S135: Chemical Rxns – Precipitation – Pb(NO3)2 + KI → PbI2(s)

Introduction  

A 100mm petri dish containing water is placed on an overhead projector.  When solid Pb(NO3)2 is place on one side and solid KI on the other, PbI2 precipitates in the center.

Pb(NO3)2(aq) + 2KI(aq) → PbI2(s) + 2KNO3(aq)

To Conduct Demonstration

  1. Place petri dish on stage of overhead projector.
  2. Pour water into dish to a depth of ¼” to 3/8”
  3. Scoop a small amount of Pb(NO3)2 into the water at one side of the dish.
  4. Scoop a small amount of KI into the water directly opposite the Pb(NO3)2
  5. A precipitate of PbI2 will form near the center of the dish.

Demo Time: ~1 minute

Safety 

Pb(NO3)2 is toxic.  Care should be taken to avoid breathing KI dust.  

Acknowledgment

Margaret Asirvatham & Lyn Pierce, Summer 1987
Lora Ruffin and Michael Polk, Summer 2009