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A levels > AS Chemistry AQA Unit 2 > Flashcards

AS Chemistry AQA Unit 2 Flashcards

0
Q

Enthalpy change

A

Heat energy transferred in a reaction at constant pressure

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1
Q

Le Chatelier’s principle

A

If a system in equilibrium is disturbed, the point of equilibrium will shift to counteract the change

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2
Q

Mean bond enthalpy

A

Average value for a bond enthalpy over the range of compounds it is found in

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3
Q

Enthalpy change of a reaction

A

Total energy absorbed - Total energy released

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4
Q

Standard enthalpy of reaction

A

The enthalpy change when a reaction occurs in the molar quantities shown in the chemical equation, with all reactants and products in their standard states and under standard conditions

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5
Q

Standard enthalpy of formation

A

The enthalpy change when one mole of a product is formed from its elements, under standard conditions with all reactants and products in their standard states

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6
Q

Standard enthalpy of combustion

A

The enthalpy change when one mole of a substance is completely burned in excess oxygen, under standard conditions, with all reactants and products in their standard states

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7
Q

Measuring enthalpy change

A

q = mcΔt
q= heat change, m=mass of solution heated, c=specific heat capacity of water (4.18) Δt= change in temp
standard enthalpy change = q/n

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8
Q

Activation energy

A

The energy required for a reaction to start

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9
Q

Catalyst

A

Increases the rate of a reaction by providing an alternate reaction pathway with a lower activation energy

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10
Q

Steam Hydration of ethene

A

C2H4 + H2O <–> C2H5OH

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11
Q

Conditions for steam hydration of ethene

A

6000-7000kPa (60-70 atm)
Temperature of 300 degrees
SOLID phosphoric acid catalyst

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12
Q

Methanol production

A

2H2 + CO <—> CH3OH

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13
Q

Conditions for methanol production

A

5000-10000 kPa (50-100 atm)
250 degrees
Mixture of catalysts: copper, zinc oxide, aluminium oxide

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14
Q

Uses of ethanol

A

Alcoholic beverages

Fuel

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15
Q

Uses of methanol

A

Fuel

Mainly used to produce other chemicals

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16
Q

Redox reaction

A

Reaction in which oxidation and reduction occurs simultaneously

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17
Q

Oxidation state of oxygen

A

-2 except for peroxides, where it is -1

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18
Q

Oxidation state of hydrogen

A

+1 except for in metal hydrides, where it is -1

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19
Q

Half equations

A

Electrons and ions, and element

Show reduction or oxidation

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20
Q

Halogen boiling point trend

A

Increase down group

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21
Q

Halogen electronegativity trend

A

Decrease down group (shielding, atomic radius)

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22
Q

Reaction: Bromine water and potassium iodide

A

Iodine is displaced; brown solution

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23
Q

Reaction: Chlorine water and potassium bromide

A

Bromine is displaced; orange solution

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24
Q

Making bleach

A

2NaOH + Cl2 —> NaClO + NaCl + H2O

Sodium hydroxide + Chlorine= Sodium chlorate(l) + Sodium chloride + water

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25
Q

Disproportionation

A

The oxidation and reduction of the same element in a redox reaction

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26
Q

Reaction: Chlorine and water

A

Cl2 + H2O <—> HClO + HCl

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27
Q

Risks of chlorine

A

Irritate respiratory system
Chemical burns
Chlorinated hydrocarbons are carcinogenic

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28
Q

Equation: Conc. sulphuric acid and sodium chloride/fluoride

A

H2SO4 + NaCl —> NaHSO4 + HCl
Steamy fumes of HCl as it meets moisture in air
HCl or HF cannot reduce sulfuric acid; reaction ends

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29
Q

Equation: Conc. sulphuric acid and sodium bromide

A

H2SO4 + NaBr —> NaHSO4 + HBr
Steamy fumes of HBr
HBr is stronger reducing agent than HCl or HF; reduces sulfuric acid
2HBr + H2SO4 —> SO2 + Br2 + 2H2O

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30
Q

Equation: Conc. sulfuric acid and sodium iodide

A 
H2SO4 + NaI ---> NaHSO4 + HI
Steamy fumes of HI
HI is strong reducing agent; reduces sulfuric acid
2HI + H2SO4 ---> SO2 + I2 + 2H2O
HI continues to reduce SO2
6HI + SO2 ---> H2S + 2H2O + 3I2
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31
Q

Observations: Conc sulfuric acid and sodium chloride/fluoride

A

Steamy fumes of HCl or HF

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32
Q

Observations: conc sulfuric acid and sodium bromide

A

Steamy fumes of HBr, choking fumes of SO2, orange fumes of Br2

33
Q

Observations: conc sulfuric acid and sodium iodide

A

Steamy fumes of HI, choking fumes of SO2, purple fumes of I2, bad egg smell of H2S, black solid (iodine)

34
Q

Test for halides

A

Silver Nitrate test;
Add nitric acid to remove carbonate ions (ions that interfere)
Add silver nitrate
White ppt indicates chloride, cream ppt indicates bromide, yellow ppt indicates iodide
Dissolves in dilute ammonia=chloride, dissolves in conc ammonia=bromide, doesn’t dissolve in conc ammonia=iodide

35
Q

Melting point of group 2 metals

A

Decrease down group; blip at magnesium bc crystal structure

36
Q

Group 2 metal reactions with water

A

Form metal hydroxide and hydrogen

37
Q

Group 2 hydroxide solubility

A

solubility increases down group

38
Q

Group 2 sulphate solubility

A

solubility decreases down group

39
Q

Test for sulfate ions

A

Barium ions, e.g. barium chloride (acidified with HCl)

