The $Chromyl$ $Chloride$ test is performed to detect which of the following ions?

$AgNO_3$ gives a red precipitate with:

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

The brown ring test is used to detect the presence of which ion?

When salt $BA$ is treated with concentrated $H_2SO_4$, a reddish-brown gas is liberated. The aqueous solution of $BA$ gives a pale yellow precipitate with $AgNO_3$ solution. Which of the following anions $(A^-)$ is present in the salt $BA$?

Aqueous solution of a salt $(A)$ forms a dense white precipitate with $BaCl_{2}$ solution. The precipitate dissolves in dilute $HCl$ to produce a gas $(B)$ which decolourises acidified $KMnO_{4}$ solution. $A$ and $B$ respectively are