JEE Main · 2022 · Shift-IIeasyRDX-010

Which one of the following is an example of disproportionation reaction?

Redox Reactions · Class 11 · JEE Main Previous Year Question

Question

Which one of the following is an example of disproportionation reaction?

Options
  1. a

    3MnO42−+4H+→2MnO4−+MnO2+2H2O\mathrm{3MnO_4^{2-} + 4H^{+} \rightarrow 2MnO_4^{-} + MnO_2 + 2H_2O}

    ✓
  2. b

    MnO4−+4H++4e−→MnO2+2H2O\mathrm{MnO_4^{-} + 4H^{+} + 4e^{-} \rightarrow MnO_2 + 2H_2O}

  3. c

    10I−+2MnO4−+16H+→2Mn2++8H2O+5I2\mathrm{10I^{-} + 2MnO_4^{-} + 16H^{+} \rightarrow 2Mn^{2+} + 8H_2O + 5I_2}

  4. d

    8MnO4−+3S2O32−+H2O→8MnO2+6SO42−+2OH−\mathrm{8MnO_4^{-} + 3S_2O_3^{2-} + H_2O \rightarrow 8MnO_2 + 6SO_4^{2-} + 2OH^{-}}

Correct Answera

3MnO42−+4H+→2MnO4−+MnO2+2H2O\mathrm{3MnO_4^{2-} + 4H^{+} \rightarrow 2MnO_4^{-} + MnO_2 + 2H_2O}

Detailed Solution

Disproportionation = same element simultaneously oxidised and reduced in the same reaction.

Step 1 — Check option (1): 3MnO42−+4H+→2MnO4−+MnO2+2H2O\mathrm{3MnO_4^{2-} + 4H^{+} \rightarrow 2MnO_4^{-} + MnO_2 + 2H_2O}

  • Mn in MnO42−\mathrm{MnO_4^{2-}}: +6+6 (reactant)
  • Mn in MnO4−\mathrm{MnO_4^{-}}: +7+7 → oxidised
  • Mn in MnO2\mathrm{MnO_2}: +4+4 → reduced
  • Same element (Mn) both oxidised and reduced → Disproportionation ✓

Step 2 — Eliminate others:

  • (2): Half-reaction only (reduction only) ✗
  • (3): I−\mathrm{I^-} oxidised, Mn\mathrm{Mn} reduced — two different elements ✗ (not disproportionation)
  • (4): S\mathrm{S} oxidised, Mn\mathrm{Mn} reduced — two different elements ✗

Answer: Option (1)

Practice this question with progress tracking

Want timed practice with adaptive difficulty? Solve this question (and hundreds more from Redox Reactions) inside The Crucible, our adaptive practice platform.

Practice in The Crucible →Browse Redox Reactions chapter →

More JEE Main Redox Reactions PYQs

2025hard

Which of the following oxidation reactions are carried out by both K2Cr2O7 and KMnO4 in acidic medium? (A) I- - I2 (B) S2- - S (C) Fe2+ - Fe3+ (D) I- - IO3- (E) S2O32- - SO42- Choose the correct…

2024medium

Match List-I with List-II. | List-I (Reaction) | List-II (Type) | |---|---| | (A) N2(g) + O2(g) 2NO(g) | (I) Decomposition | | (B) 2Pb(NO3)2(s) 2PbO(s) + 4NO2(g) + O2(g) | (II) Displacement | | (C)…

2024medium

Among the following halogens F2, Cl2, Br2 and I2. Which can undergo disproportionation reactions?

2024medium

Which of the following reactions are disproportionation reactions? (1) Cu+ Cu2+ + Cu (2) 3MnO42- + 4H+ 2MnO4- + MnO2 + 2H2O (3) 2KMnO4 K2MnO4 + MnO2 + O2 (4) 2MnO4- + 3Mn2+ + 2H2O 5MnO2 + 4H+ Choose…

2023easy

Which of the following options are correct for the reaction? 2[{Au(CN)_2}]^{-}({aq}) + {Zn}({s}) 2{Au}({s}) + [{Zn(CN)_4}]^{2-}({aq}) A. Redox reaction B. Displacement reaction C. Decomposition…

View all 49 Redox Reactions PYQs →