Unit 3c- Electrolysis

Question 1

What is electrolysis?

Answer 1

Using electricity to break down a substance

Question 2

What happens to an ionic substance when it is melted or dissolved in water?

Answer 2

The ions become free to move around

Question 3

What is an ionic bond?

Answer 3

Strong electrostatic attraction between oppositely charged ions

Question 4

What is the name for a substance made of billions of oppositely charged ions joined together?

Answer 4

Giant ionic lattice

Question 5

Why do sodium ions and chlorine ions form an ionic bond?

Answer 5

There is an electrostatic force of attraction between oppositely charged ions

Question 6

Define giant ionic lattice

Answer 6

A huge 3D network of ions

Question 7

State the melting points of ionic substances

Answer 7

High

Question 8

Explain why ionic substances have high melting points.

Answer 8

Strong bonds between oppositely charged ions are hard to break

Question 9

Explain why ionic compounds do not conduct electricity when solid

Answer 9

Because the ions are not free to move

Question 10

Explain why ionic compounds conduct electricity in solution

Answer 10

Because the ions are free to move

Question 11

Explain why ionic compounds conduct electricity when molten

Answer 11

Because the ions are free to move

Question 12

What does soluble mean?

Answer 12

Dissolves in water

Question 13

What does insoluble mean?

Answer 13

Does not dissolve in water

Question 14

Define oxidation in the context of loss and gain of electrons (Higher only)

Answer 14

Oxidation is the loss of electrons

Question 15

Define reduction in the context of loss and gain of electrons
(Higher only)

Answer 15

Reduction is the gain of electrons

Question 16

Which of the substances below has been oxidized and which has been reduced? Al³⁺ + Fe → Fe³⁺ + Al

Answer 16

Aluminium has been reduced and iron has been oxidised

Question 17

What happens to an ionic substance when it is melted or dissolved in water?

Answer 17

The ions become free to move around

Question 18

What is the name for the positive electrode?

Answer 18

What is the name for the positive electrode?

Question 19

What is the name for the negative anode?

Answer 19

The cathode

Question 20

Do positive ions move to the anode or the cathode?

Answer 20

Cathode- as opposites attract

Question 21

Do negative ions move to the anode or the cathode?

Answer 21

Anode- as opposites attract

Question 22

At which electrode would Zn²+(aq) turn into Zn(s)?

Answer 22

Cathode (needs to gain electrons)

Question 23

At which electrode would Cl⁻(aq) turn into Cl₂(g)?

Answer 23

Anode (needs to lose electrons)

Question 24

Balance the equation: Al³⁺ + e⁻ → Al

Answer 24

Al³⁺ + 3e⁻ → Al

Question 25

Balance the equation: Cl⁻ → Cl₂ + e⁻

Answer 25

2Cl⁻ → Cl₂ + 2e⁻

Question 26

Balance the equation: O²⁻ → O₂ + e⁻

Answer 26

2O²⁻ → O₂ + 4e⁻

Question 27

In molten electrolysis what are the two products?

Answer 27

The elemental metal and non-metal

Question 28

What will be the products for the electrolysis of molten iron bromide?

Answer 28

Iron and bromine

Question 29

What will be the products for the electrolysis of molten zinc oxide?

Answer 29

Zinc and oxygen

Question 30

For the extraction of which metals is electrolysis needed?

Answer 30

Ones more reactive than carbon, e.g. Group 1,2 and 3

Question 31

What are the two main disadvantages of using electrolysis to extract metals?

Answer 31

Requires a large amount of energy to melt the compounds and to produce the necessary electricity

Question 32

Why is aluminium oxide mixed with cryolite when extracting aluminium?

Answer 32

To lower the melting point

Question 33

What is produced at the anode and cathode in the electrolysis of aluminium oxide?

Answer 33

Aluminium at the cathode and oxygen at the anode

Question 34

Why does the anode need to be replaced in the electrolysis of aluminium oxide?

Answer 34

The oxygen reacts with the carbon electrode to produce carbon dioxide.

Question 35

In the electrolysis of sodium chloride solution, what are the products?

Answer 35

Chlorine gas and hydrogen gas

Question 36

Why is sodium not produced in the electrolysis of sodium chloride solution?

Answer 36

It is more reactive than hydrogen so hydrogen is produced instead.

Question 37

What is produced at the anode in electrolysis of solutions?

Answer 37

Either a halogen or oxygen (when there is no halogen present)

Question 38

When is hydrogen produced in aqueous electrolysis?

Answer 38

When the metal is more reactive than carbon (group 1,2 and 3)

Question 39

When is the metal produced in aqueous electrolysis?

Answer 39

When the metal is less reactive than carbon (transition metal)

Question 40

When is the group 7 element produced in aqueous electrolysis?

Answer 40

When the salt has a halogen in it

Question 41

When is oxygen produced in aqueous electrolysis

Answer 41

When the salt does not contain a halogen in it

Question 42

What is the anode rule for aqueous electrolysis?

Answer 42

If a group 7 element is present it is produced, if not oxygen is produced

Question 43

What is the cathode rule for aqueous electrolysis?

Answer 43

If the metal is more reactive than hydrogen (Group 1,2 or 3) hydrogen is produced,

If not oxygen is produced

Question 44

What are the two ions in water?

Answer 44

H+ and OH-