What is the oxidation state of nitrogen in the oxide of nitrogen formed by heating ammonium nitrate?

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

When $SO_2$ is passed through an acidic solution of potassium dichromate,chromium sulphate is formed. What is the change in the oxidation state of chromium?

The oxidation states of $S$ in peroxodisulphuric acid $(H_{2}S_{2}O_{8})$ and sodium tetrathionate $(Na_{2}S_{4}O_{6})$ are respectively:

In acidic medium,$H_2O_2$ changes $Cr_2O_7^{2-}$ to $CrO_5$ which has two $(-O-O-)$ bonds. Oxidation state of $Cr$ in $CrO_5$ is

The oxidation number of phosphorus in $Ba(H_2PO_2)_2$ is $:-$