Electrolysis

Question 1

During electrolysis, what is discharged at Cathode (Negative electrode)?

Answer 1

Hydrogen is produced unless the metal is less reactive than hydrogen. More reactive ions want to stay
within the solution.

Question 2

During electrolysis, what is discharged at the Anode (Positive electrode)?

Answer 2

If OH- and halide ions (Cl-, Br-, I-) are present, then the halide ions will be produced.

If no halide is present, oxygen is formed. This happens because in the aqueous solution water molecules break down producing H+ ions and OH- ions that are discharged

Question 3

Why is electrolysis used?

Answer 3

Metals that are more reactive than carbon (e.g aluminium), so too reactive to be extracted by reduction with carbon, are extracted by electrolysis of molten compounds.

Question 4

How is Aluminium manafactured using electrolysis?

Answer 4

Electrolysis of a molten mixture of aluminium oxide and cryolite using carbon as the positive electrode (anode).
Aluminium oxide has a very high melting point, so it is expensive to melt it. Mixed with cryolite to reduce melting point.
Carbon Anodes need to be continually replaced because oxygen is formed, which reacts with the carbon forming carbon dioxide, and they gradually burn away.

Question 5

Explain the methods used to electrolyse Copper (III) Chloride solution

Include terms such as: Beaker, Measuring cylinder, Lid, Electrodes, Crocodile leads, Power supply, Damp blue litmus paper

Answer 5

1. Pour 50cm^3 of copper chloride solution into beaker using measuring cylinder
2. Place lid with holes over beaker and insert electrode through holes making sure they do no touch.
3. Attach crocodile leads to electrode and connect rods to DC terminals of low voltage power supply.
4. Select 4v on power supply and switch on.
5. Hold damp blue litmus paper near Anode using forceps or stick onto inside of beaker.
6. Turn off power supply after a few minutes and observe Cathode.
7. Record observations

Question 6

During electrolysis of copper III chloride solution what is produced at the anode and cathode?

Answer 6

Anode - Chlorine gas produced (halide - litmus paper will be bleached white by chlorine gas)
Cathode - Copper layer ( Copper less reactive than hydrogen )

Question 7

What would be the results of the electrolysis of sodium chloride using the same exact methods?

Answer 7

Anode - Chlorine gas
Cathode - Hydrogen ( sodium more reactive than hydrogen so not discharged) - squeaky pop test