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CHEMSITRY > CHAPTER 15 > Flashcards

CHAPTER 15 Flashcards

1
Q

what is corrosion caused by

A

chemical reactions between the metal and chemicals in the environment

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2
Q

what is rusting

A

the corrosion of iron

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3
Q

what two conditions are needed for iron to rust

A

oxygen and water

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4
Q

why des the mass of iron increase as it rusts

A

the atom bond with the oxygen and water molecules which makes a compound that is heavier than iron

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5
Q

equation for the rusting of iron III

A

iron + oxygen+ water-> hydrated iron III oxide

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6
Q

what happens to the iron when it rusts

A

it is oxidised

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7
Q

3 ways of barriers to stop rusting

A

paint
oil
plastic

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8
Q

what is the sarcrifical method of preventing rusting

A

a more reactive metal is placed onto the iron so the iron stays intacts

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9
Q

what happens when iron is galvanised

A

it is covered with a layer of zinc so the oxygen and water oxidise and react with zinc and not iron

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10
Q

why isn’t aluminium completely destroyed by corrosion

A

aluminium oxide forms a protective layer that stops any further reaction taking place

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11
Q

why is iron completely destroyed by rusting

A

iron oxide is flaky and will fall off to leave more iron exposed to react again

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12
Q

what is an alloy

A

a mixture of a metal and another material

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13
Q

why are allows much harder than normal metals

A

the structure of the metal so disrupted so the layers cant slide over eachother

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14
Q

what is bronze made from

A

copper + tin

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15
Q

why is bronze better than copper

A

it is much harder

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16
Q

uses of bronze 3

A

makes medals
decorative
ornaments and statues

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17
Q

what is brass made from

A

cooper + zinc

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18
Q

why is brass better than bronze

A

it is more malleable and is used where there needs to be little friction

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19
Q

uses of brass 3

A

musical
instruments taps
door fittings

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20
Q

what is the most useful property of aluminium

A

it is low density

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21
Q

why is aluminium alloyed

A

to make it stronger

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22
Q

uses of aluminium alloys 2

A

aircraft

plating on military vehicles

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23
Q

why is gold alloyed

A

to make it stronger

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24
Q

why is copper mixed with gold

A

it is more long wearing

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25
Q

uses of gold alloys

A

jewellery

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26
Q

what is 24 carat gold

A

pure gold

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27
Q

how to work out how much gold is in a carat

A

divide by 24

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28
Q

what are steels

A

alloys of iron with carbon and other elements

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29
Q

what are the simplest steels

A

carbon steels

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30
Q

how are carbon steels made

A

most of the carbon is removed from the iron

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31
Q

uses of carbon steels 3

A

car bodies
ships
structural ships

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32
Q

properties of high carbon steels

A

strong but brittle

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33
Q

properties of low carbon steels 2

A

soft and easily shaped

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34
Q

what are nickel steel alloys used for and why

A

long span bridges , bicycle chains resistant to stretching forces

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35
Q

what is stainless steel made from

A

chromium and nickel

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36
Q

characteristics of stainless steel 2

A

don’t rust

very strong

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37
Q

uses of stainless steels

A

cutlery

cooking utensils

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38
Q

what do the properties of a polymer depend on

A

the monomers used to make it

the conditions under which the reaction happened

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39
Q

what are the two types of polyethene

A

low density polyethene

high density polyethene

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40
Q

how is low density polyethene made

A

very high

temperaatures and a catalyst

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41
Q

what is ld polyethene used for and why

A

plastic bad and bottles

it is very flexible

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42
Q

what gives ld polyethene its lolw density

A

the polymer chains are randomly branched and cant pack closely together

43
Q

how is hd polyethene made

A

lower temperature and a different catalyst

44
Q

uses of LD polyethene and why

A

water tanks

it is very rigid

45
Q

what gives HD polyethene its high density

A

the polyethene chains are straighter and can pack together more closely

46
Q

what are thermosetting polymers

A

the don’t soften when heated because of cross links between polymer chains

47
Q

what are thermosoftening polymers

A

they soften when heated

made of individual polymer chains tangled together

48
Q

what allows thermosoftening polymers to soften under heat

A

weak intermolecular forces between polymer chains that need little energy to overcome
when it cools the forces bring the polymer back together again

49
Q

what stops thermosetting polymers from softening under heat

A

the monomers from covalent cross links between polymer chains which are strong an wont soften

50
Q

what is glass mainly made from

A

sand

51
Q

how is glass made

A

the raw materials are heated - sand limestone and sodium carbonate
they melt and react to form molten glass
when they cool, they remain in this disorganised structure

52
Q

how to make different types of glass

A

use different raw materials

53
Q

what is different about borosilicate glass and what is it used for

A

it has boron trioxide in it

it is used for oven ware as it has a high melting point

54
Q

what are ceramics

A

non metal solids with high melting points that aren’t made from carbon based compounds

55
Q

examples of ceramics made from clay 3

A

bricks crockery and toilets

56
Q

how are clay ceramics made

A

wet clay is moulded into desired shape and heated

57
Q

why do the properties of clay change so drastically when heated

A

there is ionic bonding between metals and non metals in clay covalent bonding
between non metals arranged in giant layers when wet water gets between layers and makes them slimy
when they are heated water is driven out and strong bonds for between layers

