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Cues
What are the charges and
masses of the three types of
subatomic particles

Notes
Proton → +1 charge and mass of 1
Neutron → 0 charge and mass of 1
Electron → -1 charge and mass of 1/2000

Mass number (A)
Atomic number (Z)
Ions

The total number of protons and neutrons in the nucleus
The number of protons in the nucleus – identifies the element
Have a different number of protons and electrons - negative have more
electrons than protons and positive have less electrons than protons
...
J
...
Most of the
apha particles passed straight through the gold atoms but a very small
number were deflected backwards
...
He came up with the nuclear
model – a tiny positively charged nucleus at the cetre
surrounded by a cloud of negative electrons
...

- Each shell has a fixed energy
...

- Because the energy of shells is fixed, the radiation will have a fixed
frequency
...

The average mass of a molecule on a scale where an atom of carbon-12 is
exactly 12
...

Add up the relative atomic masses of all the ions in the formula unit

How to find relative formula
mass
Summary
-(Charge) (Mass) → Proton (+1) (1), electron (-1) (1/2000), neutron (0) (1)
- (A) – protons + neutrons, (Z) protons
-Ions → diff n
...
of neutrons
-n
...


Cues
Information found using a
Mass Spectrometer
Four stages of TOF mass
spectrometer

Notes
The relative atomic mass of an element and the relative abundance of its
isotopes, or relative molecular mass of a molecule
1
...
Acceleration
3
...
Detection

Electrospray ionisation

Sample dissolved in a solvent and pushed through a small nozzle at high
pressure, high voltage is applied to it so each particle gains a H+ ion, solvent
is then removed, leaving a gas made up of positive ions
...
Lighter ions experience a greater acceleration
...

Lighter ions reach the detector in less time
...
The data is used to calculate the mass/charge ratio which
can be used to produce a mass spectrum
...

- Consits of ionisation, acceleration, ion drift and detection
- The two types of ionisation are electrospray and electron impact
- The molecular ion peak is the meak with the largets m/z ratio

Cue
Principle Quantum Number

4 Sub shells, number of orbitals
and maximum number of
electrons
Rules for working out electron
configurations

Electron configuration of
transition metals
First Ionisation energy

Is ionisation endothermic or
exothermic?
Important point for ionisation
Energy
Factors affecting Ionisation
energy:

Why second IE is greater than
first
Why does IE decrease down
group 2

Why do IE increase across
period 3

Notes
Each shell is given a number called the principle quantum number, the
further a shell is from the nucleus, the higher the energy and the larger the
principle quantum number
...

The first ionisation energy is the energy needed to remove one electron from
each atom in one mole of gaseous atoms to form one mole of gaseous 1+
ions
...

- always refer to 1 mole of atoms rather than single atom
...

Nuclear charge – more protons, more positive nucleus, stronger attraction to
electrons
Distance from the nucleus – electrons closer to the nucleus will be more
strongly attracted
Shielding – The lessening of the pull of the nucleus by inner shells
The electron is being removed from a positive ion rather than an atom, which
will require more energy
...

The number of protons is increasing
...

-Aluminium’s outer electron is in 3p rather than 3s which has a slightly
higher energy so is further from the nucleus + extra shielding
Electron repulsion

Why does the 1st IE drop for G2
and G3?
Why does the 1st IE drop for G5
and G6?
Summary
-Sub-shells are divided into s, p, d and f sub-shells, which are each divided into orbitals
- 1st IE is energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of
gaseous 1+ ions
...

-One mole of any specified entity contains 6
...

-Converts between number of particles and number of moles
-Number of particles = Number of moles x Avogadro’s constant
Number of moles = (mass of substance) / Mr
or
Number of moles = concentration x volume(dm3)
pV = nRT
(p) → pressure measured in pascals (Pa)
(V) → volume measured in m3
(n) → number of moles
(T) → Temperature measured in kelvin (K)
(R) → 8
...

Any solution that you know the exact concentration of – involves reacting a
known amount of solid in a known amount of water to create a known
concentration
...
1 of
each other

Summary
-Moles = mass/Mr or moles = concentration x volume
-Ideal gas equation → pV = nRT
-You can do a titration to find the concentration of an acid or an alkali
-A standard solution is one that you know the exact concentration of
-Titration method → rise equipment, pipette 25cm3 of alkali into conical flask, add acid to burette, add a
few drops of indicator (phenolphthalein (pink in alkali, colourless In acid)), add acid to alkali and swirl
and add dropwise near end point, note volume before and after, repeat till 2 concordant results
...


