1. The lead-acid cell

2. Dilute (2.0 mol L –1 ) sulfuric acid is put in a beaker.

3. Two clean lead plates are connected to wires. The block of wood just keeps them from touching each other.

4. The lead plates are placed in the acid, with the wires connected to a power supply with a voltage of about 3 V. Charging the cell

5. We see small bubbles of hydrogen (from the acid) forming at the negative electrode. 2H + + 2e – → H 2 If Pb 2+ had been present in the solution, then Pb metal would form at this electrode instead.

6. When the plates are withdrawn from the beaker, we see that the left-hand plate (connected to the positive terminal of the power supply) is coated in a very dark substance. Compare the bottom of this plate to the colour at the very top. It is PbO 2 (s).

7. The plates are put back in the acid and the wires connected to a 2V light bulb. The bulb glows brightly. Discharging the cell

8. The charge-discharge cycle can occur many times: the lead-acid cell is rechargable.

9. Each cell of a commercial lead-acid battery contains 2 lead plates suspended in a sulfuric acid solution. The cells are connected in series, and each delivers 2 V, so a 12 V car battery contains 6 cells.