58
Q

what are composites made from

A

one materials embedded in another

59
Q

4 examples of composites

A

fibreglass
carbon fibre
concrete
wood

60
Q

why is natural wood so srong

A

cellulose

61
Q

what is a matrix in a composite

A

it acts as a bonder and holds everything together

62
Q

what is fibreglass made from

A

fibre of glass embedded in a matrix made of plastic

63
Q

properties of fibreglass 2

A

low density

very strong

64
Q

what is fibreglass used for 3

A

skis
boats
surfboards

65
Q

what is concrete made from

A

aggregate embedded in cement

66
Q

use of concrete

A

buiding materials

67
Q

what is carbon fibre made form

A

long chains of carbon atoms in plastic

carbon nanotubes in plastic

68
Q

use of carbon fibres

A

aerospace
sports car
manufacturing

69
Q

what do most fertilisers contain

A

nitrogen

phosphorous and potassium

70
Q

why do fertilisers contain nitrogen and similar nutrients

A

crops grow and absorbs nutrients for growth
farmers harvets plants so little of the plant is allowed to decompose and add nutrient back into the soil
so farmers hve to replace the missing nutrients or provide more of them

71
Q

even though there is a lot of nitrogen in the air why don’t plants absorb it

A

the gas is insoluble in water and plants can only absorb a soluble form of nitrogen

72
Q

even though there is a lot of nitrogen in the air, why don’t plants absorb it

A

the gas is insoluble in water and plants can only absorb a soluble form of ntirogen

73
Q

what is the haber process

A

nitrogen and hydrogen are converted to ammonia which is used in fertilisers

74
Q

who created the haber process

A

german scientist

fritz haber

75
Q

what I the most important us of ammonia

A

fertilisers

76
Q

how is the nitrogen for the haber process sources

A

obtained from the air

77
Q

how is hydrogen sourced for the haber process

A

methane is reacted with steam to form hydrogen and carbon dioxide

78
Q

what are the three conditions used in the haber process

A

iron catalyst
high temperature
high pressure

79
Q

the haber process

A

nitrogen and methane are sourced they are passed over an iron catalyst at high temperature and pressure
this reaction is reversible so some ammonia formed is converted back to the raw materials a dymanic equilibrium is reached. ammonia formed as a gas it is collected condensed and turned into fertiliser. the unused reactants are recycled so nothing is wasted

80
Q

how is ammonia obtained from the haber process

A

te gases are cooled ammonia liquefies and can be separated

81
Q

equation for haber process

A

nitrogen + hyfrogen ammonia + heat

82
Q

equation for the formation of hydrogen

A

methane + steam-> hydrogen + carbon dioxide

83
Q

why are fertilisers used

A

replace missing nutrients increases crop yield

crops grow faster and bigger

84
Q

how to create ammonia nitrate

A

ammonia + nitric acid

85
Q

how is ammonia phosphate formed

A

ammonia + phosphoric acid

86
Q

when are salts formed

A

when acids and alkalis react together in a neutralisation reaction

87
Q

is ammonia solution alkali or acid

A

alkali

88
Q

how is ammonium nitrate formed in industry

A

in gaint vats high concentrations very exothermic reaction

then heat released evaporates water, leaving a very concentrated ammonium nitrate product

89
Q

how is ammonim nitrate formed in the lab

A

smaller scale titration and crystallisation reactants are at a lower concentration less heat produced after titration, the solution is crystallised to result in pure ammonium nitrate crystals

90
Q

why is crystallisation not used in industry

A

it is too slow

91
Q

ho to make ammonium sulfate

A

react ammonia with sulfuric acid

92
Q

what is npk fertiliser

A

nitogren , phosphorous and potassium fertiliser

93
Q

where to source phosphorous

A

rocks

94
Q

why is acid added to phosphorous rocks

A

plants cant use it as it is insoluble in water

95
Q

what is produced when phosphate rock is reacted with nitric acid

A

phosphoric acid and calcium nitratr

96
Q

what is produced when phosphate rock is react with sulfuric acid

A

calcium suflate and calcium phosophate also known as single superphosphate

97
Q

what is produced when phosphate rock is reacted with phosphoric acid

A

tripe superphosphate

98
Q

how is nitrogen obtained from air

A

air Is cooled to -200 c to liquefy it fractional distillation happens

99
Q

reaction for methane+ steam

A

methane + steam-> hydrogen + carbon monoxide

100
Q

what is the main cost of producing ammonia

A

sourcing the methane, which is a natural gas

101
Q

why is 200 atmospheres of pressure used

A

there are less moles of ammonia then reactants so higher pressure - higher yield
but higher pressure is also expensive and dangerous so 200 atmospheres is a compromise

102
Q

why is an iron catalyst used

A

it speeds up both the forward and reverse reaction doesnt affect yield of ammonia but makes it be produced quicker

103
Q

what is the forward reaction of the production of ammonia

A

exothermic

104
Q

why is 450 c used for the haber process

A

forward reaction is exothermic increasing temperature = less yield
bbut decreasing temperature = slower rate of reaction and minimises effect of catalyst
450 c is a compromise between maxiumum yield and speed of reaction

CHEMSITRY (13 decks)

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