1. Unit 7: Redox
Cell Potentials

2. What is going on in the Copper Lab?
What did you observe at the pencil that was connected to the red + terminal?
Orange/brown stuff collected on the pencil
What did you observe at the pencil that was connected to the black - terminal?
Bubbles, smell of chlorine.

3. The Electrochemical Cell
Source:
Source:
Alkaline Battery
Lead-Acid (car) Battery

4. The Electrochemical Cell
The species being oxidized LOSES electrons
Occurs at the anode (both start with vowels!)
Is the reducing agent
Is the more active metal
Will go from metal to ion, thus putting out electrons

5. The Electrochemical Cell
The species being reduced GAINS electrons
Occurs at the cathode (both start with consonants!)
Is the oxidizing agent
Is the less active metal
Will go from ion to metal, thus taking in electrons

6. The Electrochemical Cell
Cu2+ + Zn → Zn2+ + Cu
Copper
Zinc
CuSO4
ZnSO4
Write the oxidation half-reaction
Write the reduction half-reaction
What is the oxidizing agent?
What is the reducing agent?
Where is the cathode?
Where is the anode?
Image:

7. The Electrochemical Cell
Cu2+ + Zn → Zn2+ + Cu
Write the oxidation half-reaction
Write the reduction half-reaction
What is the oxidizing agent?
What is the reducing agent?
Where is the cathode?
Where is the anode?

8. The Electrochemical Cell
Cu2+ + Zn → Zn2+ + Cu
Copper
Zinc
CuSO4
ZnSO4
How can we determine the voltage (the cell potential) created by an electrochemical cell?
Electrons flow from anode to cathode. We can measure this.
Image:

9. Determining Cell Potentials
Write the oxidation and reduction half-reactions
Use the standard reduction table to determine:
Ecell = Eoreduction + Eooxidation
*Remember to flip the sign if you flip the half-reaction!

10. Cell Potential Example
Determine the standard reduction potentials and say if the reaction is spontaneous as written:
Mn2+ + 4H2O + Sn2+ → MnO4- + 8H+ + Sn