CHEM 2C Farahat Batteries

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Lead (Acid) Storage

Typical car battery, anode is Pb, cathode is Pb/PbO, both are dipped into sulfuric acid.

Anode rxn: Pb + HSO₄^- → PbSO₄ + H⁺ + 2e^-

Cathode rxn: PbO₂ + HSO₄^- + 3H⁺ + 2e^- → PbSO₄ + 2H₂O

-6 cells x 2V = 12V, charged by alternator, recharged by jump-start

-Only Wet Battery

Dry Cell (Leclanche) Acid Version

Anode is Zn inner case, cathode is NH₄Cl _(s)/C in MnO_{2 (s)}

Anode rxn: Zn → Zn⁺² + 2e^-

Cathode rxn: 2NH₄⁺ + 2MnO₂ + 2e^- → Mn₂O₃ + 2NH₃ + H₂O

-Cell potential is 1.5 V

-Calculator, watch, portable radio

Dry Cell (Leclanche) Alkaline Version

Anode is Zn inner case, cathode is NaOH _(s) or KOH _(s)/C in MnO_{2 (s)}

Anode rxn: Zn + 2OH^- → ZnO + H₂O + 2e^-

Cathode rxn: 2MnO₂ + H₂O + 2e^- → Mn₂O₃ + 2OH^-

-Zinc corrodes less rapidly in basic conditions, so batteries hold charge for long time, have longer shelf life, and longer working time

Silver Cell

Anode is Zn, cathode is Ag₂O/basic medium

-Ag₂O is an oxidizing agent

Mercury Cell

Cathode is Zn, anode is HgO/basic medium

-Calculators

-HgO is an oxidizing agent

Nickel-Cadium Battery

Anode is Cd/OH^-, cathode is NiO₂

Anode rxn: Cd + 2OH^- → Cd(OH)₂ + 2e^-

Cathode rxn: NiO₂ + 2H₂O + 2e^- → Ni(OH)₂ + 2OH^-

-Rechargable

Lithium-Ion Batteries

Anode is Li,C6. Cathode is LiCoO₂

-Used in a wide variety of appliances; cell phones, laptop computers, power tools, GPS, etc.

Fuel Cells

Anode is H₂/OH^-, cathode is O₂

Anode rxn: 2H₂ + 4OH^- → 4H₂O + 4e^-

Cathode rxn: 4e^- + O₂ + 2H₂O → 4OH^-

-Burns cleanly with water as the only by-product

-More efficient than mechanical electrical generators

-Very expensive