Passing electricity through compounds: electrolysis
3 marks · EasyDescribe an experiment to investigate the electrolysis of aqueous copper(II) sulfate solution using copper electrodes.
Name the apparatus needed for this investigation.
State what you would observe at the electrodes during electrolysis.
Explain briefly why a change occurs at the anode.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Beaker, copper electrodes, copper(II) sulfate solution, power supply (and wires)
(b) Copper is deposited at the cathode; the anode slowly dissolves/disappears.
(c) At the anode, copper atoms lose electrons forming Cu^{2+} ions that go into solution; the anode mass decreases.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Names all essential apparatus (beaker, copper electrodes, copper(II) sulfate solution, power supply/wires).
B1 (b) · 1 mark · States correct observation: copper forms at cathode, anode dissolves/diminishes.
B1 (c) · 1 mark · Explains the change: copper at anode forms Cu^{2+} ions by losing electrons and goes into solution.
Worked solution
a) Apparatus: beaker, copper electrodes, copper(II) sulfate solution, power supply, connecting wires.
b) Observation: copper coats the cathode; the anode gets thinner or dissolves.
c) At the anode, copper metal loses electrons to become Cu^{2+} ions that enter the solution, causing the anode to decrease in mass.