The correct formula of permanganic acid is

In the chromyl chloride test for the confirmation of $Cl^{-}$ ion,a yellow solution is obtained. Acidification of the solution and the addition of amyl alcohol and $10\% H_2O_2$ turns the organic layer blue,indicating the formation of chromium pentoxide. The oxidation state of chromium in that compound is:

In the reaction,$MnO_{4(aq)}^{-} + Br_{(aq)}^{-} \rightarrow MnO_{2(s)} + BrO_{3(aq)}^{-}$,the correct change in oxidation number of the species involved is

In which of the following compounds is the oxidation state of nitrogen correctly represented?

What is the oxidation number of the oxygen atom in the $O_2^{2-}$ ion?

The oxidation state of $P$ in $KH_2PO_2$ is .........