19: Electrochemistry & its AppsSecondary BatteriesSecondary BatteriesSecondary BatteriesClicker19.10 Fuel Cells19.11 ElectrolysisElectrolysisElectrolysisElectrolysisElectroplatingCorrosion: Product-Favored ReactionsCorrosion: Product-Favored ReactionsCorrosion ProtectionCorrosion PreventionSlide 1611: Solids and Materials11: Liquid vs Solid, Macro-Nano11: Liquid vs Solid, ORDER!11: Mechanical Properties Differ11.5 Types of SolidsWhat type of solid does ammonium nitrate, NH4NO3, form?19: Electrochemistry & its Apps19.1 Redox Reactions19.2 Using Half-Reactions19.3 Electrochemical Cells19.4 Echem Cells and Voltage19.5 Using Reduction Potentials19.6 E° and Gibbs Free Energy19.7 Concentration on Cell Potential19.8-10 Applications of Redox19.11 Electrolysis19.12 Electron Counting19.13 CorrosionFriday October 17, 2014Read: Sections 19.10-19.13 for FridayEnd of Chapter 19 Problems: 6, 7, 10, 12, 14, 16, 18, 20, 22, 26, 28, 30, 32, 34, 36, 38, 40, 42, 46, 48, 50, 52, 56, 58, 59, 61, 63, 80, 82Friday October 17, 2014Read: Sections 19.10-19.13 for FridayEnd of Chapter 19 Problems: 6, 7, 10, 12, 14, 16, 18, 20, 22, 26, 28, 30, 32, 34, 36, 38, 40, 42, 46, 48, 50, 52, 56, 58, 59, 61, 63, 80, 82Cd(s) + 2 NiO(OH)(s) + 2 H2O(ℓ) →Cd(OH)2(s) + 2 Ni(OH)2(s)net: E° = +1.299 VSecondary BatteriesCd(s) + 2 OH–(aq) → Cd(OH)2(s) + 2 e–2[NiO(OH)(s) + H2O(ℓ) + e– → Ni(OH)2(s) + OH–(aq)]Nickel-Cadmium (Nicad)Secondary BatteriesMH(s) + OH–(aq) → M(s) + H2O(ℓ) + e– NiO(OH)(s) + H2O(ℓ) + e– → Ni(OH)2(s) + OH–(aq)Nickel-metal hydride (NiMH)Avoids toxic Cd. E°cell = +1.4 Vmetal alloy (Ni or rare earth)in KOH electrolyteMH(s) + NiO(OH)(s) → M(s) + Ni(OH)2(s)Secondary BatteriesLi(s) (in polymer) → Li+ (in polymer) + e– Li+ ( in CoO2 ) + e– + CoO2 → LiCoO2 Lithium Ion. Low mass, high energy density.Li(s) + CoO2(s) → LiCoO2(s) Ecell = 3.4 VClickerAre there any “perfect” batteriesA.NoB.YesTo make a rechargeable battery, you wantA. The products to be insoluble- solidsB. The products to sit close to the electrodes- need closeC. Cheap and light-weight materialsD. To worry about the entire cycle of reactantsand productsE. All of the above19.10 Fuel CellsConvert bond energy directly into electricity.Proton-Exchange Membrane (PEM) fuel cell.•Porous graphite electrodes.•Pt catalyst coated on both sides of the membrane.H2 → 2 H+ + 2 e–½ O2 + 2 H+ + 2 e–→ H2OH2 + ½ O2→ H2O E° = 0.7 VElectrolytic cell: Applied voltage forces a reaction to occur. e.g. electrolysis of molten NaCl:Na(ℓ) and Cl2(g) produced if > 4.1 V is applied.However, melting NaCl takes lots of energy…19.11 Electrolysis2 Na+(in melt) + 2 e–→ 2Na(ℓ)2 Cl–(in melt) → Cl2(g) + 2 e–2 Na+(melt) + 2 Cl–(melt) → Cl2(g) + 2 Na(ℓ) E°red/ V –2.714 1.358 –4.072Aqueous solutions? Other reactions can occur. Consider KI(aq):ElectrolysisK+(aq) + e– → K(s) 2 H2O(ℓ) + 2 e– → H2(g) + 2 OH–(aq)E° = –2.925 VE° = –0.828 VreductionsI2(aq) +2e– → 2I–(aq) O2(g) + 4 H3O+ + 4e– → 6 H2O(ℓ) E° = +0.535 VE° = +1.229 VoxidationsAqueous reduction will not occur.Aqueous oxidation will not