Consider the reaction that takes place at the cathode during the charging of a lead acid battery

Question

What are the reactants of this reaction?

A) PbO2(s), HCl(aq)

B) PbSO4(s), H2O(l)

C) Pb(s), H2SO4(aq)

D) PbSO4(s), H

E) Pb(s), HCl(aq)

Answer 1

A lead acid battery works through the reaction of PbO2 and Pb.  These species must therefore be consumed when the battery is used, and produced when it is charged.  Reduction always takes place at the cathode.  Thus, we will be making the reduced reactant, Pb, at the cathode.  This leaves answers C and E.  The "acid" in lead acid batteries is sulfuric acid, H2SO4.  When the PbO2, Pb, and H2SO4 react, PbSO4 is formed.  When the battery is charged, this is disproportionated into Pb and PbO2.  The sulfate gets released as H2SO4, so the answer is C.