Chapter 5 - Salts And Electrolysis

Question 1

What happens when a base reacts with an acid

Answer 1

It neutralises the acid

Question 2

What ions do acids produce when added to water

Answer 2

Hydrogen ions

Question 3

What is produced when a metal reacts with an acid

Answer 3

A salt and hydrogen gas

Question 4

What happens when an acid reacts with a base

Answer 4

A neutralisation reaction takes place and a salt and water are produced

Question 5

How do you make a salt

Answer 5

A metal or a base that is insoluble in water, is added a little at a time to the acid until all of the acid has reacted. The mixture is then filtered to remove the excess solid reactant, leaving a solution of the salt. To make the solution a solid, water is evaporated so that the solution crystallises

Question 6

What happens when an ammonia solution reacts with acids

Answer 6

It produces ammonium salts

Question 7

What are ammonium salts used as

Answer 7

Fertilisers

Question 8

How are insoluble salts made

Answer 8

By reacting two solutions to produce a precipitate

Question 9

How can pollutants such as metal ions be removed from water

Answer 9

By precipitation. This is done by adding substances that react with the pollutant metal ions dissolved in the water to form insoluble salts.

Question 10

What is electrolysis

Answer 10

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

Question 11

What must be done to ionic compounds before they can be electrolysed

Answer 11

The ionic compounds have to be molten or in solution because then their ions are free to move to the electrodes

Question 12

What is the name of the substance that is broken down when electricity passes through the compound

Answer 12

The electrolyte

Question 13

Describe the process of electrolysis

Answer 13

• The electrical circuit has two electrodes that make contact with the electrolyte
• Ions in electrolyte move to the electrodes where they are discharged to produce elements.
• Positively charged ions are attracted to the negative electrode where they form metals or hydrogen, depending on the ions in the electrolyte
• Negatively charged ions are attracted to the positive electrode where they lose their charge to form non-metallic elements.

Question 14

What happens when positively charged ions reach the negative electrode

Answer 14

They gain electrons to become neutral atoms.

Question 15

What is the term used for gaining electrons

Answer 15

Reduction- as the positive ions have been reduced

Question 16

How many electrons do ions with a single positive charge gain and how many do they gain when they have a 2+ charge

Answer 16

They gain one electron if they have a single positive charge and gain two electrons when they have a 2+ charge

Question 17

What is the term given when losing electrons

Answer 17

Oxidation

Question 18

What does

OILRIG stand for

Answer 18

Oxidation Is Loss (of electrons)

Reduction Is Gain (of electrons)

Question 19

When aqueous solutions are electrolysed what gas is produced at the positive electrode

Answer 19

Oxygen

Question 20

When aqueous solutions are electrolysed what gas is produced at the negative electrode

Answer 20

Hydrogen

Question 21

How is aluminium extracted from its ore and why

Answer 21

By electrolysis because it’s more reactive than carbon

Question 22

Why is aluminium oxide mixed with molten cryolite

Answer 22

To lower its melting point

Question 23

At the negative electrode what are the aluminium ions reduced to

Answer 23

Aluminium atoms by gaining electrons.

Question 24

At the positive electrode what are the oxide ions oxidise to

Answer 24

Oxygen atoms by losing electrons

Question 25

Why do the positive carbon electrodes have to be replaced regularly

Answer 25

At the high temperature of the cell the oxygen reacts with the carbon electrodes to produce carbon dioxide. This means the carbon electrodes gradually burn away

Question 26

What three products are produced when brine is electrolysed

Answer 26

Chlorine gas, hydrogen gas and sodium hydroxide solution

Question 27

What are some of the uses of sodium hydroxide

Answer 27

• Making soap
• Making paper
• Making bleach
• Neutralising acids
• Controlling PH

Question 28

What are they uses of chlorine

Answer 28

• Kill bacteria in drinking water and swimming pools
• Make bleach
• Make disinfectants
• Make plastics

Question 29

What is hydrogen used for

Answer 29

• Making margarine

* Making hydrochloride acid

Question 30

What is electroplating

Answer 30

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

Question 31

Why is electroplating done

Answer 31

• To make the object look more attractive
• To protect a metal object from corroding
• To increase hardness of surface
• To reduce costs by using thin layer of metal instead of pure metal

Question 32

What is the process of plating

Answer 32

The object to be played is used as the negative electrode. The positive electrode is made from the playing metal. The electrolyte is a solution containing ions of the plating metal. At the positive electrode, atoms of the plating metal lose electrons to form metal ions which go into the solution. At the negative electrode, metal ions from the solution gain electrons to form metal atoms which are deposited on the object to be plated