Electrochemical CellsElectrochemical Cells(voltaic cells)(voltaic cells)

Electrochemical CellsElectrochemical Cells::

**Spontaneous Redox

Zn0 + Cu+2 Zn+2 + Cu0

Table J (Activity Series)Table J (Activity Series)::Single Replacement the more active metal replaces the less active metal

Oxidation: Zn Zn2+ + 2e-

Reduction: Cu+2 + 2e- Cu0

Voltaic CellsVoltaic Cells::**When the half reactions are separated and they force a flow of electricity.

Zn

Zn2+ ions

Cu

Cu2+ ions

wire

saltbridge

electrons

*Salt bridge allows ions to move between half cells.

Anode:Where oxidation takes place

Cathode:Where reduction takes place

Voltaic Cell Animation

1. Electrons are produced at the Zn electrode (anode)

Zn Zn2+ + 2e-

SummarySummary

Electrons produced causes negative charge

2. Electrons leave Zn electrode and pass through external circuit (wire)

3. Electrons at Cu electrode are used to reduce (cathode)

Cu+2 + 2e- Cu0

SummarySummary

Electrons used up causes positive charge

4. Salt bridge completes the circuit allowing ions to move

Dry CellsDry CellsZinc-Carbon batteries

Anode (-):OxidationZn Zn2+ + 2e-

Cathode (+):ReductionMn4++e- Mn3+

Fuel CellsFuel CellsOxidation of a fuel to produce electricity

2H2 + O2 2H2O

Anode (-):Oxidation2H2

0 4H+ + 4e-

Cathode (+):ReductionO2 + 4e- 2O2-

Electrolytic CellsElectrolytic Cells**Requires electricity for the reaction (called electrolysis)**Reverse of electrochemical cell

2NaCl 2Na + Cl2Cathode (-):ReductionNa+(aq) + e- Na(s)

Anode (+):Oxidation2Cl-(aq) Cl2(g) + 2e-

Used to get active metals: Na, K, Mg

Electrolysis of WaterElectrolysis of Water