Redox Titrations and Applications
Permanganate and dichromate titrations and their end points. (Chemistry › Redox Reactions, NEET UG syllabus.)
What is Redox Titrations and Applications?
A quantitative analytical method based on an oxidation-reduction reaction between an analyte and a standard titrant to determine the concentration of the analyte.
Key formula / rule: Normality Equation
Key points
- Define redox titration, equivalence point, and end point.
- Identify common oxidizing and reducing agents used in redox titrations.
- Explain the principle of permanganate and dichromate titrations.
- Identify the indicators used in permanganate and dichromate titrations and explain their working.
Common exam trap
Incorrectly balancing redox reactions or determining n-factors.
Definitions
- Term
Redox Titration
- Meaning
A quantitative analytical method based on an oxidation-reduction reaction between an analyte and a standard titrant to determine the concentration of the analyte.
- Term
Equivalence Point
- Meaning
The theoretical point in a titration where the amount of titrant added is stoichiometrically exactly equivalent to the amount of analyte present.
- Term
End Point
- Meaning
The experimentally observed point in a titration, usually indicated by a sharp color change, which is assumed to be very close to the equivalence point.
- Term
n-factor (Valency Factor)
- Meaning
For a redox reaction, it is the number of electrons gained or lost per mole of the substance.
- Term
Self-indicator
- Meaning
A substance that acts as its own indicator in a titration, typically by undergoing a distinct color change at the end point.
Learning objectives
Define redox titration, equivalence point, and end point.
Identify common oxidizing and reducing agents used in redox titrations.
Explain the principle of permanganate and dichromate titrations.
Identify the indicators used in permanganate and dichromate titrations and explain their working.
Balance redox reactions involved in these titrations.
Perform stoichiometric calculations related to redox titrations to find unknown concentrations.
Formulae
- Name
Normality Equation
- Note
Used for calculations where N is normality and V is volume. N = M × n-factor.
- Expression
N1V1 = N2V2
- Name
Molarity Equation (Redox)
- Note
noxidant and nreductant are the stoichiometric coefficients from the balanced redox reaction or the n-factors (number of electrons exchanged per mole).
- Expression
(Moxidant * Voxidant) / noxidant = (Mreductant * Vreductant) / nreductant
- Name
n-factor for KMnO4 (acidic)
- Note
MnO4- (Mn+7) → Mn2+ (Mn+2), change in oxidation state = 5.
- Expression
5
- Name
n-factor for K2Cr2O7 (acidic)
- Note
Cr2O72- (2Cr+6) → 2Cr3+ (2Cr+3), total change in oxidation state = 2 × (6-3) = 6.
- Expression
6
- Name
n-factor for Fe2+
- Note
Fe2+ → Fe3+, change in oxidation state = 1.
- Expression
1
- Name
n-factor for C2O42-
- Note
C2O42- (2C+3) → 2CO2 (2C+4), total change in oxidation state = 2 × (4-3) = 2.
- Expression
2
Prerequisites
Basic concepts of oxidation and reduction.
Ability to assign oxidation numbers.
Balancing redox reactions (ion-electron method).
Stoichiometry, molarity, and normality calculations.
Understanding of equivalent weight and n-factor.
Common mistakes
Incorrectly balancing redox reactions or determining n-factors.
Confusing equivalence point with end point.
Not using the correct acidic medium (e.g., using HCl with KMnO4).
Over-titration or under-titration due to poor observation of the end point.
Errors in stoichiometric calculations (e.g., using molarity equation instead of normality or vice-versa without proper n-factors).
Keywords
Redox titration
Permanganometry
Dichromatometry
KMnO4
K2Cr2O7
n-factor
Equivalence point
End point
Indicator
Oxidation
Reduction
Stoichiometry
Practice preview
Which of the following acts as a self-indicator in permanganate titrations?…
easy
Which of the following is commonly used as a primary standard for standardizing a potassium permanganate solution?…
easy
If 25.0 mL of 0.1 M FeSO4 solution requires 20.0 mL of KMnO4 solution for complete oxidation in an acidic medium, what is the molarity of the KMnO4 solution? (Reaction: MnO4- + 5Fe2+ + 8H+ -> Mn2+ + 5Fe3+ + 4H2O)…
medium