Unit 7 Oxidation – Reduction Reactions

Unit 7 Oxidation – Reduction and Electrochemistry
Chapter 18
18.1 Oxidation Reduction Reactions
Oxidation is
Reduction is
You must be able to identify an oxidation-reduction reaction.
Practice: p. 576 #’s 3-6
18.2 Oxidation States
Allows us to keep track of electrons in oxidation-reduction reactions.
Assigns charges to various atoms in a compound.
In a binary ionic compound (Type I) –
In an uncombined element –
In a covalent compound –
See rules on p. 556
Practice: p. 557 Self Check 18.2
p. 577 #’s 13-22
18.3 Oxidation-Reduction Reactions between Nonmetals
Objectives: To understand oxidation and reduction in terms of oxidation states.
To learn to identify oxidizing and reducing agents.
Remember “LEO the lion says GER”
Practice: Find which species has been oxidized and reduced in the following
N2(g) + 3H2(g)  2NH3(g)
Oxidizing Agent:
Reducing Agent:
Practice: p. 577-578 #’s 29-36
18.4 Balancing Oxidation-Reduction Reactions by the Half-Reaction Method
Why can’t we use the old way?
Reduction Half-reaction (example):
Oxidation Half-reaction (example):
Balancing Half Reactions:
Practice: p. 578 #’s 41-42
Balancing Oxidation-Reduction Reactions in acidic solutions
See Steps on p. 562.
Example: Balance the following reaction in an acidic solution:
Ce4+(aq) + H3AsO3(aq)  Ce3+(aq) + H3AsO4(aq)
Example: Balance the following reaction in an acidic solution:
MnO4-(aq) + I-(aq)  Mn2+(aq) + I2(s)
Practice: p. 578 #’s 45-48
18.5 Electrochemistry: An Introduction
Electrochemistry –
Two types of processes:
How can we use a REDOX reaction to produce useful work?
Ex: MnO4- + Fe2+  Mn2+ + Fe3+
In the same vessel no work is done, but if we separate the two half-reactions we can
accomplish work.
What happens after the reaction proceeds?
Salt Bridge:
Now we have an electrochemical battery, or galvanic cell.
Salt Bridge
Oxidation Chamber:
Reduction Chamber:
Real life example of an oxidation-reduction reaction:
2H2(g) + O2(g)  2H2O(l)
Fuel cell
We can make the reverse reaction occur by applying an electrical current to the REDOX reaction. This is
18.6 Batteries
18.7 Corrosion
18.8 Electrolysis
Electrolysis of Water
Electrolysis of Aluminum