Overview
The lecture covers the process and reactions involved in the electrolysis of copper chloride and sodium sulfate, focusing on the chemical changes at each electrode and the importance of balanced half-equations.
Electrolysis of Copper Chloride
- Electrolysis uses electricity to break down compounds into elements.
- Copper chloride solution is used as the electrolyte in the experiment.
- Electrodes must be submerged in the solution, but not touching crocodile clips.
- The power pack is set to about 4 volts; red wire to anode (positive), black to cathode (negative).
- At the anode (positive), chloride ions (Cl⁻) lose electrons (oxidation) to form chlorine gas (Cl₂).
- Chlorine gas is detected by holding blue litmus paper above the anode; if it bleaches, chlorine is present.
- At the cathode (negative), copper ions (Cu²⁺) gain electrons (reduction) to form copper metal.
- Half-equations show what happens at each electrode and must balance both elements and charges.
Electrolysis of Sodium Sulfate
- Sodium sulfate solution is used as the electrolyte for the second experiment.
- Sodium is more reactive than hydrogen, so hydrogen gas forms at the cathode.
- Bubbles are seen at both electrodes during electrolysis.
- At the cathode, hydrogen ions (H⁺) are reduced to hydrogen gas (H₂).
- At the anode, oxygen forms instead of sulfate ions; hydroxide ions (OH⁻) are oxidized to produce oxygen gas (O₂).
- The oxidation of hydroxide ions also produces water and releases electrons.
- Half-equations must balance both the atoms and the electrical charges.
Key Terms & Definitions
- Electrolysis — the process of using electricity to break down compounds into elements.
- Electrolyte — a substance that conducts electricity by the movement of ions.
- Anode — the positive electrode where oxidation occurs.
- Cathode — the negative electrode where reduction occurs.
- Oxidation — loss of electrons during a chemical reaction.
- Reduction — gain of electrons during a chemical reaction.
- Half-equation — an equation showing the changes at one electrode, including electrons.
Action Items / Next Steps
- Practice writing balanced half-equations for both electrodes.
- Review the test for chlorine using litmus paper.
- Ensure understanding of the role of ion reactivity in determining products during electrolysis.