1. Catalyst
Calculate the standard reduction potential for the reaction:
Ni (s) + 2 Ce4+ (aq)  Ni2+ (aq) + 2 Ce3+
Cu2+ (aq) + Ca (s)  Cu (s) + Ca2+ (aq)
Which of the following is a
stronger oxidizing agent:
Fe (s) or Mg (s)
End

2. Michael Faraday

4. Lecture 8.5 – Nernst Equation

5. Today’s Learning Targets
LT 8.14 – I can calculate non-standard electrode potentials and/or concentrations for a reaction from data utilizing the Nernst equation.

6. Eo vs. E
We can calculate standard reduction potentials using our reduction potential table
Problem: Most reactions do not occur under standard conditions (1 M, 25 oC, and 1 atm)
For a reaction, it proceeds until E = 0

7. The Nernst Equation We know: We also know (more on this next week):
Therefore:

8. Nernst Equation E = Non-standard reduction potential
Eo = Standard reduction potential
R = Gas Constant
T = Temperature (in Kelvin)
n = Moles of electrons transferred
F = Faraday’s constant
Q = Reaction quotient

9. Class Example
Calculate the emf (E) at 298 K generated by a voltaic cell in which the reaction is:
Cr2O72- (aq) + 14 H+ (aq) + 6 I- (aq)  2 Cr3+ (aq) + 3 I2 (s) + 7 H2O (l)
When [Cr2O72-] = 2.0 M, [H+] = 1.0 M, [I-] = 1.0 M, and [Cr3+] = 1.0 x 10-5 M

10. Table Talk You run the following reaction at 298 K:
2 Al (s) + 3 I2 (s)  2 Al I-
Calculate the emf generated by this cell when [Al3+] = 4.0 x 10-3 M and [I-] = M

11. Class Example
You create a Zn/H cell and the potential is V at 25 oC when [Zn2+] = 1.0 M and PH2 = 1.0 atm, what is the [H+]

12. Table Talk
What is the pH of the solution in the cathode half – cell for a Zn/H cell where PH2 = 1.0 atm, [Zn2+] = 0.10 M, and the cell emf is V.

13. Levels Red – Easy Level Nernst Problems
Yellow – Medium Level Nernst Problems
Blue – Expert Chemist Level Nernst Problems

15. Closing Time Read 20.6 Homework: Pre – Lab
Quiz Thursday/Friday (on Ksp, no redox)!
Unit 7 Exam next Thursday/Friday
Saturday School this weekend – 2 to 5