Storage cells and fuel cellsEdexcel A-Level Chemistry: Mind map

Exam questions on Storage cells and fuel cells

1. A car battery contains six identical lead–acid cells connected in series. Standard electrode potentials: PbO₂(s) + 4H⁺(aq) + SO₄²⁻(aq) + 2e⁻ ⇌ PbSO₄(s) + 2H₂O(l), E° = +1.69 V; PbSO₄(s) + 2e⁻ ⇌ Pb(s) + SO₄²⁻(aq), E° = −0.36 V.
   Explain why this battery can be recharged but a typical disposable cell cannot.2 marks
2. A bus company is testing a hydrogen–oxygen fuel cell with an alkaline electrolyte. Standard electrode potentials: O₂(g) + 2H₂O(l) + 4e⁻ ⇌ 4OH⁻(aq), E° = +0.40 V; 2H₂O(l) + 2e⁻ ⇌ H₂(g) + 2OH⁻(aq), E° = −0.83 V.
   Deduce the overall equation for the reaction in the fuel cell, and state one environmental advantage of this fuel cell at the point of use.2 marks
3. A company is developing portable fuel cells that use an acidic electrolyte. One design is supplied with hydrogen gas and the other is supplied with liquid methanol. In both designs the oxidant is oxygen from the air.
   Write the half-equation at each electrode of the hydrogen design, and the overall equation.3 marks