Electrochemical Cell

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Electrochemical Cell

• Electrochemical cells a device that converts
  chemical energy into electrical energy or vice
  versa
• Electric current is produced by movement of
  electrons
• Redox transfer of electrons
• Soelectrochemical cells make use of redox
  reactions to produce a current

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Voltaic Cells

• Voltaic Cells a type of electrochemical cell
  that converts chemical energy to electrical
  energy
• The first voltaic cell was invented by Alessandro
  Volta in 1800.
• Voltaic cells take advantage of spontaneous (a
  reaction that will happen naturally) redox
  reactions

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Voltaic Cell

• Requires two half-cells, a salt bridge, and a
  wire to connect the two half-cells
• Half-cell where one part of the redox occurs
  (either the oxidation or the reduction)
• Salt bridge allows ions to pass from 1
  half-cell to the other without allowing the
  solutions to mix completely

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Voltaic Cells

• The half-cell that contains the oxidation is the
  Anode (where the electrons are produced)
• The half-cell that contains the reduction is the
  Cathode (where the electrons are consumed)

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Voltaic Cell

• Anode Oxidation occurs here
• Cathode Reduction occurs here
• e- flow from the anode to the cathode
• Anions (from the salt bridge) flow toward the
  anode
• Cations (from the salt bridge) flow toward the
  cathode
• Cathode will increase in mass

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Electrical Potential

• Electrical Potential measure of a cells
  ability to produce an electric current (in Volts)
• Ecell Ered Eoxid
• We want a positive electrical potential
• Positive electrical potential spontaneous
  reaction

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Electrical Potential

• Example 1
• Cu e- ? Cu E 0.52 V
• Ag e- ? Ag E 0.80 V
• Ecell Ered Eoxid
• Ecell 0.80 0.52
• Ecell 0.28 V
• SoAg is reduced, Cu is oxidized
• Cu ? Cu e- Oxidized - Anode
• Ag e- ? Ag Reduced Cathode
• Ag Cu ? Ag Cu

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Dry Cell

• Type of voltaic cell in which the electrolyte
  (salt bridge) is a paste

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Lead Storage Battery

• Battery group of connected cells

Car battery
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Lead Storage

• Oxidation Pb(s) SO4-2(aq) ? PbSO4(s) 2e-
• Reduction
• PbO2 (s) 4 H (aq) SO4-2(aq) 2e- ?
  PbSO4(s) 2H2O (l)

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Lead Storage Batteries

• The redox reaction is spontaneous
• The battery recharges itself (the reverse
  reaction). This reaction is not spontaneous, it
  requires the alternator to make it go
• Thereotically batteries would last forever
• Butsome lead sulfate will fall from the
  electrodes (no longer making it able to recharge)

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Fuel Cell

• Another type of voltaic cell
• Renewable electrodes (continuous energy supply)
• Electrodes are gases, not metals
• Earth Friendly

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Fuel Cell

• Anode side2H2 gt 4H 4e-
• Cathode sideO2 4H 4e- gt 2H2O
• Net reaction2H2 O2 gt 2H2O
• Fuel Cell animation

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Electrolytic Cells

• Use electrical energy to make chemical energy
• Used to make non-spontaneous reactions occur
• Need an outside power source to push electrons
• Uses only 1 solution
• Used for electroplating

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Electrolytic Cell
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Electroplating

• Anode Cathodeoxidation
  reduction
• Ag ? Ag e- Ag e- ? Ag
• Overall reaction Ag ? Ag e- ? Ag or
• Ag ? Ag