Question

You have read a new brand of hair tonic is supposed to contain lead (an ingredient in Grecian Formula). Devise a simple test to confirm the presence or absence of lead in that hair tonic. Use your observation from the experiments you have performed.

Answer 1

Explanation:

If the hair tonic contains lead, then these test will be positive:

1. To the tonic, add dilute sulfuric acid. The appearance of white precipitate confirms lead.

Pb²⁺ + SO₄²⁻ ⇒ PbSO₄ (White precipitate)

2. Add 2-3 mL of potassium chromate solution to the tonic. The appearance of yellow precipitate confirms lead.

Pb²⁺ + CrO₄²⁻ ⇒ PbCrO₄ (Yellow precipitate)

3. To the tonic, add 2-3 mL of potassium iodide solution. The appearance of yellow precipitate confirms lead.

Pb²⁺ + 2I⁻ ⇒ PbI₂ (Yellow precipitate)