2- Salts And Electolysis

Question 0

What is an aqueous solution? (aq)

Answer 0

A substance dissolved in water

Question 1

What are acids (how can you tell)?

Answer 1

They produce hydrogen ions when dissolved in water (H+)

Question 2

What are alkalis (how can you tell)?

Answer 2

Bases (acid neutralisers) which dissolve in water to make alkaline solutions and produce hydroxide ions (OH-)

Question 3

What happens when an acid reacts with a metal?

Answer 3

A salt and hydrogen gas are produced

Acid +,metal –> a salt + hydrogen

Question 4

What will acid react with?

Answer 4

Metals above hydrogen in the reactivity series (but not too high or it is unsafe)

Question 5

What happens when an acid reacts with a base?

Answer 5

Neutralisation reaction takes place and a salt and water are produced

Question 6

How do you make an acidic aqueous solution if the acid is insoluble?

Answer 6

You add it a little at a time and then, once all the acid has reacted, filter the mixture to remove excess solid reactant

Question 7

How do you make soluble salts from acids and alkali’s? (Equation)

Answer 7

Acid + alkali –> salt + water

Question 8

How (using an equation) show a neutralisation reaction?

How can you tell the reaction has happened?

Answer 8

H+ + OH- –> H2O

You can’t tell by sight, you have to use a universal indicator

Question 9

How can the solid salt be obtained from the solution?

Answer 9

Through crystallisation

Question 10

What is produced when ammonia solution reacts with acids? What are they used for?

Answer 10

Ammonia salts, used as fertilisers

Question 11

How can you make insoluble salts?

Answer 11

Mixing solutions of soluble salts that contain the ions needed

Question 12

What is a precipitate?

Answer 12

An insoluble solid formed by a reaction taking place in solution

Question 13

What is electrolysis?

Answer 13

The process that uses electricity to break down ionic compounds into elements called electrolyte

Question 14

When does electrolysis take place?

Answer 14

When electricity passes through a molten ionic compound or a solution containing ions

Question 15

How does electrolysis happen?

Answer 15

Two inert (not reactive) electrodes make contact with the electrolyte. positively charged ions in the electrolyte are attracted by the negative electrode where they form metals or hydrogen
negatively charged ions are attracted to the positive electrode where they lose their charge and form non-metallic

Question 16

What happens to 1)positively charged ions 2)negatively charged ions when they reach the electrode?

Answer 16

1) They gain electrons to become neutral atoms (a reduction)
2) They lose electrons to become neutral atoms (oxidation)

Question 17

What happens if the ions in water are electrolysed?

Answer 17

Hydrogen may be produced at the negative electrode if the positive ions in the solution are a metal more reactive than hydrogen

Question 18

How is oxygen usually produced in electrolysis?

Answer 18

From the positive electrode from an aqueous solution

Question 19

Why must aluminium be extracted by electrolysis?

Answer 19

It is more reactive than carbon

Question 20

How do you prepare aluminium for electrolysis?

Answer 20

Get aluminium oxide from the ore, purify it and then melt it

Question 21

What are the products of aluminium when it has been through electrolysis?

Answer 21

Pure aluminium and oxygen

Question 22

What is the overall reaction of aluminium in electrolysis? (Equation)

Answer 22

Aluminium oxide –> aluminium + oxygen

Question 23

What happens at the negative electrode with aluminium oxide?

Answer 23

Aluminium ions are reduced to aluminium atoms by gaining electrons

Question 24

What happens at the positive electrode with aluminium oxide?

Answer 24

Oxide ions are oxidised to oxygen atoms (which form oxygen molecules) by losing electrons

Question 25

What is brine?

Answer 25

A solution of sodium chloride in water

Question 26

What happens when Brine is electrolysed? Why is the solution left useful?

Answer 26

Hydrogen is produced at the negative electrode and chlorine is produced at the positive.
Leaving a solution of sodium ions and hydroxide ions (sodium hydroxide) which is used for many things such as soap, paper and bleach

Question 27

Why is chlorine useful?

Answer 27

Killing bacteria in drinking water and swimming pools

Question 28

Why is hydrogen useful?

Answer 28

Used to make margarine and hydrochloric acid

Question 29

What is electroplating? Why is it done?

Answer 29

Using electrolysis to put a thin coating of metal onto an object

It is used to make an object look appealing, protect against corrosion, increase the hardness of the metal and to reduce costs (not having to use the pure metal)

Question 30

How is electroplating done?

Answer 30

The object to be plated on is the negative electrode and the electrolyte (contains plating metals ions) is the positive.
At the positive electrode plating metal atoms lose electrons, at the negative, metal ions gain electrons to form metal atoms which are deposited onto the object to be plated