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Charging a Battery

Charging a Battery.

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Charging a Battery

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  1. Charging a Battery When you charge a battery, you are forcing the electrons backwards (from the + to the -). To do this, you will need a higher voltage backwards than forwards. This is why the ammeter in your car often goes slightly higher while your battery is charging, and then returns to normal. In your car, the battery charger is called an alternator. If you have a dead battery, it could be the battery needs to be replaced OR the alternator is not charging the battery properly.

  2. Zn (s) Zn2+ (aq) + 2e- + 2NH4(aq) + 2MnO2(s) + 2e- Mn2O3(s) + 2NH3(aq) + H2O (l) Zn (s) + 2NH4 (aq) + 2MnO2 (s) Zn2+ (aq) + 2NH3 (aq) + H2O (l) + Mn2O3 (s) Batteries Dry cell Leclanché cell Anode: Cathode: 19.6

  3. Pb (s) + SO2- (aq) PbSO4 (s) + 2e- 4 PbO2(s) + 4H+(aq) + SO2-(aq) + 2e- PbSO4(s) + 2H2O (l) 4 Pb (s) + PbO2 (s) + 4H+ (aq) + 2SO2- (aq) 2PbSO4 (s) + 2H2O (l) 4 Batteries Lead storage battery Anode: Cathode: 19.6

  4. Electrolysis is the process in which electrical energy is used to cause a nonspontaneous chemical reaction to occur. 19.8

  5. Electrolysis of Water 19.8

  6. Electrolysis and Mass Changes charge (Coulombs) = current (Amperes) x time (sec) 1 mole e- = 96,500 C = 1 Faraday 1 amp = 1 Coulomb / sec 19.8

  7. How much Ca will be produced in an electrolytic cell of molten CaCl2 if a current of 0.452 A is passed through the cell for 1.5 hours? 2 mole e- = 1 mole Ca mol Ca = 0.452 x 1.5 hr x 3600 C s 2Cl- (l) Cl2 (g) + 2e- hr s Ca2+(l) + 2e- Ca (s) 1 mol Ca 1 mol e- x x 96,500 C 2 mol e- Ca2+ (l) + 2Cl- (l) Ca (s) + Cl2 (g) Anode: Cathode: = 0.0126 mol Ca = 0.50 g Ca 19.8

  8. A 40.0 amp current flowed through molten iron(III) chloride for 10.0 hours (36,000 s).  Determine the mass of iron and the volume of chlorine gas (measured at 25oC and 1 atm) that is produced during this time.

  9. Write the half-reactions that take place at the anode and at the cathode. Calculate the number of moles of electrons

  10. Calculate the moles of iron and of chlorine produced using the number of moles of electrons calculated and the stoichiometries from the balanced half-reactions.  According to the equations, three moles of electrons produce one mole of iron and 2 moles of electrons produce 1 mole of chlorine gas.

  11. Calculate the mass of iron using the molar mass and calculate the volume of chlorine gas using the ideal gas law (PV = nRT).

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