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AQA Chemistry > Cramming Chemistry Paper 2 > Flashcards

Cramming Chemistry Paper 2 Flashcards

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1
Q

General formula (1 mark)

A

Algebraic formula for a homologous series

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2
Q

Functional group (1 mark)

A

Group of atoms which when present in different molecules, cause them to have similar chemical properties

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3
Q

Homolytic fission (1 mark)

A

When a covalent bond breaks and each atom gets one electron

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4
Q

Heterolytic fission (1 mark)

A

When a covalent bond breaks and one atom gets both electrons

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5
Q

Describe briefly how fractional distillation can be used to convert crude oil into a small number of fractions (6 marks)

A
  • Crude oil is heated and vaporised
  • It is passed into column
  • The hydrocarbons condense at different heights
  • Temperature gradient in column (cooler at the the top)
  • Larger molecules condense at the bottom of the column
  • Similar molecules (in terms of size and boiling point) condense together
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6
Q

Thermal Cracking:
- Conditions
- Main Products
(3 marks)

A
  • High temperature (450 degrees)
  • High pressure (7000kPa)
  • Mainly alkenes and sometimes hydrogen
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7
Q

Catalytic Cracking:
- Conditions
- Main Products
(5 marks)

A

Conditions:

  • Zeolite catalyst
  • High temperature (450 degrees)
  • Moderate pressure

Main products:

  • Cyclic alkanes
  • Aromatic hydrocarbons
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8
Q

Explain how SO₂ can be removed from waste gases in power stations (4 marks)

A
  • Flue gas desulfurisation
  • Gases passed through scrubber containing basic CaO
  • Which reacts with SO₂ in a neutralisation reaction:
  • CaO + SO₂ –> CaSO₃
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9
Q

Environmental consequence of nitrogen oxides (2 marks)

A
  • Toxic

- Can form acid rain

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10
Q

Environmental consequence of carbon monoxide (1 mark)

A
  • Poisonous / toxic
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11
Q

Environmental consequence of carbon dioxide (1 mark)

A

Contributes towards global warming

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12
Q

Environmental consequence of unburnt hydrocarbons (1 mark)

A

Contributes towards formation of smog

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13
Q

Environmental consequence of soot (2 marks)

A
  • Global dimming

- Can lead to respiratory problems

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14
Q

Greenhouse effect (4 marks)

A
  • UV radiation heats surface of Earth
  • Earth radiates IR radiation
  • C=O bonds in CO₂ vibrate at similar frequency to IR bonds so C=O absorb IR
  • Therefore IR does not escape the atmosphere and the atmosphere is warmed
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15
Q

Explain why, even though bromine molecules are non-polar, they react with the double bonds in alkenes (2 marks)

A
  • The electrons of the double bond repel the electron pair in the Br-Br bond
  • This induces a dipole and so Br₂ becomes polar and electrophilic
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16
Q

Explain how you would distinguish between an alkene and alkane (3 marks)

A
  • Bromine water
  • Orange to colourless with alkene
  • Stays orange with alkane
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17
Q

Describe and explain the properties and uses of PVC (4 marks)

A
  • Water proof polymer
  • Electrical Insulator
  • Rigid plastic due to strong intermolecular bonding between the polymer chains (therefore, they cannot move over each other)
  • Used to make window frame coverings and guttering
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18
Q

Describe how PVC can be made more flexible and state the uses of PVC in this form (3 marks)

A
  • Add a plasticiser to weaken the intermolecular forces
  • Used to make insulation on electrical wires
  • Used in waterproof clothing
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19
Q

Conditions for formation of carboxylic acid from alcohol (2 marks)

A
  • Excess potassium dichromate

- Heat under reflux

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20
Q

Equation for reaction of ethanal with Tollen’s reagent (1 mark)

A

CH₃CHO + 2Ag⁺ + H₂O –> CH₃COOH + 2Ag + 2H⁺

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21
Q

Equation for reaction of ethanal with Fehling’s solution (1 mark)

A

CH₃CHO + 2Cu²⁺ + 2H₂O –> CH₃COOH + Cu₂O + 4H⁺

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22
Q

Reagent and condition for hydrogenation of carbonyls (2 marks)

A
  • H₂ + Nickel catalyst

- High pressure

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23
Q

Explain why KCN is preferred over NaCN during nucleophilic addition reactions (2 marks)

