$Na_2CO_3$ cannot be used to identify which of the following ions?

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

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

$A$ solution of a salt in dilute sulphuric acid imparts a deep blue colour with starch-iodine solution; it confirms the presence of which of the following?

An aqueous solution of a salt,when treated with $AgNO_3$ solution,gives a white precipitate which dissolves in $NH_4OH$. The radical present in the salt is:

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