Chapter 18, Problem 65E

Interpretation Introduction

Interpretation:

The valid conclusions needs to be determined.

Concept introduction:

Major objective of qualitative cation analysis is identifying the cations present in a mixture. In qualitative cation analysis, cations are categorized into 5 groups depending on the solubilities of their compounds. Pb²⁺, Hg₂²⁺, Ag₊ belong to the first group which form insoluble chlorides when HCl(aq) is added. When the remaining solution is added with H₂S in an acidic medium (0.3 M HCl), a group of sulfides precipitate. The remaining solution from this is next treated with H₂S in a buffer mixture of NH₃ and NH₄+ ions which then gives a mixture of insoluble hydroxides and sulfides. Filtrate of above reaction mixture is then treated with CO₃^2-. This yield carbonate precipitates of cations. In the final solution, all the water soluble cations include.