Electrolysis

Question 1

What is electrolysis?

Answer 1

The splitting up of a compound using electricity

Question 2

What type of compound is electrolysis for?

Answer 2

Ionic compounds

Question 3

What does electrolysis split a compound into?

Answer 3

A metal and a non metal

Question 4

What is electrolysis typically for?

Answer 4

Separating a metal from a metal ore

Question 5

What is a electrolyte?

Answer 5

Either:
- An ionic compound in the molten state
- An ionic compound dissolved in water

Question 6

What is an electrode?

Answer 6

A charged piece of material used in electrolysis

Question 7

What is an anode?

Answer 7

A positively charged electrode

Question 8

What is a cathode?

Answer 8

A negatively charged electrode

Question 9

What is an aqueous solution?

Answer 9

A solution where the solvent has been dissolved in water

Question 10

How would you charge an electrode?

Answer 10

With a DC power supply

Question 11

What happens to the cations during the electrolysis of a molten compound?

Answer 11

They migrate to the cathode where they are reduced

Question 12

What happens to the anions during the electrolysis of a molten compound?

Answer 12

They migrate to the anode where they are oxidised

Question 13

What metal oxides would you use electrolysis for?

Answer 13

Those where the metal is more reactive than carbon

Question 14

What would you do to an insoluble metal oxide prior to electrolysis?

Answer 14

Melt it into molten form

Question 15

What would you do to a soluble metal oxide prior to electrolysis?

Answer 15

Dissolve it in water

Question 16

Why can’t electrolysis be done with solids?

Answer 16

Because the ions need to be able to move and cannot do that when a solid

Question 17

What happens to the cations during the electrolysis of an aqueous solution?

Answer 17

They migrate to the cathode where the least reactive (out of the metal and hydrogen) cation will be reduced

Question 18

What happens to the anions during the electrolysis of an aqueous solution?

Answer 18

They migrate to the anode where the hydroxide ions will be oxidised unless a halide is present and that will be oxidised instead

Question 19

What is a redox reaction?

Answer 19

When both oxidation and reduction happen in the same reaction

Question 20

Write a half equation for the reduction of aluminium (from aluminium oxide)

Answer 20

Al³⁺ + 3e^- —-> Al

Question 21

What is added to aluminium oxide before electrolysis? Why?

Answer 21

Cryolite, to reduce the melting point

Question 22

Write a half equation for the oxidation of oxide ions (from aluminium oxide)

Answer 22

2O^2- —-> O₂ + 4e^-

Question 23

Why would an anode need regularly replacing in electrolysis?

Answer 23

Because any oxygen produced would react with the graphite electrode to produce CO₂