Electrolysis

DESCRIPTION:
Electrodes made from pencil lead are attached to a 9V battery to electrolyze various solutions. Oxidation occurs and the anode and reduction occurs at the cathode. When a solution of tin (II) chloride is electrolyzed tin metal and chlorine gas are produced:
SnCl2 (aq) → Sn (s) + Cl2 (g)
When a solution of copper (II) chloride is electrolyzed copper metal and chlorine gas are produced:
CuCl2 aq) → Cu (s) + Cl2 (g)

TOPICS COVERED:
charging by conduction
chemical change
conductors
decomposition reactions
evolution of a gas
redox

MATERIALS NEEDED:
– petri dish or microwell plate
– dilute solution of SnCl2
– dilute solution of CuCl2
– 9V battery
– mechanical pencil lead
– battery clips with alligator clip leads

PROCEDURE:
1. Add a few drops of each solution to a well
2. Attach a piece of pencil lead to each alligator clip
3. Attach the battery clip to the battery
4. Place leads in solutions (rinse between solutions)

ADDITIONAL COMMENTS:
The thicker the pencil lead, the harder it is to break. Potassium iodide also works well, students can see iodine dissolving in the water.

SAFETY:
Safety goggles should be worn at all times.

REFERNCES:
Lysher, Rita. Personal Interview by Kevin Caran. 20 Jul 2012.

Handout