$A$ solution of a salt in dilute $H_2SO_4$ gives a blue color with starch iodide solution. This indicates the presence of which ion?

When $BaCl_2$ is added to a clear solution of compound $(X)$,a heavy white precipitate is formed,which is insoluble in dilute $HCl$. What is compound $(X)$?

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 vapours of bromine. Why?

The solution of a chemical compound $X$ reacts with $AgNO_3$ solution to form a white precipitate of $Y$,which dissolves in $NH_4OH$ to give a complex $Z$. When $Z$ is treated with dilute $HNO_3$,$Y$ reappears. The chemical compound $X$ can be:

Which of the following silver precipitates dissolves in $dil. \, HNO_3$ to produce a clear solution?

Neutral ferric chloride is added to the aqueous solution of acetate. $A$ blood-red colour is obtained; this is due to the formation of which compound?