$Cr$નો ઓક્સિડેશન આંક $x$ લેતાં,
$\therefore 2\left( K \right) + 2\left( {Cr} \right) + 7\left( O \right) = 0$$\therefore 2\left( 1 \right) + 2x + 7\left( { - 2} \right) = 0$
$\therefore x = + 6$
$14{H^ + } + C{r_2}O_7^{2 - } + 3Ni \to 2C{r^{3 + }} + 7{H_2}O + 3N{i^{2 + }}$