Bleaching powder is a mixed calcium salt of

$1$. $KClO_3 \xrightarrow{\Delta }$
$2$. $XeF_2 \xrightarrow{H_2O}$
$3$. $XeF_4 \xrightarrow{H_2O}$
$4$. $PbO_2 \xrightarrow{\Delta }$
$5$. $XeF_6 \xrightarrow{H_2O}$
In how many of the above processes,$O_2$ will be one of the products?

The weakest acid $HX$ $(X = F, Cl, Br, I)$ is

One gas bleaches the colour of flowers by reduction while the other by oxidation. The two gases respectively are:

Which of the following statements is correct regarding halogens?

Which of the following halogens exhibits metallic character?