Electrolysis

Question 1

What is electrolysis?

Answer 1

The process of using electrical energy to decompose ionic compounds

Question 2

What is the process of electrolysis?

Answer 2

An electric current is passed through an electrolyte (a molten or dissolved ionic compound), causing it to decompose.

Question 3

What occurs in electrolysis?

Answer 3

In electrolysis, oxidation (loss of electrons) and reduction (gain of electrons) occur.

Question 4

What is the electrolyte?

Answer 4

The liquid that is a molten or dissolved ionic compound used in electrolysis

Question 5

What is the Anode?

Answer 5

Positive electrode

Question 6

What is the cathode?

Answer 6

Negative electrode

Question 7

What is oxidation?

Answer 7

The loss of electrons

Question 8

What is reduction?

Answer 8

The gain of electrons

Question 9

What is the cation?

Answer 9

Positive ion that is attracted to the cathode

Question 10

What is the anion?

Answer 10

Negative ion that is attracted to the anode

Question 11

What is PANIC?

Answer 11

Positive Anode Negative Is Cathode

Question 12

What is OILRIG?

Answer 12

Oxidation Is Loss Reduction Is Gain

Question 13

What do the positive ions (cations) in the electrolyte do?

Answer 13

They move towards the cathode (negative electrode) and are reduced (gain electrons) +This creates a flow of charge through the electrolyte

Question 14

What do the negative ions (anions) in the electrolyte do?

Answer 14

They move towards the anode (positive electrode) and are oxidised (lose electrons) +This creates a flow of charge through the electrolyte

Question 15

What are half equations?

Answer 15

They show how electrons are transferred during reactions +They’re useful for showing what happens at each electrode during electrolysis.

Question 16

What occurs at the cathode?

Answer 16

Reduction

Question 17

What occurs at the anode?

Answer 17

Oxidation

Question 18

What is inert?

Answer 18

Unreactive

Question 19

What happens when the electrolyte is a solution?

Answer 19

Question 20

What happens when the electrolyte is a molten ionic substance?

Answer 20

Question 21

Why can’t an ionic solid be electrolysed?

Answer 21

Because the ions are in fixed positions and can’t move

Question 22

Why can molten ionic compounds be electrolysed?

Answer 22

Because their electrons are delocalised so the ions can move freely and conduct electricity

Question 23

In a molten ionic compund, what are positive metal ions reduced to?

Answer 23

Metal atoms at the cathode

Question 24

In molten ionic compounds, what are negative ions oxidised to?

Answer 24

Atoms or molecules at the anode

Question 25

What are the half equations for the table of molten electrolytes?

Answer 25

Question 26

What happens in aqueous solutions?

Answer 26

+As well as the ions from the ionic compound, there will be hydrogen ions [H⁺] and hydroxide ions [OH^-]

Question 27

In aqueous solutions, what happens at the cathode?

Answer 27

+If H⁺ ions and metal ions are present, hydrogen gas will be produced if the metal is more reactive than hydrogen [eg. sodium] +If the metal is less reactive than hydrogen, [eg. copper or silver] then a solid layer of the pure metal will be produced instead.

Question 28

In aqueous solutions, what happens at the anode?

Answer 28

If OH^- and halide ions [Cl^-, Br^-, I^-] are present, molecules of chlorine, bromine or iodine will be formed. +If no halide ions are present, then oxygen will be formed

Question 29

What are the half equations of the table of aqueous electrolytes?

Answer 29

Question 30

What does the electrolysis of copper sulfate with inert electrodes produce?

Answer 30

Oxygen

Question 31

What does a solution of copper sulfate contain?

Answer 31

* Cu²⁺ * SO_4+^2- * H⁺ * OH^-

Question 32

What happens at the cathode when you electrolyse copper sulfate solution with inert electrodes?

Answer 32

+Copper is less reactive than hydrogen, so copper metal is produced at the cathode [you see a coating of copper on the electrode] Cu²⁺+2e^- ----\> Cu

Question 33

What happens at the anode when you electrolyse copper sulphate solution with inert electrodes?

Answer 33

+They're aren't any halide ions present, so oxygen and water are produced at the anode [you see bubbles of oxygen gas forming] 4OH^-----\> O₂ + 2H₂O + 4e^-

Question 34

What do non-inert electrodes take part in?

Answer 34

Electrolysis reactions [eg. copper electrodes]

Question 35

What happens to the anode and cathode when using copper electrodes?

Answer 35

As the reaction continues, the mass of the anode will decrease and the mass of the cathode will increase. +This is because the copper is transferred from the anode to the cathode

Question 36

How long does the non-inert electrolysis reaction take place?

Answer 36

+You need to leave the cell running for 30mins in order to get a decent change in mass

Question 37

What is electroplating?

Answer 37

Coating the surface of a metal using electrolysis

Question 38

What is the cathode in electroplating?

Answer 38

+The object you're going to electroplate

Question 39

What is the anode in electroplating?

Answer 39

The bar of metal you're using for the plating

Question 40

What is the electrolyte in electroplating?

Answer 40

The solution containing the metal ions of the metal you're plating with

Question 41

Why is electroplating useful?

Answer 41

It is used for household objects like cutlery, and cooking utensils are electroplated with metals to stop them from corroding. +The metals used for electroplating are unreactive and don't corrode easily. +Jewellery and decorative items are often electroplated with metals like gold or silver - this improves the appearance of the metals, making them look shiny and attractive.

Question 42

What is the chemical test for chlorine?

Answer 42

Damp blue litmus paper test - hold damp blue litmus paper over chlorine. +Chlorine will bleach the litmus paper, turing it white

Question 43

What is the chemical test for oxygen?

Answer 43

+Use a glowing splint +You can test for oxygen by checking if the gas will relight a glowing splint

Question 44

What is the chemical test for hydrogen?

Answer 44

+Use a lighted splint +Hydrogen makes a "squeaky pop" with a lighted splint. +The noise comes from the hydrogen burning with the oxygen in the air to form water.

Question 45

What is the test for carbon dioxide?

Answer 45

+Bubbling the gas through limewater +If it is carbon dioxide, the limewater will turn cloudy