When H 2 S gas is passed into a mixture of Mn 2 + , Ni 2 + , Cu 2 + and Hg 2 + ion in an acidified aqueous solution, the precipitates formed are

Step-by-step solution

In presence of acidic medium, ionisation of H 2 S is supressed so less number of S 2 - ions are produced. So only those sulphides are precipitated which have low solubility product K sp value. Thus, in acidic medium, H 2 S is very feebly ionised giving very small concentration of sulphide ion for precipitation. Therefore, the most insoluble salts CuS and HgS are precipitated.