Question 1
Write the anode equation when the anode is copper.
Need a hint for Question 1?
Draw a simple tally of Cu²⁺ entering and leaving the solution.
Check Question 1
Cu → Cu²⁺ + 2e⁻.
STUDENT SPACE · TOPIC 4
Brine and copper electrolysis
Explain how concentration and electrode material affect observations.
The essentials
- Brine produces hydrogen and chlorine; sodium hydroxide remains in solution.
- In CuSO₄(aq) with inert electrodes, Cu²⁺ forms pink-brown copper at the cathode. Oxygen bubbles at the anode.
- With copper electrodes in CuSO₄(aq), copper forms at the cathode while the copper anode dissolves.
Key vocabulary
| English | Chinese |
|---|---|
| brine | 浓盐水 |
| deposit | 沉积物 |
| copper electrode | 铜电极 |
| electrolytic refining | 电解精炼 |
Quick practice
Try each question before opening its hint or answer. Use paper for calculations and diagrams.
Question 2
Name the three useful products of brine electrolysis.
Need a hint for Question 2?
Consider both electrode gases and the solution left behind.
Check Question 2
Hydrogen, chlorine and sodium hydroxide solution.
Question 3
Why does CuSO₄(aq) fade with inert electrodes but not with copper electrodes?
Need a hint for Question 3?
Compare whether the anode can supply replacement copper ions.
Check Question 3
Inert anodes do not replace Cu²⁺. Copper anodes dissolve and replace the Cu²⁺ removed at the cathode.
Use Lesson 4 in your worksheet for written practice. Your teacher will discuss those answers in class.
Electrolytic cell · a power supply drives change
Electrons carry charge in metal wires. Ions carry charge in the electrolyte.
Predict first: Name both products and write the half-equations. What changes if you change the anode material?
Schematic teaching model: motion and particle numbers are illustrative. Moving anions do not necessarily discharge: electrode material and competing ions determine products.
PREDICT · TRY · EXPLAIN · 3–5 MINUTES
Inside an electrolytic cell
Predict the product at each electrode. Run the cell, then explain where ions and electrons move.
Molten PbBr₂; inert electrodes. This is a model, not a home experiment.
DC power supply
− supplies electrons to cathode · + removes electrons from anode
− supplies electrons to cathode · + removes electrons from anode
− Cathode
Reduction+ Anode
Oxidation
Reduction+ Anode
Oxidation
← Pb²⁺ cationsBr⁻ anions →
Electrons travel through wires and electrodes. Ions carry charge through the electrolyte. Movement towards an electrode does not mean an ion must be discharged there.