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Chemistry Paper 2 > C15 Using our resources > Flashcards

C15 Using our resources Flashcards

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1
Q

What makes one metal more reactive than another?

A

How easily they form ions - more reactive ones form ions more readily

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2
Q

What is corrosion?

A

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

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3
Q

What is rusting?

A

The corrosion of iron, both air and water are necessary for iron to rust

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4
Q

What is the word equation for rusting?

A

iron + water + oxygen –> hydrated iron (III) oxide

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5
Q

Describe how rusting can be prevented

A

Providing a barrier between iron and any oxygen and water protects the iron from rusting. For example, coating the iron or steel with:
- paint
- oil or grease
- plastic
- a less reactive metal (electroplating)
- a more reactive metal (galvanising)

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6
Q

What is galvanising?

A

When items are coated with a layer of zinc

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7
Q

What is electroplating?

A
  • This uses electrolysis to place a layer of a less reactive metal over iron
  • The solution contains Cu2+ ions which are replaced by the copper cathode
  • The copper ions are attracted to the cathode, where they are reduced to form copper atoms and are deposited on the object
  • The layer can be made thicker by leaving the equipment running for longer
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8
Q

What is sacrificial protection?

A
  • The covering of iron with zinc
  • Zinc is more reactive than metal such as iron, so will oxidise in preference to the iron
  • Magnesium can also be used
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9
Q

What is an alloy?

A

A mixture of a metal and at least one other element

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10
Q

Why are alloys stronger than pure metals?

A
  • The atoms in pure metals are arranged in densely packed layers
  • These layers can slide over each other
  • When other elements, of different sizes, are added to a pure metal, the layers are distorted
  • These layers can no longer slide over each other
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11
Q

What types of alloys are there?

A

Bronze - an alloy of copper and tin, was commonly used by civilisation before iron extraction methods were developed, it is used today for sculptures, musical instruments
Brass - an alloy of copper and zinc, it does not tarnish and is used for door knobs, buttons and musical instruments
Aluminium alloys - these are lightweight and strong, used in planes and trains

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12
Q

Explain how alloys are used in jewellery

A
  • Gold used in jewellery is usually an alloy as pure gold would be too soft
  • Gold is often alloyed with copper, zinc and/or silver
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13
Q

What do the properties of a polymer depend on?

A
  • The monomers used to make it
  • The conditions chosen to carry out the reaction
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14
Q

Explain the differences between thermosoftening and thermosetting polymers

A
  • Thermosoftening polymers melt when heated, themsofetting polymers do not melt when they are heated
  • Thermosoftening, the polymer chains can move around and over each other, with only weak forces between them, so can be melted easily
  • Themosetting, the polymer chains have covalent bond cross links between chains, meaning that they have very high melting points
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15
Q

What are the raw materials for the production of ammonia?

A
  • Nitrogen from the air
  • Hydrogen, mainly from natural gas
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16
Q

Explain how the ammonia produced is separated from the unreacted nitrogen and hydrogen in the Haber process

A
  • The mixture of gases is cooled
  • So that only the ammonia liquifies
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17
Q

How is the hydrogen for the Haber process formed?

A

Made by reacting methane gas with steam at very high temperatures:
methane + steam –> hydrogen + carbon monoxide

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18
Q

Explain how the Haber process works

A
  • The purified gases are passed over an iron catalyst at a high temperature (about 450 degrees) and a high pressure (about 200 atmospheres)
  • Some of the hydrogen and nitrogen reacts to form ammonia
  • The reaction is reversible so some of the ammonia produced breaks down into nitrogen and hydrogen
  • On cooling, the ammonia liquifies and is removed
  • The remaining nitrogen and hydrogen are recycled to the reactor
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19
Q

What is a polymer?

A

A long chain of repeating monomers

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20
Q

What are some of the properties of glass?

A
  • Transparent
  • Waterproof
  • Brittle
  • High melting point
  • Poor conductor of heat and electricity
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21
Q

How is most glass made?

A

Heating a mixture of sand, sodium carbonate and limestone

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22
Q

What is borosilicate glass?

A
  • Made from sand and boron trioxide
  • Melts at higher temperatures than soda-lime glass
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23
Q

Why is sand a useful component in glass?

A

Sand is silicon dioxide, which is a giant covalent structure, hence the high melting points

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24
Q

What are ceramics?

A

Made by shaping wet clay and then heating in a furnace

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25
Q

What are the typical properties of ceramics?

A
  • Hard
  • Wear-resistant
  • Brittle
  • Heat resistant
26
Q

what are some practical uses of ceramics?

A
  • Pottery
  • Bricks
  • Dinnerware
  • Porcelain
  • Tiles
27
Q

What are composites?

A

Materials produced from two or more constituent materials that have notably dissimilar chemical or physical properties

28
Q

Examples of composites

A

Concrete and fibreglass

29
Q

What are composites made of?