How to calculate
theoretical yield

-Assume you’ve got 100g of the compound - turn percentages straight into
masses, then work out how many moles of each element are in 100g of the
compound
-Divide each number of moles by the smallest number of moles you found in
step 1, this gives the ratio of elements in the compound
...

-Economic advantages – will make more efficient use of its raw materials, also
less waste to deal with
...


Calculating atom
economy
Summary

-Having a high atom economy has a number of benefits to both the economy and the environment
...


Cue
Ionic formulas of Ammonium,
Carbonate, Hydroxide, Nitrate
and Sulfate

Electrostatic attraction
Electrical conductivity of ionic
compounds
Melting point of ionic
compounds
Solubility of ionic compounds
Molecules
Simple covalent compounds

Giant covalent structures
Graphite

Graphite’s properties

Diamond

Diamonds properties

Co-ordinate (dative covalent)
bonds
Summary
Bonding
Mp/Bp
Ionic
High
Simple covalent
Low
Giant covalent
High

Notes
Ammonium → NH4+
Carbonate → CO32Hydroxide → OHNitrate → NO3Sulfate → SO42Holds positive and negative ions together – is very strong
Ionic compounds conduct electricity when they’re molten or dissolved but
not when they’re solid, because the ions in a liquid are free to move and can
carry a charge
...

Compounds that are made up of lots of individual molecules are called simple
covalent compounds
...
In general, they have low melting and boiling points and are
electrical insulators
Are a type of crystal structure – have a huge network of covalently bonded
atoms (aka macromolecular structures)
...
The fourth outer electron of each carbon is
delocalised
...

-High melting point
-Extremely hard – used in diamond tipped drills and saws
-Good thermal conductor as vibrations travel easily through the stiff lattice
-Can’t conduct electricity
-Wont dissolve in any solvent
Where one of the atoms provides both of the shared electrons

State (standard c)
Solid
Usually fluid
Solid

Conduct electricity
Molten/dissolved
No
No (Ex graphite)

Soluble in water
Yes
Depend how polar
No

Cue
Charge clouds
Valence Shell Electron Pair
Repulsion Theory

Notes
Is an area where you have a bug chance of finding an electron – bonding
pairs and lone pairs of electrons exist as charge clouds
...
Lonepair charge clouds repel more than bonding-pair charge clouds, so bonding
pairs are pushed together by lone-pair repulsion

Drawing shapes of
molecules

How to find the number of
electron pairs

Awkward molecules

1
...
Work out how many atoms are in the outer shell of the central atom
3
...
If you’re looking at ions take its charge into account
5
...
Compare number of electron pairs to number of bonds to find the
number of lone pairs and bonding pairs
...
5
Shape: T-shape

Central atom with six
bonding pairs

Bond angle: 90
Shape: octahedral

Central atom with five
bonding pairs and one lone
pair

Bond angle: 90
Shape: square pyramidal

Bond angle: 109
...
5
Shape: bent / non-linear

Central atom with four
Bond angle: 90
bonding pairs and two lone Shape: square planar
pairs
Summary
-As a general rule, each lone pair decreases the bond angle by about 2
...
Its measured
on the Pauling Scale (higher number = more electronegative)
...
g
...

The bonding electrons are pulled towards the more electronegative atom,
this makes the bond polar, the greater the difference in electronegativity the
more polar the bond
In a polar bond, the difference in electronegativity between two atoms
causes a dipole
...
Whether or not a molecule is polar depends
on whether it has any polar bonds and its overall shape
...

Cause all atoms and molecules to be attracted to each other
...
This dipole can cause a temporary dipole in
the opposite direction on a neighbouring atom, the two dipoles are the
attracted to each other
...


Permanent dipole-dipole
forces

In a substance made up of molecules that have permanent dipoles, there will
be weak electrostatic forces of attraction between the δ+ and δ- charges on
neighbouring molecules
If you put an electrostatically charged rod next to a jet of polar liquid, the
liquid will move towards the rod
...
They are very
electronegative so draw the bonding electrons away from the hydrogen
atom
...
More delocalised
electrons mean that bonding is stronger and melting point is higher
...
They can also carry a charge so are good electrical
conductors
Metals are insoluble, except in liquid metals, because of the strength of the
metallic bonds
Has its particles very close together, so has a high density
and
is incompressible, the particles vibrate about a fixed point
and
can’t move about freely
...
They
form a lattice of closely packed positive ions in a sea of
delocalised electrons

Properties of liquid

Has a similar density to solids and is virtually
incompressible, the particles move about freely and
randomly allowing it to flow

Properties of gas

Particles have lots of energy and are far apart, so the
density is pretty low and its very compressible
...


