Electrolysis of Aqueous Solutions Lecture Notes
Introduction
- Objective: Describe how to investigate the electrolysis of aqueous solutions
- Focus on two solutions: Copper(II) chloride and sodium chloride
- Recommended Pre-requisite: Watch videos on electrolysis of aqueous solutions
Practical Experiment Overview
- Goal: Carry out electrolysis on two solutions and explain the different products formed
Experiment 1: Electrolysis of Copper(II) Chloride
Materials and Setup
- 50 cm³ of copper(II) chloride solution in a beaker
- Plastic petri dish with two holes
- Carbon graphite rods as electrodes (inert and unreactive)
- Crocodile leads for connection
- Low-voltage power supply set to 4 volts
Procedure
- Pour 50 cm³ of copper(II) chloride solution into a beaker.
- Place petri dish over the beaker.
- Insert carbon graphite rods into the holes in the dish (ensure electrodes do not touch).
- Attach crocodile leads to rods and connect to power supply.
- Turn on power supply at 4 volts.
Observations
- Cathode (Negative Electrode):
- Coated with copper (Copper is less reactive than hydrogen, so it is discharged)
- Anode (Positive Electrode):
- Bubbles observed; smell of chlorine detected
- Chlorine gas confirmed using damp blue litmus paper (it becomes bleached)
Summary
- Products: Copper at the cathode, chlorine gas at the anode
Experiment 2: Electrolysis of Sodium Chloride
Materials and Setup
- 50 cm³ of sodium chloride solution in a beaker
- Same setup as copper(II) chloride experiment
Procedure
- Pour 50 cm³ of sodium chloride solution into a beaker.
- Use same electrode setup as previous experiment.
- Turn on power supply.
Observations
- Anode (Positive Electrode):
- Bubbles observed; gas bleaches damp blue litmus paper (Chlorine gas)
- Cathode (Negative Electrode):
- Bubbles observed; hydrogen gas is discharged
- Hydrogen is more reactive than sodium, hence discharged at cathode
Confirmation Test for Hydrogen
- Collect gas and test with a lit splint
- Hydrogen gas produces a characteristic 'squeaky pop'
Conclusion
- Copper(II) Chloride: Produces copper and chlorine gas
- Sodium Chloride: Produces chlorine gas and hydrogen gas
Additional Resources
- Revision workbook available for practice questions
These notes should help in understanding the key points of the electrolysis of aqueous solutions, explaining the process, setup, and results of the required practical experiments.