CHAPTER 16 (pages 776-792)

1. Oxidation and Reduction2. Galvanic Cells, Half Reactions (E°anode &

E°cathode)3. Standard Reduction Potential (E°)4. Nernst Equation, and the dependence of

Potential on Concentration5. Relationship between Equilibrium

Constant and Standard Potential

6. Driving Force, ΔG and ε1

REDOX REACTIONS

MnO2 + 4 HBr ⇋ MnBr2 + Br2 + 2 H2O

3 H2S + 2 NO3– + 2 H+ ⇋ 3 S + 2 NO + 4

H2O

2

OBSERVED REDOX PROCESSES

3

GALVANIC CELLS

4

INERT ELECTRODES

6

STANDARD REDUCTION POTENTIALS

7

8

MEASURING STANDARD POTENTIALS

9

CALCULATING STANDARD CELL POTENTIAL

Al(s) + NO3−

(aq) + 4 H+(aq)

⇋ Al3+

(aq) + NO(g) + 2 H2O(l)

10

ADDITIONAL EXAMPLE

Fe(s) + Mg2+(aq)

⇋ Fe2+

(aq) + Mg(s)

11

ox: Fe(s) Fe2+(aq) + 2 e− E = +0.45 V

red: Pb2+(aq) + 2 e− Pb(s) E = −0.13 V

tot: Pb2+(aq) + Fe(s) Fe2+(aq) + Pb(s) E = +0.32 V

ELECTROMOTIVE POTENTIAL

13

E°CELL, ΔG° AND K

Under standard state conditions, a reaction will spontaneously proceeds in the forward direction if:

– ΔG° < 1 (negative)– E° > 1 (positive)– K > 1

Design a voltaic cell with the following halfcells and complete the calculations:

Ag+ (aq) + 1e- Ag (s) Eo = 0.80 VPb2+ (aq) + 2e- Pb (s) Eo = -0.13 V

a. Calculate the Eocell

(potential at standard conditions)

b. Calculate Go.c. Calculate d. Calculate the Ecell if [Ag+] = 2.0 M and

[Pb2+] = 1.0 x 10-4 M.

Williams, spring 2009stop here

Design a voltaic cell with the following halfcells and complete the calculations:

Ag+ (aq) + 1e- Ag (s) Eo = 0.80 VPb2+ (aq) + 2e- Pb (s) Eo = -0.13 V

Calculate the Eocell

(potential at standard conditions)

Design a voltaic cell with the following halfcells and complete the calculations:

Ag+ (aq) + 1e- Ag (s) Eo = 0.80 VPb2+ (aq) + 2e- Pb (s) Eo = -0.13 V

Calculate Go.

Design a voltaic cell with the following halfcells and complete the calculations:

Ag+ (aq) + 1e- Ag (s) Eo = 0.80 VPb2+ (aq) + 2e- Pb (s) Eo = -0.13 V

Calculate

Design a voltaic cell with the following halfcells and complete the calculations:

Ag+ (aq) + 1e- Ag (s) Eo = 0.80 VPb2+ (aq) + 2e- Pb (s) Eo = -0.13 V

Calculate the Ecell if [Ag+] = 2.0 M and Pb2+] = 1.0 x 10-4 M.

OBJECTIVE 11.4: PROVIDE A THOROUGH OVERVIEW OF APPLICATIONS OF ELECTROCHEMICAL CELLS INCLUDING FUEL CELLS, CORROSION, AND OTHER TOPICS

AS TIME PERMITS.

23

CORROSION

• corrosion is the spontaneous oxidation of a metal by chemicals in the environment

• since many materials we use are active metals, corrosion can be a very big problem

RUSTING

• rust is hydrated iron(III) oxide• moisture must be present• electrolytes promote rusting• acids promote rusting– lower pH = lower E°red

Dry Cell Batteries

Lead – Acid Storage Battery

Biological Electrochemistry

Lithium Ion Battery