Melting and boiling simple
covalent substances

To melt or boil simple covalent substances you only have to overcome the
weak intermolecular forces that hold the molecules together so they have
relatively low melting and boiling points
To melt or boil a giant covalent substance you do need to break the covalent
bonds holding the atoms together, so they have very high melting and boiling
points
...

-A substance will only conduct electricity if it contains charged particles that are free to move
-How soluble a substance is in water depends on the type of particles that it contains
...


Cue
Define Enthalpy Change

Define Standard Enthalpy
Change of Formation

Notes
The heat energy change of a reaction measured at a constant pressure
-⦵ is standard symbol and shows the enthalpy change was measured under
standard conditions and the substances are in their standard states
The enthalpy change when one mole of a
compound is formed from its constituent elements
in their standard states, under standard conditions

Define Standard Enthalpy
Change of Combustion

The enthalpy change when one mole of a substance is burned completely in oxygen,
under standard conditions

Define Standard Enthalpy
Change of Reaction
Endothermic

The enthalpy change when the reaction occurs in the molar quantities shown in the
chemical equation, under standard conditions
-Take in energy from their surroundings, so the
temperature in the reaction usually falls
...
The products of the reaction end
up with less energy than the reactants
...


What is thermochemistry?
What is mean bond
enthalpy?
What is bond dissociation
energy?
What’s the difference
between heat and
temperature?
How can you calculate
enthalpy change from
experimental data?
What are standard
conditions?

The study of heat changes during chemical reactions
The mean value of the bond dissociation energies of one mole of a covalent bond
from its range of compounds
The energy needed to break (or the energy released when formed) a covalent bond
with all species in the gaseous state
Heat is the sum of all particles energy, therefore it is affected by the amount of
substance; temperature is related to the mean kinetic energy of the particles in a
system, so is independent of the number of particles present
...
18gJ-1K -1) and ΔT is the change in temperature
100 kPa pressure
298 K (room temperature or 25oC)
Solutions at 1mol dm-3
all substances should have their normal state at 298K
The total enthalpy change for a reaction is independent of the route

What is Hess’s law?
Summary
• Enthalpy change is the amount of heat energy taken in or given out during any change in a system
provided the pressure is constant
...


• washes the equipment (cup and pipettes etc) with the solutions to be used
• dry the cup after washing
• put polystyrene cup in a beaker for insulation and support
• Measure out desired volumes of solutions with volumetric pipettes and
transfer to insulated cup
• clamp thermometer into place making sure the thermometer bulb is immersed
in solution
• measure the initial temperatures of the solution or both solutions if 2 are used
...
If a solid reagent is used then add
the solution to the cup first and then add the solid weighed out on a balance
...
The method assumes all
solutions have the heat capacity of water
...

• reaction or dissolving may be incomplete or slow
...

1
...
Work out
the moles of the reactants used 3
...
Add a sign and unit (divide by a thousand to
convert Jmol-1 to kJmol-1
The heat capacity of water is 4
...
In any reaction where the reactants
are dissolved in water, we assume that the heat capacity is the same as pure
water
...
The flame is enclosed
2
...
The flame heats up a copper spiral chimney placed in water, so less heat is
lost

Summary
-Calorimetry us a method of finding how much energy is given out or taken in by a reaction, by measuring the
temperature change that takes place during the reaction

Cue
What must particles do
in order to react?
What is activation
energy?
Maxwell-Boltzmann
Distribution

Notes
Collide with sufficient energy (activation energy) and the correct orientation

How does temperature
affect the rate of a
chemical reaction?

-Increasing the temperature gives the particles more energy
-Therefore more off the particles have enough energy to exceed the activation
energy
-Therefore a greater proportion of collisions are successful
-Therefore the rate of reaction increases
OR
-Increasing temperature will make the particles move faster-Therefore they'll
collide more frequently
-Therefore there will be more successful collisions per second
-Therefore the rate of reaction increases

How is the rate of
reaction affected by
pressure and
concentration?

