H2S is passed through the solution in an acidic medium to precipitate the sulphides of group II cations, but in an alkaline medium to precipitate the sulphides of group IV cations because:

Question

Prashant Kotian · Accepted Answer

Correct answer: B. Step 1: Adding NH4Cl and NH4OH followed by H2S gas is the group reagent for analytical Group IV. Step 2: Group IV cations include Co2+, Ni2+, Mn2+, and Zn2+. These are precipitated as sulfides (CoS, NiS, MnS, ZnS). Step 3: Since both Co2+ and Ni2+ belong to Group IV, both will precipitate as black sulfides (CoS and NiS) simultaneously, meaning they cannot be separated by this procedure, matching option (c).

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