Which reagent below would enable you to remove sulphate ions from a solution containing both sulphate and chloride ions?

Chromyl chloride test is used for the detection of:

When $Y$ is treated with $KMnO_4$,then the final precipitate is of:
$'X' \xrightarrow[BaCl_{2} \text{ solution}]{} 'Y' \quad (\text{White ppt., insoluble in dil. } HCl)$
$'X' \xrightarrow[\text{Flame test}]{} \text{Golden yellow flame}$

$A$ white crystalline salt $A$ reacts with dilute $HCl$ to liberate a suffocating gas $B$ and also forms a yellow precipitate. The gas $B$ turns potassium dichromate acidified with dilute $H_{2}SO_{4}$ to a green coloured solution $C$. $A$,$B$ and $C$ are respectively

An anion solution gives a white precipitate with $AgNO_3$ solution. The precipitate dissolves in dilute ammonia due to the formation of:

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