Question

Which of the following ion forms a precipitate on addition of \(NH_4OH\) and \(H_2S\)?

• A. \(Pb^{2+}\)
• B. \(Mn^{2+}\)
• C. \(Cu^{+}\)
• D. \(Fe^{3+}\)

Answer 1

The Correct Option is B

Concept: In qualitative inorganic analysis, cations are separated into groups based on their reactions with group reagents. \(NH_4OH\) and \(H_2S\) are used as group IV reagents. Group IV cations include: \[ Ni^{2+},\; Co^{2+},\; Mn^{2+},\; Zn^{2+} \] These ions form sulfide precipitates in basic medium when treated with \(H_2S\).
Step 1: Identify ions belonging to group IV Among the given options: \[ Mn^{2+} \in \text{Group IV} \] Thus it forms a precipitate with \(NH_4OH\) and \(H_2S\).
Step 2: Conclusion \[ \boxed{Mn^{2+} \text{ forms the precipitate}} \]