Question

Find the oxidation number of elements in each case :

$Cr$ in $Cr{O}_{2}C{l}_2,N{a}_{2}C{r}_3{O}_{10},C{r}_2(S{O}_4{)}_3$ and $[Cr{O}_8{]}^{3-}$.

• A. $+6,+6,+3,+5$
• B. $+5,+6,+3,+4$
• C. $+4,+6,+2,+5$
• D. None of the above

Answer 1

The correct option is A $+6,+6,+3,+5$

The oxidation numbers of
$Cr$ in $Cr{O}_{2}C{l}_2,N{a}_{2}C{r}_3{O}_{10},C{r}_2(S{O}_4{)}_3$ and $[Cr{O}_8{]}^{3-}$ are $+6,+6,+3,+5$ respectively. Let X be the oxidation number of Cr in $Cr{O}_{2}C{l}_2$
$X+2(-2)+2(-1)=0$
$X=+6$
Let X be the oxidation number of Cr in $N{a}_{2}C{r}_3{O}_{10}$
$2+3X+10(-2)=0$
$X=+6$
Let X be the oxidation number of Cr in $C{r}_2(S{O}_4{)}_3$
$2X+3(-2)=0$
$X=+3$
Let X be the oxidation number of Cr in $[Cr{O}_8{]}^{3-}$
As Cr has maximum oxidation number +5.