C6 - Electrolysis

Question 1

What does “Molten” mean?

Answer 1

A melted solid e.g. a liquid

Question 2

What does “Cation” mean?

Answer 2

A positive ion

Question 3

What does a ‘Anion’ mean?

Answer 3

A negative ion

Question 4

What does “Cathode” mean?

Answer 4

A negative electrode

Question 5

What does an “Anode” mean?

Answer 5

A postive Electrode

Question 6

What is an “Electrolyte”?

Answer 6

A molten ionic compound that is able to conduct electricty because their ions are free to move and carry charge

Question 7

What does the term “Electrolysis” mean?

Answer 7

Splitting up an ionic compound using electricity

Question 8

When an 1 is MELTED, the ions are 2 to move about within the liquid.
These liquids are able to conduct electricity and are called 3.
Passing an electric current through ELECTROLYTES causes the ions to move to the 4.
5 (positive ions) move to the 6 (negative electrode) and 7 (negative ions) move to the 8 (positive electrode).
lons are DISCHARGED at the electrodes producing elements.
This process is called 9 - the breaking down of a compound by electricity.

Answer 8

1 - IONIC COMPOUND
2 - FREE
3 - ELECTROLYTES
4 - ELECTRODES
5 - CATIONS
6 - CATHODE
7 - ANIONS
8 - ANODE
9 - ELECTROLYSIS

Question 9

What are electrodes?

Answer 9

Solid conductors made of metal or carbon

Question 10

What happens first during electrolysis?

Answer 10

Using a battery, an electric current is passed through the electrolyte so that the anions move toward the anode and cations move to the cathode

Question 11

What happens to the ions in electrolysis after the compound decomposes?

Answer 11

The positive ions move towards the cathode and gain electrons
The negative electrons move towards the anode to lose electrons

Question 12

When the positive ions in electrolysis move towards the cathode and gain electrons, what we say they become?

Answer 12

Reduced

Question 13

When the negative ions in electrolysis move towards the anode and lose electrons, what do we say they become?

Answer 13

Oxidised

Question 14

What happens when +/- ions get to the electrode?

Answer 14

They become discharged (neutral ions)

Question 15

Why cant ionic compound solids be electrolysed?

Answer 15

The ions cant move freely so cant conduct electricity

Question 16

Why is the extraction of metal from ores expensive?

Answer 16

Requires alot of energy which costs alot of money

Question 17

Why is aluminium mixed with cryolite when extracting it from bauxite ore?

Answer 17

Cryolite reduces almuniums very high melting point

Question 18

What is the ion equation happening in the negative electrode when extracting aluminium oxide from bauxite?

Answer 18

Al3 + 3e- > Al

Question 19

What is the ion equation happening at the positive electrode when extracting aluminium oxide from bauxite?

Answer 19

2O2 —–> O2 + 4e-

Question 20

What do metals react with to form metal oxides?

Answer 20

Oxygen

Question 21

What does PANIC stand for?

Answer 21

Positve Anode
Negative is Cathode

Question 22

Which side is the Anode and the Cathode in the process of electrolysis?

Answer 22

Anode - left
Cathode - right

Question 23

What is the apparatus needed for the process of electrolysis?

Answer 23

A beaker full of an electrolyte
Two electrodes made up of metal or Carbon
A wire and power supply to connect the electrodes and generate electricity

Question 24

What is the cheap way of removing oxygen from a metal oxide?

Answer 24

React the metal oxide with carbon

Question 25

What are the disadvantages of removing oxygen from a metal oxide through carbon reaction?

Answer 25

It will only work with metals less reactive than Carbon Releases CO2 as a product

Question 26

Where is Aluminium oxide found?

Answer 26

Found in a solid called bauxite

Question 27

Copper nitrate solution is blue. Suggest why the blue colour of the copper nitrate solution fades during the electrolysis.

Answer 27

The copper ions, that give the blue colour are removed at the electrode

Question 28

Give two reasons why graphite is used for the electrodes.

Answer 28

Graphite can conduct electricity Graphite is inert

Question 29

Explain the difference between the processes in electrolysis and in a chemical cell.

Answer 29

Electrolysis use electricity to produce a chemical reaction Whereas Cells use a chemical reaction to produce electricity

Question 30

Copper nitrate solution is blue. Suggest why the blue colour of the copper nitrate solution fades during the electrolysis.

Answer 30

Copper ions are discharged

Question 31

Why when you extract aluminium in electrolysis, it cannot be extracted by heating with carbon?

Answer 31

Because carbon is less reactive than aluminium

Question 32

What happens during 'discharge' stage in electrolysis?

Answer 32

When the cation/anion goes from a charged ion to a neutral atom

Question 33

What happens to the cations in electrolysis after a battery is turned on?

Answer 33

The positive cations will be attracted to the negative cathode and becomes discharged To form pure metal which will sink to the bottom, forming a layer of pure molten metal

Question 34

What happens to the anions in electrolysis after a battery is turned on?

Answer 34

The negative anions are attracted to the positive anode and becomes discharged This causes the atoms to pair up and form a gas which floats off

Question 35

What is the rule for the negative cathode when it can only displace one type of ion when theres lots?

Answer 35

The ion of the least reactive element will be discharged (PSLCCZIHC)

Question 36

What is the rule for the positive anode when it can only discharge one type of ion when theres lots?

Answer 36

If a Halide is present they will be discharged But if its not present, its always the hydroxide that gets discharged

Question 37

Explain what forms at the cathode during the electrolysis of molten aluminium oxide.

Answer 37

Positive cations (aluminium ions) are attracted to the cathode and gets displaced This results in aluminium gaining three electrons

Question 38

Write the balanced half-equation for the reaction at the cathode during the electrolysis of aluminium oxide.

Answer 38

Al3 + 3e- -------->> Al