Which one of the following conversions does not involve either oxidation or reduction?

Which one of the following conversions does not involve either oxidation or reduction?
  1. $\mathrm{VO}_2^{+} \rightarrow \mathrm{V}_2 \mathrm{O}_3$
  2. $\mathrm{Na} \rightarrow \mathrm{Na}^{+}$
  3. $\mathrm{CrO}_4^{2-} \rightarrow \mathrm{Cr}_2 \mathrm{O}_7^{2-}$
  4. $\mathrm{Zn}^2 \rightarrow \mathrm{Zn}$

Solution

$\stackrel{+6}{\mathrm{CrO}_4^{-2}} \rightarrow \stackrel{+6}{\mathrm{Cr}_2} \mathrm{O}_7^{-2}$

Asked in: MHT CET 2022 (10 Aug Shift 2)

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