Balancing the Redox reaction equation.

redox reaction, balancing chemical reaction methods, applications

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3. Table of content
REDOX
REACTION
Oxidation
reduction
Types
Method for balancing equation
Oxidation methods
Ion electron
methods
Oxidation no.
Rules for O.S
Examples

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Oxidation-Reduction
Reactions

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It is definedas .
addition of oxygen
removal of hydrogen
The loss of electron
Oxidation Reaction
EXAMPLES

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It is definedas
the gain of electrons.
the addition of hydrogen
oxygen from a substance.
EXAMPLES
Reduction Reaction

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Oxidation-reduction reactions are also known as redox reactions
DEFINITION
Achemical reactionin which electrons are transferred between
two reactants participating in it. This transfer of electrons can be
identified by observing the changes in the oxidation states of the
reacting species.
REACTIONS
• It is a class of reactions that include:
REDOX REACTION
formation of a
compound from its
elements
–all
combustion
reactions
–reactions
that generate
electricity
–reactions
that produce
cellular energy

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EXAMPLE
EXAMPLES
General Reaction

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EXAMPLE

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Decomposition
Reaction
Combination
Reaction
Displacement
Reaction
Disproportionation
Reactions
Types of Redox Reactions

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• Oxidation number (O.N.) is also known
as oxidation state
• It is defined as the chargethe atom
would have if electrons were not shared
but were transferred completely.
• For a ionic compound, the O.N. is
equivalent to the ionic charge
• For covalent compounds or polyatomic
ions, the O.N. is less obvious and can be
determined by a given set of rules
OXIDATION NUMBER

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BALANCING REDOX REACTIONS

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Oxidation number method
1.Assign oxidation numbersto all elements in the
reaction
2.From the changes in O.N, identify the oxidizedand
reduced species.
3.Compute the number of electrons lost in the
oxidation and gained in the reduction from the O.N.
changes.
4.Multiply one or both of these numbers by
appropriate factors to make the electrons lost equal
the electronsgained, and use the factors as
balancing coefficients
5.Complete the balancing by inspection, adding states
of matter
Balancing Redox Equations Method 1

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EXAMPLES
Balance the equation by oxidation no. method

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Half-reaction method or Ion electron method
•1.Divide the skeleton reaction into two half-reactions, each
of which contains the oxidized and reduced forms of one of
the species
•2.Balance the atoms and charges in each half-reaction –
Atoms are balanced in order: atoms other than O and H, then
O, then H –Charge is balanced by adding electrons
•To the left in reduction half-reactions
•To the right in oxidation half-reactions
•3.If necessary, multiply one or both half-reactions by an
integer to make the number of e-gained equal to the number
of e lost
•4.Add the balanced half-reactions, and include states of
matter Check that the atoms and charges are balanced
Balancing Redox Equations Method 2

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Balancing Redox Equations Method 2

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Balancing Redox Equations Method 2

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• The only difference in balancing a redox equation
that takes place in basic solution is in Step 4.
• At this point, we add one OH ion to both sides of
the equation for every H+ ion present
• The H+ ions on one side are combined with the
added OH ions to form H2O, and OH ions appear on
the other side of the equation

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Practice –Balance the Following Equation
Cu
+
+ I
2→ Cu
2+
+ I
–

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Practice –Balance the Following Equation
Cu
+
+ I
2→ Cu
2+
+ I
–
+1 0 +2 -1
oxid
red
ox: Cu
+
→ Cu
2+
red:I
2→ I
–
ox: Cu
+
→ Cu
2+
red:I
2→ 2 I
–
ox: Cu
+
→ Cu
2+
+ 1 e
-
red:I
2+ 2 e
-
→ 2 I
–
ox: Cu
+
→ Cu
2+
+ 1 e
-
} x 2red:I
2+ 2 e
-
→ 2 I
–
2 Cu
+
+ I
2→ 2 Cu
2+
+ I
2

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Practice –Balance the Following Equation
I
–
+ Cr
2O
7
2-
→ Cr
3+
+ I
2

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Practice –Balance the Following Equation
I
–
+ Cr
2O
7
2-
→ Cr
3+
+ I
2
+6 0+3-1
oxid
red
ox: I
–
→ I
2 red:Cr
2O
7
2–
→ Cr
3+
-2
ox: 2 I
–
→ I
2 red:Cr
2O
7
2–
→ 2 Cr
3+
red:Cr
2O
7
2–
→ 2 Cr
3+
+ 7 H
2O
red:Cr
2O
7
2–
+ 14H
+
→ 2Cr
3+
+ 7H
2O
ox: 2 I
–
→ I
2+ 2e
-
red:Cr
2O
7
2–
+ 14H
+
+ 6e
-
→ 2Cr
3+
+ 7H
2O
ox: 2 I
–
→ I
2+ 2e
-
}x3red:Cr
2O
7
2–
+ 14H
+
+ 6e
-
→ 2Cr
3+
+ 7H
2O
Cr
2O
7
2–
+ 14 H
+
+ 6 I
–
→ 2 Cr
3+
+ 7 H
2O + 3 I
2

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1.Applications of Redox
Reaction in Electrochemistry
APPLICATION

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2.Redox Reaction in Combustion.
3.Applications in Photosynthesis.
APPLICATION

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Production of important chemicals is based
onelectrolysiswhich is based on redox reactions.
Many chemicals like caustic soda, chlorine etc. are produced
using redox reactions.
Oxidation-Reduction reactions also find their application in
sanitizing water and bleaching materials.
The surfaces of many metals can be protected from corrosion
by connecting them to sacrificial anodes A common example
of this technique is the galvanizationof steel.
Real Life Uses of Redox Reaction

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The industrial production of cleaning products involves
the oxidation process.
Nitric acid, a component of many fertilizers, is produced
from the oxidation reaction of ammonia.
Electroplating is a process that uses redox reactions to
apply a thin coating of a material on an object.
Electroplatingis used in the production of gold-plated
jewelry.
Many metals are separated from their ores with the help
of redox reactions.
The main source of oxidation is oxygen and therefore
redox reaction or oxidation-reduction reactions are
responsible for food spoilage.
Real Life Uses of Redox Reaction

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