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CHEMISTRY > SC9: separate chemistry 2 > Flashcards

SC9: separate chemistry 2 Flashcards

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1
Q

flame test method

A

1) dip a clean wire loop into a solid sample of the compound being tested
2) put the loop into the edge of the blue flame from a bunsen burner
3) observe and record the flame colour produced

(sterilise by dipping into acid and putting into flame)

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2
Q

each metal ion produces a …
flame test colour

A

different

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3
Q

flame test: lithium

A

red

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4
Q

flame test: sodium

A

yellow

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5
Q

flame test: potassium

A

lilac

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6
Q

flame test: calcium

A

orange-red

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7
Q

flame test: barium

A

green

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8
Q

flame test: copper

A

blue-green

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9
Q

precipitate test for positive ions (steps)

A

1) add sodium hydroxide to the metal ion solution

2) look at the colour

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10
Q

precipitate test for positive ions: aluminium

A

white

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11
Q

precipitate test for positive ions: calcium

A

white

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12
Q

precipitate test for positive ions: copper

A

blue

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13
Q

precipitate test for positive ions: iron (II)

A

green

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14
Q

precipitate test for positive ions: iron (IIII)

A

brown

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15
Q

how to distinguish between aluminium and calcium ions

A

if excess is added to aluminium hydroxide, a colourless solution forms

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16
Q

test for ammonium ions

A

1) add dilute sodium hydroxide solution to the sample

2) warm the mixture over a bunsen burner

3) ammonia gas is given off if ammonium ions are present

4) damp red litmus turns blue is ammonia is present

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17
Q

testing for carbonate ions (negatively charged ions)

A

-an acid, such as dilute hydrochloric acid, is added to the test compound
-bubbles are given off due to carbon dioxide
-limewater is used to confirm that the gas is carbon dioxide, it turns milky when carbon dioxide is bubbled through it

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18
Q

testing for sulfate ions (negatively charged ions)

A

-add a few drops of dilute hydrochloric to the sample
-add a few drops of dilute barium chloride solution
-a white precipitate forms if sulfate ions are present

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19
Q

why is hydrochloric acid added before barium chloride solution in testing for sulfate ions?

A

to remove carbonate ions, which also forms a white precipitate with barium chloride solution, this way no false positive result is made

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20
Q

testing for halide ions (negative ions)

A
  1. add a few drops of dilute nitric acid to the sample
  2. add a few drops of dilute silver nitrate solution (silver reacts with halide ions to form precipitates)
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21
Q

negative ion test for halide ions: chloride

A

white

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22
Q

negative ion test for halide ions: bromide

A

cream

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23
Q

negative ion test for halide ions: iodide

A

yellow

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24
Q

why, in a test for halide ions, is the sample acidified with dilUte nitric acid first?

A

-carbonate ions also produce a white precipitate with silver nitrate solution
-the acid reacts with any carbonate ions present
-removing silver nitrate solutions stops them giving an incorrect positive result for chloride ions

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25
Q

why, in a test for halide ions, can’t dilute hydrochloric acid be used to acidify the sample?

A

-hydrochloric acid, contains chloride ions these would react with silver ions in the test, giving a false positive result

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26
Q

how to identify the ions in unknown salts

A

-flame tests (observe the flame colour)
-hydroxide precipitate tests (add a few drops of dilute sodium hydroxide solution & observe the colour of the precipitate formed)
-test for ammonium ions (add a few drops of dilute sodium hydroxide solution, then warm gently, ammonia gas is produced if ammonium ions are present; tested with litmus)
-test for carbonate ions (few drops of dilute hydrochloric acid, bubbles prod if carbonate ions are present; limewater turns milky)
-test for sulfate ions (few drops of dilute hydrochloric acid, then barium chloride solution, white precipitate formed if sulfate ions are present)
-test for halide ions (few drops of dilute nitric acid, few drops of silver nitrate solution, observe colour of precipitate)

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27
Q

instrumental methods of analysis

A

-faster, more accurate and more sensitive than simple chemical tests
-some are suitable for detecting and identifying elements, while others are better suited to compounds

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28
Q

the flame photometer

A

a scientific instrument based on flame testing

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29
Q

what can data from a flame photometer be used to do?

A

-identify metal ions in a sample
-determine the concentration of metal ions in dilute solutions

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30
Q

each metal ion produces a…

A

unique emission spectrum

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31
Q

emission spectrum

A

light given off by a substance, split into its component colours or wavelengths

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32
Q

how is the metal present in a sample identified?

A

by comparing its spectrum with reference spectra

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33
Q

what does it mean if two spectra match?

A

they must be from the same metal ion

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34
Q

what is an addition reaction?

