Types of Redox Reactions
Redox Reactions
5
JEE Qs
8%
Hard
60
min
Always systematically calculate and track the oxidation states of all relevant elements in reactants and products to correctly identify the type of redox reaction.
✅ Key Points for JEE
- 1Redox reactions are classified into five main types: Combination, Decomposition, Displacement, Disproportionation, and Comproportionation.
- 2Combination reactions: Two or more substances combine to form a single product; at least one element changes its oxidation state.
- 3Decomposition reactions: A single compound breaks down into two or more products; at least one element changes its oxidation state.
- 4Displacement reactions: An atom or ion in a compound is replaced by an atom or ion of another element. This includes metal displacement (more reactive metal displaces less reactive) and non-metal displacement (e.g., H₂ displacement from acids/water, halogen displacement).
- 5Disproportionation reactions: A single element in a *single reactant* is simultaneously oxidized and reduced, meaning its oxidation state increases and decreases in the products.
- 6Comproportionation reactions: The reverse of disproportionation, where two reactants containing the *same element* in *different oxidation states* combine to form a product where that element is in an *intermediate oxidation state*.
⚠️ Common Mistakes
- ✕Confusing disproportionation with other redox reactions where multiple elements change oxidation states. Disproportionation requires *one element* in *one reactant* to be both oxidized and reduced.
- ✕Incorrectly assigning oxidation states to elements, leading to misclassification of the reaction type.
- ✕Not recognizing comproportionation reactions, especially when they are presented as a reverse disproportionation scenario.
📝 Practice Questions
See allQ63.Given below are two statements: Statement I: In the oxalic acid vs KMnO4 (in the presence of dil H2SO4 ) titration the solution needs to be heated initially to 60∘C, but no heating is required in Ferrous ammonium sulphate (FAS) vs KMnO4 titration (in the presence of dil H2SO4 ) Statement II: In oxalic acid vs KMnO4 titration, the initial formation of MnSO4 takes place at high temperature, which then acts as catalyst for further reaction. In the case of FAS vs KMnO4 , heating oxidizes Fe2+ into Fe3+ by oxygen of air and error may be introduced in the experiment. In the light of the above statements, choose the correct answer from the options given below (1) Both Statement I and Statement II are false (2) Both Statement I and Statement II are true (3) Statement I is false but Statement II is true (4) Statement I is true but Statement II is false 2025 (28 Jan Shift 1) JEE Main Previous Year Paper
Q69.Given below are two statements : Statement (I): In partition chromatography, stationary phase is thin film of liquid present in the inert support. Statement (II) : In paper chromatography, the material of paper acts as a stationary phase. In the light of the above statements, choose the correct answer from the options given below : (1) Statement I is true but Statement II is false (2) Statement I is false but Statement II is true (3) Both Statement I and Statement II are false (4) Both Statement I and Statement II are true
Q57.The species which does not undergo disproportionation reaction is : (1) ClO−3 (2) ClO− (3) ClO−2 (4) ClO−4
Q53.Which of the following oxidation reactions are carried out by both K2Cr2O7 and KMnO4 in acidic medium? A. Γ−→I2 B. S 2−→S C. Fe2+ →Fe3+ D. Γ−→IO3− E. S2O32−→SO42− Choose the correct answer from the options given below: (1) C, D and E Only (2) B, C and D Only (3) A, D and E Only (4) A, B and C Only
Q54.Only 2 mL of KMnO4 solution of unknown molarity is required to reach the end point of a titration of 20 mL of oxalic acid (2M) in acidic medium. The molarity of KMnO4 solution should be M.
Q58.The difference in the 'spin-only' magnetic moment values of KMnO4 and the manganese product formed during titration of KMnO4 against oxalic acid in acidic medium is _______ BM. (nearest integer)
NCERT Chapters
- Class 11 Chemistry Ch 8: Redox Reactions