Y12 exams Flashcards
1
Q
What is ionisation energy?
A
The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous ions
2
Q
What three factors affect the ionisation energy?
A
Charge of the nucleus
Distance from the nucleus
Shielding
3
Q
What happens to the ionisation energy when the charge of the nucleus increases?
A
The ionisation energy increases as there is a stronger attraction to the nucleus
4
Q
What happens to the ionisation energy when distance from the nucleus increases?
A
The ionisation energy decreases because the attraction decreases
5
Q
What happens to the ionisation energy when shielding increases?
A
The ionisation energy decreases because the attraction decreases
6
Q
What happens to ionisation energies down the groups?
A
Decreases due to increased distance and shielding
7
Q
What happens to ionisation energies across periods?
A
Increases as distance is decreasing and nucleus charge is increasing
8
Q
What are the four stages of a Time of Flight Mass Spectrometer?
A
Ionisation
Acceleration
Ion drift
Detection
9
Q
How are atoms ionised in a TOF mass spectrometer?
A
Electron gun fires high energy electrons which knock off electrons to create cations
10
Q
Explain acceleration in TOF mass spectrometer?
A
Kinetic energy is transferred to the ions as they are attracted through the electric field and accelerated (all ions are given same KE)
11
Q
Explain ion drift in TOF mass spectrometer?
A
Ion drift allows the ions of different masses to separate
12
Q
Explain detection in TOF mass spectrometer?
A
The detector creates a current by ‘taking’ an electron from the ion when it hits it (the greater the current, the greater the abundance)
13
Q
Why do ionic lattices have high melting points?
A
Strong attraction between oppositely charged ions so requires lots of energy to break
14
Q
Why are ionic substances electrical conductors when molten or dissolved in solution?
A
The ions are free to move so can carry charge
15
Q
Why do covalent macromolecular have high melting points?
A
Lots of strong covalent bonds so lots of energy is needed to break them (also why they’re hard and strong)
16
Q
Why is graphite slippery?
A
Weak Van der Waals forces between layers so layers can slide over each other easily
17
Q
Why does graphite conduct electricity?
A
The non-bonded delocalised electron can move throughout the structure and carry a charge
18
Q
Why do molecular covalent have low boiling point?
A
Weak Van der Waals forces between molecules so little energy is required to overcome them
19
Q
Why do metals have high melting points?
A
Strong attraction between positive ions and delocalised electrons so lots of energy required to break them
20
Q
Why do metals conduct electricity?
A
Delocalised electrons can move throughput structure and carry a charge
21
Q
What is the shape and bond angle when co-ordination no. is 2?
A
linear
180
22
Q
What is the shape and bond angle when co-ordination no. is 3?
A
trigonal planar
120
23
Q
What is the shape and bond angle when co-ordination no. is 4?
A
tetrahedral
109.5
24
Q
What is the shape and bond angle when co-ordination no. is 5?
A
trigonal bipyradimal
90 and 120
25
What is the shape and bond angle when co-ordination no. is 6?
octahedral
| 90
26
Why do lone pairs decrease bond angles and by how much?
Decrease by 2.5 because the lone pairs repel more than the bonding pairs
27
Define the term electronegativity
The ability of an atom to withdraw its electrons in a covalent bond
28
How do hydrogen bonds arise?
Large difference in electronegativity creates a permanent dipole and a hydrogen bond (attraction) is formed between the Hδ+ and the lone pair on the other atom
29
What is the trend in melting points down Group 2?
Decreases because the size of the ions increase so the electron density decreases causing a weaker attraction so less energy is required
30
Why does a lone pair of electrons repel more strongly than a bonding pair?
More compact
31
How is a coordinate/dative covalent bond formed?
Both electrons in a shared pair of electron come from one atom
32
What is a permanent dipole?
Unequal sharing of electrons leading to δ+ and δ- ends
33
What is meant by the term polar bonds?
Partial charges on the atoms of the bond
34
What is a redox reaction where the same element/thing is being both oxidised and reduced?
Disproportionation
35
What is the trend in electronegativity across period 3?
Increases because the nuclear charge increases and they have similar shielding
36
What is the meaning of covalency?
Shared pair of electrons
37
What is the meaning of dative?
Both electrons from one atom
38
What is meant by the term mean bond enthalpy?
Energy required to break a bond, averaged over a range of compounds
39
What is Hess’s Law?
The enthalpy change of a reaction is independent of the route taken
40
What is the trend in electronegativity down group 7?
Decreases as shielding and atomic radius increases so weaker attraction to electron pair in the covalent bond
41
Give an example of a reagent that could be used to show that the reducing ability increases down group 7
Concentrated sulfuric acid
42
Write an equation for the reaction between chlorine and cold, dilute aqueous hydroxide and give two uses
Cl2 + 2NaOH ——> 2NaCl + NaOCl + H20
bleach
disinfectant
43
Which halogen is the strongest oxidising agent?
Fluorine
44
Which halogen is the strongest reducing agent?
