Lesson 9: Electrolytic Cells, Chloride Anomaly, Change of Reference Half Cell

Standard Reference Half Cell

• E not cell half reaction can’t be determined

• Voltmeters measure the diff between two half cells

• Zero point is chosen to comapre other half reactions

Electrolytic Cell

• External power source used to make a non spontaneous redox reaction

• Involves two electrodes and an electrolyte

Electrolysis

• Forcing a non spontaneous redox reaction by supplying electrical NRG

• External power source acts like an electron pump using electrical NRG to do work on electrons and promote electron transfer

Procedure to Analyze Electrolytic Cells

1. Identify SOA and SRA

2. Write half reactions

3. Balance electrons and write net cell reaction + cell potential

4. IF required state the minimum electric potential (V)

5. If diagram is needed write one down (shown on pic)

Voltaic Cell

• Anode to cathode

• Spontaneous

• Anions = Anode = SRA = Oxidation

• Cations = Cathode = SOA = reduction

• Positive standard cell potential

• Porous boundary

• Produces electricity

Electrolytic Cell

• Anions = Anode = SRA = Oxidation

• Cations = Cathode = SOA = reduction

• Anode to cathode

• Non spontaneous

• Negative standard cell potential

• Non porous boundary

• Requires electricity

Chloride Anomaly

• When chloride ions and water are the only RA’S the chlorine becomes the SRA despite water being the SRA

• Chlorine gas will be formed

Pure Copper

Cathode

Impure Copper

Anode