What is the oxidation number of As in $\mathrm{H}_{3} \mathrm{AsO}_{3}$ ?

What is the oxidation number of As in $\mathrm{H}_{3} \mathrm{AsO}_{3}$ ?
  1. +4
  2. +2
  3. +3
  4. -3

Solution

$\begin{aligned} \mathrm{H}_{3} \mathrm{AsO}_{3} &=(1 \times 3)+\mathrm{As}+[(-2) \times 3] \\ &=3+\mathrm{As}-6 \end{aligned}$ $\therefore \quad \mathrm{As}=+3$

Asked in: MHT CET 2020 (16 Oct Shift 1)

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