Practical activity - investigating electrolysis using inert electrodes
It is important in this practical activity to use appropriate apparatus safely to carry out The decomposition (breakdown) of a compound using an electric current., and to use appropriate techniques to identify gases.
This outlines one way to carry out the practical. Eye protection must be worn.
Aim
To investigate the electrolysis of copper(II) sulfate solution, and of sodium chloride solution, using Unreactive. A conductor used to establish electrical contact with a circuit. The electrode attached to the negative terminal of a battery is called a negative electrode, or cathode. The electrode attached to the positive terminal of a battery is the positive electrode, or anode..
Method
Copper(II) sulfate solution
1. Pour some copper(II) sulfate solution into a beaker.
2. Place two graphite rods into the copper sulfate solution. Attach one electrode to the negative terminal of a dc supply and the other electrode to the positive terminal.
3. Use a dropping A piece of apparatus used to measure accurate and repeatable volumes of liquid. Also called a volumetric pipette. to completely fill two small test tubes with copper(II) sulfate solution. Quickly turn each test tube upside down, keeping its mouth under the surface of the copper(II) sulfate solution. Position a test tube over each electrode. Rinse any copper sulfate solution off your hands.
4. Make sure the electrodes do not touch each other, then turn on the power supply. If no bubbles are observed, check all the electrical connections and the dc supply.
5. Continue to collect any gases in the test tubes, then turn off the dc supply.
6. Oxygen should be produced at the positive electrode. Confirm this by holding a glowing splint just inside the open mouth of its test tube. Record whether the splint relights.
Sodium chloride solution
7. Repeat steps 1 to 5, but using sodium chloride solution instead of copper(II) sulfate solution.
8. Hydrogen should be produced at the negative electrode. Confirm this by holding a lighted splint near the open mouth of its test tube. Record whether a squeaky pop is obtained.
9. Chlorine should be produced at the positive electrode. Confirm this by holding a piece of damp blue A type of indicator that can be red or blue. Red litmus turns blue in alkalis, while blue litmus turns red in acids. just inside the open mouth of its test tube. Record whether this turns red then white.
Results
Record what happens at each electrode, including the results of the gas tests.
Analysis
Identify the gases produced during the two experiments.
Question
Name the brown substance produced at the negative electrode during the electrolysis of copper(II) sulfate.
The brown substance was copper.
Evaluation
Question
Suggest an explanation for why it may be difficult to obtain positive results in the tests for gases.
The volumes of gas collected are very small, making it difficult to carry out the tests.
Hazards, risks and precautions
Evaluate the hazards and the precautions needed to reduce the risk of harm. For example:
| Hazard | Possible harm | Possible precaution |
| Copper(II) sulfate solution | Harmful through skin contact and can cause serious eye irritation | Wear gloves, wear eye protection and rinse hands after contact |
| Chlorine gas | Toxic if inhaled | Make sure the lab is well ventilated and avoid inhaling the gas and do not run the experiment longer than is necessary to collect a sample |
| dc electricity supply | Electric shock | Make sure electrodes do not touch and make sure that electricity supply is switched off before handling apparatus |
| Hazard | Copper(II) sulfate solution |
|---|---|
| Possible harm | Harmful through skin contact and can cause serious eye irritation |
| Possible precaution | Wear gloves, wear eye protection and rinse hands after contact |
| Hazard | Chlorine gas |
|---|---|
| Possible harm | Toxic if inhaled |
| Possible precaution | Make sure the lab is well ventilated and avoid inhaling the gas and do not run the experiment longer than is necessary to collect a sample |
| Hazard | dc electricity supply |
|---|---|
| Possible harm | Electric shock |
| Possible precaution | Make sure electrodes do not touch and make sure that electricity supply is switched off before handling apparatus |
Fran Scott demonstrates how to perform practical experiments with electrolysis