7. Chemical Reactions

Question 1

Describe oxidation and reduction in chemical reactions [2]

Answer 1

Oxidation is the gain of oxygen / reduction is the loss of oxygen

Question 2

Describe oxidation and reduction in a redox reaction [2]

Answer 2

OILRIG - Oxidation is loss of electrons / reduction is gain of electrons

Question 3

Describe metallic bonding [2]

Answer 3

Lattice of positive metal ions in a sea of delocalised electrons

Question 4

Describe general physical properties of metals [4]

Answer 4

High melting and boiling points, malleable, ductile, good conductors of heat and electricity

Question 5

Define malleable [1]

Answer 5

Can be bent of hammered into shape

Question 6

Define ductile [1]

Answer 6

Can be drawn into wires

Question 7

Define an alloy [1]

Answer 7

A mixture of a metal with another substance

Question 8

Explain why an alloy is more useful than the pure metal [3]

Answer 8

It is harder (more difficult to scratch) because the other element disrupts the lattice structure and makes it more difficult to remove the layers from the metal

Question 9

What is brass [1]

Answer 9

An alloy of copper and zinc

Question 10

What do we call an alloy that contains iron and other substances? [1]

Answer 10

Steel

Question 11

Why is nickel and chromium alloyed with iron? [2]

Answer 11

Chromium prevents steel from rusting, nickel makes it harder

Question 12

Place in order of reactivity the following elements: Al, C, Ca, Cu, Fe, H₂, K, Mg, Na, Zn [1]

Answer 12

K, Na, Ca, Mg, Al, C, Zn, Fe, H₂, Cu

Question 13

How does the reactivity of a metal relate to how easy it is to extract from its ore? [1]

Answer 13

The more reactive a metal is the more difficult it is to extract from its ore

Question 14

How does the reactivity of a metal relate to its tendency to form a positive ion? [1]

Answer 14

The more reactive a metal the easier it is to lose its valence electron(s) and form a positive ion

Question 15

Write a symbol equation for the reaction between magnesium and hydrochloric acid [1]

Answer 15

Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g)

Question 16

Write a symbol equation for the reaction between magnesium and oxygen [1]

Answer 16

2Mg (s) + O₂ (g) → MgO (s)

Question 17

Write a symbol equation for the reaction between sodium and cold water [1]

Answer 17

2Na (s) + 2H₂O (l) → 2NaOH (aq) + H₂O (g)

Question 18

Write a symbol equation for the reaction between magnesium and steam [1]

Answer 18

Mg (s) + 2H₂O (g) → MgO (s) + H₂ (g)

Question 19

Define an ore [1]

Answer 19

A rock that contains a high enough percentage of metal for economic extraction

Question 20

Why is it important that metals are recycled?

Answer 20

Because metal ores are finite

Question 21

How are elements above carbon in the reactivity series extracted from their ores? [1]

Answer 21

Electrolysis

Question 22

How is iron extracted from the metal ore haematite in the blast furnace [1]

Answer 22

By heating with carbon

Question 23

Write 3 symbol equations to show how carbon is used to extract iron from haematite [3]

Answer 23

C + O₂ → CO₂ C + CO₂ → 2CO Fe₂O₃ + 3CO → 2Fe + 3CO₂

Question 24

Explain with the use of 2 symbol equations why limestone (CaCO₃) is used in the blast furnace [3]

Answer 24

To remove acidic impurities such as silicon (IV) oxide CaCO₃ → CaO + CO₂ CaO + SiO₂ → CaSiO₃

Question 25

Explain 3 uses of aluminium [6]

Answer 25

Aircraft because of its strength and low density and in food containers because of its resistance to corrosion and overhead wires because of low density and good electrical conductivity

Question 26

Describe the uses of mild steel and stainless steel [2]

Answer 26

Mild steel for car bodies and machinery and stainless steel for chemical plants and cutlery

Question 27

Describe and explain the apparent unreactivity of aluminium [2]

Answer 27

Aluminium forms an oxide layer which protects the metal underneath

Question 28

Explain why zinc is used for galvanising steel [2]

Answer 28

As a more reactive metal zinc provides sacrificial protection, this means is reacts before the metal underneath

Question 29

Explain 1 use of Copper [2]

Answer 29

Electrical wiring because of good electrical conductivity

Question 30

Explain why metals have a high melting point and boiling point [3]

Answer 30

Because of strong electrostatic force of attraction between positive metal ions and sea of delocalised electrons that requires a lot of energy to overcome

Question 31

Explain why metals are good conductors [2]

Answer 31

Delocalised electrons can move and carry charge through the structure

Question 32

Explain why metals are ductile and malleable [2]

Answer 32

Positive metal ions are arranged in layers layers can slide over each other