Transcript Redox Reactions - Alfred State College

Electrochemistry
(Oxidation/Reduction)
CHEM 2124 – General Chemistry II
Alfred State College
Professor Bensley
Learning Objectives
 Define oxidation-reduction reaction.
 Learn the oxidation number rules and assign
oxidation numbers.
 Write the half-reactions of an oxidationreduction reaction.
 Determine the species undergoing oxidation
and reduction.
 Describe and construct basic galvanic cells
 Calculate cell potential for basic galvanic cells
Oxidation and Reduction
I.
General Features
II.
Oxidation Numbers
Assign oxidation numbers to Carbon in each of the following compounds:
1. Carbon Monoxide
2. Carbon Dioxide
3. C6H12O6 (Glucose)
4. Sodium Bicarbonate
For each of the following chemical reactions, determine whether or not the reaction
is an example of an oxidation-reduction reaction.
LiOH + HCN  H2O + LiCN
LiCl + AgNO3  AgCl + LiNO3
P4 (s) + 5O2 (g)  P4O10 (s)
CuCl2 (aq) + Al (s)  AlCl3 (aq) + Cu (s)
Oxidation and Reduction
III. Half Reactions
What happens when copper wire is placed
in a silver nitrate solution?
For each of the following Redox reactions, write the
individual half-reactions.
1.
2.
Fe (s) + CuSO4 (aq)  Cu (s) + FeSO4 (aq)
Co (s) + Cl2 (g)  CoCl2 (g)
In each of the following reactions, identify the oxidizing
agent and the reducing agent.
1.
Co (s) + Cl2 (g)  CoCl2 (g)
2.
2Al (s) + 3F2 (g)  2AlF3 (s)
3.
PbS (s) + 4H2O2 (aq)  PbSO4 (aq) + 4H2O (l)
Oxidation and Reduction
IV. Examples of Oxidation–Reduction Reactions
1. Combination Reactions
2. Decomposition Reactions
3. Displacement Reactions
4. Combustion Reactions
Oxidation and Reduction
V. Galvanic or voltaic cells
Anode
Zn (s)  Zn 2+ (aq) + 2e-
Cathode
Cu 2+ (aq) + 2e-  Cu (s)
Oxidation and Reduction
VI. Galvanic Cell Terminology
A. Half cells
B. Anode
C. Cathode
D. Salt Bridge
E. Cell Notation
F. Cell Potential
E0 (cell) = E0 (red) – E0 (ox)
Order the following oxidizing agents from
weakest to strongest.
Cu2+ (aq),
Fe2+ (aq),
Fe3+ (aq)
Order the following reducing agents from
weakest to strongest.
H2 (g),
Al (s),
Cu (s)
Example
• Sketch the cell formed by Cd in Cd(NO3)2
and Ag in AgNO3.
• Write the half-reactions, label the anode,
cathode, salt bridge, and direction of
electron flow.
• Write the cell notation.
• Calculate the overall cell potential for this
cell.
Oxidation and Reduction
VII. Biological Applications
• Respiration
– Oxidation of glucose to CO2
– Reduction of O2 to H2O
C6H12O6 (s) + 6O2 (g)  6CO2 (g) + 6H2O (g)
• Photosynthesis
– Oxidation of H2O to O2
– Reduction of CO2 to glucose
– 6CO2 (g) + 6H2O (g) + light  C6H12O6 + 6O2 (g)