40
Q

Test for hydroxide ions

A

Magnesium ions, e.g. magnesium chloride

41
Q

Slaked lime

A

Ca(OH)2 calcium hydroxide used to neutralise acidic soil

42
Q

Extracting metals from sulfide ores

A
  1. Turn into oxide; roast in air

2. Reduce oxide

43
Q

Roasting

A

Heating in plenty of air

44
Q

Reducing iron(lll) oxide

A

Blast furnace, over 700 degrees
Carbon or carbon monoxide reducing agent
2Fe2O3 + 3C —> 4Fe + 3CO2
Fe2O3 + 3CO —> 2Fe + 3CO2

45
Q

Reducing manganese(lV) oxide

A

Blast furnace, 1200 degrees
Carbon or carbon monoxide
MnO2 + C —> Mn + CO2
MnO2 + 2CO —> Mn + 2CO2

46
Q

Reducing copper carbonate

A

heat with carbon, or decompose into oxide and reduce with carbon

47
Q

Malachite

A

contains CuCO3, iron ore

48
Q

Extracting tungsten

A

Hydrogen

Furnace, above 700 degrees

49
Q

Extracting aluminium

A

Electrolysis; remove impurities, bauxite dissolved in molten cryolite, pure aluminium collects as molten metal

50
Q

Bauxite

A

Al2O3, aluminium ore

51
Q

Cryolite

A

Na3AlF6 reduces aluminium melting point

52
Q

Extracting titanium

A

Carbon and chlorine to form titanium chloride

React with more reactive metal eg sodium to get pure metal

53
Q

Evaluation recycling metals

A

+ ores are a finite resource - saves raw materials; saves energy; reduces landfill waste; mining damages landscape
-collecting and sorting metals is expensive and hard; purity of metal varies; recycling may not produce consistent supply

54
Q

Using scrap iron

A

Dissolve copper ores in acidified water, scrap iron added. Iron dissolves and reduces copper ions; copper precipitate forms

55
Q

Synthesis of chloroalkanes

A

free radical substitution; react alkane with halogen with UV

56
Q

Ozone layer

A

O2 breaks down into O radicals under UV
O2 + O’ —> O3
ABSORBS UV IN THIS WAY

57
Q

Ozone breakdown by CFCs

A

CCl3F —> CCl2F’ + Cl’
Cl’ + O3 —> ClO’ + O2
ClO’ + O3 —> 2O2 + Cl’
OVERALL: 2O3 —> 3O2

58
Q

CFC uses

A

propellant in aerosols, coolant gas in fridges

59
Q

Nucleophile

A

Electron pair donor

60
Q

Electrophile

A

Electron pair acceptors

61
Q

Nucleophilic substitution

A

Nucleophile attacks polar molecule, replaces it

62
Q

Examples of nucleophiles

A

:NH3, :CN-. :OH-

63
Q

Synthesising amines

A

Warm haloalkane with ethanolic ammonia (ammonia dissolved in ethanol)
Ammonia swaps with halogen; NUCLEOPHILIC SUBSTITUTION

64
Q

Synthesising nitriles

A

Warm haloalkane with ethanolic potassium cyanide

NUCLEOPHILIC SUBSTITUTION

65
Q

Hydrolysis of haloalkanes

A

Warm aqueous sodium hydroxide and haloalkane

66
Q

Nucleophilic sub vs elimination

A

React haloalkane with water, under reflux = nucleophilic sub, not much elimination
React haloalkane with ethanol under reflux= elimination

67
Q

Test for unsaturation

A

Shake with bromine water- orange to colourless means unsaturation

68
Q

Carbocation

A

Organic ion containing positively charged carbon atom

69
Q

Hydration of alkenes

A

React alkene with water, with cold concentrated sulfuric acid

  1. alkene and sulfuric acid
  2. add cold water and warm; hydrolysed to ethanol
70
Q

Synthesis of bromoalkanes

A

ELECTROPHILIC ADDICTION

C2H4 + HBr —> C2H5Br

71
Q

Unsymmetrical alkanes

A

Br bonds to most stable carbocation (tertiary most stable, primary least stable)

72
Q

Polymerisation

A

n (H2C=CH2) —> n(-CH2-CH2-)

73
Q

Polyethene uses

A

Soft flexible plastic, plastic bags and squeezy bottles

74
Q

Polypropene uses

A

Tough, strong plastic. Bottle crates, rope.

75
Q

Production of ethanol by fermentation

A 
30-40 degrees
yeast
anaerobic conditions
C6H12O6 ---> 2C2H5OH + 2CO2
around 15% alcohol, yeast dies
Fraction distillation increases conc of alcohol
76
Q

Dehydration of ethanol

A

react with conc sulfuric acid (or phosphoric acid) REFLUX
C2H5OH + H2SO4 —> C2H5OSO2OH + H2O
C2H5OSO2OH —> C2H4 + H2SO4

77
Q

Oxidation of alcohols

A

Acidified potassium dichromate, orange to green
Primary: distilling: Aldehyde reflux: Carboxylic acid
Secondary: reflux: ketone
Tertiary: not oxidised

78
Q

Tollens reagent

A

Silver mirror with aldehyde, none with ketone

Reduced to silver with aldehyde

79
Q

Fehlings solution

A

Blue to brick red with aldehyde, not ketone

A levels (5 decks)

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