Which of the following pairs of cations cannot be separated by adding NH4Cl and NH4OH to the mixture — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

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).