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All AO1 Flashcards

1
Q

Why is it necessary to ionise the isotopes of an atom before they can be analysed in a TOF mass spectometer

A

(Ions will interact with and) be accelerated (by an electric
field)
Ions create a current when hitting the detector OR
ions create a current in the detector/electron multiplier.

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2
Q

Isotope

A

Have same number of electron and proton but different number of neutrons.

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3
Q

Why isotopes of an atom have same chemical properties

A

Have same electronic configuration and chemical properties depend on the number of electrons in an atom

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4
Q

Relative atomic mass

A

Average mass of an atom of an element compared to 1/12 of mass of one atom in C12 isotope

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5
Q

Find the mass of ^53Cr

A

(53x10^-3)/6.02 x10^23

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6
Q

Why TMS is used as standard NMR

A

It generates on shears peak
Peak is always found in far right of spectrum
It is highly volatile this means can be removed from sample being tested after analysis fairly easily
Non reactive so won’t affect the sample being analysed

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7
Q

Resonance

A

The nuclei in lower energy state can absorb energy in form of radio waves and flip between the lower and higher levels
This is called resonance

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8
Q

C spectrum

A

No of peaks is same as no of carbon environment
Location of peaks tell u about the location of carbon environment

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9
Q

TMS

A

Reference of NMR spectrum
Tetra methylsilane

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10
Q

Why solutions with Fe3+ ions have lower pH than Fe2+ ions

A

Fe3+ ions have smaller atomic radius and a greater charge
Fe3+ ions can polarise water molecules easily
More O-H bonds can be broken so more H+ ions
More H+ ions more acidic the solution is and lower the pH is ,

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11
Q

Trend of atomic radius across period 3

A

Decreases because of increase in nuclear charge however sheilding remains same

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12
Q

Trend of electronegativity across P3

A

Inceases

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13
Q

Trend of 1st ionisation energy

A

increases along the period
same shielding effect and increase in nuclear charge

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14
Q

Why Al has lower IE than Mg

A

Mg has a 3s electron removed
Al has 3p electron removed
3p is higher energy than 3s

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15
Q

Why S has lower IE than P

A

P has a 3p electron removed which is unpaired
S has a 3p electron removed which is paired
S has a lower ionisation energy than P becuse of electron pair repulsion

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16
Q

Cl recation with water

A

Cl2 + H2O = HClO + HCl
this reaction is reversible

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17
Q

Cl + H2O =

A

HCl + O2

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18
Q

2Na + 1/2O2 =

A

Na2O

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19
Q

observation when Na reacts with oxygen

A

orange flame and white solid ppt

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20
Q

2Mg + O2 =
and observation?

A

2MgO
White flame
white solid ppt

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21
Q

4Al + 3O2 =
observation

A

2Al2O3
if you sprinkle aluminium powder you get bright white flames/ sparks
white solid

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22
Q

Si + O2
Observation

A

SiO2
Orange flame
white solid ppt

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23
Q

P4 + 5O2 =
Observation

A

P4O10
white flame
white fumes poduce (no ppt)

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24
Q

S + O2 =
observation

A

SO2
pale blue flame
no ppt ( colourless gas)

