Batteries Zn(Hg) + 2OH - (aq) ZnO (s) + H 2 O (l) + 2e - Anode: Cathode: HgO (s) + H 2 O (l) + 2e - Hg (l) + 2OH - (aq) Zn(Hg) + HgO (s) ZnO (s) + Hg (l) Mercury Battery 19.6
Batteries Anode: Cathode: Lead storage battery PbO 2 (s) + 4H + (aq) + SO 2- (aq) + 2e - PbSO 4 (s) + 2H 2 O (l) 4 Pb (s) + SO 2- (aq) PbSO 4 (s) + 2e - 4 Pb (s) + PbO 2 (s) + 4H + (aq) + 2SO 2- (aq) 2PbSO 4 (s) + 2H 2 O (l) 4
What is the standard emf of an electrochemical cell made of a Cd electrode in a 1.0 M Cd(NO 3 ) 2 solution and a Cr electrode in a 1.0 M Cr(NO 3 ) 3 solution? Cd 2+ (aq) + 2e - Cd (s) E 0 = -0.40 V Cr 3+ (aq) + 3e - Cr (s) E 0 = -0.74 V Cd is the stronger oxidizer Cd will oxidize Cr E 0 = E cathode - E anode cell 00 E 0 = -0.40 – (-0.74) cell E 0 = 0.34 V cell
Electrolysis Electrolysis of Water: Requires an electrolyte species, that is less easily oxidized and reduced than water, to carry the current. Anode: Water is oxidized to oxygen gas. –2 H 2 O(l) O 2 (g) + 4 H + (aq) + 4 e – Cathode: Water is reduced to hydrogen gas. –4 H 2 O(l) + 4 e – 2 H 2 (g) + 4 OH – (aq)
Niagara Falls and Typhoid How Does Niagara Falls Helps to Fight Typhoid ?
19.8 Electrolysis is the process in which electrical energy is used to cause a nonspontaneous chemical reaction to occur.
Electrolysis Electrolysis of Molten Sodium Chloride: Electrolysis of Aqueous Sodium Chloride: uses different processes to molten sodium chloride. The observed product at the anode is Cl 2, and Na metal at the cathod.