$A$ solid $A$ which has photographic effect reacts with the solution of a sodium salt $B$ to give a pale yellow precipitate $C$. The sodium salt $B$ on heating with concentrated $H_2SO_4$ gives brown vapours. Identify $A$,$B$,and $C$.

Which of the following halogens does not form oxyacid?

Who established the elemental nature of chlorine?

With respect to hypochlorite,chlorate,and perchlorate ions,choose the correct statement$(s)$.
$A.$ The hypochlorite ion is the strongest conjugate base.
$B.$ The molecular shape of only the chlorate ion is influenced by the lone pair of electrons on $Cl$.
$C.$ The hypochlorite and chlorate ions disproportionate to give rise to an identical set of ions.
$D.$ The hypochlorite ion oxidizes the sulfite ion.

The acid used for making permanent markings on the glass surface is:

When $1 \ mol$ of fluorine reacts with $2 \ mol$ of hot and concentrated $KOH$,the products formed are $KF$,$H_2O$,and $O_2$. What is the molar ratio of $KF$,$H_2O$,and $O_2$ produced?