What exactly are batteries? Batteries Connects objects Converts chemical---electrical energy Two or more voltaic cells connected to each other Types of Batteries 1)Dry Cells Alkaline batteries 2)Lead Storage Batteries 3)Fuel Cells Dry CellsGeneral Composed of primary cells Irreversible redox reactions, not capable of being recharged Fairly expensive and maximum voltage of 1.55V Typical batteries---seen with flashlights, other electronics Dry CellsIn Detail Anode: Zn (s) Zn +2 (aq) + 2e - Cathode: Mixture of carbon rod and MnO 2(s) Electrolyte mixture of NH 4 Cl and ZnCl 2 2MnO 2(s) +NH 4 + (aq) + 2e - Mn 2 O 3(s) + 2NH 3(g) + H 2 O (l) Dry CellsAlkaline Cells Longer shelf-life, more current generated over time, more expensive Different electrolyteKOH Same half-reactions but occur in basic solution. Reduction: 2MnO 2(s) + H 2 O (l) + 2e - Mn 2 O 3(s) + 2OH - (aq) Oxidation: Zn (s) + 2OH - ZnO (s) + H 2 O (l) + 2e - No decrease in voltage as current is generated. Lead Storage Battery Made by several lead plates connected together and all in a H 2 SO 4 solutioncomposed of secondary cells Reversible Rechargeable Lead Storage BatteryIn Detail Many voltaic cellsincrease current capacity Each voltaic cell has approximately 2V capacity, 6 cells connected together and results in a 12V battery PbSO 4(s) produced at both electrodes Lead Storage BatteryIn Detail Anode: Pb (s) + SO 4 -2 (aq) PbSO 4(s) + 2e - Cathode: PbO 2(s) + SO 4 -2 (aq) + 4H + + 2e - PbSO 4(s) + 2H 2 O (l) Electrolyte solution is sulfuric acid (H 2 SO 4 ) Lead Storage Battery Discharging/Recharging Discharging PbSO 4 collects at electrodes Water dilutes sulfuric acid solution Recharging Requires external energy source Forces electrons to move in the direction of the reverse reaction Produces negative cell potential, nonspontaneous Fuel Cells Electrochemical cell that uses a reaction with oxygen for electrical energy Components exist outside typical battery Fuel + Oxygen Oxidation products Example HydrogenOxygen Fuel Cell Homework Electrochemistry Test Study Guide