The brown ring test is used for the detection of which radical?

Which of the following reagents would you use to separate $SO_4^{2-}$ ions from a solution containing a mixture of $SO_4^{2-}$ and $Cl^-$ ions?

$A$ solution of a salt in dilute $H_2SO_4$ gives a blue color with starch iodide solution. This indicates the presence of which ion?

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

$A$ sodium salt gives a white precipitate with $MgCl_2$ only upon heating. What is the anion of the sodium salt?

$A$ white sodium salt dissolves readily in water to give a solution which is neutral to litmus. When silver nitrate solution is added to the aforementioned solution,a white precipitate is obtained which does not dissolve in dilute nitric acid. The anion is: