Introduction
The reaction of zinc metal with iodine shows direct combination, decomposition, recrystallization of sublimed I2, and electrolysis.
Zn(s) + I2(s) → No Reaction
Zn(s) + I2(s) H2O→ ZnI2(aq)
Zn2+ + 2I- → Zn + I2
To Conduct Demonstration
- Mix Zn and I2 in a dry beaker on the overhead projector (no reaction).
- Add 40mL of di water a bit of a time with ventilation (copious violet fumes of iodine).
- Stir the mixture well and filter. Pour filtrate into the petri dish (clear, colorless solution).
- Connect copper wires to the DC source. Place the wires in the petri dish so that they are well-separated and immersed in solution. Turn on the power supply. (Amber coloration at anode, zinc accumulation on cathode).
Demo Time: ~4 minutes
Safety
Perform in a well-ventilated room to avoid breathing iodine vapors.
Reference
Tested Demonstration, J.Chem.Ed., 1965
Acknowledgment
John Ohlsson, Spring 1987
Reformatted by Lora Ruffin and Michael Polk, Summer 2009