Definition of Catalyst
How is the rate of
reaction affected by
catalysts?

The minimum energy which particles need to collide to start a reaction
...

-When the product is a gas, its rate of formation can be measured using a
mass balance
-When the reaction starts, start a stop clock or timer, then read off the
mass at regular time intervals
-Make a table with a column for ‘time’ and a column for ‘mass’ and fill it
in as the reactants go on
-You’ll know the reactions finished when the reading on the mass balance
stops decreasing
-This method is very accurate and easy to use but does not release gas
into the room, which could be dangerous if the gas is toxic or flammable
so best to carry out in a fume cupboard
...
1cm3
-Because no gas escapes, you can use this method for reactions that
produce toxic or flammable gases
-Vigorous reactions can blow the plunger out of the syringe, so you should
do a rough calculation of how much gas you expect the reaction to
produce

Summary
-If a precipitate is formed you can measure the rate of reaction by seeing how long it takes for a black mark
to no longer become visible through the flask as precipitate forms
-If a gas is produces you can measure rate if reaction by either measuring the change of mass over a period
of time or by measuring the volume of gas produced in a gas syringe over a set period of time

Cue
Define Dynamic Equilibrium

Give an essential condition
for an equilibrium mixture
...
At this point the concentrations of the
reactants and products are constant and appear not to change
...


Cue
What is Oxidation?

What is Reduction?

What is
disproportionation?
What are oxidising agents?
[O]
What are reducing agents?
[H]
What is the oxidation state
of all atoms (including
those in a diatomic
molecule such as H₂)?
Rules for assigning
oxidation numbers

Common oxidation
numbers

Balancing redox equations

More complex half
equations

Notes
-Increase in oxidation number
-Loss of electrons
-Addition of Oxygen
-Loss of Hydrogen
-Decrease in oxidation number
-Gain of electrons
-Loss of Oxygen
-Addition of Hydrogen
Disproportionation occurs when an element is simultaneously oxidised
and reduced to form two different products
A compound which oxidises another compound (by gaining electrons and
hence being reduced in the process)
A compound which reduces another compound (by losing electrons and
hence being oxidised in the process)
0

1
...
The oxidation numbers of the elements in a compound add up to zero
3
...
In a polyatomic ion (CO3 2-) the sum of the individual oxidation
numbers of the elements adds up to the charge on the ion
5
...

Group 1 metals = +1
Group 2 metals = +2
Al = +3
H = +1 (except in metal hydrides where it is –1 eg NaH)
F = -1
Cl, Br, I = –1 except in compounds with oxygen and fluorine
O = -2 except in peroxides (H2O2 ) where it is –1 and in compounds with
fluorine
...
Work out oxidation numbers for element being oxidised/ reduced 2
...
check to see that the sum of the charges on the reactant side equals
the sum of the charges on the product side
Multiply the half equations to get equal electrons
Add half equations together and cancel electrons
Multiply the half equations to get equal
Add half equations together and cancel electrons

Summary
-Oxidation is loss of electrons
-Reduction is gain of electrons
-Atoms and diatomic molecules have an oxidation state of 0

Cue
Define Periodicity

Notes
The repeating pattern of trends in physical and chemicals properties which
occurs across different period in the periodic table

Blocks in the periodic table

Trend in atomic radius

Trend in 1st ionisation
energy

Why is there a small drop in
ionisation energy between
Mg and Al
Why is there a small drop in
ionisation energy between P
and S

Melting and boiling points
for Na, Mg and Al

Melting and boiling point of
silicon
Melting and boiling point of
Cl2, S8 and P4

Trend in boiling point in
period 2

Atomic radii decrease from left to right across a period, because the
increased number of protons create more positive charge attraction for
electrons which are in the same shell with similar shielding
...

This is due to increasing number of protons
as the electrons are being added to the same
shell
...
Mg has its outer electrons in the 3s
sub shell, whereas Al is starting to fill the 3p subshell
...

There is a small drop between phosphorous and sulfur
...

When the second electron is added to an orbital there is a slight repulsion
between the two negatively charged electrons which makes the second
electron easier to remove
...
A
smaller sized ion with a greater positive charge
also makes the bonding stronger
...

