1. Electrolysis and Cell Voltage

2. Electrolysis
Process where a nonspontaneous redox rxn occurs from an external energy source
Ex:
a flashlight powered by batteries
Aluminum ore
Gold mining
Metal plating

3. Predicting spontaneous rxns
Use a metal activity series to predict.
Connect the metals,
if the line goes down  spontaneous
if the line goes up  nonspontaneous

4. What about Ag and Cu 2+?
spontaneous
nonspontaneous

5. Prevention of damage from spontaneous rxns
Can be damaging
Rust, corrosion
How can we prevent the damage?
Coating
Painting, coating with grease
Galvanzing
Coating with another easily oxidized metal
Cathodic protection
Placing a more easily oxidized metal on fuel tanks, pipelines, ship hulls

6. Cell Voltages Standard Reduction Potential
Chart used to determine if a redox rxn is spontaneous (pg. 667 in textbook)
If positive, then its spontaneous
If negative, then its nonspontaneous

7. How to calculate Look up reactions on a chart.
Record the ε ˚, change the sign if the rxn is oxidized
Add the reactions and the voltages
Zn  Zn e ε ˚ox =
2e- + Cu 2+  Cu ε ˚red =
Zn + Cu2+  Zn 2+ + Cu ε ˚cell =
0.76
0.34
1.10V

8. + spontaneous
- nonspontaneous
The voltages are never multiplied by a number
can only change the sign of the voltage

9. Calculate the voltage for
Cu + Ag+  Cu2+ + Ag
ε ˚ox =
ε ˚red =
ε ˚cell=
Cu  Cu2+
-0.34
0.80
(1e- + Ag +  Ag)2
Cu + 2Ag+  Cu Ag
0.46V

10. Spontaneous redox rxns
Statue of liberty
Rusting
Batteries (corrosion)