Electrolysis

Question 1

What is cryolite

Answer 1

It is added to lower the melting point of the Aluminium oxide and save energy

Question 2

Which is the positive electrode

Answer 2

Anode

Question 3

Which is negative electrode

Answer 3

Cathode

Question 4

What properties of aluminium make it suitable for it to be used as overhead power cables

Answer 4

They are good electrical conductors

Question 5

Positive ions go to…

Answer 5

• the Cathode which is the negative electrode
• because opposite charges attract

Question 6

Negative ions go to…

Answer 6

• Anode which is the positive electrode
• because opposite charges attract

Question 7

Why can’t aluminium be extracted from its ore by reduction with carbon

Answer 7

Aluminium is more reactive than the carbon

Question 8

How does the use of cryolite during electrolysis help reduce energy costs

Answer 8

Cryolite lowers the melting point of the Aluminium oxide (purified bauxite)

Question 9

What’s the word equation for the reaction that results in the anode wearing away

Answer 9

Carbon + oxygen —> Carbon Dioxide

Question 10

What’s the symbol equation for the breakdown of aluminium oxide during electrolysis

Answer 10

Question 11

Which substance is produced at the anode during the breakdown of aluminium oxide

Answer 11

Oxygen

Question 12

Which substance is produced at the cathode during the breakdown of aluminium oxide

Answer 12

Aluminium

Question 13

Why is the extraction of aluminium an expensive process

Answer 13

A lot of heat is required to melt the bauxite and big electrical current

Question 14

Why do oxide ions collect at the anode

Answer 14

• Oxide ions have a negative charge and attract to the anodes that have a positive charge
• This is because opposite charges attract

Question 15

Why must the anode be replaced regularly

Answer 15

• oxygen react with carbon anode
• This makes CO2 gas which diffuses away
• the reaction slowly wears away the anode
• so it needs to be replaced

Question 16

What can be done to conserve natural resources of aluminium

Answer 16

Recycling

Question 17

Aluminium is used for..

Answer 17

• planes
• car body parts
• bikes
• cans

Question 18

The main ore of aluminium is ….

Answer 18

Bauxite

Question 19

Electrolysis is

Answer 19

• Using electrical energy to split up an ionic compound
• (note that ionic compound has to be molten or dissolved in water so ions can move)

Question 20

What is the electrolite

Answer 20

Anything that’s having electrolysis happening to it

Question 21

What happens at negative electrode

Answer 21

• it gets electrons pumped out
• these then attract the positive metal ions
• it doesn’t really want it’s electrons back so it takes a lot of energy

Question 22

What’s happening at the positive electrode

Answer 22

• it is positively charged
• attracts the negatively charged non-metal ions
• electrons return to the battery
• gases are formed (in pairs)

Question 23

Metals collect at the…

Answer 23

Cathode

Question 24

Write a half equation for Mg

Answer 24

Mg^2+ + 2e^- —> Mg

Question 25

Does oxidation or reduction take place at the positive electrode

Answer 25

- oxidation - because it is losing an electron and oxidation is loss

Question 26

How do we know what is formed at the negative electrode

Answer 26

- Are they less reactive than hydrogen? (Must say this to get mark) - They are Au, Ag, Cu, Pt. (Think what can make Jewellery)

Question 27

How do we know what forms at the positive electrode

Answer 27

1st: halide ions (group 7) 2nd: hydroxide Never = sulfate, nitrate etc… (they remain in solution) <— remember to say this

Question 28

What is formed in Copper II chloride solution

Answer 28

Negative electrode: attracts Cu2+, H+ - Cu because it is less reactive than hydrogen - we can see copper metal and blue colour of solution fade Positive electrode: attracts Cl-, OH- - Cl because it is a halide ion - we can see bubbles and it bleaches damp indicator paper

Question 29

What is formed in Copper II sulfate solution

Answer 29

the negative electrode: attracts Cu2+, H+ - Cu formed because it is less reactive than hydrogen - we can see copper metal and blue colour of solution fades The positive electrode: attracts So4^2-, and OH- - we get equation4OH^- - 4e^- —> O2 + 2H20 - you see bubbles, you can test for it by relighting a glowing splint

Question 30

What is formed in sodium chloride solution

Answer 30

Negative electrode: attracts Na+, H+ - H+ is formed because it is less reactive - you see bubbles and test with squeaky pop Positive electrode: attracts Cl-, OH- - forms Cl2 - you can see bubbles and it bleaches damp indicator paper

Question 31

What is formed in sodium sulfate solution

Answer 31

At negative electrode: attracts Na+, H+ - H is formed because it is less reactive - you see bubbles and can test with squeaky pop At positive electrode: attracts So4^2-, OH- - we get equation4OH^- - 4e^- —> O2 + 2H20 - you see bubbles, you can test for it by relighting a glowing splint