A
  • HCN is a toxic gas which is difficult to obtain

- NaCN is a stronger acid so it will dissociate better than HCN

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24
Q

Describe and explain the uses of esters (4 marks)

A
  • Perfumes + food flavourings as they are sweet smelling
  • Solvents as they are polar so can dissolve other polar compounds
  • Glues as they have a low boiling point and can evaporate easily
  • Plasticisers to make plastics more flexible
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25
Q

State what fats and oils are composed of (2 marks)

A
  • Glycerol

- Long chain carboxylic acids

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26
Q

Draw the structure of glycerol (1 mark)

A

Propane- 1,2,3 - triol

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27
Q

Describe what biodiesel is (1 mark)

A

Mixture of methyl esters of long chain carboxylic acids

28
Q

Describe how biodiesel can be formed (2 marks)

A
  • Vegetable oils + 3 methanol

- Presence of strong alkali catalyst

29
Q

Explain why benzene is described as planar (2 marks)

A
  • C-C bonds are the same

- Bond length is intermediate between a single bond and double bond

30
Q

Explain why substitution reactions are preferred over addition reactions in aromatic compounds (2 marks)

A
  • Addition reactions would involve breaking up the delocalised system
  • Therefore as aromatic compounds have high electron density, they attract electrophiles and undergo electrophilic substitution
31
Q

Explain why the nitration of benzene is important (3 marks)

A

Useful in the synthesis of:

  • TNT
  • Explosives
  • Amines (which are used to make dyes)
32
Q

Explain why Friedel crafts acylation is an important step in synthesis (1 marks)

A
  • This reaction introduces a reactive functional group on to the benzene ring so many other reactions can occur
33
Q

State two disadvantages of preparing amines from nitriles (2 marks)

A
  • KCN is toxic

- 2 step reaction so may have low yield

34
Q

Reagent for reduction of nitriles (1 marks)

A
  • LiAlH₄ in ether
    OR
  • H₂ and nickel catalyst
35
Q

Reagent for reduction of nitroarenes (1 mark)

A

Sn + HCl
OR
Fe + HCl

36
Q

Explain why poly(alkenes) are inert (1 mark)

A
  • C-C and C-H bonds are strong
37
Q

State the uses of Terylene (1 mark)

A
  • Clothing fabric

- Tire cords

38
Q

State the use of nylon (1 mark)

A
  • Clothing fabric
39
Q

State the use of Kevlar (1 mark)

A

Bulletproof clothing

40
Q

Disadvantages of disposing plastics via landfill (4 marks)

A

Disadvantages:

  • Over time, the waste will decompose, producing greenhouse gases
  • Waste gases can leach into water and contaminate water
  • A lot of land is wasted
  • Most polymers take years to break down
41
Q

Advantages and disadvantages of disposing plastics via incineration (4 marks)

A

Advantages:

  • Energy produced whilst burning the rubbish can be used to generate electricity
  • Doesn’t waste land space (volume of rubbish is greatly reduced

Disadvantages:

  • Some toxins can be released
  • CO₂ and other greenhouse gases are released
42
Q

Advantages and disadvantages of recycling polymers (4 marks)

A

Advantages:

  • Saves raw materials
  • Cheaper to recycle plastics than to make them from scratch
  • Less CO₂ is produced when recycling plastics than when incinerating them
  • Reduces the reliance of landfill
  • Some plastics can be remoulded into other plastics

Disadvantages:

  • Plastics are often contaminated with other materials
  • Separation of the different types of plastics is expensive and time consuming
43
Q

Explain why amino acids have a high melting point (2 marks)

A
  • Amino acids exist as dipolar zwitterions

- So there is ionic interaction between them which requires a lot of energy to be overcome

44
Q

Describe the alpha helix secondary structure of a protein (2 marks)

A
  • 3D arrangement of amino acids with polypeptide chain in a corkscrew shape help by hydrogen bonds
  • R groups face the outside
45
Q

Describe the beta-pleated sheet secondary structure of a protein (2 marks)

A
  • Protein chain folds into parallel strands side by side

- Held together by hydrogen bonds

46
Q

Describe the tertiary structure of proteins (2 marks)

A
  • Folding of secondary structure into a more complex shape

- Held in place by interactions such as ionic, disulfide and hydrogen bonds between the R-side groups

