Question

When $H_{2}S$ gas is passed through $HCl$ containing aqueous solution of $CuC{l}_2$, $HgC{l}_2$, $BiC{l}_3$, and $CoC{l}_2$, then which of the following precipitate out ?

• A. $CuS$
• B. $HgS$
• C. $B{i}_2{S}_3$
• D. $CoS$

Answer 1

Answer: (A), (B), (C)

$CuS$
$HgS$
$B{i}_2{S}_3$

$H_{2}S$ gas in presence of $HCl$ is the reagent used to detect the presence of group2 basic radicals(Pb,Bi,Cu,Cd,As & Hg etc.....).
When $H_{2}S$ gas is passed through $HCl$ containing aqueous solution of $CuC{l}_2$, $HgC{l}_2$, $BiC{l}_3$it forms $CuS$,$HgS$ and $B{i}_2{S}_3$( corresponding sulfides).
But Co is group4 element and the reagent used is $H_{2}S$ gas in presence of $N{H}_{4}OH$ which precipitates to CoS.
Hence options A,B & C are correct.