Acid used in lead storage battery is sulphuric acid. Explain.

Answer

### Step-by-Step Solution:

1. **Understanding Lead Storage Battery**:
- A lead storage battery, also known as a lead-acid battery, is a type of rechargeable battery commonly used in various applications, such as in vehicles and backup power systems.

**Hint**: Think about where you commonly see lead-acid batteries used.

2. **Role of Sulfuric Acid**:
- Sulfuric acid (H₂SO₄) serves as the electrolyte in lead storage batteries. It is crucial for the chemical reactions that occur during the charging and discharging processes.

**Hint**: Consider why an electrolyte is important in a battery.

3. **Discharge Process**:
- During the discharge cycle, the battery converts chemical energy into electrical energy. The lead (Pb) and lead dioxide (PbO₂) electrodes react with sulfuric acid to produce lead sulfate (PbSO₄) and water (H₂O).

**Hint**: Recall what happens to the battery's components when it is providing power.

4. **Reactions at the Electrodes**:
- At the anode (negative electrode), lead reacts with the sulfate ions from sulfuric acid to form lead sulfate and release electrons:
- Reaction: Pb + HSO₄⁻ → PbSO₄ + 2e⁻ + 2H⁺
- At the cathode (positive electrode), lead dioxide reacts with sulfate ions and hydrogen ions to form lead sulfate and water:
- Reaction: PbO₂ + HSO₄⁻ + 3H⁺ + 2e⁻ → PbSO₄ + 2H₂O

**Hint**: Visualize the flow of electrons and ions during these reactions.

5. **Overall Reaction**:
- The overall reaction during discharge can be summarized as:
- 2Pb + PbO₂ + 2HSO₄⁻ → 3PbSO₄ + 2H₂O
- This shows how sulfuric acid is consumed and converted into lead sulfate and water.

**Hint**: Think about how the battery's capacity is affected by these reactions.

6. **Recharging the Battery**:
- When the battery is recharged, the reactions are reversed, converting lead sulfate and water back into lead, lead dioxide, and sulfuric acid, restoring the battery's original state.

**Hint**: Consider what happens to the battery when it is plugged in to recharge.

### Conclusion:
The use of sulfuric acid in lead storage batteries is essential for facilitating the electrochemical reactions that allow the battery to store and release energy efficiently.