answer

**Step-by-Step Solution:**

1. **Understand the Concept of Photocatalysis**:
- Photocatalysis is a process that uses light to accelerate a chemical reaction, specifically the breakdown of substances. The term 'photo' refers to light, and 'catalysis' refers to the acceleration of a reaction.

2. **Identify the Components of Photocatalysis**:
- Common photocatalysts include titanium oxide (TiO2) and zinc oxide (ZnO). These materials, when exposed to light, can facilitate the breakdown of various harmful substances.

3. **Recognize the Role of Hydroxyl Ions**:
- When titanium oxide and zinc oxide are illuminated, they generate hydroxyl ions (OH-). These ions are crucial in breaking down toxic chemical bonds.

4. **Identify the Types of Substances Broken Down**:
- Photocatalysis is particularly effective in breaking down toxic chemicals such as formaldehyde, gasoline (petrol), and chlorofluorocarbons (CFCs). These substances are harmful to the environment and human health.

5. **Evaluate the Given Options**:
- Option A: Acids and alkalis - Incorrect, as photocatalysis does not primarily target these.
- Option B: Chemicals containing heavy metals - Incorrect, as photocatalysis is not effective for these.
- Option C: Toxic chemicals - Correct, as photocatalysis is specifically useful for breaking down toxic substances.
- Option D: All of the above - Incorrect, since not all the options are correct.

6. **Select the Correct Answer**:
- Based on the evaluation, the correct answer is **Option C: Toxic chemicals**.