Electrolysis

Question 1

What does electrolysis mean?

Answer 1

Splitting up with electricity

Question 2

What is the process of electrolysis?

Answer 2

If you pass an electric current through an ionic substance that is molten or in a solution, it breaks down into the elements it is made of.

Question 3

What is the electrolyte?

Answer 3

A liquid that is required during electrolysis that conducts electricity.

Question 4

What do the electrolytes contain?

Answer 4

Free ions that conduct electricity and allow the whole thing to work.

Question 5

What are the electrolytes usually?

Answer 5

Molten or dissolved in a solution.

Question 6

What is required for an electrical circuit to work?

Answer 6

There has to be a flow of electron. Electrons are taken away from ions at the positive electrode and given to other ions at the negative electrode.

Question 7

What happens as ions lose or gain electrons?

Answer 7

They become atoms or molecules and are released.

Question 8

What is oxidation?

Answer 8

The loss of electrons?

Question 9

What is reduction?

Answer 9

The gain of electrons.

Question 10

What is a redox reaction?

Answer 10

An oxidation-reduction (both of them) reaction.

Question 11

What is the anode?

Answer 11

The positive electrode.

Question 12

What is the cathode?

Answer 12

The negative electrode.

Question 13

What are positive ions called?

Answer 13

Cations 🐈

Question 14

What are negative ions called?

Answer 14

Anions

Question 15

Where do the cations go?

Answer 15

To the cathode.

Question 16

Where do the anions go?

Answer 16

To the anode.

Question 17

Where does reduction happen?

Answer 17

At the cathode.

Question 18

Where does oxidation happen?

Answer 18

At the anode.

Question 19

Properties of a molten solid?

Answer 19

Only the ions of the solid are present.

Question 20

Properties of an ionic solution?

Answer 20

A mix of ions of the solid and ions of water are present.

Relies on the ionic compound being solid in water.

Question 21

What are the advantages of a molten solid?

Answer 21

Can only get pure products.

Question 22

What are the disadvantages of a molten solid?

Answer 22

It requires heating which is expensive, difficult and hazardous.

Question 23

What are the advantages of an ionic solution?

Answer 23

Safe and easy to do in a lab.

Question 24

What are the disadvantages of an ionic solution?

Answer 24

It is a mix of ions from water which means you get a greater mix of products.
If an ionic compound isn’t solid you can’t do this.

Question 25

Why does electrolysis not work with solid ionic compounds?

Answer 25

The ions are held together in a lattice structure, they are fixed in position, meaning that the separate elements cannot go to the anode or the cathode.

Question 26

What is vital to perform electrolysis?

Answer 26

In a solid ionic compound you would need to turn it into a molten compound. You would melt the compound by heating it or you would dissolve it in a solution.

Question 27

What is the electrolysis of aluminium used for?

Answer 27

To remove aluminium from its ore.

Question 28

What is aluminium’s main ore?

Answer 28

Bauxite.

Question 29

Describe aluminium.

Answer 29

A very abundant metal but is found naturally in compounds.

Question 30

What is aluminium left as after mining and purifying?

Answer 30

A white powder: pure Al2o3- aluminium oxide.

Question 31

What is cryolite used for in the electrolysis of aluminium?

Answer 31

Aluminium oxide has a very high melting point of over 2000 degrees, so melting would be very expensive. Cryolite lowers the melting point and therefore, the cost.

Question 32

How is cryolite made a part of aluminium oxide?

Answer 32

The aluminium oxide is dissolved in the molten cryolite- which is a less common ore of aluminium.

Question 33

What does the molten cryolite bring the melting point of Al2o3 to?

Answer 33

Around 900 degrees.

Question 34

What are he electrodes in the electrolysis of aluminium oxide made from?

Answer 34

Carbon.

Question 35

In the electrolysis of aluminium oxide, what forms at the negative electrode (cathode)?

Answer 35

Aluminium

Question 36

In the electrolysis of aluminium oxide, what forms at the positive electrode (anode)?

Answer 36

Oxygen

Question 37

Why does the positive electrode gradually get ‘eaten away’ and have to be replaced every now and again?

Answer 37

Because the carbon reacts with the oxygen to form carbon dioxide.

Question 38

What are the products of the electrolysis of brine and what are their uses?

Answer 38

Hydrogen- rocket fuel. Chlorine- swimming pool disinfectant, making plastics. Sodium hydroxide- bleach, removing pollutants from water, soaps and detergents.

Question 39

When a salt is molten what will it conduct?

Answer 39

Electricity

Question 40

In the electrolysis of lead bromide, what happens to the positive ions?

Answer 40

They are attracted to the negative electrode. Here they undergo reduction and lead is produced at the cathode.

Question 41

In the electrolysis of lead bromide, what happens to the negative ions?

Answer 41

They are attracted to the positive electrode. Here they undergo oxidation and bromine is produced at the anode.

Question 42

What does one lead ion accept at the cathode?

Answer 42

Two electrons in order to become one lead atom.

Question 43

At the anode, what do two bromide ions lose?

Answer 43

One electron each and they become one bromine ion.

Question 44

How does reactivity affect the products formed by electrolysis at the cathode?

Answer 44

If a salt is dissolved in water there will also be some H+ and OH- ions. At the cathode, if metal ions and H+ ions are present, the metal ions will stay in the solution if the metal is more reactive than hydrogen because the more reactive the element the keener it is to stay as an ion. Hydrogen will be produced unless the metal is less reactive than it.

Question 45

How does reactivity affect the products formed by electrolysis at the anode?

Answer 45

If OH- and halide ions (Cl-, Br-, I-) are present, then molecules of chlorine, bromine and iodine will be produced. If no halide ions are present oxygen will form

Question 46

What are the useful products of the electrolysis of sodium chloride?

Answer 46

Hydrogen, chlorine, sodium hydroxide.

Question 47

What happens at the negative electrode in the electrolysis of sodium chloride?

Answer 47

Two hydrogen ions accept two electrons to become one hydrogen molecule.

Question 48

What happens at the positive electrode during the electrolysis of sodium chloride?

Answer 48

Two chloride ions lose their electrons and become one chlorine molecule.

Question 49

What happens to the sodium ions in the electrolysis of sodium chloride?

Answer 49

They stay in the solution because they are more reactive that hydrogen. Hydroxide ions are also left behind , meaning that sodium hydroxide (NAOH) is left in the solution.

Question 50

What does Metal + water =?

Answer 50

Metal hydroxide + hydrogen

Question 51

Acid + metal =?

Answer 51

Salt + hydrogen