Electrolysis

Question 1

What type of liquids can be electrolysed?

Answer 1

Aqueous or molten solutions

Question 2

Write a method for the electrolysis for copper chloride solution.

Answer 2

1. Pour approximately 50 cm3 copper (II) chloride solution into the beaker.
2. Add the petri dish lid and insert the carbon rods through the holes. The rods must not touch each other.
3. Attach crocodile leads to the rods. Connect the rods to the dc (red and black) terminals of a low voltage power supply
4. Select 4 V on the power supply and switch on.
5. Look at both electrodes and record your initial observations in a table.
6. Use forceps to hold a piece of blue litmus paper in the solution next to the anode.

Question 3

What happens at the anode of the electrolysis of copper chloride solution?

Answer 3

Chlorine ions are oxidised and lose electrons to form chlorine gas.
(2Cl-)-(2e-)—>Cl2

Question 4

What happens at the cathode during the electrolysis of copper chloride solution?

Answer 4

Copper ions are reduced meaning they gain electrons to form solid copper.
(Cu2+)+(2e-)—>Cu

Question 5

What does electrolysis mean?

Answer 5

Chemical decomposition produced
by passing an electric current through a liquid or solution containing ions.

Question 6

Why must the rods not touch?

Answer 6

If the electrodes touch, all the current will flow directly from one electrode to the other electrode, without passing through the liquid

Question 7

Why must the cores be replaced over time?

Answer 7

Oxygen forms at the positive electrodes. This oxygen reacts with the carbon of the positive electrode, forming carbon dioxide, and they gradually burn away. As a result, the positive electrodes have to be replaced frequently. This adds to the cost of the process.