The dark purple colour of $$\mathrm{KMnO}_{4}$$ disappears in the titration with oxalic acid in acidic medium. The overall change in the oxidation number of manganese in the reaction is :

$$ \stackrel{\bullet}{\mathrm{Cl}}+\mathrm{CH}_{4} \rightarrow \mathrm{A}+\mathrm{B} $$

A and B in the above atmospheric reaction step are :

Which technique among the following, is most appropriate in separation of a mixture of $$100 \,\mathrm{mg}$$ of $$p$$-nitrophenol and picric acid ?

The difference in the reaction of phenol with bromine in chloroform and bromine in water medium is due to :