Electrolysis

Question 1

What is electrolysis?

Answer 1

In the process of electrolysis, an electric current is passed through an electrolyte. An electrolyte is a liquid or solution that contains ions and so can conduct electricity. This causes the ions to move to the electrodes when they form pure elements.

Question 2

Electrolysis of molten compounds

Answer 2

Molten or dissolved so ions are free to move
Positive metal ions attracted to the cathode to form pure metal
Non-metal ions which are negative are attracted to the anode where they will lose electrons and become a pure non-metal

Question 3

What are the half equations for electrolysis of molten compounds?

Answer 3

2Na+ + 2e- –> 2Na
2Cl- –> Cl2 + 2e-

Question 4

Why is electrolysis done on aqueous solutions?

Answer 4

Requires less energy to dissolve ionic o pounds in water than to melt them
Pure elements not always produced

Question 5

What happens at the anode in electrolysis of aqueous solutions?

Answer 5

If non-metal contains oxygen or a halogen, oxygen gas is produced
E.g 4OH- –> O2 + 2H2O + 4e-
or
2Cl- –> Cl2 + 2e-

Question 6

What happens at the cathode spring electrolysis of aqueous solutions?

Answer 6

If the emails is more reactive than hydrogen, hydrogen is formed
E.g copper, gold, silver would be formed
2H+ + 2e- –> H2

Question 7

Why is aluminium oxide different?

Answer 7

Aluminium oxide has a really high melting point

Question 8

How does electrolysis of alumnus oxide work?

Answer 8

Aluminium oxide mixed with cryolite, lowering the melting point
Mixture then heated until molten
Undergoes electrolysis

Question 9

In electrolysis of aluminium what is the anode made of?

Answer 9

Graphite

Question 10

What are the equations for aluminium oxide?

Answer 10

2Al2O3 –> 4Al + 3O2
Cathode Al3+ + 3e- –> Al
Anode 2O2- –> O2 + 4e-