Outline the steps involved in identifying anion... - SS3 Chemistry Analytical Chemistry I: Qualitative Analysis Question

Identifying anions in an unknown sample requires a systematic approach based on the unique properties of each anion. Below are the steps involved in identifying anions:

1.    Preliminary Test: As with cations, the first step is to conduct a preliminary test to determine the pH of the sample. This information can provide initial clues about the potential anions present.

2.    Group Separation: Anions are typically classified based on their behaviour with specific reagents. Common groups include Group 1 anions (Cl⁻, Br⁻, and I⁻), Group 2 anions (SO₄²⁻ and CO₃²⁻), and Group 3 anions (NO₃⁻ and ClO₃⁻).

3.    Specific Tests for Anion Groups: Within each group, specific reagents are added to the solution to perform tests and identify the anions present. For example, in Group 1, adding AgNO₃ (silver nitrate) will form a white precipitate with Cl⁻, a cream precipitate with Br⁻, and a yellow precipitate with I⁻.

4.    Confirmatory Tests for Individual Anions: After identifying the anion group, confirmatory tests are conducted to identify individual anions. These tests involve reactions specific to each anion. For example, to confirm the presence of SO₄²⁻ in Group 2, adding BaCl₂ (barium chloride) will form a white precipitate of BaSO₄.

5.    Final Confirmation: Additional tests may be performed to ensure the accuracy of the results. These could involve pH tests, redox reactions, or specific colourimetric tests.