Electrolysis

Question 1

What is Electrolysis?

Answer 1

The process in which an electrolyte is broken down by electricity; not a physical separation method.

Question 2

What is an Electrolyte?

Answer 2

An ionic compound that is either molten or dissolved this allows the ions to move within the liquid.

Question 3

What is the POSITIVELY charged electrode called?

Answer 3

Anode

Question 4

What is the NEGATIVELY charged electrode called?

Answer 4

Cathode

Question 5

What are the product rules at the ANODE?

Answer 5

• Oxygen is produced unless a halide ion is present.
• If one of the halide ions are present (Chlorine, Bromine, Iodine, Fluorine) then that element is formed.

Question 6

What are the product rules at the CATHODE?

Answer 6

• Either hydrogen or a metal is produced here
• Metal is produced at the Cathode if it is less reactive than hydrogen (Copper, Silver, Gold and Platinum)
• Hydrogen gas is produced at the Cathode if the metal is more reactive than hydrogen.

Question 7

What charge of ion does the Cathode attract?

Answer 7

Positive

Question 8

What charge of ion does the Anode attract?

Answer 8

Negative

Question 9

What do ions do when they reach an electrode?

Answer 9

They lose or gain electrons.

Question 10

What charge do elements on the left of the P.T. have?

Answer 10

Positive

Question 11

What charge do the elements on the right of the P.T. have?

Answer 11

Negative

Question 12

What are the five possible elements that can be formed at the Cathode?

Answer 12

Hydrogen, Copper, Silver, Gold and Platinum.

Question 13

What are the five possible elements that can be formed at the Anode?

Answer 13

Oxygen, Chlorine, Bromine, Fluorine and Iodine.

Question 14

In an aqueous solution what ion is positively charged? What electrode does it go to and what does it form there?

Answer 14

Hydrogen ions (H+) they go to the cathode where they form Hydrogen gas.

Question 15

In an aqueous solution what ion is negatively charged? What electrode does it go to and what does it form there?

Answer 15

Hydroxide ions (OH-) they go to the anode where they form Oxygen gas.

Question 16

What is the ratio of volume of hydrogen to oxygen being released?

Answer 16

2:1

Question 17

What product is formed at the cathode during the electrolysis of Sodium Chloride solution?

Answer 17

• Hydrogen because sodium is more reactive than hydrogen

Question 18

What product is formed at he cathode during the electrolysis of Copper Chloride solution?

Answer 18

• Copper because it is less reactive that hydrogen

Question 19

What is produced at the anode during the electrolysis of Sodium Sulphate solution?

Answer 19

Oxygen because there is no halide ion present and Sulphate is a hydroxide ion.

Question 20

What is ALWAYS produced at the anode? (think 2)

Answer 20

A molecule is formed e.g. O2 or I2.

Question 21

What is used to show the reaction that takes place at the electrodes?

Answer 21

Half-Equations

Question 22

What are the rules of half-equations?

Answer 22

• The number of atoms of each element must be the same on both sides
• Reactions at the cathode have electrons as part of the reactants (on the left of the arrow)
• Reactions at the anode have electrons as part of the product (on the right side of the arrow)

Question 23

At which electrode does reduction take place?

Answer 23

Cathode

Question 24

At which electrode does oxidation take place?

Answer 24

Anode

Question 25

What is the most abundant metal on earth?

Answer 25

Aluminium

Question 26

What is the ore of aluminium?

Answer 26

Bauxite

Question 27

What are the chemical symbols for Bauxite?

Answer 27

Al203

Question 28

What are the electrodes made of when extracting aluminium?

Answer 28

Graphite

Question 29

What is formed at the anode when extracting aluminium?

Answer 29

Purified aluminium ore dissolved in cryolite

Question 30

What is formed at the cathode when extracting aluminium?

Answer 30

Molten aluminium which is extracted from the cell.

Question 31

Name some of the factors of an aluminium extraction site:

Answer 31

-Close proximity to a power station - Near the coast Near road and railways.

Question 32

What is the chemical bond between two metals?

Answer 32

Metallic

Question 33

What is the chemical bond between two non-metals?

Answer 33

Covalent

Question 34

What is the chemical bond between a metal and a non-metal?

Answer 34

Ionic

Question 35

What is the independent variable?

Answer 35

The variable that is being changed during the experiment (concentration of solution)

Question 36

What is the dependant variable?

Answer 36

The variable being tested or measured during the experiment (amount of product at an electrode)

Question 37

What is the control variable?

Answer 37

The variable that stays the same throughout the experiment (voltage or time)