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GCSE Chemistry > C15 - Using Our Resources > Flashcards

C15 - Using Our Resources Flashcards

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1
Q

What is the Haber process?

A

A method of manufacturing ammonia from nitrogen from the air and hydrogen that increases the yield and rate of reaction

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2
Q

What do plants need nitrogen for?

A

Plants need nitrogen to grow as it is one of the elements that they need to make proteins

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3
Q

How do plants take in nitrogen?

A

Plants take in nitrogen, in the form of soluble nitrate ions, from the soil through their roots by active transport

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4
Q

Why is nitrogen not being replaced in the soil by natural cycling?

A

When farmers harvest the crop, the plant is unable to decompose back into the soil. Therefore the nitrogen absorbed from the soil during growth is not all replace by the natural cycling of nitrogen. As a result , farmers need fertilisers to replace nitrogen and other nutrients in the soil before they sow their next crop

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5
Q

Why can most plants not absorb nitrogen directly from the air (given that it is 80% nitrogen)

A

Almost 80% of the air is nitrogen gas, however, the gas is insoluble in water and most plants can only absorb a soluble form of nitrogen

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6
Q

What is fixing nitrogen?

A

fixing nitrogen is when nitrogen gas from the air is turned into nitrogen compounds (such as ammonia)

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7
Q

What is a use of ammonia?

A

It is used to make fertilisers and nitric acid

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8
Q

What is the structure type of ammonia?

A

Simple molecular

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9
Q

What is the balanced chemical equation to show the formation of ammonia

A

N₂(g) + 3H₂(g) ⇌ 2NH₃(g)

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10
Q

What type of reaction is the forward reaction in the formation of ammonia?

A

Exothermic

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11
Q

What is the raw material for nitrogen in the Haber process?

A

The air

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12
Q

What is the raw material for hydrogen in the Haber process?

A

natural gas (which contains methane)

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13
Q

What are the reactor conditions in the Haber process?

A 
Temperature = 450°C
Pressure = 200 atm
Catalyst = Iron Filings
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14
Q

What is the effect of temperature on yield in the Haber process?

A

The temperature decreases the yield, this is because it favours the endothermic direction, meaning the yield of ammonia decreases

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15
Q

What is the effect of pressure on yield in the Haber process?

A

The yield increases, this is because when pressure is increased, the point of equilibrium moves towards the side of the reaction with less particles. In this case that produces more ammonia, increasing the yield

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16
Q

What is the effect of a catalyst on yield in the Haber process?

A

The catalyst has no effect on the yield as it increases the rate of forward and backwards reaction equally

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17
Q

What is the effect of temperature on rate of reaction in the Haber process?

A

The temperature increases the rate of reaction, this is because as temperature is increased, the particles gain more kinetic energy. Therefore, there are more collisions (and therefore more successful collisions), and there are more particles with enough energy to overcome the activation energy. As a result, the rate of reaction increases

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18
Q

What is the effect of pressure on rate of reaction in the Haber process?

A

If the pressure of gaseous reactants is increased, there are more reactant particles per unit volume. Therefore, there will be more collisions (and therefore successful collisions) and so the reaction rate is increased

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19
Q

What is the effect of a catalyst on rate of reaction in the Haber process?

A

The catalyst increases the rate of reaction, this is because it provides an alternative reaction path with a lower activation energy. As a result, there are more particles with enough energy to successfully react, and so the rate of reaction increases

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20
Q

What is the effect of temperature on cost in the Haber process?

A

Higher temperatures require more energy, as a result, the cost increases

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21
Q

What is the effect of pressure on cost in the Haber process?

A

cost increases, this is because more energy is needed to compress the gas and stronger reaction vessels and pipes are required

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22
Q

What is the effect of catalysts on cost in the Haber process?

A

An iron catalyst is used, this is relatively cheap but is still a monetary expense. However, it also greatly increase the rate of reaction which increases profits.

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23
Q

Explain the process of the Haber process:

A

The hydrogen and nitrogen are purified from their pure substances. They are then pumped in and compressed to a pressure of 200atm and heated to 450°C. They then enter the reaction vessel (which contains an iron catalyst), the result of this reversible reaction is ammonia. The mixture of gases emerging from the reactor is cooled in the cooling chamber, here the ammonia liquifies and is separated from the unreacted nitrogen gas and hydrogen gas. The unreacted nitrogen and hydrogen gases are recycled back into the reaction mixture, they are re-compressed and heated before returning to the reaction vessel.

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24
Q

What is the yield of ammonia in the Haber process?

A

15%

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25
Q

What is the formula for ammonia?

A

NH₃

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26
Q

What is the main use of ammonia?

