Question:
Dichromate ion is treated with base, the oxidation number of $\mathrm{Cr}$ in the product formed is_____.
Solution:
$\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+\mathrm{OH}^{-} \longrightarrow \mathrm{CrO}_{4}^{2-}$
Oxidation state of $\mathrm{Cr}$ in $\mathrm{CrO}_{4}^{2-}$ is $+6$