Question

Alex was given a solution of an unknown salt Y for analysis. He performed the following tests and recorded his observations: To a part of the solution Y, he added silver nitrate solution and obtained a white precipitate which was soluble in ammonium hydroxide solution. To the remaining solution he added a few drops of sodium hydroxide solution and obtained a pale blue precipitate.

Based on the observations made by Alex, identify:

1. the anion and
2. the cation present in salt Y.

Answer 1

(a) Anion: The anion is the Chloride ion (Cl⁻). When silver nitrate is added to a chloride solution, it forms a white precipitate of Silver Chloride (AgCl), which dissolves in excess ammonium hydroxide to form a clear complex solution.
(b) Cation: The cation is the Copper(II) ion (Cu²⁺). The formation of a pale blue precipitate (Copper(II) hydroxide) with sodium hydroxide is a characteristic test for copper ions.