Electrolysis 1.58C-1.60C

Question 1

What does oxidisation mean?

Answer 1

Loss of electrons

Gain of oxygen

Question 2

What does electrolysis mean?

Answer 2

Breaking down of a substance using electricity

Question 3

What does reduction mean?

Answer 3

Gain of electrons

Loss of oxygen

Question 4

What is an electrolyte and what is its role in electrolysis?

Answer 4

Electric current is used to break down an electrolyte
Electrolytes are always an ionic compound that is molten or in solution –> ions are free to move so the ionic compound can conduct electrolysis

Question 5

What is the name of the positive electrode? What happens there?

Answer 5

Made of inert material
Anode
Negative ions (anions) move towards it and are oxidised (lose electrons)

Question 6

What is the name of the negative electrode? What happens there?

Answer 6

Made of inert material
Positive ions (cations) in the electrolyte move towards the cathode (negative electrode) and are reduced (gain electrons)

Question 7

What would a half equation look like for something getting reduced?

Answer 7

Ion + electrons –> element

Question 8

What would a half equation look like for something getting oxidised?

Answer 8

Ion –> electrons + element

Question 9

What happens during the electrolysis of molten lead (II) bromide?

Answer 9

Cathode:

• Positive (cations) Pb2+ ions are attracted to the negative cathode
• A lead ion accepts two electrons and is reduced to a lead atom
• Pb^2+ + 2e- –> Pb

Anode:

• Negative (anions) Br- ions are attracted to the positive anode
• Two bromide ions lose one electrons each and are oxidised to a bromine molecule
• 2Br- –> Br2 + 2e-

Question 10

What ions are always present in aqueous solutions of an ionic compound? Explain why

Answer 10

Hydrogen ions, H+ and Hydroxide ions OH-
Some of the water molecules undergo dissociation
H2O –> H+ + OH-

Question 11

In aqueous solutions what happens at the cathode?

Answer 11

The least reactive element will be produced

• If the metal is more relative than hydrogen then hydrogen gas will be produced
• If the metal is less reactive than hydrogen the metal is produced

Question 12

What is the half equation for the reduction of hydrogen?

Answer 12

2H+ + 2e- –> H2

Question 13

What happens at the anode?

Answer 13

• If the solution contains halide (Cl-, Br-, I-) then the halogen (Cl2, Br2, I2) will be produced
• If the solution contains any other anion then oxygen is produced

Question 14

What happens at the anode?

Answer 14

• If the solution contains halide (Cl-, Br-, I-) then the halogen (Cl2, Br2, I2) will be produced
• If the solution contains any other anion then oxygen is produced

Question 15

What is the half equation for the production of oxygen?

Answer 15

4OH- –> O2 + 2H2O + 4e-