A

Most is turned into soluble nitrogenous compounds, however ~10% is turned into Nitric acid

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27
Q

What are NPK Fertilisers?

A

Formulations containing water soluble compounds containing Nitrogen, Phosphorus, Potassium

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28
Q

What do the 3 numbers on the front of NPK fertilisers represent?

A

The % of mass of the N, P, or K atoms

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29
Q

What ammonium salts can be used in NPK fertilisers?

A
  • Ammonium nitrate
  • Ammonium sulfate
  • Ammonium phosphate
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30
Q

What is the formula of phosphoric acid?

A

H₃PO₄

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31
Q

What is the word and balanced symbol equation for the formation of ammonium nitrate?

A

Ammonia + Nitric acid -> Ammonium Nitrate

NH₃(aq) + HNO₃(aq) -> NH₄NO₃(aq)

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32
Q

What is the word and balanced symbol equation for the formation of ammonium sulfate?

A

Ammonia + Sulfuric acid -> Ammonium Sulfate

2NH₃(aq) + H₂SO₄(aq) -> (NH₄)₂SO₄(aq)

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33
Q

What is the word and balanced symbol equation for the formation of ammonium phosphate?

A

Ammonia + Phosphoric acid -> Ammonium Phosphate

3NH₃(aq) + H₃PO₄(aq) -> (NH₄)₃PO₄(aq)

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34
Q

Is ammonia solution an acid or alkali and why?

A

Ammonia solution is simply ammonium hydroxide, this is an alkali

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35
Q

Why do fertilisers require soluble compounds of the nutrients?

A

Plants can only absorb soluble forms of the nutrients

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36
Q

How are fertilisers made in the lab?

A

Neutralisation reactions using titration

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37
Q

What is the source of nitrogen in fertilisers?

A

Ammonia produced in the Haber process

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38
Q

What is the source of phosphorus in fertilisers?

A

deposits of phosphate containing rock which are mined from the ground

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39
Q

Why can phosphate rock not be used in fertilisers?

A

It is insoluble, so must be treated with acids to produce soluble fertiliser salts

40
Q

What is the word equation for the formation of phosphoric acid from phosphate rock?

A

Phosphate rock + Nitric Acid -> Calcium Nitrate + Phosphoric Acid

41
Q

What is the word equation for the formation of ammonium phosphate?

A

Ammonia + Phosphoric Acid -> Ammonium Phosphate

42
Q

What is single superphosphate?

A

A mixture of calcium phosphate and calcium sulfate

43
Q

What is the word equation for the formation of single superphosphate?

A

Phosphate rock + Sulfuric acid -> Calcium Phosphate + Calcium sulfate

44
Q

What is triple superphosphate?

A

Calcium phosphate (Ca₃(PO₄)₂)

45
Q

What is the word equation for the formation of triple superphosphate?

A

Phosphate rock + Phosphoric acid -> Calcium phosphate

46
Q

Why can potassium salts, such as potassium chloride or potassium sulfate, be used directly in NPK fertilisers?

A

Potassium salts are soluble in water, therefore they must just be purified before being used in NPK fertilisers

47
Q

Why are NPK fertilisers a formulation and not just 1 substance?

A

There is no compound that contains all 3 elements (yet)

48
Q

Summarise the integrated processes used to make fertilisers:

A
49
Q

Describe the production of ammonium sulfate fertilisers in a lab:
(sourcing substances and amounts, concentration, apparatus, rate of reaction, crystallisation)

A
  • Ammonia solution and sulfuric acid solutions are provided and reacted together in small quantities to make a small “batch” of ammonium sulfate crystals
  • The concentration of the solutions is dilute for safety reasons
  • The apparatus is made of glass
  • Titration was carried out slowly and carefully until the reaction was just completed
  • The crystals were slowly crystallised and collected
50
Q

Describe the industrial production of ammonium sulfate fertilisers:
(sourcing substances and amounts, concentration, apparatus, rate of reaction, crystallisation)

A
  • The process starts with raw materials to make ammonia and sulfuric acid, which are needed on a large scale
  • High concentrations at high temperatures are used in the reaction
  • The pipes and reaction vessels are made of strong stainless steel to withstand high pressures and the corrosive nature of many raw materials, reactants, and product
  • The ammonia and sulfuric acid then undergo neutralisation to make ammonium sulfate in a continuous process.
  • The energy transferred in the exothermic reaction is used to heat a neighbouring tower in which the ammonium sulfate is heated and blown with air to form granules of the fertiliser
51
Q

What salt is formed in the reaction between calcium phosphate and phosphoric acid?

A

Triple superphosphate

52
Q

What type of process is the industrial manufacture of fertilisers?

A

Continuous process

53
Q

What type of process is the laboratory manufacture of fertilisers?

