demonstrations:lead_iodide_precipitation

Lead Iodide Precipitation

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★★☆ Some safety precautions required to perform safely

Categories: Chemical Reactions, Colour Changes, Water and Solubility

Alternative titles: Golden Rain

Summary

When aqueous lead(II) nitrate reacts with aqueous potassium iodide, a double displacement reaction occurs. Potassium nitrate remains dissolved, while lead(II) iodide precipitates as a bright yellow solid.

Procedure

  1. Dissolve lead(II) nitrate in water to form a clear solution.
  2. Dissolve potassium iodide in a separate container of water.
  3. Mix the two solutions together.
  4. Observe the immediate formation of a bright yellow precipitate of lead(II) iodide.

Lead Nitrate and Potassium Iodide - Chemistry and Biochemistry Demo lab at OSU:


📄 What happens when lead nitrate reacts with potassium iodide - Unacademy: https://unacademy.com/content/question-answer/chemistry/what-happens-when-lead-nitrate-reacts-with-potassium-iodide/

Variations

  • Compare the reaction at room temperature with the heated and cooled version (Golden Rain).
  • Vary concentrations to see how the intensity of the precipitate changes.
  • Demonstrate other double displacement reactions (e.g., silver nitrate with sodium chloride) for comparison.

Safety Precautions

  • Lead salts are highly toxic — avoid ingestion, inhalation, or skin contact.
  • Always wear safety glasses, gloves, and a lab coat.
  • Do not dispose of lead-containing waste down the drain; collect and store as hazardous waste.

Questions to Consider

  • What type of reaction occurs between lead nitrate and potassium iodide? (Double displacement, also called metathesis.)
  • Why does a precipitate form immediately? (PbI₂ is insoluble in cold water, unlike KNO₃ which remains dissolved.)
  • What color is the precipitate and why? (Yellow, due to the properties of lead(II) iodide crystals.)
  • How does heating the solution change the result? (PbI₂ dissolves in hot water and recrystallizes as golden flakes upon cooling.)
  • What real-world hazards are associated with lead compounds? (They are toxic and environmentally harmful.)