Identify the weakest halogen acid from the following.

Which of the following elements is in a liquid state at room temperature?

$NaCl$ (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

Concentrated $H_2SO_4$ cannot be used to prepare $HBr$ from $NaBr$,because it

Which of the following halogens does not exhibit a positive oxidation state in its compounds?

The bond dissociation energies of $F_2, Cl_2, Br_2$ and $I_2$ are $155, 244, 193$ and $151 \ kJ \ mol^{-1}$ respectively. Which of these has the weakest bond?