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25
Trend of bonding across P3
ionic to basic
26
Why does Al2O3 have more covalent character than MgO
Al3+ ions are smaller in than Mg2+ This means the Al3+ ions is more polarising than Mg2+ ions This distorts the electron cloud around the O2- ion more so that there is more electron density shared between two ions
27
Why sodium oxide form alkaline solution when reacts with water
Sodium oxide contains O2- ions These O2- ions react with water to form OH- ions
28
Name insoluble oxides
Aluminium oxide and silicon dioxide
29
Relationship between bonding and acid/basic properties of P3 oxides
The oxides that are ionically bonded are alkaline The oxides that are covalentalt bonded tend to be acidic
30
Amphoteric oxides
Al2O3 Can act as acid and a base
31
write an ionic equation for the reaction of phosphorus oxide with an excess of NaOH solution
P4O10 + 12OH- = 4PO4^3- + 6H2O
32
Explain using the equation why SiO2 is classified as an acidic oxide
SiO2 neuttralises bases SiO2 + 2NaOH = Na2SiO3 + H2O
33
Dynamic equilibrium
The rate of forward reaction is same a rate of backward reaction the amount of reactants and products is constant
34
Le chatalier principle
The equilibrium shift to oppose change
35
condition for equilibrium
closed system
36
Why does a catalyst not affect the position of equilibrium?
Catalysts increase the rate of the forward and backward reactions equally.
37
Why are catalysts added to the Haber process, which is a reversible reaction that produces ammonia?
To reduce the time taken to reach dynamic equilibrium
38
This question is about the equilibrium which occurs at temperature T1 between compounds as shown in the equation. A(g)     2B(g)         ΔH = –50 kJ mol–1 The mixture was allowed to reach equilibrium at a different temperature T2, and the position of equilibrium had shifted to the right. State and explain which of T1 or T2 is the lower temperature.
Forward reaction is exothermic Equilibrium has shifted right to oppose the decrease in temperature T2 is lower
39
Why are compromising conditions important in equilibrium
higher pressures would be too expensive 450oC gives a good yield in a fast time
40
Why is Kc used for?
Kc is a measure of how much the equilibrium has shifted to the right or left.
41
How does an increase in pressure alter Kc? (1 Mark)
It remains unchanged
42
State the features of homologous series.
Have same chemical properties Have same functional group Same general formula Members show change in physical properties like boiling point increases as C chain gets longer
43
Functional group isomers
Functional group changes but molecular formula is same
44
To have E/Z isomerism a molecule must have
A double bond that restrict rotation Each carbon has 2 different groups attached to it
45
Alkane
alkanes are saturated hydrocarbons that contain Carbon-carbon and carbon-hydrogen single bonds only
46
Why boiling point of alkanes increases as carbon chain length increases
More electrons so stronger vander waals
47
Why increase in number of branches decreases boiling point
Less surface contact so weaker vander waals between chains
48
what is fraction
Mixture of hydrocarbon with similar boiling points
49
Explain why oil companies need to crack heavy fractions
Higher demand for more useful shorter chains (alkane and alkene)
50
Thermal cracking gives
2 alkenes and 1 alkane
51
Condition for thermal cracking
High temperature ( 700-1200 K) High pressure (7000kPa)
52
Catalytic cracking gives
High % of branched alakane and cycloalkane
53
Condition for catalytic cracking
High temperature (700K) catalyst = zeolite mild pressure = 100kPa
54
CO2, H2O are greenhouse gases and cause
Ozone depletion global warming
55
why is incomplete combustion not desirable
produces 1 CO which is toxic ..binds to heamoglobin and reduces its oxygen carrying capacity C particulate which can damage lungs and can make it difficult for asthma sufferers to breath
56
SO2
Can cause acid rain SO2 +1/2O2 +H2O = H2SO4 causes erosion of building , kill plants and aquatic animals
57
Oxides of nitrogen
Nitrogen only reacts under high temperature forms NO, NO2 and N2O4 N2 + O2 =2NO NO + O2 = NO2 4NO2 + H2O + 1/2 O2 = 4HNO3 Nitogen oxides can bind with hydrocarbons and form photochemical fog
58
Unburnt hydrocarbons can cause
cancer because they are toxic
59
catalysts used in catalytic convertors
Pt and rhodium metal
60
How can the amount of further substitution be reduced.
Add alkane in excess so halogen radical get used up by attacking alkane
61
Why alkenes are ore reactive than alkanes
They are unsaturated so there is a scope to add atoms onto the molecule on either end of double bond to make it saturated
62
Conditions for electrophillic addition with sulphuric acid
H2SO4 catalyst 70 atm pressure high temperature (300-600 C)
63
addition polymer
monomer = alkene repeating unit = alkane