A

one molecule combines with another molecule, forming one larger molecule and no other products

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35
Q

alkanes: homologous series

A

-saturated hydrocarbon

-have the same general formula
-differ by CH2 in molecular formulae from neighbouring members of the series
-show a gradual variation in physical properties, such as their boiling points
-have similar chemical properties

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36
Q

alkenes: homologous series

A

-unsaturated hydrocarbons

-have the same general formula
-differ by CH2 in molecular formulae from neighbouring compounds
-show a gradual variation in physical properties, such as their boiling points
-have similar chemical properties

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37
Q

general formula for alkenes

A

CnH2n

(where n is the number of carbon atoms in the molecule)

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38
Q

functional group of alkenes

A

C=C

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39
Q

functional groups of alkanes

A

C-C

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40
Q

what are functional groups responsible for?

A

the typical reactions of the homologous series

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41
Q

which reactions can alkanes vs alkenes go through

A

alkanes
-combustion

alkenes
-combustion
-addition reactions

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42
Q

distinguishing between alkanes and alkenes

A

-there is no change when bromine water is mixed with an alkane
-the bromine water becomes colourless when it is mixed with an alkene

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43
Q

polymer

A

a large molecule formed from many identical, repeating smaller molecules known as monomers

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44
Q

poly(ethene)

A

-a polymer made from a very large number of ethene molecules combined together

polymerisation reaction:
-ethene is the monomer
-poly (ethene) is the polymer

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45
Q

polymerisation reaction

A

many monomers combine together to form a polymer

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46
Q

how can you model addition polymers

A

-show the structure of its repeating unit
1) draw the structure of the monomer but use C–C instead of C=C
2) draw brackets around the structure with a long bond passing through each bracket
3) put an n next to the bracket on the right side

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47
Q

properties and uses of poly(ethene) / polythene

A

-flexible, cheap, can be made into thin films

-carrier bags, shampoo bottles, food wrap

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48
Q

properties of poly (propene) / polypropylene

A

-flexible, strong, resists shattering

-buckets, bowls, crates, ropes, carpets

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49
Q

properties of poly (chloroethene)/PVC

A

-tough, electrical insulator, can be made hard or flexible

-insulation for electrical wires, windows, gutters, pipes

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50
Q

properties of
poly(tetrafluoroethene)/PFTE

A

-slippery, chemically unreactive

-non-stick coatings for pans, containers for laboratory substances

51
Q

polymers & biodegradability

A

-not biodegradable, microorganisms can’t break them down
-they cause a litter problem if disposed of carelessly
-last for many years in landfill sites
-space in landfill sites is wasted if it is filled with non-biodegradable polymers

52
Q

polymers & combustion

A

-waste polymers can be incinerated, this involves combustion at very high temperatures

53
Q

problems with combustion

A

-carbon dioxide is produced (greenhouse gas)
toxic gases are produced eg: sulfur dioxide

54
Q

benefits of combustion

A

-incineration releases a lot of energy which can be used to heat homes or generate electricity

55
Q

polymers & recycling

A

-the use of landfill and incineration wastes valuable resources
-crude oil is the raw material for making most polymers, it is finite
-recycling reduces the problems of disposal & reduces the volume of crude oil used

56
Q

what does recycling of polymers include

A

-melting the waste polymer
-forming the polymer into a new product

57
Q

benefits of recycling polymers

A
58
Q

problems of recycling polymers

A

-different polymers must be separated from each other before recycling, this can be difficult and expensive to do

59
Q

biological polymers

A

made naturally by living organisms

60
Q

DNA

A

-a polymer made from four different monomers, called nucleotides
-these join together in different combinations to make long strands
-in a DNA molecule, two strands wrap around each other to form a double helix structure

61
Q

starch

A

-polymer made from sugar monomers
-starch molecules contain many glucose molecules, joined together in long chains with branches

62
Q

protein

A

-polymers made from different monomers, called amino acids
-these join together in different combinations to make long strands, which then fold into complex shapes

63
Q

condensation polymers

A

-long molecules produced during condensation polymerisation
-form in a different way to addition polymers
-instead of forming just the polymer molecule, a polymer molecule and a small molecule (often water) form

64
Q

forming esters

A

an ester forms when an alcohol reacts with a carboxylic acid

65
Q

what two monomers are formed by polyester?

