This document discusses redox titrations and methods including potassium permanganate titrations (permanganometry) and iodometry. Redox titrations involve the titration of an oxidizing agent with a reducing agent. Potassium permanganate is a strong oxidizing agent commonly used for titrations due to its intense purple color. Iodometry uses iodine and thiosulfate to indicate the endpoint of the titration reaction. Both methods have advantages such as being inexpensive but also disadvantages like potential decomposition over time.

1. Redox Titrations
Muhammad Umer Zafar

2. Redox Titrations and
methods
• Potassium Permanganate
Titrations
(Permanganometry)
• Iodometry
Muhammad Umer Zafar

3. Redox Titrations
• Redox titration is a volumetric method
of analysis which relies on oxidation or
reduction of the analyte.
• It involves the titration of an oxidising
agent with a reducing agent.
• An oxidising agent gains electrons
where a reducing agent loses electrons.
Muhammad Umer Zafar

4. Half Reaction
• It is obtained by the change in
oxidation states of individual substances
involved in the redox reaction.
• Oxidised
red – ne- ⇌
• Reduced
+ ne- ⇌ red
Muhammad Umer Zafar

5. Half Reaction
• A half reaction does not occur by itself,
it is a coupled reaction.
• Oxidation and Reduction must occur
simultaneously, this type is known as a
redox reaction.
• The couple effect of these reactions
conjugate and behaves in much a same
way when they are in acid-base pairs
Muhammad Umer Zafar

6. End Point
• End point depends on the agent being
strong or weak. If both agents are
strong then the end point is sharp in
regards to gaining or losing electrons.
• Appropriate indicators along with
electrometric means can be used to
determine the end point. The
characteristics of redox potential are
included in Nernst equation.
Muhammad Umer Zafar

7. Nernst Equation
E - redox potential of the couple
n - redox capacity (no of electrons and
oxidising agents will take on or a reductant
will supply)
- standard redox potential at 2C
[OX] and [red] - molar conc. of both the
oxidised and reduced forms
a, b - stiochiometric coefficients
Muhammad Umer Zafar

9. Permanganometry
 Potassium Permanganate is one of
the strongest oxidising agents used for
titrations.
 They do not require indicators,
because they have a very intense
purple colour.
 So to determine the end point an
excess titrant can cause the change in
colour.
 Diluted solution of KMNO4 is pink.
Muhammad Umer Zafar

10. Permanganometry
 It is being used to determine the
quantity of analyte in an unknown
solution.
 Permanganate reduction is very slow at
room temperature, which can be
enhanced at higher temperatures such
as 70-80 degrees.
 During permanganometry the potassium
permanganate is reduced to
as the titration is complete.
Muhammad Umer Zafar

11. Advantages
 Extremely powerful, hence commonly
used.
 Inexpensive
 Readily available
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12. Disadvantages
 Strong oxidising agent so it reacts with
everything.
 Difficult to store without
decomposition or a change in
concentration.
 It cannot be used as a primary
standard due to its reaction with
contaminants in distilled water.
Muhammad Umer Zafar

13. Iodometry
 Iodometry, also known
as iodometric titration, is a method of
volumetric chemical analysis, a redox
titration where the appearance or
disappearance of elementary iodine
indicates the end point.
 It is based on the reversibility of the
half-reaction
I2 + 2e- ⇌ 2
Muhammad Umer Zafar

14. Advantage
 Iodine is a weak oxidising agent can
be used to titrate strong reducing
agents.
 Iodine ion is a mild reducing agent
and serves as the basis for
determining the strong oxidising
agent.
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15. Disadvantage
 Iodide ion is not used for titration
because it lacks the convenient visual
indicator system, such as
permanganate.
 The speed of reaction is slow.
Muhammad Umer Zafar

16. Solution
 Sodium thiosulfate is a suitable
titrating agent for all of the above
mentioned three cases
 Analysis of these substances in this
method is called an iodometric method
or iodometry.
 Iodometry cannot be used as primary
standards, as it is not possible to
prepare it directly.
Muhammad Umer Zafar