Chemistry - Chemical Changes

Question 1

What is the order of the reactivity series?

Answer 1

Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Silver
Gold
Platinum

Question 2

How can metals be placed in order of their reactivity?

Answer 2

Add the metals to water or acid and see which ones react the most vigorously

Question 3

What is the name for the reaction where oxygen is removed from a compound?

Answer 3

Reduction

Question 4

What is the name for the reaction where oxygen is added to a compound?

Answer 4

Oxidation

Question 5

Why is gold found in the Earth’s crust as the metal itself?

Answer 5

It is unreactive

Question 6

What process is used to extract metals less reactive than carbon?

Answer 6

Reduction with carbon

Question 7

What process is used to extract metals more reactive than carbon?

Answer 7

Electrolysis

Question 8

What is an ore?

Answer 8

A material containing enough metal in it for it to be economically worthwhile to extract the metal

Question 9

Name two new ways of extracting copper from low-grade ores

Answer 9

Phytomining and bioleaching

Question 10

What is a low grade ore?

Answer 10

Rock with only a small amount of metal compound in it

Question 11

How is phytomining carried out?

Answer 11

Plants absorb metal compounds, are harvested and are then burned to ash

Question 12

How is bioleaching carried out?

Answer 12

Bacteria are used to produce a leachate solution

Question 13

How can copper be produced from the products of phytomining and bioleaching?

Answer 13

Electrolysis or displacement with scrap iron

Question 14

What is a displacement reaction?

Answer 14

A reaction in which a more reactive element takes the place of a less reactive element in one of its compounds or in solution

Question 15

Define oxidation in the context of loss or gain of electrons

Answer 15

Oxidation is the loss of electrons

Question 16

Define reduction in the context of loss or gain of electrons

Answer 16

Reduction is the gain of electrons

Question 17

Define acids in terms of pH

Answer 17

A substance with a pH less than 7

Question 18

Define acids in terms of ions

Answer 18

A substance which releases H+ ions in solution

Question 19

State the three common acids and give their formulae

Answer 19

Hydrochloric acid (HCl), Sulfuric acid (H2SO4), Nitric acid (HNO3)

Question 20

Which ions do the common acids form in solution?

Answer 20

HCl forms H+ and Cl -
H2SO4 forms 2H+ and SO4 2-
HNO3 forms H+ and NO3 -

Question 21

What is a neutral solution?

Answer 21

A solution with a pH of 7

Question 22

How do you measure pH?

Answer 22

An indicator or a pH probe

Question 23

What is a base?

Answer 23

A metal oxide, hydroxide or carbonate that will neutralise an acid to form a salt (e.g. copper oxide)

Question 24

What is an alkali?

Answer 24

A soluble base (e.g. NaOH)

Question 25

Which ions are always present in a solution of an alkali?

Answer 25

OH-

Question 26

What is a salt?

Answer 26

A compound formed with some or all of the hydrogen from an acid is replaced by a metal

Question 27

What type of salts are formed by the three main acids?

Answer 27

Hydrochloric acid produces chlorides Sulfuric acid produces sulfates Nitric acid produces nitrates

Question 28

Metal + Acid -->

Answer 28

Salt + Hydrogen gas

Question 29

Metal hydroxide + Acid -->

Answer 29

Salt + Water

Question 30

Metal carbonate + Acid -->

Answer 30

Salt + Water + Carbon dioxide

Question 31

Metal + Water -->

Answer 31

Metal hydroxide + Hydrogen

Question 32

Metal + Oxygen -->

Answer 32

Metal oxide

Question 33

How do you make a soluble salt from an acid?

Answer 33

React the acid with a base (e.g. to make copper sulfate, react copper oxide with sulfuric acid)

Question 34

If a salt is in solution, how do you extract it as a solid?

Answer 34

Allow the water to evaporate and it will leave the salt behind as a solid (crystallisation)

Question 35

What is corrosion?

Answer 35

The destruction of materials by chemical reactions with substances in the environment

Question 36

What is necessary for rusting to occur?

Answer 36

Water and air (oxygen)

Question 37

How can rusting be prevented?

Answer 37

By use of a barrier coating or sacrificial protection

Question 38

Give three examples of barrier coating

Answer 38

Greasing, painting, electroplating

Question 39

How does sacrificial protection work?

Answer 39

A more reactive metal is corroded rather than the base metal.