The least active halogen with hydrogen is

Which statement is correct about halogens?

Which among the following compounds is $NOT$ a colourless gas?

The mixture used for the tips of matchsticks is:

When $1 \ mol$ of fluorine reacts with $2 \ mol$ of hot and concentrated $KOH$,the products obtained are $KF$,$H_2O$,and $O_2$. The molar ratio of $KF$,$H_2O$,and $O_2$ produced is respectively:

Bleaching powder can be obtained by which of the following reactions?