Which anion of a sodium salt gives a white precipitate upon heating with a magnesium salt?

$S^{2-}$ and $SO_3^{2-}$ can be distinguished by using

Which of the following silver precipitates dissolves in $dil. \, HNO_3$ to produce a clear solution?

$A$ substance reacts with dilute $H_2SO_4$ to release a colorless gas,which turns baryta water $[Ba(OH)_2]$ turbid and decolorizes an acidic solution of dichromate. The presence of which of the following is indicated by this reaction?

When $BaCl_2$ is added to a clear solution of a compound $(X)$,a heavy white precipitate is formed which does not dissolve in $dil. HCl$. What is the compound $(X)$?

$A$ salt solution is treated with chloroform drops. Then it is shaken with chlorine water. The chloroform layer becomes violet. The solution contains: