Electrolysis 2 Types of electrochemistry 1. Battery or Voltaic Cell – Purpose? 2. Electrolysis - forces a current through a cell to produce a chemical change that would not otherwise occur.

Figure 18.6: Schematic of one cell of the lead battery. Pb + H 2 SO 4  PbSO 4 + 2H + + 2e - Anode PbO 2 + H 2 SO 4 + 2e - + 2H +  PbSO 4 + 2H 2 O Cathode

Electrolysis of salt water Na +, Cl -, and H 2 0 are present Possible oxidation reactions. 2Cl -  Cl 2 + 2e - 2H 2 O  O 2 + 4H + + 4e - Possible reduction reactions Na + + e -  Na 2e - + 2H 2 O  H 2 + 2OH -

Electroplating A thin layer of one metal is deposited onto another. There is normally only one solution that supplies the metal needed. + - Sn 2+ FeSn Sn  Sn e - Sn e -  Sn

Electrochemical Cells Comparison Voltaic Cells 2 cells 2 solutions Saltbridge Anode/oxidation e- flow e- flow  anode  cathode  oxid.  red Electrolysis 1 cell 1 solution Anode/oxidation e- flow e- flow  anode  cathode  oxid.  red

Purpose of Electrolysis Production of metals from their ores Pure aluminum was very rare until electrolysis was used Today production consumes 4.5% of all electricity in the United States

Drawing Electroplating Draw the electroplating of silver onto another metal Make sure to label the half reactions, anode, cathode, direction of electron flow, and direction of ion flow

Jumpstarting a car Order?  Positive leads then negative on good battery. Finally ground other lead far from battery Why?  Avoiding a spark with the hydrogen and oxygen gases