When potassium dichromate crystals are heated with concentrated $HCl$,which gas is evolved?

Which of the following halogens can be purified by sublimation?

Affinity for hydrogen decreases in the group from fluorine to iodine. Which of the halogen acids should have the highest bond dissociation enthalpy?

Three parts of $conc. HCl$ and one part of $conc. HNO_3$ are mixed to form aqua regia. It is used to dissolve:

An aqueous solution of a halogen salt of potassium reacts with the same halogen $X_2$ to give $KX_3$,a brown-coloured solution,in which the halogen exists as the $X_3^-$ ion,$X_2$ acts as a Lewis acid,and $X^-$ acts as a Lewis base. The halogen $X$ is:

Observe the following statements :
$I$. Bleaching powder is used in the preparation of chloroform.
$II$. Bleaching powder decomposes in the presence of $CoCl_2$ to liberate $O_2$.
$III$. Aqueous $KHF_2$ is used in the preparation of fluorine.
The correct combination is :