The transition metal in which of the following compound has zero oxidation state.

The transition metal in which of the following compound has zero oxidation state.
  1. $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$
  2. $\mathrm{KMnO}_4$
  3. $\mathrm{CrO}_5$
  4. $\mathrm{Fe}(\mathrm{CO})_5$

Solution

Oxidation states of given transition metals are as follows \begin{array}{|c|c|c|} \hline S.No. & Compound & Oxidation state of metal \\ \hline \multirow[t]{4}{*}{1.} & \mathrm{~K}_2 \mathrm{Cr}_2 \mathrm{O}_7 & \begin{array}{l} 2(+1)+2(x)+7(-2)=0 \\ x=+6 \end{array} \\ \hline & & i.e. \mathrm{Cr}=+6 \\ \hline & & Here, oxidation state of \mathrm{K}=1 \\ \hline & & Oxidation state of \mathrm{O}=-2 \\ \hline \multirow[t]{3}{*}{2.} & \mathrm{KMnO}_4 & 1+x+(-8)=0 \\ \hline & & x=+7 i.e. M n=+7 \\ \hline & & Here, oxidation state of \mathrm{K}=1 \\ \hline \multirow[t]{2}{*}{3.} & \mathrm{CrO}_5 & x+5(-2)=0 \\ \hline & & x=+10 i.e. \mathrm{Cr}=+10 \\ \hline \multirow[t]{3}{*}{4.} & \mathrm{Fe}(\mathrm{CO})_5 & x+5(0)=0 \\ \hline & & x=0 i.e. \mathrm{Fe}=0 \\ \hline & & \begin{array}{l} Here, \mathrm{CO} is a neutral ligand \\ thus \mathrm{Fe} is having oxidation \\ number =0 \end{array} \\ \hline \end{array} Hence, only $\mathrm{Fe}(\mathrm{CO})_5$ has zero oxidation state.

Asked in: AP EAMCET 2021 (25 Aug Shift 1)

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