Title: Step-by-Step Qualitative Analysis of Lead Acetate ((CH₃COO)₂Pb)
Introduction
Lead acetate ((CH₃COO)₂Pb) is a water-soluble ionic compound commonly used in analytical chemistry. This document outlines the qualitative analysis of (CH₃COO)₂Pb to identify its cation (Pb²⁺) and anion (CH₃COO⁻) through systematic tests.
Step-by-Step Analysis of (CH₃COO)₂Pb
1. Preliminary Examination
| Property | Observation |
|---|---|
| Physical Appearance | White crystalline solid |
| Solubility | Soluble in water, forming a colorless solution |
| Odor | Slight vinegar-like odor due to acetate ions |
2. Dry Heating Test
| Procedure | Observation | Inference | Chemical Equation |
| Heat a small sample in a dry test tube. | Smell of acetic acid and black residue (PbO). | Decomposition of lead acetate. | (CH₃COO)₂Pb → PbO (black) + 2CH₃COOH |
3. Flame Test
| Procedure | Observation | Inference |
| A platinum wire is dipped in (CH₃COO)₂Pb solution and introduced to a non-luminous flame. | Blue-white flame observed. | Presence of Pb²⁺ ions. |
4. Identification of Lead (Pb²⁺) Ion
| Test | Reagent Used | Observation | Inference | Chemical Equation |
| Potassium Iodide (KI) test | KI solution | Yellow precipitate | Confirms Pb²⁺ presence | Pb²⁺ + 2I⁻ → PbI₂ (yellow ppt.) |
| Dilute H₂SO₄ test | H₂SO₄ solution | White precipitate | Confirms Pb²⁺ presence | Pb²⁺ + SO₄²⁻ → PbSO₄ (white ppt.) |
| Sodium Hydroxide (NaOH) test | NaOH solution | White precipitate, soluble in excess NaOH | Confirms Pb²⁺ presence | Pb²⁺ + 2OH⁻ → Pb(OH)₂ (white ppt.) |
5. Identification of Acetate (CH₃COO⁻) Ion
| Test | Reagent Used | Observation | Inference | Chemical Equation |
| Ferric Chloride (FeCl₃) test | FeCl₃ solution | Deep red coloration | Confirms CH₃COO⁻ presence | CH₃COO⁻ + Fe³⁺ → Fe(CH₃COO)₃ (red complex) |
| Conc. Sulfuric Acid (H₂SO₄) test | Conc. H₂SO₄ + heat | Smell of vinegar (acetic acid) | Confirms CH₃COO⁻ presence | (CH₃COO)₂Pb + H₂SO₄ → PbSO₄ + 2CH₃COOH (gas) |
6. Group Analysis of Pb²⁺ (Cation Analysis)
Lead ion (Pb²⁺) belongs to Group II in cation analysis, which includes Pb²⁺, Cu²⁺, and Hg²⁺. The group reagent used for its identification is dilute HCl, forming PbCl₂ precipitate.
| Test | Reagent Used | Observation | Inference | Chemical Equation |
| Group Precipitation | Dilute HCl | White precipitate | Confirms Pb²⁺ presence | Pb²⁺ + 2Cl⁻ → PbCl₂ (white ppt.) |
| Confirmation | Hot water | Precipitate dissolves | Solubility of PbCl₂ in hot water | PbCl₂ (s) → Pb²⁺ (aq) + 2Cl⁻ (aq) |
Conclusion
The qualitative analysis of (CH₃COO)₂Pb confirms the presence of lead (Pb²⁺) and acetate (CH₃COO⁻) ions through distinct chemical reactions, solubility tests, and confirmatory tests.