1. Electrochemistry
Pg 132

2. Electrochemical Cells
Made of two half-cells
Based upon two half-reactions
Electrons travel between the two half-cells

3. Types of Cells Also called voltaic cells
Convert chemical energy into electrical energy
Spontaneous
Convert electrical energy into chemical energy
Non-spontaneous
Galvanic Cells
Electrolytic Cells

4. Making a Galvanic Cell Mg (s) + CuSO4 (aq)  MgSO4 (aq) + Cu (s)
Write the reaction for solid magnesium placed in a copper (II) sulfate solution and assign oxidation numbers.
Mg (s) + CuSO4 (aq)  MgSO4 (aq) + Cu (s)

5. Making a Galvanic Cell Mg (s)  Mg2+ (aq) + 2e-
Balance the reaction using the half-reaction method +2 +6 -2 +2 +6 -2
Mg (s) + CuSO4 (aq)  MgSO4 (aq) + Cu (s)
Mg (s)  Mg2+ (aq) + 2e-
Cu2+ (aq) + 2e-  Cu (s)

6. Making a Galvanic Cell 1(Mg (s)  Mg2+ (aq) + 2e-)
Balance the reaction using the half-reaction method +2 +6 -2 +2 +6 -2
Mg (s) + CuSO4 (aq)  MgSO4 (aq) + Cu (s)
1(Mg (s)  Mg2+ (aq) + 2e-)
1(Cu2+ (aq) + 2e-  Cu (s))
Mg (s)+CuSO4 (aq)+2e-  MgSO4 (aq)+Cu (s)+2e-

7. Making a Galvanic Cell

8. Making a Galvanic Cell Anode (Oxidation) Cathode (reduction)
Salt Bridge
Flow of electrons

9. Measuring the Output of a Galvanic Cell
Potential (either half-cell or cell)
Pull on the electrons
Voltmeter
Analog
Digital
Positive potential…spontaneous
Negative potential…nonspontaneous

10. Measuring the Output of a Galvanic Cell
Standard Reduction Potentials Chart
Only reduction reactions
Must look up the reverse of the oxidation and flip the sign of the potential
Add standard half-cell potentials to get standard cell potential

11. Measuring the Output of a Galvanic Cell
1(Mg (s)  Mg2+ (aq) + 2e-) E˚ox= V
1(Cu2+ (aq) + 2e-  Cu (s)) E˚red= V
Mg (s)+CuSO4 (aq)+2e-  MgSO4 (aq)+Cu (s)+2e-
E˚cell = V

12. Writing a Line Notation
Oxidation||Reduction
X(s)|X+(aq)||Y+(aq)|Y(s)
Mg(s)|Mg2+(aq)||Cu2+(aq)|Cu(s)
1(Mg (s)  Mg2+ (aq) + 2e-)
1(Cu2+ (aq) + 2e-  Cu (s))
Mg (s)+CuSO4 (aq)+2e-  MgSO4 (aq)+Cu (s)+2e-