Which of the following is the most active halogen?

Give two examples to show the anomalous behaviour of fluorine.

What is the reason for the bleaching action of chlorine?

Which of the following is prepared by the electrolytic method?

Write a note on hydrogen halides. Explain the reactivity of halogens with oxygen. $OR$ Write a note on oxides of halogens.

$POCl_3$ is prepared by the reaction of:
$(I)$ $P_4 + SO_2Cl_2 \to$
$(II)$ $P_4 + SOCl_2 \to$
$(III)$ $PCl_5 + SO_2 \to$
$(IV)$ $PCl_5 + C_2H_5OH \to$