Si is Macromolecular: many strong covalent bonds between atoms, high
energy needed to break covalent bonds– very high melting point and
boiling point
Cl2 (g), S8 (s), P4 (S)- simple molecular: weak van der Waals between
molecules, so little energy is needed to break them – low melting and
boiling points
S8 has a higher melting point than P4 because it has more electrons (S8
=128)(P4=60) so has stronger van der Waals between molecules
Li,Be metallic bonding (high melting point) B,C macromolecular (very high
melting point) N2 ,O2 molecular (gases- Low melting point as small van der
Waals) Ne monoatomic gas (very low melting point)

Summary
-An element is classified as s, p, d or f block according to its position in the Periodic Table, which is
determined by its proton number
...
As you go down the group, the
atoms have more shells of electrons making the atom bigger
...
The metallic bonding weakens as
the atomic size increases
...
Therefore, the electrostatic attractive forces
between the positive ions and the delocalized electrons weaken
...
In addition, the outer shell
electrons become more shielded from the attraction of the nucleus by the
repulsive force of inner shell electrons
When Group elements react with water, they are oxidised from a state of 0
to +2
...

The Mg would burn with a bright white flame
...
This is a much slower reaction than the reaction with steam
and there is no flame
...
TiO2 (solid) is converted to TiCl4 (liquid) at 900C:
2
...

3
...

Magnesium hydroxide is used in medicine (in suspension as milk of
magnesia) to neutralise excess acid in the stomach and to treat constipation
...
A suspension of calcium hydroxide
in water will appear more alkaline (pH 11) than magnesium hydroxide as it is
more soluble so there will be more hydroxide ions present in solution
...
The limewater turns cloudy as white calcium carbonate
is produced
...

-The hydroxide ions present would make the solution strongly alkaline
...
The barium absorbs the x-rays and so the gut shows up on the x-ray
image
...

BaCl2 solution acidified with hydrochloric acid is used as a reagent to test for
sulfate ions
...

-The hydrochloric acid is needed to react with carbonate impurities that are
often found in salts which would form a white barium carbonate precipitate
and so give a false result
...

Electronegativity decreases down the group
...
This is because their outer electrons are further from the
nucleus and more shielded as they have more inner electrons

Displacement reactions

Making bleach

Halogens are oxidising agents
Halide ions are colourless in a solution but when the halogen is displaced it
shows a distinctive colour
If you mix chlorine gas with cold, dilute sodium hydroxide solution at room
temperature, you get sodium chlorate(I) solution which is a common
household blech
...


Water treatment

Chlorate(I) ions kill bacteria, so adding chlorine to water can make it safe to
drink or swim on however chlorine is toxic and can cause severe chemical
burns on the eyes and skin and chlorine gas is harmful when breathed in
...
But the risk is smaller
than the risk on untreated water
...
To reduce something the halide ion needs to lose an electron
from its outer shell

Displacement reactions of
halide ions by halogens

Reactions of halide ions with
silver nitrate

Reactions with sulfuric acid
The reaction of fluoride and
chloride with concentrated
sulfuric acid

The reaction of bromide with
concentrated sulfuric acid

The reaction of iodide with
concentrated sulfuric acid

Naming chlorates/sulfates
Summary

-Test solution Is made acidic with nitric acid (remove ions which may
interfere with the test such as carbonates) and then silver nitrate solution is
added
-Fluorides: no precipitate
-Chlorides: white precipitate – dissolves in dilute NH3
-Bromides: cream precipitate – dissolves in conc
...
NH3
All the halides react with concentrated sulfuric acid to give a hydrogen halide
as a product to start with
-Aren’t strong enough reducing agents to reduce the S in H2SO4
-No redox reactions occur, only acid-base reactions occur
NaF(s) + H2SO4 (l) → NaHSO4 (s) + HF(g)
Observations: White steamy fumes of HF are evolved
...

Br- ions are stronger reducing agents than Cl- and F- and after the initial
acid-base reaction reduce the sulfur in H2SO4 from +6 to + 4 in SO2
Acid- base step: NaBr(s) + H2SO4 (l) → NaHSO4 (s) + HBr(g) Redox step: 2
HBr + H2SO4 → Br2 (g) + SO2 (g) + 2 H2O(l)
Observations: White steamy fumes of HBr are evolved
...
They can reduce the sulfur
from +6 in H2SO4 to + 4 in SO2, to 0 in S and -2 in H2S
...
g
...

-There is restricted rotation around the C=C double bond
...

