Electrolysis

Question 1

What is electrolysis

Answer 1

Electrolysis is defined as the conduction of electricity by an electrolyte, leading to the decomposition of the electrolyte

Question 2

Cathode is connected to the ____ terminal

Answer 2

Negative

Question 3

Anode is connected to the ____ terminal

Answer 3

Positive

Question 4

What is an electrolyte

Answer 4

An electrolyte is defined as a molten or aqueous ionic compound which is decomposed through the process of electrolysis

Question 5

Structure of electrolyte (ionic compounds)

Answer 5

A lattice of positive and negative ions, held together by strong electrostatic forces of attraction between oppositely charged ions

Question 6

Why is it important for electrolyte to be molten/aqueous and not solid

Answer 6

In solid, ions are held in fixed positions and hence unable to move and carry a current. In aqueous/molten, ions are free to move and carry a charge

Question 7

Disadvantage of platinum electrode

Answer 7

Expensive

Question 8

Disadvantage of graphite electrode

Answer 8

May react with oxygen to form CO2

Question 9

How does conduction of electricity in electrolyte differ from electrode

Answer 9

Electrolytes conduct electricity through mobile ions while electrodes conduct electricity through see of delocalised electrons

Question 10

What ions does cathode attract

Answer 10

Cations

Question 11

What ions does anode attract

Answer 11

Anions

Question 12

Which redox takes place at cathode

Answer 12

Reduction

Question 13

Which redox takes place at anode

Answer 13

Oxidation

Question 14

Why need maintain heat source in molten ionic compounds

Answer 14

Electrolytes are ionic compounds, solid at room temperature hence unable to conduct electricity. Heat source maintains the electrolytes in molten state so ions can move and carry charge

Question 15

Recap metal reactivity series

Answer 15

Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Mercury
Silver
Gold
Platinum

Question 16

Observations using inert electrodes

Answer 16

1. Cathode increases in size with coating
2. Bubbles of gas produced at anode
3. Solution decolourises

Question 17

Observations using non inert electrodes

Answer 17

1. Cathode increases in size with coating
2. Anode decreases in size

Question 18

Applications of electrolysis

Answer 18

1. Purification of copper
2. Electroplating

Question 19

Electroplating cathode

Answer 19

Metal to be electroplated

Question 20

Why cannot plate with more reactive metals

Answer 20

More reactive metals (above hydrogen), hydrogen would be selectively discharged instead

Question 21

Why can electroplating only be used for metallic objects

Answer 21

Only metals can conduct electricity at room temperature. Hence only metallic objects can be used as a cathode to allow cations to discharge upon it.