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Chemistry > Topic 9: Separate chemistry 2 > Flashcards

Topic 9: Separate chemistry 2 Flashcards

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1
Q

Explain why the test for any ion must be unique

A

you would never be able to know which specific ion it was if more than one ion gave the same result

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2
Q

Describe flame tests to identify the following ions in solids

A 
● Lithium ion, Li+ (red)
● Sodium ion, Na+ (yellow)
● Potassium ion, K+ (lilac)
● Calcium ion, Ca2+ (orange-red)
● Copper ion, Cu2+ (blue-green)
○ For each of the above you just need to hold a sample you wish to test on a wire in a roaring bunsen burner flame and observe the flame colour
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3
Q

Describe tests to identify the following ions in solids or solutions: Aluminium ion Al3+

A

● Aluminium ion, Al3+

○ White precipitate (dissolves when excess NaOH is added)

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4
Q

Describe tests to identify the following ions in solids or solutions:Calcium ion, Ca2+

A

● Calcium ion, Ca2+

○ White precipitate

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5
Q

Describe tests to identify the following ions in solids or solutions: Copper ion, Cu2+

A

● Copper ion, Cu2+

○ Blue precipitate

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6
Q

Describe tests to identify the following ions in solids or solutions: Iron (II) ion, Fe2+

A

● Iron (II) ion, Fe2+

○ Green precipitate

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7
Q

Describe tests to identify the following ions in solids or solutions: Iron (III) ion, Fe3+

A

● Iron (III) ion, Fe3+

○ Brown precipitate

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8
Q

Describe tests to identify the following ions in solids or solutions: Ammonium ion, NH4+

A

● Ammonium ion, NH4+
○ Pungent-smelling gas is produced
○ This gas produced turns damp red litmus paper blue

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9
Q

Describe the chemical test for ammonia

A

● Makes damp red litmus paper turn blue
● It also forms a white smoke of ammonium chloride when hydrogen chloride gas, from concentrated hydrochloric acid, is held near it

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10
Q

Describe tests to identify the following ions in solids or solutions as appropriate: Carbonate ion, CO3^2-

A

● Carbonate ion, CO3^2-, using dilute acid and identifying the CO2 evolved
○ Gas produced bubbled through limewater, if the limewater goes cloudy, the gas is CO2 (carbonates react with dilute acids to produce CO2)

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11
Q

Describe tests to identify the following ions in solids or solutions as appropriate: Sulfate ion, SO4^2-

A

● Sulfate ion, SO4^2-, using dilute hydrochloric acid and barium chloride solution
○ Add dilute HCl followed by barium chloride solution
○ A white precipitate will form when sulfate ions are in this solution

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12
Q

Describe tests to identify the following ions in solids or solutions as appropriate: Chloride ion(Cl-), Bromine ion (Br-), and Iodine ion (I-)

A

● Chloride ion, Cl-, bromide ion, Br-, iodide ion, I-, using dilute nitric acid and silver nitrate solution
○ First add dilute nitric acid, followed by silver nitrate solution
○ Chloride gives a white precipitate
○ Bromide gives a cream precipitate
○ Iodine gives a yellow precipitate

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13
Q

Describe that instrumental methods of analysis are available and that these may improve sensitivity, accuracy and speed of tests

A

● Elements and compounds can be detected and identified using instrumental methods
o These are accurate, sensitive and rapid
● instrumental methods include: gas chromatography and mass spectrometry

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14
Q

Evaluate data from a flame photometer: to determine the
concentration of ions in dilute solution using a calibration curve, and to identify metal ions by comparing the data with reference data

A

● Example of an instrumental method used to analyse metal ions in solutions
● Sample is put into a flame and the light given out is passed through a photometer
● Output is a line spectrum that can be analysed to identify the metal ions in the solution and measure their concentrations

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15
Q

Recall the formulae of molecules of the alkanes, methane, ethane, propane and butane

A

● Alkane molecules can be represented in the following forms:
● The first 4 alkanes are methane, ethane, propane and butane (MEPB: Monkeys
Eat Peanut Butter)
CnH2n+2

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16
Q

why are the alkanes are saturated hydrocarbons?

