Question

Problem 2 (chapter 18.3, 2 points): The lead-acid battery is commonly used in cars. One electrode is a lead grid filled with spongy lead Pb(s). The other electrode is a lead grid filled with spongy lead oxide PbO2(s). The net reaction that occurs is: Pb(s)+PbO (s+2H(aq) 2HSO (aq) ->2PbSO4(s2H 0(0) a) Write down the half reactions that occur at each electrode. b) Identify the oxidation state of Pb in each of the species: Pb(s), PbO2(s) and PbSO4(s). Explain. c) Identify the anode and the cathode.Explain.

Answer 1

Overall Reaction can be represented as Pb (s) + Pb o_2 (s) + 2H_2 So_4 (aq) rightarrow 2 Pb So_4 (s) + 2H_2 o (l) Half cell Reactions are At Anode Anode is one electrode in electrochemical cell where oxidation takes place. Lead loses two electron and gets oxidised to Pb^2 + ions Pb (s) rightarrow Pb^2 + (aq) + 2e^- Pb^2 (aq) + So_4^2- (aq) rightarrow Pb So_4 (s) Overall Reaction at Anode is Pb (s) + So_4^2- (aq) rightarrow Pb So_4 (s) + 2e^- At Cathode: - Cathode is an electron where Reduction takes place in an electrochemical cell Pb o_2 is reduced at cathode Pb O_2 (s) + 4H^+ + 2e^- rightarrow Pb^2 + (aq) + 2 H_2 O Pb^2 + (aq) + So_4^2- (aq) rightarrow (Pb So_4 (s) Overall Reaction at cathode is Pb o_2 (s) + 4H^+ (aq) + So_4^2- (aq) + 2e^- rightarrow Pb (So_4) (s) + 2 H_2 O (l) \r\n Oxidation state Pb (s) rightarrow Lead in its elemental form has