18.8 Electrolysis

2 Types of electrochemistry1. Battery or Voltaic Cell – Purpose?2. Electrolysis - forces a current

through a cell to produce a chemical change that would not otherwise occur.

Battery – voltaic cell

Pb + H2SO4 PbSO4 + 2H+ + 2e- Anode

PbO2 + H2SO4 + 2e- + 2H + PbSO4 + 2H2O Cathode

Electrolysis of salt waterNa+, Cl-, and H20 are present

• Possible oxidation reactions.

2Cl- Cl2 + 2e-

2H2O O2 + 4H+ + 4e-

• Possible reduction reactions

Na+ + e- Na

2e- + 2H2O H2 + 2OH-

Electrolysis

• A process where electrical energy is used to produce a chemical change.

• Involves forcing a current through a cell to produce a change that would otherwise not occur.

• Electrolysis of water produces hydrogen gas and oxygen gas.

• Electrolysis is used to recharge lead storage batteries.

Electroplating

• A thin layer of one metal is deposited onto another. There is normally only one solution that supplies the metal needed.

+ -

Cu2+

FeCuCu Cu2+ + 2e-

Cu2+ + 2e- Cu