Chemistry 102 Unit Design Electr

							Chemistry 102                                                                                                                Unit Design

                                                 Electrochemistry
                       ___________________________________________________|_____________________________
       |                             |                                                |
   Redox                       Voltaic Cells                                                Electrolysis
  Reactions                   (Galvanic Cells)                                           (Electrolytic Cells)
                          _____________|__________________                     __________________|_________________
Review                     |              |            |                     |               |                 |
Balance         Terminology       Nernst Equation  Application            Terminology       Quantitative      Applications
                  Diagram           Presentations        Diagrams          Faraday's Law
                  emf
                  cell notation
                  free energy, emf, and K



Outcomes:


   1. Review: Identifying redox reactions, reduction half reactions, oxidation half reactions, oxidizing agents, reducing agents, etc.
   2. Learn to write and balance redox reactions in acidic and basic solutions.
   3. For voltaic cells: draw diagrams and interpret, show flow of electrons, write 2 half reactions, name anode and cathode,
      show positive and negative electrodes, show mass change, show change in ions, indicate direction of ion migration, write
      voltaic cell notation, and calculate Eo.
   4. Understand the relationship of G, K, and emf.
   5. Using the Nernst Equation calculate: E, Eo, and [conc.].
   6. For electrolytic cells: draw diagrams and interpret, show electron flow, write half reactions, indicate positive and negative
      electrode, name anode and cathode, calculate Eo.
   7. For electrolysis calculate: amp., time, half reaction, mass, and amount of produce formed.
   8. Understand relationship of emf, free energy change, and equilibrium constant and be able to do calculations involving them.
   9. For electrolysis predict if reactions occur, and if they do write net ionic and balanced formula equations.
   10. Obtain understanding of dry cell, lead storage battery, and other applications of electrochemistry.

Background Information:         Writing Molecular and Ionic Equations     Redox Reactions      Chemical Equilibrium
Thermodynamics
Chemistry 102
Electrochemistry
Class Problems
                                                       Electrochemistry
                                                                  Problems
1. Balance the following redox reactions and identify the oxidizing and reducing agents.

    a. Cu (s) + HNO3 (aq)  Cu(NO3)2 (aq) + NO (g) + H2O (l)
    b. MnO4- + Fe+2  Fe+3 + Mn+2           in acidic solution
    c. S2O3 -2
                + I2  SO4  -2    -
                               + I basic solution

2. Chlorine gas was first prepared in 1774 by C.W. Scheele by oxidizing sulfuric acid with
   magnesium(IV) oxide. The reaction is:
      NaCl (aq) + H2SO4 (aq) + MnO2 (s)  Na2SO4 (ag) + MnCl2 (aq) + H2O (l) + Cl2 (g)
   Balance this reaction using the half-reaction method.

3. What is the cell voltage under standard conditions for:
 a. 10 Cl- (aq) + 2 MnO4- (aq) + 16 H+ (aq)  5 Cl2 (g) + 2 Mn+2 (aq) + 8 H2O
 b. Cl (g) + 3 H O  ClO - (aq) + 5 Cl- (aq) + 6 H+ (aq)
         2                 2                    3

4. Calculate G for:
     2 AgNO3(aq) + Cu (s)  Cu(NO3)2 (aq) + 2 Ag (s)

5. If [AgNO3] = 0.1 M and [Cu(NO3)2] = 2.0 M, what is the potential of the cell at
    25oC.          Cu | Cu(NO ) (aq) || AgNO (aq) | Ag ?
                                                3 2                      3

6. Calculate emf at 298 K for the reaction : 2 Br- (aq) + Cl2 (g)  Br2(l) + 2 Cl -(aq)
   given Eo = 0.3 v and [Br-] = 0.1 M, Cl pressure = 0.5 atm and [Cl-] = 0.01 M.
                                                              2

7. Calculate the equilibrium constant for the reaction:
   Zn (s) + Cu2+ (aq)  Zn2+ (aq) + Cu (s) Eo = 1.10 v

8. Determine whether or not the overall oxidation-reduction reaction is spontaneous and
   calculate the equilibrium constant.
   Sn (s) + Ni2+          Sn2+ + Ni (s)

9. How many grams of Cu would be deposited if a current of 1.5 amp is supplied for 2
   hours?

10. How many hours, at a current of 2 amp will it take to produce 5.0 g of Cu?




Answers: 3. 0.16, -0.11 4. -8.9 x 104 5. 0.394 v 6. 0.35 v 7. ~ 1x 10 37 8. 2x10-4 9. 3.49g 10. 2.1 hr