In acidic medium,$H_2O_2$ changes $Cr_2O_7^{2-}$ to $CrO_5$ which has two peroxy linkages. The oxidation state of $Cr$ in $CrO_5$ is

Choose the pair of species in which the oxidation number of nitrogen is the same.

The oxidation state of sulfur in the anions $SO_3^{2-}$,$S_2O_4^{2-}$,and $S_2O_6^{2-}$ increases in the order:

The difference in the oxidation numbers of the two types of sulphur atoms in $Na_2S_4O_6$ is

Assign the oxidation number to the underlined element in each of the following species:
$1$. $K_2\underline{Mn}O_4$
$2$. $Ca\underline{O}_2$
$3$. $Na\underline{B}H_4$
$4$. $KAl(\underline{S}O_4)_2 \cdot 12H_2O$

Which of the following involves the transfer of five electrons?