Oxidation and Reduction Reactions
Lesson 2
Chapter 12
Objective
You will be able to
· define oxidation and reduction both
operationally and theoretically
· write oxidation and reduction
reactions.
Oxidation and Reduction Reactions
Metallurgy
The science and technology of separating metals from
their ores.
Most metals are found as ores. These ores are
complex mixtures, many times as part of an organic
compound.
Eg. Iron ores
magnetite (Fe3O4),
goethite (FeO(OH)),
hematite (Fe2O3),
limonite (FeO(OH).n(H2O))
When metals are refined (purified), a large mass of ore
is reduced to a small mass of pure metal.
Operational definition of reduction
Producing pure metals from ore.
This is an operational definition because it does not
explain how the reaction takes place
Example of iron refinement
Fe2O3(s) + 3 CO(g) ➔ 2 Fe(s) + 3 CO2(g)
Purification of Tungsten
WO3(s) + H2(g) ➔ W(s) + 3 H2O(g)
Label the ore, reducing agent and the pure metal.
Oxidation
Operational definition: a reaction of a substance with
oxygen. (burning or rusting)
Example: 2 Mg(s) + O2(g) ➔ 2 MgO(s)
Scientist eventually realized that non-metals, other than
oxygen, could undergo similar reactions.
Ex:
2 Al(s) + 3 Cl2(g) ➔ 2 AlCl3(s)
Theoretical definition
Reduction
The gain of electrons.
GER or RIG
Example: Cu2+ (aq) + 2 e- ➔ Cu(s)
Oxidation
Loss of electrons
LEO or OIL
Example: Al(s)➔ Al3+(aq) + 3 e-
Half reactions
Reduction half reactions
Electrons are a reactant
Fe3+ + 3e- ➔ Fe(s)
Cl2(g) + 2e- ➔ 2 ClNon-metals and cations tend to be reduced!
Oxidation half reactions
Electrons are a product
Cu
(s)
➔ Cu2+ + 2 e-
2N3- ➔ N
2(g)
+ 6e-
Metals and anions tend to be oxidized!
Reducing Agent
Promotes reduction by donating electrons,
meaning it is oxidized.
Oxidizing Agent
Promotes oxidation by removing electrons and it
is reduced.
Redox reactions
Oxidation and reduction MUST always take place at the
same time. So these reactions have become known as
redox reactions.
The electrons lost by the reducing agent (RA) must be
equal to those gained by the oxidizing agent(OA).
Example
Write oxidation and reduction half reactions for the
following redox reactions. Start with a net ionic equation.
Copper is placed in a solution of silver nitrate.
Example 2
Sodium iodide is added to a solution of bromine.
Assignment
Text p. 437 #1-4
p. 440 #1,2,7