What is the oxidation number of Cr in $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ ?

What is the oxidation number of Cr in $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ ?
  1. $+2$
  2. $+12$
  3. $-6$
  4. $+6$

Solution

$\begin{aligned} \mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7} &=(1 \times 2)+(\mathrm{x} \times 2)+[(-2) \times 7] \\ &=2+2 \mathrm{x}-14 \\ &=2 \mathrm{x}-12 \\ \therefore 2 \mathrm{x} &=12 \\ \therefore \quad \mathrm{x} &=+6 \end{aligned}$ $\therefore \quad$ Oxidation number of $\mathrm{Cr}=+6$

Asked in: MHT CET 2020 (15 Oct Shift 2)

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