A

Most composites are made of two materials, a matrix or a binder surrounding and binding together fibres or fragments of the other materials, which is called reinforcement

30
Q

What are the two types of glass?

A
  • Soda-lime glass
  • Borosilicate glass
31
Q

What is ammonia used for?

A
  • Used in the manufacture of explosives, plastics, pesticides and textiles
  • Its main use is in the production of fertilisers
32
Q

What process is used to obtain the nitrogen from air?

A

Fractional distillation

33
Q

What catalyst is used for the Haber process?

A

Iron

34
Q

What conditions are needed for the Haber process?

A
  • The raw materials, nitrogen and hydrogen
  • A catalyst, iron
  • Temperatures around 450 degrees
  • A pressure of around 200 atmospheres
35
Q

What conditions affect the yield of ammonia?

A
  • concentration
  • temperature
  • pressure
36
Q

How is the concentration of ammonia kept low?

A

Ammonia is continually condensed and removed

37
Q

How does temperature affect the yield of ammonia?

A
  • A low temperature would give the best yield of ammonia
  • Because the forward reaction is exothermic
  • So equilibrium will shift right to favour the products and increase the temperature
38
Q

Why is a low temperature not used in the Haber process?

A

Although the yield would be best, the rate of reaction would be too slow for the industry

39
Q

How does pressure affect the yield of ammonia?

A
  • A high pressure would give the best yield of ammonia
  • Because there are fewer molecules of ammonia
  • So equilibrium will shift to the right to favour the reaction to form ammonia and reduce the pressure
40
Q

Why is the highest pressure not used?

A
  • Too much energy is needed to increase the pressure
  • Stronger equipment would be needed to withstand such high pressure (costly)
41
Q

How does using a catalyst effect the Haber process?

A
  • The iron catalyst also increases the rate of reaction but it has no effect on the position of equilibrium
  • As it increases the rate of the forward and backward reaction equally, it causes equilibrium to be reached faster
42
Q

Explain the effect of increasing the pressure in the Haber process on the rate of production of ammonia

A
  • An increase in pressure will increase the rate of production of ammonia
  • This is because the particles are closer together
  • Which leads to more frequent collisions and a faster rate of reaction
43
Q

Why does ammonia condense but not the other gases?

A

Ammonia has a higher boiling point

44
Q

What is a formulation?

A

A mixture that is designed to produce a useful product

45
Q

What method is used to obtain soluble salts from a solution?

A

Crystallisation

46
Q

What are fertilisers?

A
  • They are added to crops to increase agricultural productivity
  • To help crop plants grow so that farmers get a better yield
47
Q

Why is nitrogen needed in fertilisers?

A

Needed for cell growth and making proteins in plants

48
Q

Why is phosphorus used in fertilisers?

A

Needed to make DNA

49
Q

Why is potassium needed in fertilisers?

A

Needed to make enzymes involved in respiration and photosynthesis

50
Q

What are NPK fertilisers?

A
  • Formulations of various salts containing appropriate percentages of the elements (nitrogen, phosphorus and potassium)
  • The salts are water soluble so that they can be absorbed into the soil and taken up easily by plant roots
51
Q

How is ammonia made into fertilisers?

A
  • Ammonia made in the Haber process can be turned into nitric acid which can be used to neutralise alkalis to make soluble fertilisers
  • It can also be used as a solution of ammonia hydroxide and neutralised directly to make ammonium salts
52
Q

What is the source of phosphorus in NPK fertilisers and how is it obtained?

A

Phosphate rock is mined, and then treated with acids to form fertilisers, such as ammonium phosphate and calcium phosphate

53
Q

What is the source of potassium in NPK fertilisers and how is it obtained?

A

Potassium salts are mined from the ground for uses as fertilisers, such as potassium chloride and potassium sulfate

54
Q

Why can’t phosphate rock be used directly as a fertiliser?

A

It is insoluble

55
Q

What is the compound found in phosphate rock?

A

Calcium phosphate

56
Q

Which acid is made when phosphate rock is reacted with nitric acid?

A

phosphoric acid

57
Q

compare lab and industrialised production of salts

A
  • Much greater quantities can be made industrially
  • Industrial method is continuous rather than batch
  • Industrial method is much faster
  • Industrial method requires huge quantities of plant machinery
58
Q

what is produced when phosphate rock is treated with nitric acid?

A
  • phosphate rock is treated with nitric acid to produce phosphoric acid and calcium nitrate
  • the phosphoric acid is then neutralised with ammonia to produce ammonia phosphate
59
Q

what is produced when phosphate rock is treated with sulphuric acid?

A
  • phosphate rock is treated with sulphuric acid to produce single superphosphate
  • a mixture of calcium phosphate and calcium sulphate
60
Q

what is produced when phosphate rock is treated with phosphoric acid?

A
  • phosphate rock is treated with phosphoric acid to produce triple superphosphate
  • which is calcium phosphate

Chemistry Paper 2 (9 decks)

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