Question

Oxidation numbers of $P$ in $P{O}_4^{3-}$ of $S$ in $S{O}_4^{2-}$ and that of $Cr$ in $C{r}_2{O}_7^{2-}$ are respectively:

• A. +5, +5, +6
• B. +3, +6, +6
• C. +5, +6, +6
• D. +3, +6, +5

Answer 1

The correct option is C +5, +6, +6

(I) $P{O}_4^{3-}$
$\Rightarrow x+4\times (-2)=-3$
$\Rightarrow x=-3+8=+5$
$\Rightarrow x=+5$
Oxidation number of $P$ = +5
(II) $S{O}_4^{2-}$
$\Rightarrow x+4\times (-2)=-2$
$\Rightarrow x=-2+8$
$\Rightarrow x=+6$
Oxidation number of $S$ = +6
(III) $C{r}_2{O}_7^{2-}$
$\Rightarrow 2x+7\times (-2)=-2$
$\Rightarrow 2x=-2+14$
$\Rightarrow 2x=12$
$\Rightarrow x==+6$
Oxidation number of $Cr$ = +6
Hence, option (d) is correct answer.