Carbon atoms in a C=C double bond and the atoms bonded to these
carbons lie in the same plane (they’re planar)
...
Compare the atomic number of the atoms directly attached to
each side of the double bond; the atom of higher atomic number is
given priority
...
If the atoms are the same, consider the atoms at distance 2 from
the double bond
...
Arrange list in order of
decreasing atomic number
...

-E-Z isomers are due to restricted rotations around the C=C bond
-In mechanisms curly arrows show the movement of electrons

Cue
Petroleum
Fractional distillation in
industry

Fractional distillation in lab

What is cracking?
Economic reasons for
cracking

Thermal cracking

Catalytic cracking

Notes
Is a mixture consisting mainly of alkane hydrocarbons that can be
separated by fractional distillation
• Oil is pre-heated
• then passed into column
...

• Boiling point depends on size of molecules
...

• Heat the flask, with a Bunsen burner or electric mantle
• This causes vapours of all the components in the mixture to be produced
...

• The vapour of the substance with the lower boiling point reaches the top
of the fractionating column first
...

• The vapours with higher boiling points condense back into the flask
...

• The condenser cools the vapours and condenses to a liquid and is
collected
...

• To make use of excess larger hydrocarbons and to supply demand for
shorter ones, longer hydrocarbons are cracked
...

-Cracking involves breaking C–C bonds in alkanes
...

-Catalytic cracking takes place at a slight pressure, high temperature and in the presence of a zeolite
catalyst and is used mainly to produce motor fuels and aromatic hydrocarbons

Cue
Complete combustion
Incomplete combustion

Carbon monoxide

Nitrogen oxides

Ground level ozone

Notes
If you burn (oxidise) alkanes and other hydrocarbons with plenty of
oxygen you get only carbon dioxide and water
If there’s not enough oxygen when you burn a hydrocarbon you get
incomplete combustion which produces particulate carbon and
carbon monoxide gas instead of or as well as carbon dioxide
Carbon monoxide gas is poisonous as the molecules bind to the
same sites on the haemoglobin molecules in red blood cells as
oxygen molecules
...

Are a series if toxic and poisonous molecules which have the
general formula NOx
...
This can react further to produce nitrogen
dioxide
-Some unburnt hydrocarbons react with nitrogen oxides in the
presence of sunlight to form ground-level ozone, which is a major
component of smog
Irritates people’s eyes, aggravates respiratory problems and even
causes lung damage

Using catalytic converters
to remove pollutants from
the exhaust
Sulfur dioxide

Global warming

Summary

-If sulfur dioxide gets into the atmosphere, it dissolves in moisture
and is converted into sulfuric acid, this is what causes acid rain
-Acid rain destroys trees and vegetation, as well as corroding
buildings and statues and killing fish in lakes
-Can be removed from power station flue gases before it gets into
the atmosphere
...

Greenhouse gases in our atmosphere are very good at absorbing
infrared energy (heat)
...


Cue
Halogenoalkanes
Nucleophile
Nucleophilic substitution
with aqueous hydroxide ions

Notes
Halogenoalkanes can be classified as primary, secondary or tertiary depending on
the number of carbon atoms attached to the C-X functional group
...
g
...
The carbon atom and hydrogen atom are held together
with a triple bond
...


Nucleophilic substitution
with ammonia

An amine has the structure R3N
...

In amines, the nitrogen
always has a lone pair
...


Reactivity of
halogenoalkanes
Halogen elimination from a
halogenoalkane

Substitution gets faster going down the group because bond enthalpy decreases

Nucleophilic substitution vs
elimination

-By reacting a halogenoalkane with water under reflux, the molecule will
predominantly undergo nucleophilic substitution to form an alchohol
-By reacting a halogenoalkane with ethanol under reflux, the molecule will
predominantly undergo elimination to form an alkene
...

A particle with an unpaired electron
-They form when a covalent bond splits equally, giving one electron to
each species
-The unpaired electron makes them very reactive
Overall reaction: CH4 + Cl2 → CH3Cl + HCl
Free radicals are produced
Sunlight provides enough energy to break some of the Cl-Cl bonds –
photodissociation
The bond splits equally and each atom gets to keep one electron
...
Meaning you
get dichloromethane, trichloroethene and
tetrachloromethane
If methane’s in excess the chlorine will be
used up quickly and the product will be mostly chloromethane

Termination

If two free radicals join together, they make
a stable molecule – the two unpaired
electrons form a covalent bond

