electrochemistry

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  • Created by: chaztil
  • Created on: 02-01-20 15:45
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  • batteries and electrchemical cells
    • fuel cells
      • used in cars rather than an internal combustion engine -more efficient -only waste product is water so no chemical waste -dont need to be recharged
      • -energy needed to get supply of oxygen and water -hydrogen highly flammable -amny more leaks if you used the current system
    • conventional representation of cells
    • rechargeable and non-rechargeable cells
      • lithium batteries are rechargeable - lithium cobalt oxide electrode- graphite electrode- lithium salt in organic solvent = electrolyte
        • cathode (negative electrode)= Li--Li+ +e-
        • anode (positive electrode) = Li+ + CoO2 + e-
      • nickle cadium cell is also rechargeable - Ni is a good ox agent (so gets reduced) Cd is a good reducing agent (so gets oxidized)
        • Ni reduced from +3 in NiO to +2 in Ni(OH)2
        • Cd oxidised from 0 to =2 in Cd(OH)2
      • non rechargeable cells are used as batteries
        • the zinc carbon battery - short shelf life because the zinc casing also gets oxidized by O2 so zinc chloride could leak out of the battery
          • ammonium chloride reduced to ammonium hydroxide
          • zinc oxidized to zinc chloride
          • its a dry cell battery as the electrolyte is a paste
    • creating an EMF
    • required practical - measuring EMF
    • the standard hydrogen electrode
      • standard conditions: 1 atm - 25 degrees c - 0.1 mol/dm3 conc of H+ ions
      • EMF = Erhs-Elhs
        • so if you put the standardized 0.00V hydrogen electrode on the left hand side the EMF will be that of the other half cell
      • hydrogen and oxygen = water

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