47
Q

Explain how cisplatin prevents DNA replication in cancer cells (2 marks)

A
  • Ligand replacement reaction with DNA

- Dative covalent bond is formed between platinum and a nitrogen atom on guanine

48
Q

Explain why CCl₄ and CDCl₃ are good solvents to use in NMR spectroscopy (2 marks)

A
  • Inert

- No H atoms so no peaks

49
Q

State the use of TMS in H NMR spectroscopy and explain how its properties are suitable for this use (4 marks)

A
  • Used to calibrate the spectrum
  • Only gives one signal away from all the other signals
  • Non-toxic and inert
  • Low boiling point so can be removed from the sample easily
50
Q

Explain what determines the separation of molecules in chromatography (1 mark)

A

Balance between solubility in the moving phase and retention by the stationary phase

51
Q

Describe TLC (2 marks)

A
  • Plate coated with solid

- Solvent moves up the plate

52
Q

Describe column chromatography (2 marks)

A
  • Column packed with a solid

- Solvent moves down the column

53
Q

Describe gas chromatography (2 marks)

A
  • Column packed with a solid or with a solid coated by a liquid
  • And gas (e.g. nitrogen, helium, argon) is passed through the column under high pressure at a high temperature
54
Q

Outline the process of column chromatography (5 marks)

A
  • A cotton wool is placed in the tube to retain the solid in the tube
  • Glass tube is filled with a slurry formed from the stationary phase (silica) and the solvent
  • The mixture to be analysed is dissolved in a minimum amount of solvent and added to the column
  • The solvent is then run through the column and the molecules in the mixture start to separate
  • The time for each component in the mixture to reach the end of the column is recorded (retention time)
55
Q

Mobile and stationary phase in gas-liquid chromatography (2 marks)

A
  • Mobile: inert gas, e.g. helium (so that it doesn’t react with the components being separated)
  • Stationary: high boiling point liquid absorbed onto a solid
56
Q

Retention time in gas-liquid chromatography (1 mark)

A

Time taken for a particular compound to travel from the injection of the sample to where it leaves the column in the detector

57
Q

Factors which influence retention time in gas-liquid chromatography (3 marks)

A
  • Column temperature
  • Column length
  • Flow rate
58
Q

State two uses of gas-liquid column chromatography in conjunction with mass spectroscopy (2 marks)

A
  • Forensics

- Airport security

59
Q

x and y axis of Maxwell Boltzmann curve

A

x: collision energy
y: fraction of molecules with energy

60
Q

Suggest how a reaction goes to completion even if only a few particles have energy greater than Ea (1 mark)

A

Particles gain energy through collisions

61
Q

Describe how the Maxwell-Boltzmann curve changes when concentration/pressure are increased (2 marks)

A
  • Curves will be higher as more particles present

- But overall shape is the same

62
Q

State and explain the stability of benzene compared with the hypothetical cyclohexatriene (4 marks)

A
  • Benzene is more stable than cyclohexatriene
  • Expected ΔH hydrogenation of C₆H₆ is 3(–120)
  • Actual ΔH hydrogenation of benzene is 152 kJ mol-1 (less exothermic)
  • Because of delocalisation / electrons spread out
63
Q

Explain why cyclohexa-1,3-diene is more stable than cyclohexa-1,4-diene (3 marks)

A
  • Proximity − for 1,3 C=C bonds are closer together
  • Some overlap of electrons, π clouds or p orbitals
  • So extra stability for the 1,3- isomer
64
Q

State the reagents for the conversion of benzene into cyclohexane (1 mark)

A

Ni + H₂

65
Q

Explain the bonding in and the shape of a benzene molecule. Compare the stability of benzene with that of the hypothetical cyclohexa-1,3,5-triene molecule (6 marks)

A

Bonding:

  • Each C has three (covalent) bonds
  • Spare electrons (in a p orbital) overlap (to form a  cloud)
  • Delocalisation

Shape:

  • Planar
  • Hexagon/6 carbon ring/120 bond angle
  • C–C bonds equal in length / C–C bond lengths between single and double bond

Stability:

  • Expected △H of cyclohexatriene = –360 kJ mol–1
  • △H of benzene (is less exothermic) by 152 kJ mol–1
  • Benzene lower in energy than cyclohexatriene / Benzene is more stable

AQA Chemistry (32 decks)

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