Chemistry for Pharmacy Lab: Qualitative Analysis of Anions

Chemical Analysis Overview

• Chemical Analysis: Process to identify/quantify substances.

• Qualitative Analysis: Identifies which ions are present.

• Quantitative Analysis: Determines how much of each component is present.

Qualitative Analysis of Anions

• Tests determine specific anions in small sample portions.

• Results:

• Positive Test: Ion is present.

• Negative Test: Ion is absent or below detection levels.

Observations in Positive Tests

• Formation/disappearance of substances.

• Color change, precipitate formation, gas evolution, odor changes, heat, or instrument reading changes.

Anion Tests and Procedures

1. Chloride Ion (Cl⁻)

• Procedure: 1/2 mL solution + 2 drops of 6M HNO₃, check acidity + 2 drops of 0.1M AgNO₃.

• Observation: White precipitate of AgCl confirms presence.

• Net Ionic Equation: Ag⁺(aq) + Cl⁻(aq) → AgCl(s)

2. Sulfate Ion (SO₄²⁻)

• Procedure: 1/2 mL solution + 2 drops of 6M HCl + 2 drops of 0.1M BaCl₂.

• Observation: White precipitate of BaSO₄ confirms presence.

• Net Ionic Equation: Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s)

3. Nitrate Ion (NO₃⁻)

• Procedure: 1/2 mL solution + 2 drops of 6M H₂SO₄ + 10 drops of saturated FeSO₄; add concentrated H₂SO₄.

• Observation: Brown ring indicates presence.

• Net Ionic Equation: [FeNO]²⁺ indicates confirmation.

4. Carbonate Ion (CO₃²⁻)

• Procedure: 1/2 mL solution + 1 drop of 6M HCl; look for gas evolution.

• Observation: Colorless gas (CO₂) confirms presence.

• Net Ionic Equation: CO₃²⁻(aq) + 2H⁺(aq) → CO₂(g) + H₂O(l)

Summary of Observations

• Chloride: White precipitate with AgNO₃.

• Sulfate: White precipitate with BaCl₂.

• Nitrate: Brown ring with FeSO₄ and H₂SO₄.

• Carbonate: Bubbling CO₂ with HCl.

Unknown Solution Analysis

• Repeat tests for unknown samples containing 2-3 anions. .

• Record results as Present (P) or Absent (A) on Report Sheet.