JEE Main · 2023 · Shift-IIeasyDNF-031

Potassium dichromate acts as a strong oxidizing agent in acidic solution. During this process, the oxidation state…

d & f-Block Elements · Class 12 · JEE Main Previous Year Question

Question

Potassium dichromate acts as a strong oxidizing agent in acidic solution. During this process, the oxidation state changes from:

Options
  1. a

    +3 to +1

  2. b

    +6 to +3

  3. c

    +2 to +1

  4. d

    +6 to +2

Correct Answerb

+6 to +3

Detailed Solution

Concept: Reduction of K2Cr2O7\text{K}_2\text{Cr}_2\text{O}_7 in acidic medium

In acidic solution, K2Cr2O7\text{K}_2\text{Cr}_2\text{O}_7 acts as an oxidising agent:

Cr2O72+14H++6e2Cr3++7H2O\text{Cr}_2\text{O}_7^{2-} + 14\text{H}^+ + 6e^- \rightarrow 2\text{Cr}^{3+} + 7\text{H}_2\text{O}

  • Cr in Cr2O72\text{Cr}_2\text{O}_7^{2-}: +6
  • Cr in Cr3+\text{Cr}^{3+}: +3

Change: +6 → +3 (gain of 3 electrons per Cr atom, 6 electrons total for 2 Cr)

The green colour of Cr3+\text{Cr}^{3+} is observed at the end of the reaction.

Answer: Option (2) — +6 to +3

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Potassium dichromate acts as a strong oxidizing agent in acidic solution. During this process, the… (JEE Main 2023) | Canvas Classes