C15 - Using our resources

Question 1

What is corrosion?

Answer 1

the destruction of materials through chemical reactions with other substances in the environment

Question 2

Describe a specific example of corrosion:

Answer 2

rusting
-only for iron
-needs both air (oxygen) and water to occur

Rust is just hydrated iron oxide which is formed when it reacts with oxygen in the presence of water, which catalyses the reaction

Question 3

What will happen to this nail?

Answer 3

does not rust, because stainless steel is resistant to corrosion

Question 4

How can corrosion be prevented?

Answer 4

-physical barrier coating (eg greasing, painting, or electroplating)
-sacrificial coatings (attaching a more reactive metal so it gets corroded instead of the main metal, for example galvanising a metal using a zinc coating)

Galvanising also acts as a physical barrier

Electroplating is using electrolysis to coat objects with a thin layer of metal

Question 5

What stops aluminium corroding further?

Answer 5

has an aluminium oxide outer layer that protects the inner metal

Say that it is an aluminium oxide layer, not just an oxide layer

Question 6

Name 4 common alloys and their components:

Answer 6

-bronze (copper and tin)
-brass (copper and zinc)
-gold (usually mixed with silver/copper/zinc, where proportion of gold is measured in carats, with 24 being 100% gold)
-steel (iron with specific amounts of carbon)

Question 7

Describe the properties and uses of the different types of steel and aluminium alloys you can have:

Answer 7

high carbon - strong but brittle (tools/drill bits)
low carbon - soft and malleable (wires)
stainless - hard and resistant to corrosion (contains nickel and chromium, used for cutlery)

aluminium alloys - low density and resistant to corrosion (planes)

Question 8

Name and describe 2 types of glass:

Answer 8

soda-lime - made by heating sand, sodium carbonate, and limestone (calcium carbonate)

borosilicate - made from sand and boron trioxide, and has a higher melting point than soda-lime glass

Soda-lime glass is used more commonly

Question 9

Give 2 examples of ceramics, and describe how they are both made:

Answer 9

-pottery and bricks

-shaping wet clay and heating them in a furnace

Question 10

What does the properties of a polymer depend on?

Don’t mention intermolecular forces here

Answer 10

-the monomers they are made from
-the conditions they were made under (eg low density and high density polyethene are both produced from an ethene monomer, but have different properties)

Question 11

Describe the properties and structures of the 2 types of polymers:

Answer 11

thermosoftening - melts when reheated (weak IM forces between polymer chains)

thermosetting -doesn’t melt when reheated (has cross-links of strong covalent bonds between polymer chains)

Thermosetting polymers just burn when heated

Question 12

Why might a polymer melt when reheated?

Answer 12

-the polymer is thermosoftening
-because it has no cross-links, and its IM forces are weak

Question 13

What is a composite material? Describe its structure:

Answer 13

-a substance made from 2 materials:

reinforcement - fragments/fibres of material
matrix/binder - material that surrounds the reinforcement

The composition of the 2 materials makes the resulting material stronger

Question 14

Give 2 examples of composite materials:

Answer 14

-carbon fibre
-fibreglass

Question 15

What does the Haber process manufacture? What is the product used for?

Answer 15

-used to produce ammonia from nitrogen and hydrogen
-ammonia is used in nitrogen-based fertilisers

Question 16

Where are the raw materials for the Haber process sourced from?

Answer 16

nitrogen - fractionally distilled from liquid air

hydrogen - react methane (from natural gas) with steam (water vapour)

Question 17

Explain how the Haber process is used to manufacture ammonia:

Answer 17

-purified N2 + H2 are passed over an iron catalyst at 450°C, 200 atm.
-some of the reactants react to form NH3 in an exothermic reaction
-the reaction is reversible so some of the NH3 produced breaks down back into N2 + H2
-the mixture is then cooled so the NH3 condenses into a liquid and gets separated, and the still-gaseous N2 + H2 is recycled back into the reaction vessel

Question 18

Why are the conditions for the Haber process not always ideal in terms of equilibrium yield?

Answer 18

it is a compromise between high equilibrium yield, high rate of reaction, and low cost

Question 19

Why is a temperature of 450°C used for the Haber process?

Answer 19

-increases rate of reaction
-we don’t go higher because it is too expensive
-however the forward reaction is exothermic, so it is a compromise

Question 20

Why is a pressure of 200atm used for the Haber process?

Answer 20

-there are fewer moles of gas on the product’s side, so it increases yield of NH3 (and also rate of reaction)

-however it is not increased further as it is very expensive to do so due to the strong containment vessels needed to withstand the pressure

A pump is used to increase the pressure to 200atm

Question 21

What are NPK fertilisers and why are they used?

Answer 21

-a formulation of several different soluble nitrogen, phosphorus and potassium compounds that are put onto plants to supply them with mineral ions

-improves agricultural productivity by encouraging growth

The compounds must be soluble otherwise the plant’s roots would have no way of absorbing the ions used for growth

Question 22

How are the ingredients for a fertiliser sourced?

Answer 22

-some substances can be mined straight from the ground and added (eg potassium chloride/sulfate)
-others need to be processed first (eg phosphate rock)

Question 23

How is phosphate rock/ammonia treated to be put in an NPK fertiliser?

Answer 23

treated with nitric/sulfuric/phosphoric acid to produce soluble salts

Question 24

What can ammonia be used to manufacture?

Answer 24

ammonium salts and nitric acid

Question 25

Compare the production of fertilisers industrially and in the lab:

Answer 25

-industrial is larger scale

-industrial produces larger quantities faster
-industrial can do it continuously but lab can only do it once in a batch
-industry uses stainless steel apparatus but the lab uses glass (steel is much stronger, can use higher temp/pressures)

Question 26

What is formed when phosphate rock reacts with nitric acid?

Answer 26

phosphoric acid and calcium nitrate

When asked a question such as “what soluble salt is produced when x reacts with y”, don’t say phosphoric acid because it is unsurprisingly, not a soluble salt.

Question 27

What is formed when phosphate rock reacts with sulfuric acid?

Answer 27

calcium sulfate and calcium phosphate

This mixture is known as single superphosphate

Question 28

What is formed when phosphate rock reacts with phosphoric acid?

Answer 28

calcium triple superphosphate

Question 29

Why might this information be useful to farmers on a bag of a fertiliser?

Answer 29

-shows that it is a formulation, as it gives the proportions of the different N/P/K compounds in it
-this means that the farmer can choose the fertiliser with the required properties/proportions

Question 30

Why might ammonium nitrate help other substances to burn?

Answer 30

provides oxygen to burn

Question 31

Why might a different reaction not work with a certain type of catalyst?

Answer 31

different reactions require different catalysts