1. Chapter 10.7 Electrolysis

2. Electrolytic Cell Recall the galvanic cell:
Spontaneous overall reaction
Cell potential has a positive value
Converts chemical energy into electrical energy
Electrons flow from a higher potential energy to a lower potential energy
Electrical energy can be used to move electrons from a lower potential energy to a higher potential energy
A cell that uses energy to do this is called an electrolytic cell

3. Electrolytic Cell Converts electrical energy into chemical energy
Process is called electrolysis
Overall reaction is non-spontaneous, requires energy
Includes electrodes, at least one electrolyte, an external source of electricity, and external circuit
Possible for electrolytic cells to have the two half-reactions take place in the same container

4. Galvanic Cell vs. Electrolytic Cell
Spontaneous reaction
Converts chemical energy to electrical energy
Anode (negative): zinc
Cathode (positive): copper
Oxidation at anode:
Zn  Zn2+ + 2e-
Reduction at cathode:
Cu2+ + 2e-  Cu
Cell Reaction:
Zn + Cu2+  Zn2+ + Cu
Electrons move to cathode
Anions move to anode
Cations move to cathode
Non-spontaneous reaction
Converts electrical energy to chemical energy
Anode (positive): copper
Cathode (negative): zinc
Oxidation at anode:
Cu  Cu2+ + 2e-
Reduction at cathode:
Zn2+ + 2e-  Zn
Cell Reaction:
Cu + Zn2+  Cu2+ + Zn
Electrons move to cathode
Anions move to anode
Cations move to cathode

5. Predicting Products of Electrolysis
Make a list of all substances present.
Label all possible oxidizing and reducing agents present. (Don’t forget water for aqueous solutions)
Use the redox table to identify the strongest oxidizing agent.
Write the equation for the reduction half-reaction that occurs at the cathode, including the reduction potential
Use the redox table to identify the strongest reducing agent.
Write the equation for the oxidation half-reaction that occurs at the anode, including the reduction potential
Balance electrons and write the equation for the overall (or net) reaction.
Calculate the cell potential: Eor(cell) = Eor(cathode) – Eor(anode)

6. Practice
Predict the products and find the cell potential for the electrolysis of 1 mol/L LiBr(aq).

7. HOMEWORK
Read p.667 – 669 and make notes
P.670 #1-9