Which product is formed when fluorine reacts with hot and concentrated sodium hydroxide?

$Silver \ nitrate$ $(AgNO_3)$ produces a black stain on the skin due to:

When a mixture of solid $NaCl$ and solid $K_2Cr_2O_7$ is heated with concentrated $H_2SO_4$,orange-red vapours are obtained of the compound:

Chlorine cannot be used:

Which one will liberate $Br_2$ from $KBr$?

In the manufacture of bromine from sea water,the mother liquor containing bromides is treated with: