Cambridge International
A2 Level
Chapter 20:
Electrochemistry
CIE A2 Chemistry
, 6.1 The Chemistry of Redox
Recall from AS Level Chapter 7
Flash back….
➢ Redox
Reaction which involve oxidation and reduction
that take place simultaneously
➢ Oxidation
A reducing agent which loses electron with an
increase of oxidation number
➢ Reduction
An oxidising agent which gains electron with a
decrease of oxidation number
CIE A2 Chemistry
, 6.1 The Chemistry of Redox
Flash back….
➢ Oxidation number
Permanent charge exist on an individual
element if the bonding were completely ionic
➢ Half-equation
to represent the electron transfer in an
oxidation of reduction reaction
CIE A2 Chemistry
, Exercise (W09 P42 Q3c)
For each of the following equations, write
the oxidation number of the element
printed in bold underneath its symbol, and
balance the equation by adding appropriate
numbers before each species.
(i) …MnO4-+…SO2+…H2O→…Mn2+ +…SO42-+…H+
Oxidation numbers:
(ii) …Cr2O72-+…NO2+…H+→…Cr3++…NO3- …H2O
Oxidation numbers:
[2 marks]
CIE A2 Chemistry
A2 Level
Chapter 20:
Electrochemistry
CIE A2 Chemistry
, 6.1 The Chemistry of Redox
Recall from AS Level Chapter 7
Flash back….
➢ Redox
Reaction which involve oxidation and reduction
that take place simultaneously
➢ Oxidation
A reducing agent which loses electron with an
increase of oxidation number
➢ Reduction
An oxidising agent which gains electron with a
decrease of oxidation number
CIE A2 Chemistry
, 6.1 The Chemistry of Redox
Flash back….
➢ Oxidation number
Permanent charge exist on an individual
element if the bonding were completely ionic
➢ Half-equation
to represent the electron transfer in an
oxidation of reduction reaction
CIE A2 Chemistry
, Exercise (W09 P42 Q3c)
For each of the following equations, write
the oxidation number of the element
printed in bold underneath its symbol, and
balance the equation by adding appropriate
numbers before each species.
(i) …MnO4-+…SO2+…H2O→…Mn2+ +…SO42-+…H+
Oxidation numbers:
(ii) …Cr2O72-+…NO2+…H+→…Cr3++…NO3- …H2O
Oxidation numbers:
[2 marks]
CIE A2 Chemistry
