$KMnO_4$ acts as an oxidising agent in acidic medium. $X$ is the difference between the oxidation states of $Mn$ in reactant and product. $Y$ is the number of $d$ electrons present in the brown red precipitate formed at the end of the acetate ion test with neutral ferric chloride. The value of $X+Y$ is $.........$

How do you account for the following observations?
$(a)$ Though alkaline potassium permanganate and acidic potassium permanganate both are used as oxidants,yet in the manufacture of benzoic acid from toluene,we use alcoholic potassium permanganate as an oxidant. Why? Write a balanced redox equation for the reaction.
$(b)$ When concentrated sulphuric acid is added to an inorganic mixture containing chloride,we get a colourless pungent-smelling gas $HCl$,but if the mixture contains bromide,then we get red vapour of bromine. Why?

When copper is added to concentrated $H_2SO_4$,$CuSO_4$ is produced along with another sulphur-containing compound $X$. The compound $X$ is

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$BaSO_3(s) + H_2SO_4(aq) \longrightarrow BaSO_4(s) + SO_2(g) + H_2O(l)$

In the reaction of sulphur with concentrated sulphuric acid,the oxidised product is $X$ and the reduced product is $Y$. $X$ and $Y$ are respectively:

Consider the reactions:
$2S_2O_3^{2-}{(aq)} + I_{2(s)} \to S_4O_6^{2-}{(aq)} + 2I^{-}{(aq)}$
$S_2O_3^{2-}{(aq)} + 2Br_{2(l)} + 5H_2O_{(l)} \to 2SO_4^{2-}{(aq)} + 4Br^{-}{(aq)} + 10H^{+}{(aq)}$
Why does the same reductant,thiosulphate,react differently with iodine and bromine?