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:

Which of the following reagents is commonly used to detect the presence of sulfide ions?

Choose the correct tests with respective observations.
$(A)$ $CuSO_4$ (acidified with acetic acid) $+$ $K_4[Fe(CN)_6]$ $\rightarrow$ Chocolate brown precipitate.
$(B)$ $FeCl_3 + K_4[Fe(CN)_6]$ $\rightarrow$ Prussian blue precipitate.
$(C)$ $ZnCl_2 + K_4[Fe(CN)_6]$,neutralised with $NH_4OH$ $\rightarrow$ White or bluish white precipitate.
$(D)$ $MgCl_2 + K_4[Fe(CN)_6]$ $\rightarrow$ Blue precipitate.
$(E)$ $BaCl_2 + K_4[Fe(CN)_6]$,neutralised with $NaOH$ $\rightarrow$ White precipitate.
Choose the correct answer from the options given below:

$A$ precipitate of ....... would be obtained on adding $HCl$ to a solution of $(Sb_2S_3)$ in yellow ammonium sulphide.

Consider the sulphides $HgS$,$PbS$,$CuS$,$Sb_{2}S_{3}$,$As_{2}S_{3}$ and $CdS$. Number of these sulphides soluble in $50\% \ HNO_{3}$ is .... .

Which of the following options is incorrect?