A

Batch process

54
Q

Which method is more suitable for producing a large mass of ammonium sulfate (fertiliser)

A

Industrial

55
Q

Why is the industrial process more suitable for producing a large mass of ammonium sulfate (fertiliser)

A

°Larger Scale
°Faster Process
°Continuous Process

56
Q

What is corrosion?

A

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

57
Q

What is an example of corrosion?

A

Rusting

58
Q

What is required for iron to rust?

A

Air and water

59
Q

How can corrosion be prevented?

A

applying a coat which acts as a barrier

60
Q

What are example of barrier protections from corrosion?

A
  • greasing
  • Painting
  • electroplating
61
Q

How is aluminium protected from corrosion?

A

The outer layer reacts with oxygen to produce aluminium oxide. This aluminium oxide forms a layer protecting the metal from further corrosion

62
Q

What is carbon steel?

A

Alloy of iron containing small amounts of carbon

63
Q

What is galvanised?

A

Iron or steel objects which have been protected from rusting by a thin layer of zinc on the surface

64
Q

What is rusting?

A

The corrosion of iron

65
Q

What is sacrificial protection?

A

A method of preventing rusting by using a metal more reactive than iron on the surface of the object

66
Q

What is stainless steel?

A

A nickel-chromium alloy of steel which does not rust

67
Q

What is steel?

A

Alloys of iron

68
Q

What is a thermosetting polymer?

A

Polymer that can form extensive cross-linking between chains, resulting in rigid materials which are heat resistant

69
Q

What are thermosoftening polymers?

A

Polymer that forms plastics which can be softened by heating, then remoulded into different shapes as they cool down and set

70
Q

What is an example of sacrificial protection?

A

Galvanising

71
Q

How do barrier protection methods prevent rusting?

A

They prevent the metal coming into contact with air or water

72
Q

What is bronze?

A

An alloy of copper and tin

73
Q

What is brass?

A

An alloy of copper and zinc

74
Q

What carat gold would 100% pure gold be?

A

24 carat

75
Q

What is aluminium used to make aircraft?

A

it is lightweight but strong

76
Q

What is high-carbon steel and what are its uses?

A

High-carbon steel is very strong but brittle, it is used in cutting tools

77
Q

What is low-carbon steel and what are its uses?

A

Softer and more easily shaped that high-carbon steel. Used to make car bodies

78
Q

What is teh density of aluminium alloys?

A

Low-density

79
Q

How is high density polyethene produced?

A

It is produced from ethene using a catalyst at 50*C and a slightly raised pressure

80
Q

What are the 2 types of polyethene?

A
  • High density polyethene

* Low density polyethene

81
Q

How is low density polyethene produced?

A

It is produced from ethene at very high pressure and a trace of oxygen

82
Q

What are the differences in properties between hdpe and ldpe?

A

hdpe has a higher softening point and is stronger than ldpe

83
Q

Explain the molecular structure of thermosoftening polymers and how this determines their properties:

A

Thermosoftening polymers are made up of individual polymer chains that are tangled together. The forces between the polymer chains are weak and when you heat the polymer, these weak intermolecular forces are broken and the polymer becomes soft. When the polymer cools down, the intermolecular forces bring the polymer molecules back together so the polymer hardens again. This means it can be heated to mould it into shape and it can be remoulded by heating it again

84
Q

Explain the molecular structure of thermosetting polymers and how this determines their properties:

A

The polymers set hard when they are first moulded because strong covalent bonds form cross-links between the polymer chains. The strong covalent bonds hold the polymer chains in position

85
Q

What are the 2 types of glass?

A
  • Soda-lime glass

* borosilicate glass

86
Q

What is the most common type of glass?

A

Soda-lime glass

87
Q

How is soda-lime glass produced?

A

Sand, limestone, and sodium carbonate are heated together to produce glass

88
Q

How is borosilicate glass produced?

A

it is produced from sand and boron trioxide

89
Q

What are the differences in properties between soda-lime glass and borosilicate glass?

A

Borosilicate glass has a much higher melting point than soda-lime glass

90
Q

How are ceramics produced?

A

They are made by moulding wet clay into shapes and then heating them in a furnace

91
Q

What are the properties of ceramics?

A

They are electrical insulators and resistant to chemical attack. They are brittle

92
Q

What 2 materials are composites produced from?

A
  • Matrix (binder)

* Reinforcement (fibres/fragments of another material)

93
Q

Name 3 examples of composites:

A
  • Glass-ceramic composite
  • Fibreglass
  • concrete
94
Q

What is the process of producing a composite called?

A

Reinforcement

95
Q

What does a matrix do?

A

It surrounds and binds together fibres of another material

GCSE Chemistry (15 decks)

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