What is the oxidation number of $Xe$ in $Ba_2XeO_6$?

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:

The oxidation state of iodine in $I_3^{-}$ is:

The oxidation states of $S$ in Peroxodisulphuric acid $(H_2S_2O_8)$ and Sodium tetrathionate $(Na_2S_4O_6)$ are respectively:

What is the oxidation state of $Cl$ in $KClO_3$?

In which of the following pairs is the difference in the oxidation number of the underlined elements the greatest?