Iodine/Astatine
45
How can the presence of H2S be recognised?
Bad egg smell
46
Explain the term homogeneous
All reactants in the same state or phase
47
Explain the term dynamic
Continuous or ‘on going’
48
Explain the term equilibrium
Rates of forward and backward reactions are equal
49
What is the trend in solubility in group 2?
Decreases down the group
50
What type of reaction is cracking?
Decomposition reaction
51
What are the conditions for catalytic cracking and what does it produce?
450 °c
slight pressure
catalyst (silica or alumina)
Aromatic hydrocarbons (benzene ring)
Motor fuels
Cycloalkanes
52
What are the conditions for thermal cracking and what does it produce?
high temp - 1000°c
high pressure
alkenes
53
How do we remove SO2 and what is this process called?
A base such as CaO
| Flue-gas desulphurisation
54
How are nitrogen oxides produced from combustion in the engine?
Due to the high heat and pressure the oxygen can react with the nitrogen in the air
55
What’s the problem with nitrogen oxides?
Toxic acid rain and can cause respiratory problems
56
What do we use as a catalytic converter and how does it work?
Platinum and Rhodium
| Exhaust gases pass through mesh and the catalyst which allows them to removed and not enter the atmosphere
57
Why do we use mesh in a catalytic converter?
Gives it a larger surface area to increase rate of reaction and means we can use less of the expensive catalysts
58
What’s the issue with unburnt hydrocarbons?
Causes respiratory problems
59
What are the features of a homologous series?
```
Same general formula
Same functional group
Chemically similar (react similarly)
Gradual change in physical properties
```
60
What is a commercial use of propene?
Producing polymers
61
What is meant by the term stereoisomers?
Compounds with the same structural formula but different spatial arrangements
62
What is meant by the term nucleophile?
Electron pair donor
63
What mechanism is alkenes to haloalkanes?
Electrophilic addition
64
Test to distinguish between alkane and alkene
Bromine water
Alkane - NVC
Alkene - orange solution to colourless
65
Test to distinguish aqueous silver nitrate and aqueous sodium nitrate?
Any soluble chloride e.g HCl
Silver nitrate - white ppt
Sodium nitrate - NVC
66
Test to distinguish aqueous magnesium chloride and aqueous barium chloride
Soluble sulfate e.g H2SO4
MgCl2 - NVC
BaCl2 - white ppt
67
What toxic gases are produced when NaBr reacts with conc. H2SO4?
SO2
HBr
Br2
68
How do you make ethanol?
Fermentation
| Hydration of ethene
69
What are the conditions for fermentation?
Yeast
Anaerobic conditions (no oxygen)
temp 30-40°c
70
What is the equation for fermentation?
C6H12O6 ——> 2C2H5OH + 2CO2
71
What are the advantages and disadvantages of fermentation?
Advantages
Sugars renewable
Cheap equipment
Disadvantages
Ethanol needs distilling
Batch process
72
What are the conditions for the hydration of ethene?
catalyst - conc. acid (H2SO4 or H3PO4)
temp 300°c
pressure 60 atm
73
What is the equation for the hydration of ethene?
C2H4 + H2O ——> C2H5OH
74
What are the advantages and disadvantages of the hydration of ethene?
Advantages
Continuous
Produces purer product
Disadvantages
Ethene is non-renewable
75
What does carbon neutral mean?
No net release of CO2
76
Why is fermentation not necessarily carbon neutral?
Transport produces CO2
| Machinery produces CO2
77
What is the mechanism for an alcohol to an alkene?
Elimination
78
What is the mechanism for an alkene to an alcohol?
Electrophilic addition
| Hydration
79
What are the conditions when alcohols are oxidised?
Acidic conditions
| Distillation
80
What is meant by the term dehydration?
Removal of water
81
What compound is formed by the dehydration of alcohols?
Alkenes
82
What are the reagents and conditions for the dehydration of alcohols?
Conc. H2SO4
High temp
Reflux
83
What are the conditions for nucleophilic substitution with NH3?
Reflux in ethanol
Sealed and pressure
Excess conc. NH3
84
What are the conditions for nucleophilic substation of cyanide?
Reflux in ethanol
85
What are the conditions for nucleophilic substitution when it’s haloalkane to alcohol?
Aqueous solution
| Warm, gentle reflux
86
What are the conditions for elimination?
High temp.
Dissolve in ethanol
No water
87
What is the positive result for Fehlings solution?
Aldehyde blue solution to brick red
| Ketone NVC
88
What is the positive result for Tollens reagent?
Aldehyde silver mirror
| Ketone NVC
89
What are the conditions for hydration/Electrophilic addition of alkene to alcohol?
Steam
| Acid catalyst
90
Why is the enthalpy change found via calorimetry usually less than real value?
Heat lost to surrounding
Incomplete combustion
Heating up the calorimeter
Evaporation of alcohol being burned (if relevant)
Experiment not done under standard conditions
91
What is the enthalpy change of formation?
