Electrolysis

Question 1

Explain how to investigate what happens when copper/sodium chloride is electrolysed using inert electrodes

Answer 1

1. Pour 50cm³ of copper chloride/sodium solution to a beaker
2. Add the lid and insert electrodes through the holes making sure they don’t touch
3. Attach crocodile leads to the electrodes and connect to DC terminals of a low voltage power supply
4. Set power supply to 4V and switch on
5. Hold the litmus paper near the anode
6. After a few minutes turn off power supply and observe the negative electrode
7. Record observations

Question 2

What are the observations and element formed at the anode when
Copper chloride is electrolysed?

Answer 2

Bubbles of gas, bleaches blue litmus white

Chlorine gas formed

Question 3

What are the observations and element formed at the anode when
Sodium chloride is electrolysed?

Answer 3

Bubbles of gas, bleaches blue litmus white

Chlorine gas formed

Question 4

What are the observations and element formed at the cathode when
Copper chloride is electrolysed?

Answer 4

Brown/red solid coating on rod

Copper solid formed

Question 5

What are the observations and element formed at the cathode when
Sodium chloride is electrolysed?

Answer 5

Bubbles of gas

Hydrogen gas produced

Question 6

What are the safety precautions to be taken when carrying out electrolysis?

Answer 6

Safety goggles must be worn
Glassware should be handled carefully
Room should be well ventilated because large quantities of chlorine gas is toxic

Question 7

State the rule for what is produced in the cathode

Answer 7

Hydrogen is produced if the metal is more reactive than hydrogen

Question 8

State the rule for what is produced at the anode

Answer 8

Oxygen is produced unless there is a halide ion present, then the halogen will be produced

Question 9

What is the equation for oxygen being produced in the anode

Answer 9

4OH- → O2 + 2H20 + 4e-

Question 10

What is the equation for hydrogen being produced in the cathode

Answer 10

2H+ + 2e- → H2