Electrolysis

Question 0

What is electrolysis used for and why is it so expensive?

Answer 0

• used for metals HIGH in the reactivity series

* more expensive because it requires more energy

Question 1

Electrolysis is the extraction of…?

Answer 1

Aluminium

Question 2

At the cathode what type ions are attracted in electrolysis?

Answer 2

Cations

Question 3

At the anode in electrolysis what type if ions are attracted?

Answer 3

Anions

Question 4

Aluminium is unreactive, state 3 of it’s uses… (They don’t rust!)

Answer 4

Car bodies
Window frames
Structures

Question 5

Why does aluminium seem unreactive?

Answer 5

OXIDE LAYER

Question 6

What does the oxide layer on aluminium prevent?

Answer 6

Oxide layer prevents chemicals from colliding with aluminium. If the oxide later is removed, aluminium will react quite vigorously.

Question 7

Why can’t you use carbon to extract aluminium?

Answer 7

Carbon is lower in the reactivity series.

Question 8

Why do the anodes need continuously replacing? (4)

Answer 8

• oxygen forms at the carbon anode
• carbon reacts with the oxygen to form carbon dioxide gas
• carbon electrode therefore gradually disappears

Question 9

What temperature does electrolysis occur at?

Answer 9

955’c

Question 10

Why do the carbon electrodes need to be replaced?

Answer 10

Burns away

Question 11

Name a metal that can be added to aluminium to make an alloy…

Answer 11

Magnesium

Question 12

What is the overall equation for ELECTROLYSIS OF ALUMINIUM OXIDE?

Answer 12

2Al2O3 -> 4Al + 3O2

Question 13

Electrode equation at the cathode..

Answer 13

Al3+ + 3e -> Al

Question 14

Electrode equation at the anode..

Answer 14

2O2- -> O2 + 4e-

Question 15

What is cryolite?

Answer 15

A mixture of cryolite and aluminium oxide has a lower melting point than pure aluminium.

Question 16

Give 4 properties of aluminium…

Answer 16

• low density
• strong
• ductile
• malleable

Question 17

How does electrolytic reduction work in the extraction of aluminium?

Answer 17

Electricity is used to reduce aluminium oxide.

Question 18

What kind if metals is electrolysis used for?

Answer 18

Metals high up in the reactivity series

Question 19

When molten lead bromide undergoes electrolysis what forms at the cathode?

Answer 19

Grey solid coating on the electrode

Question 20

What is the electrode equation at the cathode? (Lead bromide)

Answer 20

Pb2+ + 2e- = Pb (Pb gains electrons; REDUCTION)

Question 21

What is the electrode equation at the anode (lead bromide)

Answer 21

2Br- = Br2 + 2e- (lose electrons; oxidation)

Question 22

When molten lead bromide undergoes electrolysis what forms at the anode?

Answer 22

Bubbling and orange gas given off.