Part a: To write the balanced equation for the net cell reaction:
Pb(s) l PbSO4 (s) l H2SO4 (aq) l PbO2(s), PbSO4 (s) l Pb (s)
Step 1: Identify cathode and anode from E°(refer to textbooks/online)
PbO2(s) + SO42-(aq) + 4 H+(aq) + 2e- → PbSO4(s) + 2 H2O(l) E° = 1.69 V
PbSO4(s) + 2 e- → Pb(s) + SO42-(aq) E° = -0.36 V
The cell diagram for the lead-acid cell that is used in automobile and truck batteries is
Pb(s) l PbSO4 (s) l H2SO4 (aq) l PbO2(s), PbSO4(s) l Pb (s)
where the comma between PbO2 (s) and PbSO4 (s) denotes a heterogeneous mixture of the two solids and the right-hand lead electrode is nonreactive.
a) Write a balanced equation for the net cell reaction:
b) Look up standard potentials for the oxidation and the reduction reactions, then calculate the value of E°cell.
c) Calculate the value of ΔG°rxn
d) Calculate the value of Ecell at 25°C is [H2SO4] = 10.0M
e) How many lead-acid cells are in a 12 V car battery? Round to the nearest integer.
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