A

-a ‘dicarboxylic acid’ which contains two carboxylic acid groups (–COOH)
-a ‘diol’ which contains two alcohol groups, –OH

66
Q

addition polymerisation vs condensation polymerisation

A

-addition polymerisation needs one type of monomer and forms one product
-to form polyesters, condensation polymerisation needs two types of monomer and forms two products

67
Q

what do the alcohols form

A

a homologous series

68
Q

homologous series’s…

A

-have the same general formula
-differ by CH2 in molecular formulae from neighbouring compounds
-show a gradual variation in physical properties, such as their boiling points
-have similar chemical properties

69
Q

functional group of the alcohols

A

-the hydroxyl group, –OH.
-It is responsible for the typical reactions of alcohols

70
Q

general formula for the alcohols

A

CnH2n+1OH
(where n is the number of carbon atoms in the molecule)

71
Q

complete combustion of alcohols

A

alcohol + oxygen → carbon dioxide + water

72
Q

chemical oxidisation of alcohols

A

-alcohols can also be chemically oxidised, without combustion in oxygen (with an oxidising agent), to produce carboxylic acids

73
Q

how are oxidising agents shown?

A

[O]

74
Q

ethanol + oxidising agent → ethanoic acid + water

A

CH3CH2OH + 2[O] → CH3COOH + H2O

75
Q

how to name a carboxylic acid

A

-oic acid

76
Q

where is ethanol found?

A

-alcoholic drinks
-used as a fuel for vehicles, either on its own or mixed with petrol

77
Q

how can ethanol be produced?

A

fermentation

78
Q

how can ethanol be concentrated?

A

using fractional distillation

79
Q

what type of process is fermentation

A

anaerobic

80
Q

fermentation equation

A

glucose → ethanol + carbon dioxide

81
Q

yeast for fermentation

A

-yeast is a type of single-celled fungus, -it provides the enzymes needed for fermentation
-if the yeast cells become too cold, fermentation happens very slowly, or may not happen at all
-if the yeast cells become too hot, their enzymes become denatured and fermentation stops

82
Q

typical conditions needed for fermentation

A

-sugars dissolved in water, and mixed with yeast
-an air lock to allow carbon dioxide out, while stopping air getting in
-warm temperature, 25-35°C

83
Q

when does yeast die in fermentation?

A

when the ethanol concentration reaches about 15%

84
Q

how long does fermentation take to finish?

A

several days or weeks (slow process)

85
Q

what happens if air is present in fermentation?

A

the oxygen causes the ethanol to oxidise to ethanoic acid, so the drink tastes of vinegar

86
Q

test for carbon dioxide

A

the gas is bubbles through limewater and the limewater turns cloudy

87
Q

what does the fermentation mixture contain once fermentation has finished?

A

yeast cells and insoluble substances, which are separated from the impure ethanol solution by filtration

88
Q

ethanol from fractional distillation

A

-fractional distillation is used to produce a concentrated solution of ethanol from the filtrate
-this works because ethanol and water have different boiling points
-when the mixture is heated, ethanol evaporates more readily

89
Q

steps of ethanol’s fractional distillation

A
  1. water and ethanol solution is heated
  2. the ethanol evaporates first, cools, then condenses after being led out
  3. the water left evaporates, cools, then condenses
90
Q

why is is better to use an electric heater than bunsen burner in fractional distillation?

A

ethanol liquid and vapour are highly flammable, and could be set on fire by accident

91
Q

what are carboxylic acids

A

a homologous series

92
Q

what is the functional group in the carboxylic acids?

A

-the carboxyl group, –COOH
-it is responsible for the typical reactions of carboxylic acids

93
Q

what strength are carboxylic acids?

A

weak

94
Q

carboxylic acid properties

A

-dissolve in water to form acidic solutions
-react with metals to form a salt and hydrogen
-react with bases to form a salt and water
-react with carbonates to form a salt, water and carbon dioxide

95
Q

core practical: investigate the combustion of alcohols (aim)

A

-to investigate the temperature rise produced in a known mass of water by the combustion of ethanol, propanol, butanol and pentanol
-these alcohols can be supplied in spirit burners that have a wick and a lid

96
Q

core practical: investigate the combustion of alcohols (steps)

A
  1. use a stand, boss and clamp to secure a conical flask over a spirit burner. adjust the height of the can so that the lid of the burner can be removed and replaced safely
  2. measure and record the mass of a spirit burner with its lid
  3. use a measuring cylinder to add 100 cm³ of cold water to the conical flask. measure and record its temperature
  4. place the spirit burner underneath the conical flask, remove the lid and light the wick
  5. stir the water carefully with the thermometer. when the temperature has increased by about 20°C, replace the lid to put the flame out
  6. measure and record the mass of the spirit burner with its lid, and the maximum temperature of the water
  7. repeat steps 2 to 6 with different alcohols, starting with fresh water each time
97
Q

how to calculate the change in temperature per gram of each alcohol burned

A

change in temperature/mass of fuel burned

98
Q

why should the height of the can
above the wick be kept the same for each experiment?