A

● They contain no C=C double bonds and are compounds made of hydrogen and carbon only

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17
Q

Recall the formulae of molecules of the alkenes, ethene, propene, butene,

A

CnH2n

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18
Q

Explain why the alkenes are unsaturated hydrocarbons, describing that their molecules contain the functional group C=C

A

● Contain one or more C=C double bonds and are compounds made of hydrogen and carbon only

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19
Q

Recall the addition reaction of ethene with bromine, showing the structures of reactants and products, and extend this to other alkenes

A

● Ethene + bromine -> 1,2-dibromoethane

● this reaction works the same for any alkene or any halogen

20
Q

Explain how bromine water is used to distinguish between alkanes and alkenes

A

● Alkenes react with bromine water, turning it from orange to colourless – alkanes DO NOT react with bromine water

21
Q

]Describe how the complete combustion of alkanes and alkenes involves the oxidation of the hydrocarbons to produce carbon dioxide and water

A

● The combustion of hydrocarbons releases energy. During combustion, the carbon and hydrogen in the fuels are oxidised to produce carbon dioxide and water
alkane/alkene + oxygen → carbon dioxide + water

22
Q

What is a polymer?

A

● A polymer is a substance of high average relative molecular mass made up of small repeating units

23
Q

Describe: how ethene molecules can combine together in a polymerisation reaction

A

● Alkenes can be used to make polymers such as poly(ethene) and poly(propene) by addition polymerisation.

In this reaction, many small molecules (monomers) join together to create very large molecules (polymers).

● The repeat unit has the same atoms as the monomer because no other molecule is formed in the reaction

24
Q

Describe how other addition polymers can be made by combining together other monomer molecules containing C=C

A

any alkene can be used as a monomer to create a polymer due to the C=C bond

25
Q

Deduce the structure of a monomer from the structure of an addition polymer and vice versa

A

▪ Monomer is the same as the repeat unit, just replace C-C with C=C and remove brackets and “n”

26
Q

Explain how the uses of polymers are related to their properties:
Poly(ethene)

A

● Poly(ethene)
○ Properties: flexible, cheap, electrical insulator
○ Uses: plastic bags and bottles, coating on electrical wires

27
Q

Explain how the uses of polymers are related to their properties:
Poly(propene)

A

● Poly(propene)
○ Properties: flexible & strong
○ Uses: buckets and crates

28
Q

Explain how the uses of polymers are related to their properties:
Poly(chloroethene) or PVC

A

● Poly(chloroethene) or PVC
○ Properties: tough, cheap and long lasting
○ Uses: window frames

29
Q

Explain how the uses of polymers are related to their properties:
poly(tetrafluoroethene) (PTFE)

A

● PTFE
○ Properties: tough & non-stick
○ Uses: non-stick coating on pans

30
Q

Why polyesters are condensation polymers:

A

○ In condensation polymerisation, a small molecule is formed as a by-product each time a bond is formed between two monomers

○ Alcohol and carboxylic acid functional groups react, losing a small molecule – water

○ This is an ester – therefore a polyester is a lot of these monomers (esters)

31
Q

How a polyester is formed when a monomer molecule containing two carboxylic acid groups is reacted with a monomer molecule containing two alcohol groups

A

○ the dicarboxylic acid loses the OH group off of each COOH group
○ the di-alcohol loses the H off of each OH group
○ the remaining molecules join together to make a polyester

32
Q

How a molecule of water is formed each time an ester link is formed?

A

○ the OH and H groups combine to make H2O

33
Q

Evaluate the advantages and disadvantages of recycling polymers

A

● Advantages
○ Reuse waste materials – better for environment than burning them or
putting them in landfills
○ Saves crude oil (a finite resource)
○ More economically viable instead of making more polymers

● Disadvantages
○ Difficult and expensive to first separate the different polymers (they need
to be sorted into types)

34
Q

DNA

A

DNA is a polymer made from 4 different monomers called nucleotides (names of
nucleotides not required)
● Starch is a polymer based on sugars
● Proteins are polymers based on amino acids

35
Q

Recall the formulae of molecules of the alcohols

A

● Alcohols contain the functional group –OH
● The first 4 members of the series are methanol, ethanol, propanol and butanol
methanol CH3OH
ethanol CH3CH2OH
propanol CH3CH2CH2OH
butanol CH3CH2CH2CH2OH

36
Q

What is the functional group in alcohols?