64
plasticers
They are used to make polymers more flexible or less rigid
65
Mechanical recycling for plastics
Plastics are sorted into different types They are ground into pallet Pallets are melted down and remould into new objects
66
Feedstock recycling of plastics
Plastics are sorted into different types They are then heated to break the polymer bonds They are then repolymerised to make new plastics
67
Why is reflux used to oxidise alchohol into carboxylic acid
It does not allow the reactants vapours to escape
68
Test for H2 gas
Add a lit splint A squeaky pop occurs
69
Test for CO2
Bubble through lime water Solution turns cloudy
70
Test for O2
Add a glowy splint The splint will re light
71
What is low resolution mass spectrometery
Measure the Mr to 1 dp Mr is same as m/z value
72
Why high resolution spectrometry cannot measure the mr of propan-1-ol and propan-2-ol
Because they have same mr because they have same molecular formula
73
Why does C has a relative molecular mass of 12
12C is standard reference
74
Why can nucleophillic addition of aldehyde and ketones can form receamic mixture
The bonding about C double bond O is planer This means 50 50 chance of nucleophile attacking on either side of molecule or other This results in equal proportion of both optical isomer being made and so receamic mixture is formed Receamic mixture is not optically active. The rotation of polarised light cancel out.
75
Uses of quaternary ammonium salt
Hair conditioner and fabric softener Also called catoinic sufacant
76
How to ensure the higher yield of primary amine
Use large excess of ammonia
77
What is the condition for further substitution in amines
Require excess haloalkane
78
How is nitrile converted into amine
Reduction reaction Requires H2 and nickle catalyst CH3 CN + 2H2 = CH3CH2NH2
79
Aycle chloride + water
Carboxylic acid
80
Acyl chloride + alchohol
Ester
81
Acyl chloride + ammonia
Amide
82
Acyl chloride + amine
N substituted amide
83
Why acid anhydrides are used more than Acyl chloride
Cheaper Less corrosive Don’t react with water Less voilent so less exothermic
84
What is the stationary phase in TLC
Silica gel
85
how is a mixture seperated in chromatography?
Mixture is seperated either due to the difference in solubility in mobile phase or due to different affinities to stationary phase.
86
Rf value
Distance moved by the component/ distance moved by solvent front
87
Advantages of TLC
faster than paper chromatography Will work on very small samples Can be used to determine when a chemical reaction is complete
88
Limitation of TLC
similar compounds may have similar Rf values Condition must be kept same to fairly compare the Rf value It can be difficult to find the solvent which separates all components of mixture Cannot be used to separate large quantities
89
Advantage of column chromatography
larger quantities can be separated
90
What happens to the solubility of a polar compound if polar solvent is used in TLC?
solubility of compound increases and it travels further up the TLC plate
91
What happens to the affinity of a polar compound if polar stationary phase is used in TLC?
Affinity increases and compound will not move very far
92
column chromatography and polarity
If polar solvent is used,the polar molecule will dissolve well and will be collected at the bottom first and if a polar stationary phase is being used, the polar molecule will have a higher affinity and it will take longer for the polar compound to be collected at the bottom.
93
Limitation of GC
Not all substances in the sample may ne separated and detected/peaks may be hidden behind others Unknown compounds have no reference retention time
94
GC-MS
GC can separate the components of the mixture but cannot identify them conclusively MS cannot seperate the components in mixture but can identify them.
95
USES of GC-MS
Forensics- minute particles at the scene of crime can be identified, often providing evidence in court trial Environmental analysis- Used to identify organic pollutants Airport security- used to detect traces of explosive in luggage and on human Space probes - spectometers have been sent to the Mars and Venus to collect and analyse materials and their environments
96
Why data book do not usuall contain values of Ka for a strong acid
Strong acid dissociates completely Ka value for strong acids tend to infinity/ very large/ cannot be divided by zero
97
Explain how vander waals arise between between molecules
Electrons movement in first molecule forms a temporary dipole This induces dipole in the other molecule Attraction between opposite charges in adjacent molecules
98
Identify the reagent or test that could distinguish between aqeous solution of SO2 or SO3 with same concentration
Reagent: pH meter SO2 2-3 SO3 0-1 ORRR Universal indicator SO2 orange red SO3 red

Chem (7 decks)

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