The correct order of acidity of the following hydra acids is:

The gas produced on heating $MnO_2$ with conc. $HCl$ is

Which of the following halogens has the highest bond energy?

Which among the following is $\underline{\text{NOT}}$ a mineral of chlorine?

$NaCl$ (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

Manganese dioxide on heating with concentrated hydrochloric acid gives a greenish yellow gas,$X$. With excess of ammonia,$X$ gives $Y$ and $Z$. $Y$ and $Z$ respectively are: