In acidic medium, ${\mathrm{H}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{2}}$ changes ${\mathrm{Cr}}_{\mathrm{2}}{{\mathrm{O}}_{\mathrm{7}}}^{\mathrm{2-}}\text{ to} {\mathrm{CrO}}_{\mathrm{5}}$ which has two $(-\mathrm{O}-\mathrm{O}-)$ bonds. Oxidation state of $\mathrm{Cr} \text{in }{\mathrm{CrO}}_{\mathrm{5}}$ is ____.

 

Which metal is used as a part of the catalyst in the Fischer-Tropsch method?

Which one of the following statements is CORRECT when ${\mathrm{SO}}_{\mathrm{2}}$ is passed through acidified ${\mathrm{K}}_{\mathrm{2}}{\mathrm{Cr}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{7}}$ solution?

The colour and magnetic nature of manganate ion ${({\mathrm{MnO}}_{\mathrm{4}}}^{\mathrm{2-}}\mathrm{)}$ are ______, respectively.

The purple colour of the permanganate ion ${{\text{(MnO}}_{\text{4}}}^{\text{-}}\text{)}$ arises due to the _____.

Lanthanoids are ______.

The atomic number of cerium $\left(\mathrm{Ce}\right)$ is $58$. The correct electronic configuration of the ${\text{Ce}}^{\text{3+}}$ ion is _____.

Which is NOT the correct statement about the chemistry of $3\mathrm{d}$ and $4\mathrm{f}$ series elements?