Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$Ca(OH)_2 + CO_2 \longrightarrow CaCO_3 \downarrow + H_2O$

What change does not occur when $K_2Cr_2O_7$ reacts with $H_2O_2$ solution in an acidic medium?

$Zn_{(s)} + CuSO_{4(aq)} \rightarrow ZnSO_{4(aq)} + Cu_{(s)}$ is an example of which type of process?

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?

Which one of the following compounds does not decolourise an acidified aqueous solution of $KMnO_4$?

In which of the following redox reactions is a precipitate $NOT$ formed?