C6 - Electrolysis

Question 1

What is Electrolysis? What does it mean?

Answer 1

1) Electrolysis is the process of using electricity to extract elements from a compound.
2) Electrolysis means splitting up with electricity.

Question 2

What happens during electrolysis?

Answer 2

1) An electrical current is passed through an electrolyte.

2) These ions then move towards electrodes which is where they react and where the compound decomposes.

Question 3

What is the name of the positive and negative electrode and which electrodes are the metals and non-metals formed?

Answer 3

1) The positive electrode is known as the anode. Non-metals are formed here.
2) The negative electrode is known as the cathode. Metals are formed here

Question 4

Explain what an electrolyte is.

Answer 4

1) An electrolyte is a liquid or solution that contains ions so that it can conduct electricity.

Question 5

Explain why an ionic substance can be electrolysed but why a solid ionic substance cannot.

Answer 5

1) An ionic substance can be electrolysed by melting/dissolving it and then passing a direct current through it.
2) A solid ionic substance cannot be electrolysed because they do not conduct electricity and the ions cannot move.

Question 6

When is the metal not produced at the cathode in electrolysis?

Answer 6

1) Metal is not produced at the cathode when the metal is more reactive than the hydrogen.

Question 7

In the electrolysis of a metal halide solution, what is produced at the anode?

Answer 7

1) A halogen is produced.

Question 8

In the electrolysis of a metal sulfate solution, what is produced at the anode?

Answer 8

1) Oxygen is produced at the anode.

Question 9

What is the half equation for the ionisation of water?

Answer 9

H20 (l) –> H+ (aq) + OH-(aq)

Question 10

What other way can metals be extracted using electrolysis?

Answer 10

1) Metals can be extracted from their ORES using electrolysis.

Question 11

What ore is Aluminium extracted from? What does this ore contain?

Answer 11

1) Aluminium is extracted from the ore “bauxite”.

2) Bauxite contains Aluminium Oxide (Al2O3)

Question 12

Due to Aluminium having a very high melting point, what is it mixed with to lower the melting point?

Answer 12

1) Aluminium is mixed with CRYOLITE to lower the melting point.

Question 13

Which electrode is the Al3+ ions attracted to and why?

Answer 13

1) The Al3+ ions are attracted to the cathode (the negative electrode)
2) This is because opposites attract.

Question 14

Which electrodes are the O2- ions attracted to and why?

Answer 14

1) The O2- ions are attracted to anode (positive electrode).

2) This is because opposites attract.

Question 15

What is eventually produced at the anode and at the cathode after the electrolysis of Aluminium?

Answer 15

1) At the anode, oxygen is produced.

2) At the cathode, Aluminium is produced

Question 16

Write the balanced equation at each electrode after the electrolysis of Aluminium Oxide. What type of reactions are they?

Answer 16

1) Anode (Oxidation) : 2O2 (-) —-> O2 + 4e(-)

2) Cathode (Reduction) : Al (3+) + 3e(-) —-> Al

Question 17

What are the electrodes made out of in the electrolysis of aluminium? Why?

Answer 17

1) The anode is made out of graphite.

2) It is made out of graphite because it reacts with oxygen to form carbon dioxide. It needs to be replaced frequently.

Question 18

Can Ionic compounds be electrolysed when dissolved in water? If so, what are the benefits?

Answer 18

1) Solid ionic compounds can undergo electrolysis when dissolved in water.
2) It requires less energy to dissolve ionic compounds in water than it does to melt them

Question 19

Which electrode is the OH- ion attracted to after the electrolysis of Aqueous solutions and which electrode is the H+ ion attracted to?

Answer 19

1) The OH- ions are attracted to the anode after the electrolysis of an aqueous solution.
2) The H+ ion is attracted to the cathode after the electrolysis of an aqueous solution.

Question 20

Why is quarrying/mining copper bad for the environment? Give TWO reasons

Answer 20

1) Releases pollution

2) Loss of habitat for animals and plants.

Question 21

Give TWO uses of purified copper.

Answer 21

1) Used in electrical wires

2) Used in plumbing systems since it doesn’t react with water

Question 22

Give 2 other methods of extracting copper from their ores.

Answer 22

1) Phytomining

2) Bioleaching

Question 23

What is Phytomining? What is the process of it?

Answer 23

1) Phytomining is the extraction of copper using PLANTS.
2) Copper ions are absorbed by plants from the soil, these copper ions then become concentrated.
3) The plants are burnt and then copper ions combine with oxygen.
4) The copper compounds are dissolved and electrolysis is performed.

Question 24

What is Bioleaching?

What is the process given to it?

Answer 24

1) Bioleaching involves using bacteria to extract copper.
2) When bacteria breaks down materials, they will absorb copper.
3) Then the bacteria releases the compounds, these are called leachates.
4) Solutions are collected and then electrolysis is performed.

Question 25

What is oxidation?

Answer 25

1) Oxidation is a reaction where electrons are lost.

Question 26

What is reduction?

Answer 26

1) Reduction is a reaction where electrons are gaines

Question 27

Why do the graphite electrodes in the electrolysis of aluminium oxide need to be removed?

Answer 27

1) The oxygen reacts with Carbon which forms Carbon Dioxide.

2) The graphite burns and therefore needs to be replaced regularly.

Question 28

What is discharged at the Anode and Cathode after the electrolysis of a chloride solution?

Answer 28

1) At the cathode, hydrogen is discharged.

2) At the anode, Chlorine is discharged.

Question 29

What are the half equations at the Anode and Cathode after the electrolysis of Aqueous Sodium Chloride?

Answer 29

1) Cathode : 2H(+) + 2e(-) —-> H2

2) Anode : 2Cl (-) —-> Cl2 + 2e(-)

Question 30

When is electrolysis used to extract metals?

Give 2 reasons.

Answer 30

1) Electrolysis is used to extract metals when the metals are to reactive to be extracted by reduction with carbon.
2) Electrolysis is used to extract metals when the metal reacts with Carbon.

Question 31

In the Electrolysis of Aqueous Solutions, what are the ions dependant on?

Answer 31

1) The ions are dependent on their charge to decide which electrode they attract to.

Question 32

How can you work out which charge ions have to decide which electrode they attract to?

Answer 32

1) Use the Periodic Table. Metals will have a positive charge and non metals have a negative charge.

Question 33

What products do you bet when Brine is electrolysed?

Answer 33

1) Chlorine Gas (at the anode)
2) Hydrogen has (at the cathode)
3) Sodium Hydroxide is also formed.

Question 34

What are the half equations for the Electrolysis of Copper Sulphate (Aqueous Solution).

Answer 34

1) Anode (Oxidation) : 4OH (-) —-> 02 + 2H20 + 4e(-)

2) Cathode (Reduction) : Cu (2+) + 2e(-) —-> Cu

Question 35

List the reactivity series.

Answer 35

1) Potassium
2) Sodium
3) Lithium
4) Calcium
5) Magnesium
6) Carbon
7) Zinc
8) Iron
9) Hydrogen
10) Copper

Question 36

Why does metal conduct electricity?

Answer 36

1) Metal conducts electricity because of the delocalised electrons which are able to carry the electric charge.