Question

Oxidation number of $Cr$ in the following compounds are $x,y,z$ and $w$ respectively.
$K\left[\underset{x}{Cr}O\right(O_2\left)\right(OH\left)\right],K_3\left[\underset{y}{Cr}{\left(O_2\right)}_4\right],{\left({NH}_3\right)}_3\left[\underset{z}{Cr}{\left(O_2\right)}_2\right],\underset{w}{Cr}{O}_2{Cl}_2$
These values are, respectively :

• A. $6,13,5,6$
• B. $4,4,4,6$
• C. $4,5,4,6$
• D. $4,5,6,6$

Answer 1

The correct option is C $4,5,4,6$

$\underset{\uparrow +1}{K}\underset{\uparrow +x}{\left[\right(Cr}\underset{\uparrow -2}{O)}\underset{\uparrow -2}{\left(O_2\right)}\underset{\uparrow -1=0}{OH]}$
$x=4$
$\underset{\uparrow 3}{K_3}\underset{\uparrow +y}{[Cr}\underset{\uparrow -8=0}{{\left(O\right)}_4}]$
$y=5$
$\underset{\uparrow 0}{{\left({NH}_3\right)}_3}\left[\underset{\uparrow +z}{Cr}\underset{\uparrow -4=0}{{\left(O_2\right)}_2}\right]$
$z=4$
$\underset{\uparrow w-4-2=0}{Cr}{O}_2{Cl}_2$
$w=6$
Thus, the values of $x,y,z$ and $w$ are $4,5,4$ and $6$ respectively.