Download Chemistry II Demonstration Assessment

Decomposition of Zinc Iodide
Purpose:
To observe a decomposition chemical reaction involving the formation of the constituent
elements from a compound. To use electrical energy to break the chemical bonds of a
compound.
Background Information:
Chemical reactions occur when atoms are separated, rearranged, and/or joined in a new
way. In this experiment you will decompose the chemical compound you synthesized in
the laboratory yesterday. Energy is always required to break the bonds of a compound.
You will use a 9 volt battery to supply the energy for the reaction.
The reaction is an example of electrolysis. Electrolysis is the process of using electricity
to decompose compounds in an aqueous solution. You should observe the formation of
zinc crystals at one electrode and the formation of iodine at the other.
Equipment:
Micropipet with water
9 Volt Battery
Lead Wires with Clamps
Watch Glass
Copper Wire
Chemicals:
Product from the laboratory experiment completed yesterday.
Experimental Procedure:
Wear your safety glasses throughout the experiment!
1. Carefully take your sample of zinc iodide out of the oven. The watch glass will
be hot and Mr. Gensits will demonstrate how to safely remove the sample.
Record your observations of the product.
2. Using a micropipet, add a small amount of distilled water to the sample on the
watch glass.
3. Carefully stir with a clean, dry glass stirring rod until the sample is completely
dissolved.
4. Place two small pieces of copper wire in the solution in the watch glass. The ends
of the two wires should be about 1 inch apart. Attach them to the watch glass
using two small pieces of tape to prevent them from moving.
5. Attach the other ends of the two copper wires to the terminals of a 9 volt battery
using the wire leads. For the best results do not move or disturb the wires.
6. Observe what happens at ends of the copper wires.
7. Wash the watch glass with soapy water and place it in the white plastic bin.