Assertion: The correct order of oxidising power is : VO_2^ + < Cr_2 O_7^ 2- < MnO_4^ - Reason: The oxidation state of Mn is +7 .

Correct answer: B. If both assertion and reason are true but reason is not the correct explanation of assertion. The oxidation states of the given compounds are aligned & VO_2^ + : x+2(-2)=+1 & x=+5 & Cr_2 O_7^ 2- : 2 x+7(-2)=-2 & 2 x=+12 & x=+6 & MnO_4^ - : x+4(-2)=-1 & x=-1+8=+7 aligned The correct order of oxidising power is VO_2^ + < Cr_2 O_7^ 2- < MnO_4^ - due to the increasing stability of the lower species to which they are reduced.

AIIMS 2014

Exam: AIIMS
Year: 2014
Subject: Chemistry
Chapter: Redox Reactions

AIIMS 2014 · Chemistry · Redox Reactions

Assertion: The correct order of oxidising power is : VO_2^ + < Cr_2...

Assertion: The correct order of oxidising power is :

\mathrm{VO}_2^{+} < \mathrm{Cr}_2 \mathrm{O}_7^{2-} < \mathrm{MnO}_4^{-}

Reason: The oxidation state of

\mathrm{Mn}

is +7 .

Options

AIf both assertion and reason are true and reason is the correct explanation of assertion.
BIf both assertion and reason are true but reason is not the correct explanation of assertion.
CIf assertion is true but reason is false.
DIf both assertion and reason are false.

Correct answer

B. If both assertion and reason are true but reason is not the correct explanation of assertion.

Step-by-step solution

The oxidation states of the given compounds are

\begin{aligned} & \mathrm{VO}_2^{+}: x+2(-2)=+1 \\ & \Rightarrow x=+5 \\ & \mathrm{Cr}_2 \mathrm{O}_7^{2-}: 2 x+7(-2)=-2 \\ & \Rightarrow 2 x=+12 \\ & \Rightarrow x=+6 \\ & \mathrm{MnO}_4^{-}: x+4(-2)=-1 \\ & \quad x=-1+8=+7\end{aligned}

The correct order of oxidising power is

\mathrm{VO}_2^{+} < \mathrm{Cr}_2 \mathrm{O}_7^{2-} < \mathrm{MnO}_4^{-}

due to the increasing stability of the lower species to which they are reduced.

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