A

-the distance between the bottom of the can and the wick affects the amount of energy transferred to the water by heating
-it would affect the temperature rise if it was not kept the same

99
Q

core practical: investigate the combustion of alcohols (hazards, risks & precautions)

A

hazard: alcohols are highly flammable liquids, and produce highly flammable vapours

risks: this can cause: burns to the skin, damage by fire

precautions: light the wick with a lighted splint; do not move a spirit burner while it is alight; keep the lab well ventilated

2.
hazard: methanol is toxic in contact with the skin

risks: damage to health

precautions: avoid skin contact

100
Q

nanoparticles

A

tiny particles which are between 1 and 100 nanometres (nm) in size

101
Q

the ____ it’s particles, the greater it’s surface area to volume ratios

A

smaller

102
Q

how to calculate surface area to volume ratio

A

surface area divided by volume

103
Q

what is a nanoparticulate substance?

A

a substance that consists of nanoparticles

104
Q

nanoparticulate substances in sunscreen

A

-titanium dioxide blocks ultraviolet light, so it is used in sunscreens
-in bulk titanium dioxide is white -however, nanoparticulate titanium dioxide has no colour and cannot be seen when it is spread on the skin
-many people prefer nanoparticulate sunscreen because it is not obvious that they are wearing it

105
Q

disadvantages of nanoparticulate sunscreen

A

-tend to clump together, making them difficult to apply
-it may be more difficult to tell where you have applied the sunscreen if you can’t see it on your skin

106
Q

why can nanoparticulate substances act as catalysts

A

-they have large surface area to volume ratios

107
Q

nanoparticulate catalysts compared to normal catalysts

A

-catalyse reactions more efficiently
-catalyse different reactions
-produce different products
-more expensive

108
Q

nanoparticulate substances & self cleaning windows

A

-self-cleaning window panes have nanoparticulate coatings
-these catalyse the breakdown of dirt in the presence of sunlight

109
Q

nanoparticulate substances for wound dressings

A

-silver has antibacterial properties
-nanoparticulate silver is used in some dressings for wounds

110
Q

hazards of nanoparticulate silver

A

could harm or kill useful bacteria in the environment when these dressings are thrown away after use

111
Q

possible risks of nanoparticles

A

-small size of nanoparticles makes it possible to breathe them in, or for them to pass into cells, once inside the body, they might catalyse reactions that are harmful
-toxic substances could bind to them because of their large surface area to volume ratios, harming health if the nanoparticles do get into the body
-modern nanoparticulate materials have only become common recently, so it is difficult for scientists to determine their risks

112
Q

appearance of glass, clay & metals

A

glass: transparent
clay: opaque
metal: shiny

113
Q

melting point of glass, clay & metals

A

glass: high
clay: high
metal: high

114
Q

shapeability of glass, clay & metals

A

glass: brittle
clay: brittle
metal: malleable

115
Q

electric conduction of glass, clay & metals

A

glass:poor
clay: poor
metal: good

116
Q

thermal conduction of glass, clay & metals

A

glass: poor
clay: poor
metal: good

117
Q

composite materials

A

-consists of two or more materials with different properties
-they are combined to produce a material with improved properties

118
Q

what do most composite materials consist of?

A

-the reinforcement (fibres that make up the bulk of a composite material)
-the matrix, which binds the reinforcement together

119
Q

examples of composite materials:

A

reinforced steel:
steel (r) & concrete (m)

fibreglass:
glass fibres (r) & polymer resin (m)

carbon fibre reinforced polymer:
carbon fibres (r) & polymer resin (m)

chipboard
wood chips (r) & resin glue (m)

120
Q

separation of composite materials

A

-it is often possible to separate the reinforcement from the matrix by physical processes

121
Q

fibreglass and carbon fibre

A

-the fibres in these composite materials have a low density
-strong in tension, but they are flexible
-polymer resin which binds the fibres together is not strong, but it is stiff

-the composite materials show a combination of these properties: they are strong, stiff and lightweight

122
Q

chipboard

A

-wood itself is a natural composite material (it consists of a reinforcement of cellulose fibres bonded together by a matrix of lignin, the fibres are aligned alongside each other, so wood is stronger in one direction than it is in the other)

-chipboard contains randomly arranged wood chips bonded together by a glue, so it is strong in all directions

123
Q

chipboard may be supplied with a thin polymer layer glued to its surfaces. suggest reasons that explain why this material is more suitable than chipboard alone for making self-assembly furniture

A

-the polymer can be coloured or patterned to look like wood
-it makes the surface waterproof so it protected from spills and can be cleaned more easily

124
Q

reinforced concrete

A

-properties of concrete can be improved by reinforcing it with steel rods or mesh
-compressive strength of concrete is higher than its tensile strength
-the tensile strength of steel is higher than its compressive strength
-the combination of the two materials is strong in tension and in compression
-reinforced concrete is strong and slightly flexible, which is important when constructing large buildings and structures

CHEMISTRY (9 decks)

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