Chapter 10.7
Electrolysis
Electrolytic Cell
• Recall the galvanic cell:
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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
Electrolytic Cell
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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 halfreactions take place in the same container
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
Predicting Products of Electrolysis
1. Make a list of all substances present.
Label all possible oxidizing and reducing agents present. (Don’t
forget water for aqueous solutions)
2. 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
3. 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
4. Balance electrons and write the equation for the overall
(or net) reaction.
5. Calculate the cell potential: Eor(cell) = Eor(cathode) – Eor(anode)
Practice
• Predict the products and find the cell potential
for the electrolysis of 1 mol/L LiBr(aq).
HOMEWORK
• Read p.667 – 669 and make notes
• P.670 #1-9