Question

The low concentration of S-2 ions help to do precipitation of radicals of group basic radicals in which group
​

Answer 1

In group II sparingly soluble sulphides

$(Hg2+,Pb2+,Cu2+,Cd2+andBi3+)$

ions and in addition the sparingly soluble covalent sulphide

$(As2S3,Sb2S3,SnS) ar$

are precipitated by the passing hydrogen sulphide (H

2 S) through an acidic solution whose concentration of hydrogen ion is small.

The K

sp

value of group II sulphide is quite low in comparison to K

sp

values of group IV sulphides, hence they do not get precipitated in acidic medium, where S

2

−

ion concentration is quite low.

Hence, in the analysis of group II, H

2

S is passed through acidic medium,whereas for group IV H

2

S is passed through alkaline medium.