$A$ black sulphide is formed by the action of $H_2S$ on

In the fifth group of qualitative analysis,$(NH_4)_2CO_3$ is added to precipitate out the carbonates. We do not add $Na_2CO_3$ because

When $H_2S$ gas is passed through a solution,it reacts to form a white precipitate. Which ion is present in the solution?

Consider the following reactions:
$X(aq.) \xrightarrow{K_4[Fe(CN)_6]}$ Chocolate brown ppt.
$X(aq.) \xrightarrow{AgNO_3}$ White ppt. (insoluble in dil. $HNO_3$)
Then $X$ will be:

During the qualitative analysis of a salt with cation $y^{2+}$,the addition of a reagent $(X)$ to an alkaline solution of the salt gives a bright red precipitate. The reagent $(X)$ and the cation $(y^{2+})$ present are respectively .... .

The incorrect statement out of the following is: