Tests d'Identification des Anions

Détection des anions courants par des réactions chimiques sélectives

Qualitative Analysis Intermediate (High School) 60 min ~$10,00

Objectif

Identifier les anions inconnus à l'aide de tests spécifiques de précipitation, de décomposition acide et d'oxydo-réduction.

Contexte

Anion analysis complements cation identification in classical qualitative analysis. Unlike cations, anions do not follow a single systematic separation scheme. Instead, they are identified through a series of specific tests: chloride with silver nitrate, sulfate with barium chloride, carbonate with acid, and so on. Understanding these tests reinforces knowledge of solubility rules and reaction types.

Avertissements de sécurité

  • AgNO₃ stains skin and clothing permanently
  • Use dilute acids only — concentrated acids can produce toxic gases
  • BaCl₂ is toxic if ingested
  • Dispose of silver waste in designated containers

EPI requis

goggles gloves lab_coat

Matériaux

  • Unknown anion solution (10 mL)
    Prepared by instructor
  • Silver nitrate (0.1M AgNO₃) (10 mL)
    For halide tests
  • Barium chloride (0.1M BaCl₂) (5 mL)
    For sulfate test
  • Dilute HNO₃ (2M) (10 mL)
    Acidification
  • Dilute H₂SO₄ (1M) (5 mL)
    For carbonate test
  • Limewater (Ca(OH)₂ solution) (10 mL)
    CO₂ detection
  • Brown ring test reagent (FeSO₄) (5 mL)
    For nitrate test

Équipement

Test tubes (8) Dropper pipettes Bunsen burner Delivery tube Test tube rack

Procédure

1

Carbonate test: Add dilute H₂SO₄ to 2 mL of unknown solution and pass any gas through limewater. A milky appearance confirms CO₃²⁻.

8 min
2

Sulfate test: Add BaCl₂ solution to 2 mL of unknown acidified with HNO₃. A white precipitate insoluble in acid confirms SO₄²⁻.

8 min
3

Chloride test: Add AgNO₃ to 2 mL of unknown acidified with HNO₃. A white curdy precipitate soluble in NH₄OH confirms Cl⁻.

8 min AgNO₃ stains skin
4

Bromide test: Add AgNO₃ as above. A pale yellow precipitate slightly soluble in NH₄OH confirms Br⁻.

8 min
5

Iodide test: Add AgNO₃ as above. A yellow precipitate insoluble in NH₄OH confirms I⁻.

8 min
6

Nitrate test (brown ring): Layer concentrated H₂SO₄ under a mixture of unknown solution and FeSO₄. A brown ring at the junction confirms NO₃⁻.

10 min Handle concentrated H₂SO₄ with extreme care
7

Record all observations, precipitate colors, and solubility behavior. Cross-reference results to identify the anion(s) present.

10 min

Résultats attendus

Each anion produces a characteristic response: carbonates effervesce with acid, sulfates give a white BaSO₄ precipitate, halides give colored AgX precipitates, and nitrates produce a brown ring.

Nettoyage

Collect silver-containing waste separately. Neutralize acid waste before disposal. Rinse all glassware thoroughly.

Détails

Catégorie
Qualitative Analysis
Difficulté
Intermediate (High School)
Durée
60 min
Coût estimé
$10,00
Étapes
7
Matériaux
7

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Frequently Asked Questions

What is the objective of Tests d'Identification des Anions?
Identifier les anions inconnus à l'aide de tests spécifiques de précipitation, de décomposition acide et d'oxydo-réduction.
How difficult is Tests d'Identification des Anions?
This experiment is rated as Intermediate (High School). It takes approximately 60 minutes to complete.
What safety precautions are needed for Tests d'Identification des Anions?
Key safety precautions include: AgNO₃ stains skin and clothing permanently; Use dilute acids only — concentrated acids can produce toxic gases; BaCl₂ is toxic if ingested.
What materials are needed for Tests d'Identification des Anions?
The main materials required are: Unknown anion solution, Silver nitrate (0.1M AgNO₃), Barium chloride (0.1M BaCl₂), Dilute HNO₃ (2M), Dilute H₂SO₄ (1M).
What results should I expect from Tests d'Identification des Anions?
Each anion produces a characteristic response: carbonates effervesce with acid, sulfates give a white BaSO₄ precipitate, halides give colored AgX precipitates, and nitrates produce a brown ring.