Which of the following oxidation reactions are carried out by both K_2 Cr_2 O_7 and KMnO_4 in acidic medium? A. \Gamma^- arrow I_2 B. S^2- arrow S C. Fe^2+ arrow Fe^3+ D. I^- arrow IO_3^- E. S_2 O_3 ^2- arrow SO_4^2- Choose the correct answer from the options given below :

Redox Reactions PYQ — JEE Main 2025 · 28 Jan · Shift 1 · Q18 with Solution

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Correct answer: A

Compare oxidizing strengths in acidic medium

Both acidified potassium dichromate and acidified potassium permanganate are strong oxidizing agents:

\ce{Cr2O7^{2-} + 14H+ + 6e- -> 2Cr^{3+} + 7H2O}, \qquad E^\circ \approx 1.33\,V

\ce{MnO4^- + 8H+ + 5e- -> Mn^{2+} + 4H2O}, \qquad E^\circ \approx 1.51\,V

So we check which oxidations are commonly carried out by both reagents in acidic medium.

Examine each proposed oxidation

(A) $\ce{I^- -> I2}$

This is a standard oxidation by both acidified $\ce{K2Cr2O7}$ and acidified $\ce{KMnO4}$ .

Half-reaction:

\ce{2I^- -> I2 + 2e^-}

So A is correct.

(B) $\ce{S^{2-} -> S}$

Sulphide ion is readily oxidized to sulphur by both strong oxidizing agents under acidic conditions.

Half-reaction:

\ce{S^{2-} -> S + 2e^-}

So B is correct.

(C) $\ce{Fe^{2+} -> Fe^{3+}}$

This is one of the most common oxidations by both reagents.

Half-reaction:

\ce{Fe^{2+} -> Fe^{3+} + e^-}

So C is correct.

(D) $\ce{I^- -> IO3^-}$

Oxidation of iodide all the way to iodate is not the usual reaction for both acidified dichromate and permanganate. In acidic medium, iodide is typically oxidized to $\ce{I2}$ .

Thus D is not carried out by both.

(E) $\ce{S2O3^{2-} -> SO4^{2-}}$

Thiosulfate can undergo oxidation, but complete oxidation to sulfate is not the standard/common oxidation by both acidified dichromate and permanganate in this context.

Thus E is not accepted here.

Select the correct set

The reactions carried out by both are:

\boxed{A,\ B,\ C}

This corresponds to Option A.

Comparison with stored answer

Stored correct answer: A

My derived answer: A

So they agree.

More from Redox Reactions

View written solutionFree

Correct answer: A

Compare oxidizing strengths in acidic medium

Both acidified potassium dichromate and acidified potassium permanganate are strong oxidizing agents:

\ce{Cr2O7^{2-} + 14H+ + 6e- -> 2Cr^{3+} + 7H2O}, \qquad E^\circ \approx 1.33\,V

\ce{MnO4^- + 8H+ + 5e- -> Mn^{2+} + 4H2O}, \qquad E^\circ \approx 1.51\,V

So we check which oxidations are commonly carried out by both reagents in acidic medium.

Examine each proposed oxidation

(A) $\ce{I^- -> I2}$

This is a standard oxidation by both acidified $\ce{K2Cr2O7}$ and acidified $\ce{KMnO4}$ .

Half-reaction:

\ce{2I^- -> I2 + 2e^-}

So A is correct.

(B) $\ce{S^{2-} -> S}$

Sulphide ion is readily oxidized to sulphur by both strong oxidizing agents under acidic conditions.

Half-reaction:

\ce{S^{2-} -> S + 2e^-}

So B is correct.

(C) $\ce{Fe^{2+} -> Fe^{3+}}$

This is one of the most common oxidations by both reagents.

Half-reaction:

\ce{Fe^{2+} -> Fe^{3+} + e^-}

So C is correct.

(D) $\ce{I^- -> IO3^-}$

Oxidation of iodide all the way to iodate is not the usual reaction for both acidified dichromate and permanganate. In acidic medium, iodide is typically oxidized to $\ce{I2}$ .

Thus D is not carried out by both.

(E) $\ce{S2O3^{2-} -> SO4^{2-}}$

Thiosulfate can undergo oxidation, but complete oxidation to sulfate is not the standard/common oxidation by both acidified dichromate and permanganate in this context.

Thus E is not accepted here.

Select the correct set

The reactions carried out by both are:

\boxed{A,\ B,\ C}

This corresponds to Option A.

Comparison with stored answer

Stored correct answer: A

My derived answer: A

So they agree.

Redox Reactions question

Redox Reactions question

(A) $\ce{I^- -> I2}$

(B) $\ce{S^{2-} -> S}$

(C) $\ce{Fe^{2+} -> Fe^{3+}}$

(D) $\ce{I^- -> IO3^-}$

(E) $\ce{S2O3^{2-} -> SO4^{2-}}$

More from Redox Reactions

Redox Reactions question

Redox Reactions question

(A) $\ce{I^- -> I2}$

(B) $\ce{S^{2-} -> S}$

(C) $\ce{Fe^{2+} -> Fe^{3+}}$

(D) $\ce{I^- -> IO3^-}$

(E) $\ce{S2O3^{2-} -> SO4^{2-}}$

More from Redox Reactions

(A) \ceI−−>I2\ce{I^- -> I2}\ceI−−>I2

(B) \ceS2−−>S\ce{S^{2-} -> S}\ceS2−−>S

(C) \ceFe2+−>Fe3+\ce{Fe^{2+} -> Fe^{3+}}\ceFe2+−>Fe3+

(D) \ceI−−>IO3−\ce{I^- -> IO3^-}\ceI−−>IO3−

(E) \ceS2O32−−>SO42−\ce{S2O3^{2-} -> SO4^{2-}}\ceS2O32−−>SO42−

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(A) \ceI−−>I2\ce{I^- -> I2}\ceI−−>I2

(B) \ceS2−−>S\ce{S^{2-} -> S}\ceS2−−>S

(C) \ceFe2+−>Fe3+\ce{Fe^{2+} -> Fe^{3+}}\ceFe2+−>Fe3+

(D) \ceI−−>IO3−\ce{I^- -> IO3^-}\ceI−−>IO3−

(E) \ceS2O32−−>SO42−\ce{S2O3^{2-} -> SO4^{2-}}\ceS2O32−−>SO42−

More from Redox Reactions

(A) $\ce{I^- -> I2}$

(B) $\ce{S^{2-} -> S}$

(C) $\ce{Fe^{2+} -> Fe^{3+}}$

(D) $\ce{I^- -> IO3^-}$

(E) $\ce{S2O3^{2-} -> SO4^{2-}}$

(A) $\ce{I^- -> I2}$

(B) $\ce{S^{2-} -> S}$

(C) $\ce{Fe^{2+} -> Fe^{3+}}$

(D) $\ce{I^- -> IO3^-}$

(E) $\ce{S2O3^{2-} -> SO4^{2-}}$