Which one is the anhydride of $HClO_4$?

An explosive compound $(A)$ reacts with water to produce $NH_4OH$ and $HOCl$. Then,the compound $(A)$ is

One of the hydrolysed products of the following compound does not react with the silica of a glass vessel.

Euchlorine is a mixture of which of the following?

$NaCl$ (solid) $+ K_2Cr_2O_7$ (solid) $+$ conc. $H_2SO_4 \xrightarrow{\text{warm}} X$. Reddish brown fumes of $X$. The oxidation state of central atom in compound $X$ is

The correct reactivity order of halogens with hydrogen is?