occur.Reduction Half Reaction E° (V)F2(g) +2 e– → 2 F-(aq) +2.87H2O2(aq) + 2 H3O+2 e– → 4 H2O(ℓ) +1.77Cl2(g) +2 e– → 2 Cl-(aq) +1.358O2(g) + 4 H3O+(aq) + 4 e– → 6 H2O(ℓ) +1.229Br2(g) +2 e– → 2 Br-(aq) +1.066Ag+(aq) + e– → Ag(s) +0.7992 H3O+(aq) + 2 e– → H2(g) + 2 H2O(ℓ) 0.00Ni2+(aq) + 2 e– → Ni(s) –0.25Fe2+(aq) + 2 e– → Fe(s) –0.44Zn2+(aq) + 2 e– → Zn(s) –0.7632 H2O(ℓ) + 2 e– → H2(g) + 2 OH-(aq) –0.8277Al3+(aq) + 3 e– → Al(s) –1.66Na+(aq) + e– → Na(s) –2.714K+(aq) + e– → K(s) –2.925ElectrolysisSummaryMetal ions are reduced if E°red > −0.8 VAqueous Na+, K+, Mg2+, Al3+ … cannot be reduced.ElectrolysisAnions can be oxidized if E°red < +1.2 VAqueous F– … cannot be oxidized.In practice Eexpt > E calc. An Overvoltage is needed.ElectroplatingMetal objects can be used as a cathode and have another metal plated on to them.Nonmetal objects can be made conducting if lightly dusted with graphite powder.Gold platingPlatings are used to:•decorate•protect an underlying materialAu3+ + 3e– → Au(s)Anode: M(s) Mn+ + n e–Corrosion: Product-Favored ReactionsOxidation of metals by the environment.Cathode: Often involve water and/or O2 O2(g) + 2 H2O(ℓ) + 4 e– → 4 OH–(aq) 2 H2O(ℓ) + 2 e– → 2 OH–(aq) + H2(g)Anode: 2[Fe(s) Fe2+ + 2 e–]Cathode: O2(g) + 2 H2O(ℓ) + 4 e– 4 OH–(aq) 2 Fe(s) + O2(g) + 2 H2O(ℓ) 2 Fe(OH)2(s)Corrosion: Product-Favored ReactionsIron “rusts”Metal salts (NaCl, CaCl2…) act as salt bridges between anode and cathode speeding corrosion.Converted to rust by O2 and H2ORust(Fe2O3·xH2O(s); x = 2 – 4)Corrosion ProtectionAnodic inhibition•Paint or coat the surface.Cathodic protection •Force another metal to act as the anode•Attach a more reactive metal which will corrode first.•Sacrificial anode•Form thin metal oxide coat, e.g., stainless steel2 Fe(s) + 2 Na2CrO4(aq) + 2 H2O(ℓ)→ Fe2O3(s) + Cr2O3(s) + 4 NaOH(aq)Corrosion PreventionIron can also be galvanized (coated with Zn):Zn(OH)2 (insoluble film) forms on the surface.Zn2+ + 2e– → Zn E° = –0.763 V Ox1 or Fe2+ + 2e– → Fe E° = –0.44 V Ox2 ?O2(g) + 2 H2O(ℓ) + 4 e– → 4 OH–(aq) +1.229 (Red)Stephen C. Foster • Mississippi State UniversityJohn W. MooreConrad L. StanitskiPeter C. Jurswww.cengage.com/chemistry/mooreChapter 11Liquids, Solids and Materials11: Solids and Materials11.5 Types of Solids11.6 Crystalline Solids11.7 Network Solids11.8 Materials Science11.9 Metals, Semiconductors, and Insulators11.10 Silicon and the Chip11.11 Cement, Ceramics and GlassWednesday, March 5, 2014Read: Sections 11.5, 11.6 for WednesdaySections 11.7, 11.8 and 11.9 for FridayEnd of Chapter 11 Problems: 59, 61, 63, 65, 72Wednesday, March 5, 2014Read: Sections 11.5, 11.6 for WednesdaySections 11.7, 11.8 and 11.9 for FridayEnd of Chapter 11 Problems: 59, 61, 63, 65, 7211: Liquid vs Solid, Macro-Nano11: Liquid vs Solid, ORDER!A. Liquid-like crowdsB. Solid-like paradesWhich arrangement has more order?11: Mechanical Properties DifferSolids will flex and liquids will flow11.5 Types of SolidsIonic (ionic bonding)•Hard, brittle, high mp. Some are water soluble.Metallic (metallic bonding,