A

the functional group in alcohols is –OH

37
Q

Core Practical: Investigate the temperature rise

produced in a known mass of water by the combustion of the alcohols ethanol, propanol, butanol, and pentanol

A

● in this experiment, you should find that the temperature is raised more as the chain length of the alcohols increases, because the combustion of longer chain alcohols releases more energy

38
Q

Recall the formulae of molecules of the carboxylic acids

A

● Ethanoic acid is a member of the carboxylic acids, they have the functional group –COOH.
● First four members are: methanoic acid, ethanoic acid,
propanoic acid and butanoic acid
methanoic acid CHOOH
ethanoic acid CH3COOH
propanoic acid CH3CH2COOH
butanoic acid CH3CH2CH2COOH

39
Q

What is the functional group in carboxylic acids?

A

The functional group in carboxylic acids is –COOH

40
Q

Recall that ethanol can be oxidized to produce ethanoic acid and extend this to other alcohols (reagents not required)

A

● Ethanol can be oxidised to form ethanoic acid.

● any alcohol can be oxidised to produce a carboxylic acid (e.g. propanol →propanoic acid)

41
Q

Why do members of a given homologous series have similar reactions?

A

members of a given homologous series have similar reactions because their molecules contain the same functional group

42
Q

Describe the production of ethanol by fermentation of carbohydrates

A

● Ethanol can be produced by fermentation with yeast, using renewable sources.

● it is produced from carbohydrates (can be sugars from
fruit or starch)

● mixture must be kept warm and under anaerobic conditions (warm- so reaction is fast enough but yeast doesn’t denature. Anaerobic- only carbon dioxide and
water would be produced if not)

glucose → ethanol + carbon dioxide
C6H12O6 → 2C2H5OH+ 2CO2

43
Q

Explain how to obtain a concentrated solution of ethanol by fractional distillation of the fermentation mixture

A

● Ethanol concentration is about 15% from fermentation, ethanol is separated from the reaction mixture using fractional distillation

○ water and ethanol solution are heated
○ ethanol evaporates first (has a lower boiling point than water), cools, then condenses
○ water left evaporates, cools, then condenses

44
Q

Compare the size of nanoparticles with the sizes of atoms and molecules

A

● Nanoparticles are 1-100 nanometers across.
● They contain a few hundred atoms.
● Nanoparticles, are smaller than fine particles, which have diameters between 100 and 2500 nm (1 x 10-7 m and 2.5 x 10-6 m).
● As the side of cube decreases by a factor of 10 the surface area to volume ratio increases by a factor of 10

45
Q

Describe how the properties of nanoparticulate materials are related to their uses

A

● Nanoparticles involve fullerenes.
● A nanoparticle has different properties to the ‘bulk’ chemical it’s made from, because of their high surface area to volume ratio. It may also mean that smaller
quantities are needed to be effective than for materials with normal particle sizes. e.g fullerenes have different properties to big lumps of carbon.
● They have a high surface area to volume ratio, and therefore would make good catalysts.
● They can also be used to produce highly
selective sensors.
● Nanotubes could make stronger, lighter
building materials.
● New cosmetics, e.g sun tan cream and
deodorant. They make no white marks.
● Lubricant coatings, as they reduce
friction. These can be used for artificial joints and gears.
● Nanotubes conduct electricity, so can be
used in small electrical circuits for computers.

46
Q

Explain the possible risks associated with some nanoparticulate materials

A

● Some worries that they may be harmful to health – i.e. enter bloodstream and cause harm
● A lot of effects of nanoparticulate materials are unknown and this is worrying for some people as risks are not fully known

47
Q

Compare the physical properties of glass and clay

ceramics, polymers, composites and metals

A

● glass ceramics: transparent, hard, brittle, poor heat and electrical conductors
o uses: windows, bottles

● clay ceramics: opaque, hard, brittle, poor heat and electrical conductors
o uses: bricks and porcelain

● polymers: can be made transparent/translucent/opaque, poor heat and
electrical conductors, can be tough or ductile
o uses: plastic bags, bottles

● metals: shiny, good heat and electrical conductors, hard, tough
o uses: cars, bridges, electrical cables

Chemistry (10 decks)

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