Introduction to electrolytic processes
To show the different tendencies of metals to oxidise, and to introduce students to the basic redox reactions of metals.
The science behind this experiment
Electrolytic processes occur according to redox reactions. Chemical species, particularly metals, can exchange electrons. The element which acquires electrons is said to be reduced; the element which loses electrons is said to be oxidised.
Equipment used
- Copper electrodes — CHE-018
- Zinc electrodes — CHE-017
- Beaker 50 ml — CHE-002
Chemicals and reagents
- Copper sulphate 1 M — R:22-35/38-50/53 S:22-60-61
- Zinc sulphate 1 M — R:36/38-50/53 S:22-25-60-61
- Silver nitrate 0.1 M — R:34-50/53 S:26-45-60-61
Questions for students
- Write a description of what you see in the cells and on the electrodes.
- What has happened in the cells? Write down the balanced equations for the reactions.
- Compare the results. Can you arrange these elements according to their affinity for the oxidised state?
What to expect
The bright blue colour of the copper sulphate solution becomes paler; on the electrode a dark spongy deposit forms which easily drops to the bottom of the cell. After 2 or 3 hours the solution turns colourless and a bulky dark deposit is left on the bottom of the cell. On the electrode a spongy and bright metallic deposit forms that easily drops to the bottom. On close observation, the copper electrode surface is seen not to be smooth any more. The zinc electrode is oxidized while the copper ions in solution are reduced and drop as a powder on the bottom of the beaker. Cu SO4 + Zn → ZnSO4 + Cu↓ Beaker 2. Cu + 2 AgNO3 → Cu(NO3)2 + 2 Ag. In the In beaker 1, the copper is reduced and the zinc is oxidized and so zinc shows a higher affinity for the Zn2+ state than. This fact is confirmed by beaker 2 in which no reaction occurs because metals are already in their more stable oxidation states. In beaker 3, the silver is reduced whereas the copper is oxidized and so copper has a higher affinity for the Cu2+. It is worth noting that this order will be confirmed by the values of their standard potentials.
Disposal
Dispose of the solution in the waste container.
Run this experiment in your classroom
This experiment is part of ATP Volta — a self-contained mobile science lab that turns an ordinary classroom into a working STEM laboratory, with over 200 experiments in physics, chemistry, biology, robotics and engineering. Gali, the AI tutor built into ATP Connect, guides students through each step and answers their questions at the bench.
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