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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
Making bleach
2NaOH + Cl2 ---> NaClO + NaCl + H2O | Sodium hydroxide + Chlorine= Sodium chlorate(l) + Sodium chloride + water
25
Disproportionation
The oxidation and reduction of the same element in a redox reaction
26
Reaction: Chlorine and water
Cl2 + H2O <---> HClO + HCl
27
Risks of chlorine
Irritate respiratory system Chemical burns Chlorinated hydrocarbons are carcinogenic
28
Equation: Conc. sulphuric acid and sodium chloride/fluoride
H2SO4 + NaCl ---> NaHSO4 + HCl Steamy fumes of HCl as it meets moisture in air HCl or HF cannot reduce sulfuric acid; reaction ends
29
Equation: Conc. sulphuric acid and sodium bromide
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
30
Equation: Conc. sulfuric acid and sodium iodide
``` 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 ```
31
Observations: Conc sulfuric acid and sodium chloride/fluoride
Steamy fumes of HCl or HF
32
Observations: conc sulfuric acid and sodium bromide
Steamy fumes of HBr, choking fumes of SO2, orange fumes of Br2
33
Observations: conc sulfuric acid and sodium iodide
Steamy fumes of HI, choking fumes of SO2, purple fumes of I2, bad egg smell of H2S, black solid (iodine)
34
Test for halides
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
Melting point of group 2 metals
Decrease down group; blip at magnesium bc crystal structure
36
Group 2 metal reactions with water
Form metal hydroxide and hydrogen
37
Group 2 hydroxide solubility
solubility increases down group
38
Group 2 sulphate solubility
solubility decreases down group
39
Test for sulfate ions
Barium ions, e.g. barium chloride (acidified with HCl)
40
Test for hydroxide ions
Magnesium ions, e.g. magnesium chloride
41
Slaked lime
Ca(OH)2 calcium hydroxide used to neutralise acidic soil
42
Extracting metals from sulfide ores
1. Turn into oxide; roast in air | 2. Reduce oxide
43
Roasting
Heating in plenty of air
44
Reducing iron(lll) oxide
Blast furnace, over 700 degrees Carbon or carbon monoxide reducing agent 2Fe2O3 + 3C ---> 4Fe + 3CO2 Fe2O3 + 3CO ---> 2Fe + 3CO2
45
Reducing manganese(lV) oxide
Blast furnace, 1200 degrees Carbon or carbon monoxide MnO2 + C ---> Mn + CO2 MnO2 + 2CO ---> Mn + 2CO2
46
Reducing copper carbonate
heat with carbon, or decompose into oxide and reduce with carbon
47
Malachite
contains CuCO3, iron ore
48
Extracting tungsten
Hydrogen | Furnace, above 700 degrees
49
Extracting aluminium
Electrolysis; remove impurities, bauxite dissolved in molten cryolite, pure aluminium collects as molten metal
50
Bauxite
Al2O3, aluminium ore
51
Cryolite
Na3AlF6 reduces aluminium melting point
52
Extracting titanium
Carbon and chlorine to form titanium chloride | React with more reactive metal eg sodium to get pure metal
53
Evaluation recycling metals
+ 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
Using scrap iron
Dissolve copper ores in acidified water, scrap iron added. Iron dissolves and reduces copper ions; copper precipitate forms
55
Synthesis of chloroalkanes
free radical substitution; react alkane with halogen with UV
56
Ozone layer
O2 breaks down into O radicals under UV O2 + O' ---> O3 ABSORBS UV IN THIS WAY
57
Ozone breakdown by CFCs
CCl3F ---> CCl2F' + Cl' Cl' + O3 ---> ClO' + O2 ClO' + O3 ---> 2O2 + Cl' OVERALL: 2O3 ---> 3O2
58
CFC uses
propellant in aerosols, coolant gas in fridges
59
Nucleophile
Electron pair donor
60
Electrophile
Electron pair acceptors
61
Nucleophilic substitution
Nucleophile attacks polar molecule, replaces it
62
Examples of nucleophiles
:NH3, :CN-. :OH-
63
Synthesising amines
Warm haloalkane with ethanolic ammonia (ammonia dissolved in ethanol) Ammonia swaps with halogen; NUCLEOPHILIC SUBSTITUTION
64
Synthesising nitriles
Warm haloalkane with ethanolic potassium cyanide | NUCLEOPHILIC SUBSTITUTION
65
Hydrolysis of haloalkanes
Warm aqueous sodium hydroxide and haloalkane
66
Nucleophilic sub vs elimination
React haloalkane with water, under reflux = nucleophilic sub, not much elimination React haloalkane with ethanol under reflux= elimination
67
Test for unsaturation
Shake with bromine water- orange to colourless means unsaturation
68
Carbocation
Organic ion containing positively charged carbon atom
69
Hydration of alkenes
React alkene with water, with cold concentrated sulfuric acid 1. alkene and sulfuric acid 2. add cold water and warm; hydrolysed to ethanol
70
Synthesis of bromoalkanes
ELECTROPHILIC ADDICTION | C2H4 + HBr ---> C2H5Br
71
Unsymmetrical alkanes
Br bonds to most stable carbocation (tertiary most stable, primary least stable)
72
Polymerisation
n (H2C=CH2) ---> n(-CH2-CH2-)
73
Polyethene uses
Soft flexible plastic, plastic bags and squeezy bottles
74
Polypropene uses
Tough, strong plastic. Bottle crates, rope.
75
Production of ethanol by fermentation
``` 30-40 degrees yeast anaerobic conditions C6H12O6 ---> 2C2H5OH + 2CO2 around 15% alcohol, yeast dies Fraction distillation increases conc of alcohol ```
76
Dehydration of ethanol
react with conc sulfuric acid (or phosphoric acid) REFLUX C2H5OH + H2SO4 ---> C2H5OSO2OH + H2O C2H5OSO2OH ---> C2H4 + H2SO4
77
Oxidation of alcohols
Acidified potassium dichromate, orange to green Primary: distilling: Aldehyde reflux: Carboxylic acid Secondary: reflux: ketone Tertiary: not oxidised
78
Tollens reagent
Silver mirror with aldehyde, none with ketone | Reduced to silver with aldehyde
79
Fehlings solution
Blue to brick red with aldehyde, not ketone

A levels (5 decks)

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