Notebook Theme

Analysis of Lead(II) Carbonate (PbCO₃)

Qualitative analysis

Aim

To analyse the given inorganic salt for one acidic and one basic radical.

Preliminary Test

  • Colour: White
  • Odour: Odourless
  • State: Crystalline solid
  • Solubility: Insoluble in water

Test of Anion (CO₃²⁻)

ExperimentObservationInference
Take 0.1 g of salt, add 1–2 mL of dilute H₂SO₄Colourless odourless gas is evolved with brisk effervescence; lime water turns milkyCO₃²⁻ may be present
Confirmatory Test
Lime Water Test
Pass the gas through lime water
Lime water turns milky; milkiness disappears on passing excess gas (soluble calcium bicarbonate)CO₃²⁻ is confirmed

Test of Cation (Pb²⁺)

ExperimentObservationInference
Original solution + Dilute HClWhite precipitatePb²⁺ may be present
Confirmatory Tests
Potassium Iodide Test
Dissolve one part of the hot precipitate in hot water and add potassium iodide solution
Yellow precipitate is formedPresence of Pb²⁺ is confirmed
Potassium Chromate Test
To the acidified solution obtained above, add potassium chromate solution
Yellow precipitate is formedPresence of Pb²⁺ is confirmed
Lead Sulphate Test
Dissolve lead sulphide precipitate in dilute HNO₃, then add a few drops of dilute H₂SO₄ and alcohol
White precipitate of lead sulphate is formedPresence of Pb²⁺ is confirmed

Result

The given salt contains Pb²⁺ as the cation (basic radical) and CO₃²⁻ as the anion (acidic radical). The salt is Lead(II) Carbonate (PbCO₃).

Precautions

  1. Handle the chemicals with care.
  2. Don't use excess of chemicals.
  3. Keep the mouth of the test tube away from the face.