Topic 7; Electrochemistry

Question 1

Definition of electrolysis

Answer 1

Chemical change caused by passage of electrical current through a liquid

Question 2

What is the electrolyte

Answer 2

Liquid formed after electrolysis took place
It will be an ionic compound, either molten or dissolved in water

Question 3

What are electrodes

Answer 3

When metal strips or graphite rods are placed in the liquid and are connected to a source of electricity. these are known as electrodes

Question 4

What is a negative electrode

Answer 4

Cathode

Question 5

Properties of cathodes

Answer 5

Attracts positive ions or cations
When ions reach cathode they gain electrons to become neutral atoms

Question 6

What is a positive electrode

Answer 6

Anode

Question 7

Properties of Anodes

Answer 7

Attracts negative ions or anions
When ions reach anode they lose electrons to become neutral atoms

Question 8

What is molten electrolytes

Answer 8

`When ionic solids become molten they consist of + and - ions. these ions can move. + ion will move towards cathode and gain electrons, whilst - ion anion will move towards anode and lose electrons

Question 9

Extraction of aluminium through electrolysis

Answer 9

Ore is crushed, dried and purified. Then the aluminium oxide is dissolved in molten cryolite. This lowers melting point of aluminium oxide
Electrolysis then takes place in a steel tank lined with carbon. Lining acts as cathode and carbon rods are the anodes

Question 10

What is the main ore of aluminium

Answer 10

Bauxite, contains hydrated aluminium oxide

Question 11

What happens at the cathode in the extraction of aluminium

Answer 11

Molten aluminium deposited at the cathode sinks to bottom of tank where its tapped off

Question 12

What happens at the anode in extraction of aluminium

Answer 12

O2 given off at the anodes