阴离子鉴定测试

通过选择性化学反应检测常见阴离子

Qualitative Analysis Intermediate (High School) 60 分钟 ~$10.00

目标

用特定的沉淀、酸分解和氧化还原测试鉴定未知阴离子。

背景

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.

安全警告

  • 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

所需PPE

goggles gloves lab_coat

材料

  • 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

设备

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

步骤

1

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

8 分钟
2

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

8 分钟
3

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

8 分钟 AgNO₃ stains skin
4

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

8 分钟
5

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

8 分钟
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 分钟 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 分钟

预期结果

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.

清理

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

详情

类别
Qualitative Analysis
难度
Intermediate (High School)
时长
60 分钟
预估费用
$10.00
步骤数
7
材料
7

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Frequently Asked Questions

What is the objective of 阴离子鉴定测试?
用特定的沉淀、酸分解和氧化还原测试鉴定未知阴离子。
How difficult is 阴离子鉴定测试?
This experiment is rated as Intermediate (High School). It takes approximately 60 minutes to complete.
What safety precautions are needed for 阴离子鉴定测试?
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 阴离子鉴定测试?
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 阴离子鉴定测试?
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.