S120: Prep Notes

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

Supplies

Short List

  •   250 or 400mL beaker
  •   100mm petri dish
  •   Two 15cm insulated copper wires
  •   Funnel, filter paper, and flask
  •   Stirring rob
  •   DC power source (9V battery)
  •   Distilled water
  •   Goggles and gloves

Chemicals

  •   6g Zn dust
  •   4g I2 crystals

Prior to Lecture  (prep time ~ 10 min.)

1. Assemble the following equipment:

  •   Two 150 mL beakers, with a glass funnel with filter paper dampened
  •   100mm petri dish
  •   Two 15cm insulated copper wires w/alligator clips to attach to battery
  •   Two 8cm copper wire folded in half
  •   Stirring rod
  •   DC power source

     2. Distilled Water

  Prepare the following chemicals if vials are not filled

  •   6g zinc dust
  •   4g I2 crystals

To Conduct Demonstration

  1. Mix Zn and I2 in a dry beaker on the overhead projector (no reaction).
  2. Add 40mL of di water a bit of a time with ventilation (copious violet fumes of iodine).
  3. Stir the mixture well and filter.  Pour filtrate into the petri dish (clear, colorless solution).
  4. 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 and Disposal

Perform in a well-ventilated room to avoid breathing iodine vapors.  Copper wires can be cleaned off and reused.  Place filter with filtrate and tag for EH&S (possible waste container for filtrate in Demo room).  Pour liquid contents into Qual drum in lab M124.