U4 S1 L1

U4 S1 L1
Defining Oxidation and reduction
LEO & Mervin
Textbook Readings MHR
•page 712: Oxidation-Reduction Reactions
•pages 713-715: Defining Oxidation and Reduction
•pages 715-716: Half Reactions
Textbook Practice Items MHR
•page 715: items 1, 2, 3 and 4
•page 716: items 5, 6, 7 and 8
•page 720: items 1, 2, 3, 4, 5 and 6
Upon completion of this lesson, you should be able to:
• define oxidation and reduction in terms or loss or gain of electrons
• identify electron transfer in redox equations
• state that a chemical entity loses electrons when it is oxidized and
that a chemical entity gains electrons when it is reduced
• identify oxidation and reduction half-reaction equations in an
oxidation reduction (redox) equation
• identify a redox equation as the sum of the oxidation half-reaction
and the reduction half-reaction
• identify the species oxidized, the species reduced, the oxidizing
agent, and the reducing agent in simple redox equations
• Oxidation-reduction reactions involve the transfer of electrons
from one species to another.
• The species that loses electrons is said to be oxidized
• The species that gains electrons is said to be reduced
• In order for an oxidation-reduction reaction to take place, we
need both process to occur. That is, we cannot have oxidation
with out reduction. Why not?
• LEO is an OX
– Loss of Electrons is Oxidation
Oxidation Is Loss
Reduction Is Gain
2 Na( s )  Cl2( g )  2 NaCl( s )
Interpret using a Lewis dot diagram:
Net ionic equations:
Write a net ionic equation for the reaction of solid zinc and an aqueous solution of
copper (II) sulphate.
Word equation:
Balanced Chemical equation:
Total Ionic equation
Net ionic equation
Zn(s) + Cu2+(aq) →
Half reactions:
Zn2+(aq) + Cu(s)
→ Zn2+(aq) + 2 e-
• Zn(s) lost 2 electrons (thus Zn(s) was oxidized.)
Cu 2+ (aq) + 2 e- → Cu(s)
• Cu 2+ gained 2 electrons (thus Cu 2+ was reduced.)
• In this case, the electrons were transferred from zinc to copper.
– Zn(s) was oxidized by Cu2+ so we say that Cu2+ was an oxidizing agent.
• the oxidizing agent is the species causes the the oxidation (it gets reduced)
– Similarly we can say that Zn(s) was acting as the reducing agent.
• the reducing agent is the species that causes the reduction (it gets oxidized)
• Why?
• Write a net ionic equation and half reactions for the reaction of
magnesium with aqueous aluminum sulphate.
• Identify the species oxidized, reduced, the reducing agent and the
oxidizing agent.
• Disproportionation reaction:
– An oxidation reduction reaction in which a single species
is both oxidized and reduced.
( aq )
( aq )
 Cu( s )  Cu
2Hg(aq )  Hg(l )  Hg(2aq )