Lead Acetate (Pb(CH₃COO)₂) Salt Analysis – Class 12 CBSELead Acetate (Pb(CH₃COO)₂) Salt Analysis – CBSE Class 12
1. Preliminary Examination
- Appearance: White, crystalline solid, soluble in water.
- Flame Test: Faint bluish-white flame (not very distinct).
2. Dry Heating Test
- Observation: Decomposes with white fumes (acetic acid smell), black residue of lead oxide (PbO) remains.
3. Action with Dilute and Concentrated H₂SO₄
- With Dilute H₂SO₄: White ppt. of PbSO₄ formed (insoluble in water and acids).
- With Concentrated H₂SO₄: Similar reaction as dilute, more vigorous.
4. Confirmatory Tests for Pb²⁺ (Lead) – with Chemical Reactions
| Test | Procedure | Observation | Inference | Chemical Reaction |
|---|
| Potassium Iodide (KI) | Add KI to salt solution. | Bright yellow ppt. of PbI₂ | Pb²⁺ confirmed | Pb(CH₃COO)₂ + 2KI → PbI₂↓ (yellow) + 2CH₃COOK |
| Dilute H₂SO₄ | Add dilute H₂SO₄ to salt solution. | White ppt. of PbSO₄ | Pb²⁺ confirmed | Pb(CH₃COO)₂ + H₂SO₄ → PbSO₄↓ (white) + 2CH₃COOH |
| Potassium Chromate (K₂CrO₄) | Add K₂CrO₄ to salt solution. | Yellow ppt. of PbCrO₄ | Pb²⁺ confirmed | Pb(CH₃COO)₂ + K₂CrO₄ → PbCrO₄↓ (yellow) + 2CH₃COOK |
| Ammonium Hydroxide (NH₄OH) | Add NH₄OH dropwise to salt solution. | White ppt. of Pb(OH)₂ | Pb²⁺ confirmed | Pb(CH₃COO)₂ + 2NH₄OH → Pb(OH)₂↓ (white) + 2CH₃COONH₄ |
| Dilute HCl (Group I test) | Add dilute HCl to salt solution (then heat). | White ppt. of PbCl₂ (soluble in hot water) | Pb²⁺ confirmed | Pb(CH₃COO)₂ + 2HCl → PbCl₂↓ (white, soluble in hot) + 2CH₃COOH |
5. Tests for Anion (CH₃COO⁻: Acetate) – with Chemical Reactions
| Test | Procedure | Observation | Inference | Chemical Reaction |
|---|
| Acetic Acid Odor Test | Warm salt with conc. H₂SO₄. | Pungent smell of vinegar (acetic acid vapors). | CH₃COO⁻ confirmed | Pb(CH₃COO)₂ + H₂SO₄ → PbSO₄ + 2CH₃COOH↑ |
| Ferric Chloride (FeCl₃) | Add neutral FeCl₃ to salt solution. | Blood-red coloration (ferric acetate). | CH₃COO⁻ confirmed | 6CH₃COO⁻ + 2Fe³⁺ → 2[Fe(CH₃COO)₃] |
| Ester (Fruity Smell) Test | Warm salt with ethanol and conc. H₂SO₄. | Fruity smell of ethyl acetate. | CH₃COO⁻ confirmed | CH₃COO⁻ + C₂H₅OH + H⁺ → CH₃COOC₂H₅ + H₂O |
6. Summary of Identification
- Cation: Pb²⁺ (Lead)
- Anion: CH₃COO⁻ (Acetate)
- Salt: Pb(CH₃COO)₂ (Lead(II) acetate)
7. Key Points for Practical Exam
- Observe color and solubility of precipitates carefully.
- Write balanced chemical reactions for all confirmatory tests.
- Do not forget characteristic odors and solubility properties for acetate and lead compounds.
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