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Ch15 - Coggle Diagram

- - - - The only not steady voltage in daily (fall rapidly)
      - Small current
    - - Dry cell
        
        Thick paste, not aq solution
        
        Light, cheap, durable, small, easily available, portable
      - Long time
      - Large and steady-falling V
    - - Long service life
      - Very small and steady current
      - Constant V
    - - Materials do not disintegrate
      - Fking toxic
      - Usually contain small amount of Mercury, highly toxic
      - Solution
        
        Use mains electricity when possible
        
        Use rechargeable ones
        
        Produce alkaline-Mn cells with little or no Mercury
        
        Green cells
  - - - Make use of fuel to generate electricity
        
        Electrodes not involved int chemical reaction
        
        Never be used up as "unlimited" supply of oxygen on Earth
        
        H2 can be produced from
        
        Water
        
        Natural gas
        
        Landfill gas
        
        Methane
        
        Methanol
    - - Fuel: H2
      - Oxidizing agent: O2
      - 2 electrodes separated by an electrolyte
        
        Thin layer of metal coated on each electrode
        
        To catalyze reaction of H2, O2
        
        Anode-: Porous nickel electrode
        
        2H2(g)+4OH-(aq) -> 4H2O(g) + 4e-
        
        Cathode+: Porous nickel electrode coated with nickel oxygen
        
        O2(g) + 2H2O(l) + 4e- ->
        
        Electrolyte: Hot concentrated KOH(aq)
- - - - Steady V of 1.2V - 7.2V
      - High energy density
      - Eco friendly
      - High discharge currents
    - - Large and steady V and current: 3.6-4.0V
      - Heavy and continued use
    - - Wet cell
      - H2SO4 (aq)
      - Accumulate/store electrical energy
      - Corrosive