Calculate the oxidation number of Cr in $\mathrm{CrO}_4^{2-}$ ion and $\mathrm{K}_2 \mathrm{Cr}_2…

Calculate the oxidation number of Cr in $\mathrm{CrO}_4^{2-}$ ion and $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ respectively.
  1. +4 and +6
  2. +3 and +2
  3. +6 and +6
  4. +8 and +2

Solution

Let x be the oxidation number of Cr in $\mathrm{CrO}_4^{2-}$ $\begin{array}{ll} \therefore & x+4 \times(-2)=-2 \\ & x-8=-2 \\ \therefore & x=8-2=+6 \end{array}$
Let $y$ be the oxidation number of Cr in $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ $\begin{array}{ll} \therefore \quad & 2 \times(+1)+2(y)+7 \times(-2)=0 \\ & +2+2 y-14=0 \\ & 2 y=12 \\ \therefore \quad & y=+6 \end{array}$

Asked in: MHT CET 2024 (15 May Shift 1)

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