State which of these reactions occurs at the positive electrode in a lead-acid cell during discharge, explaining your answer.\n\nI: $\text{Pb} + \text{SO}_4^{2-} \rightarrow \text{PbSO}_4 + 2e^-$.\nII: $\text{PbO}_2 + 4\text{H}^+ + \text{SO}_4^{2-} + 2e^- \rightarrow \text{PbSO}_4 + 2\text{H}_2\text{O}$.
Use the Data Booklet and the equations I and II above to calculate the voltage produced by a lead-acid cell under standard conditions.
State the oxidation state for nickel in $\text{NiO(OH)}$.
Suggest a likely advantage of these batteries compared with lead-acid batteries.
Hydrogen fuel cells have been proposed as the next major advance in electrically powered vehicles. In these fuel cells, hydrogen is oxidized to produce water, using a catalyst and inert electrodes.\n\nSuggest a material for the electrodes.
Use your knowledge of hydrogen to suggest a disadvantage of these fuel cells in powering vehicles.
Many countries around the world are developing methods for recycling materials that are valuable or that need large amounts of energy to make.\n\nFor each of the recyclable materials below, state whether recycling this material is important for saving energy or for saving resources. Use your chemical knowledge to explain each choice.\n\nglass\n\nsteel\n\nplastics