Question

In the wet tests for identification of various cations by precipitation, which transition element cation doesn’t belong to group IV in qualitative inorganic analysis?

• A. \(Fe^{3+}\)
• B. \(Zn^{2+}\)
• C. \(Co^{2+}\)
• D. \(Ni^{2+}\)

Answer 1

The Correct Option is A

In the context of qualitative inorganic analysis, various cations are grouped based on the precipitation reactions they undergo under specific conditions. These groups help in systematically identifying the presence of cations in a given sample.

In such a scheme:

1. Group IV cations typically include metals that precipitate as sulfides in neutral or mildly acidic conditions using hydrogen sulfide gas (\(\text{H}_2\text{S}\)).
2. Common transition metal cations in Group IV include \(Zn^{2+}\), \(Co^{2+}\), and \(Ni^{2+}\). These cations form insoluble sulfides.
3. \(Fe^{3+}\), however, does not belong to Group IV, as it tends to form complexes and is typically precipitated as hydroxide in earlier steps of the qualitative analysis (Group III).

Hence, among the given options, \(Fe^{3+}\) is the cation that does not belong to Group IV.

Conclusion: The transition element cation that doesn't belong to Group IV is \(Fe^{3+}\), due to its different precipitation characteristics and group classification in qualitative analysis.