Chapter C6 Electrolysis

Question 1

What does electrolysis mean?

Answer 1

Breaking down using electricity

Question 2

What do you do in electrolysis?

Answer 2

Use a current to break down an ionic compound

Question 3

What is the compound called that is broken down in electrolysis?

Answer 3

The electrolyte

Question 4

What is the posture electrode called?

Answer 4

Anode

Question 5

What is the negative electrode called?

Answer 5

Cathode

Question 6

What are electrodes commonly made from?

Answer 6

Unreactive substance

Such as graphite

Question 7

Why are electrodes made from unreactive substances?

Answer 7

So electrodes do not react with the electrolyte or products made

Question 8

What happens when the ions in electrolysis reach the electrodes?

Answer 8

Lose their charge and become elements

Question 9

Who was the first person to work on electrolysis?

Answer 9

Michael faraday

Question 10

Do ionic compounds conduct electricity?

Answer 10

As a solid- no as their ions are in fixed positions

As a liquid- yes as the ions can move towards the electrodes

Question 11

Can covalent compounds undergo electrolysis?

Answer 11

Only if they from ions when reacting with water

Question 12

What is a half equation?

Answer 12

An equation that describes reduction or oxidation

Question 13

Do a half equation for the electrolysis of Pb

Answer 13

Pb—-> 2E- + pb^2+

Question 14

Complete the half equation for electrons being removed from negative ions for Br

Answer 14

2br- - 2e- ——> br^2

Question 15

Why is electrolysis more complicated in aqueous solutions?

Answer 15

Because of the ions formed by water as it ionises

Question 16

What happens at the anode in the electrolysis of aqueous solutions?

Answer 16

Oxygen gas is given off and hydroxide ions are discharged

Question 17

What happens when a Solution contains a large concentration of halide?

Answer 17

Forms a halogen

Question 18

What happens if two elements can be formed at an electrode?

Answer 18

The less reactive one will be formed

Question 19

What is the compound electrolysed when performing electrolysis on aluminium?

Answer 19

Aluminium oxide

Question 20

What is the ore of aluminium?

Answer 20

Bauxite

Question 21

Describe the process of electrolysis of aluminium oxide?

Answer 21

The aluminium oxide requires free moving ions but the pure melting of it is very high 2050C.
So mix it with cryolite, and it melts at 850C
Aluminium forms on the cathode
Oxygen forms at the anode

Question 22

What is the equation that results in the product of aluminium oxide?

Answer 22

Aluminium oxide

——> electrolysis ——>

aluminium +oxygen

Question 23

What is brine?

Answer 23

Concentrated sodium chloride solution

Question 24

What is produced from electrolysis of brine?

Answer 24

Chlorine gas (anode) 
Hydrogen gas (cathode) 
Sodium hydroxide

Question 25

Half equation for anode of brine?

Answer 25

2CL- —-> electrolysis Cl^2 + 2e-

Question 26

When electrolysis of brine occurs, why doesn’t sodium form at the cathode?

Answer 26

As hydrogen is the less reactive element and so if formed, whilst sodium remains in the aqueous solution

Question 27

How do you test the solution at the cathode?

Answer 27

Acid base indicator

Question 28

With electrolysis of aluminium oxide, why must the anode be regularly replaced?

Answer 28

As oxygen reacts with the graphite (carbon) to make carbon dioxide

Question 29

Problems with electrolysis?

Answer 29

Is expensive To melt the ionic compounds requires lots of bond energy A lot of energy is required to produce the electric current

Question 30

Process of aluminium electrolysis

Answer 30

Add aluminium to cryolite Melts at 850C Put carbon anode in water- the aluminium ions will go to the cathode, turning into aluminium atoms, whilst oxygen will be produced at the anode. This oxygen will wear at the anode, which is made of graphite, resulting in the formation of carbon dioxide. This means the anode will slowly get used up in the reaction and so must be replaced. A siphon is then used to collect the aluminium atoms

Question 31

What are the products of sodium chloride in electrolysis

Answer 31

Sodium hydroxide Chlorine Hydrogen

Question 32

What are the products if sodium sulfate in electrolysis

Answer 32

Hydrogen and oxygen

Question 33

What are the products of copper chloride in electrolysis

Answer 33

Chlorine gas | Copper

Question 34

What are the products of copper sulfate in electrolysis

Answer 34

Copper | Oxygen gas

Question 35

Test for hydrogen gas

Answer 35

Squeaky pop

Question 36

Test for oxygen

Answer 36

Glowing splint

Question 37

Test for chlorine gas

Answer 37

Bleaches damp litmus paper