The enthalpy change when one mole of a compound is formed from its constituent elements in their standard states and under standard conditions
92
What is the enthalpy change of combustion?
The enthalpy change when one mole of a compound is burned completely in oxygen with all the reactants and products in their standard states
93
What are the conditions of equilibria?
Rate of forward and backward reactions are equal
Concentrations of reactants and produces are not changing
Its a closed system
94
What is Le Chateliers Principle?
When a factor is changed, an equilibrium will shift to oppose that change
95
What happens when the temp. is decreased in an equilibrium?
The EXOthermic direction is favoured because energy is released to the surroundings causing the temp. to increase
96
What happens when the temp. is increased in an equilibrium?
The ENDOthermic direction is favoured because energy is absorbed from the surroundings causing the temp. to decrease
97
What happens when pressure is increased in an equilibrium?
Equilibrium will shift to favour the direction with fewer moles to counteract the change
98
What happens when the pressure is decreased in an equilibrium?
Equilibrium will shift to favour the direction with more moles to counteract the change
99
What happens when a catalyst is added to an equilibrium?
Doesn't affect the position of the equilibrium as it increases the forwards and backwards rate of reaction equally so it will reach equilibrium faster
100
In the Haber process what are the theoretical conditions for the max. yield of ammonia?
(N2 + 3H2 ----> 2NH3)
High pressure
| Low temp
101
What are the actual conditions used for the Haber process and why?
Compromised conditions:
200atm - expensive and engineeringly difficult
450 oc - faster rate of reaction
102
What is the exception for oxygens oxidation state?
H2O2 where it is -1
103
What is the meaning of the term oxidising agent?
Electron acceptor (it gets reduced)
104
What is the meaning of the term reducing agent?
Electron donor (it gets oxidised)
105
What is the meaning of the term oxidation state?
The charge on the ion
106
Write an equation for the reaction of chlorine with water
Cl2 + H2O -----> ClOH + HCl
107
Why is chlorine not formed when solid potassium chloride reacts with conc. H2SO4?
Chloride ions can not reduce sulphuric acid
108
How do you test for halide ions?
Add nitric acid and then aqueous silver nitrate
Cl2 - white ppt
Br2 - cream ppt
I2 - yellow ppt
109
What reagent is used to show that the reducing ability of halide ions increases down the group?
Conc. H2SO4
110
What is a homologous series?
A family of compounds with the same general formula
111
What is crude oil?
A mixture of alkanes
112
What is the relationship between length of carbon chain and boiling point with alkanes?
Bigger alkane = higher b.p.
| Stronger Van der Waals forces
113
What are the fractions in industrial fractional distillation?
```
Refinery gases
Gasoline (petrol)
Naphtha
Kerosine
Diesel (gas oil)
Fuel oil
Bitumen
```
114
What are refinery gases used for?
Bottled fuels for camping
115
What is gasoline used for?
Fuel for cars
116
What is naphtha used for?
Petrochemicals
117
What is kerosine used for?
Jet fuel
118
What is diesel (gas oil) used for?
Central heating fuel
119
What is mineral oil used for?
Lubrication
120
What is fuel oil used for?
Ship fuel
121
What is Bitumen used for?
Roads
122
What do we do with fuels?
Combust them
123
What is produced when sulphur is oxidised and and what is the problem?
SO2
It forms acid rain which ruins habitats and is a pollutant
(remove it using a base)
124
What are the free stages of free-radical substation?
Initiation
Propagation
Termination
125
What is the mechanism for alkanes to haloalkanes?
Free radical substitution
126
What does ozone do?
Protects us from UV radiation
127
How is ozone depleted?
Cl• + O3 ——> ClO• + O2
| ClO• + O3 ——> 2O2 + Cl•
128
Write the overall equation for the breakdown of ozone?
2O3 ----> 3O2
129
What is a nucleophile?
An electron pair donor
130
What is the mechanism for haloalkanes to alkenes?
Elimination
131
What is an electrophile?
An electron pair acceptor
132
Why does the atomic radius decrease across periods?
As they are in the same energy level they have the same shielding but they have more protons across the period so there is a stronger attraction to the electrons causing the atomic radius to decrease
133
Show the reaction between Group 2 metals and water?
M + H2O ----> M(OH)2 + H2
134
Which group 2 metal reacts differently with steam?
Magnesium
135
Show the reaction between magnesium and steam?
Mg + H2O ----> MgO + H2
136
What is the trend in reactivity down group 2?
Reactivity increases as it becomes easier to oxidise atoms
137
How do we use BaSO4?
barium meal (used in X-rays)
138
How do we use Ca(OH)2?
Neutralising acidic soil
139
How do we test for the (SO4) 2- ion?
Add HCl and BaCl2
| positive result is white ppt
140
Show the formation of bleach from sodium hydroxide and chlorine?
2NaOH + Cl2 ----> NaOCl + NaCl + H2O
NaOCl - sodium chlorate is the bleach
141
What is PVC and what is it used to make?
Poly(chloroethene)
Pipes
Window frames
Electrical insulation