Chlorofluorocarbons

Halogenoalkane molecules where all the hydrogen atoms have been
replaced by chlorine and flurine atoms
Ozone absorbs a lot of UV stopping it
reaching us
Chlorine free radicals act as catalysts

Chlorofluorocarbons and the
ozone layer

Environmental problems of
-Cause damage to the ozone layer so HFCs and HCFCs were developed
CFCs
as a safer alternatve
Summary
-An unpaired electron in a free radical is represented by a dot
-Ozone, which is formed naturally in the upper atmosphere, provides protection from the suns UV rays
-Chlorine atoms are formed in the upper atmosphere when energy from ultraviolet radiation causes CCl bonds in chloroflurocarbons (CFCs) to break
-Chlorine atoms catalyse the decomposition of ozone and have helped form a hole in the ozone layer

Cue
Alkenes

Notes
Alkenes are unsaturated hydrocarbons
They have the general formula CnH2n
Have at least one C=C covalent double bond

Electrophile
Electrophilic addition
reactions

An elecotrophile is an electron-pair acceptor
The double bond in the alkene opens up and atoms are added to the carbon
atoms
...
Bromine is added across the double bond to
form a colourless dibromoalkane which happens by electrophilic addition

Summary
-In electrophilic addition the double bond in the alkene opens up and atoms are added to the carbon atoms
...
g
...
g
...

Addition polymers are produced from alkenes where the double bond is
broken to form a repeating unit

The reaction conditions used in the production of these polymer chains can
be altered to give the plastics produced different properties
-High pressures and temperatures produce branched chain polymers with
weak intermolecular forces
...
The main carbon chain of polyalkenes is also usually
non-polar
...

The monomers within a polymer chain have strong covalent bonds
...
Longer chains with
fewer branches have stronger intermolecular forces, making these polymer
materials more strong and rigid
...

The covalent bonds between the chlorine and the carbon atoms are
polar, with chlorine being more electronegative
...

Its used in drain pipes and window frames
You can add chemicals such as plasticisers, to polymers to modify their
properties
...

The plasticiser molecules get between the polymer chains and push
them apart
...

Plasticised PVC is more flexible than rigid PVC it is used to make
electrical cable insulation, flooring tiles and clothing

Summary
- Polymers are long chain molecules formed when lots of small molecules called monomers join together
-Addition polymers are unreactive

Cue
General formula
Primary, secondary and
tertiary alcohols

Notes
CnH2n+1

Bond angles in alcohols

Boiling points
How to dehydrate an
alcohol

The alcohols have relatively low volatility and high boiling points due to their
ability to form hydrogen bond between alcohol molecules
-Alkenes can be formed from alcohols by acid-catalysed elimination
reactions
-You can do this by eliminating water from alcohols in an elimination
reaction
-This allows you to produce alkenes from renewable resources

Purifying the product of a
reaction

-Distillation (a technique which uses the fact that different chemicals have
different boiling points, to separate them)
-Separation (with funnel and allow to settle into layers)
-Purification

Hydrating alkenes

-The standard industrial method for producing alcohols is to hydrate an
alkene using steam in the presence of an acid catalyst
-Steam hydration of ethene is used industrially to produce ethanol
...
The reaction is reversible and the yield is low
...
If its too
cold the reaction is slow, if its too hot the enzyme is denatured
...

Fermentation is low teach, uses cheap equipment and renewable resources
...

For example, sugars from sugar cane can be fermented to produce ethanol,
which can be added to petrol
...

-It is almost a carbon neutral process

Cue
Oxidation of primary
alcohols

Oxidation of secondary
alcohols

Oxidation of tertiary
alcohols
Tollens reagent

Fehling’s solution

Notes

A primary alcohol is first oxidised to an aldehyde, this can then be
oxidised to a carboxylic acid
1
...
Alcohol is mixed with excess oxidising agent and heated under
reflux
...
The only way to oxidise tertiary
alcohols is by burning them
Reagent: Tollens’ reagent formed by mixing aqueous ammonia and
silver nitrate
...

Conditions: heat gently
Reaction: aldehydes only are oxidised by Tollens’ reagent into a
carboxylic acid
...
Ketones result in no visible change
CH3CHO + 2Ag+ + H2O → CH3COOH + 2Ag + 2H+
Reagent: Fehling’s solution containing blue Cu 2+ ions
...
The copper (II) ions are reduced to copper(I) oxide
...
Ketones do not react Fehling’s solution
CH3CHO + 2Cu2+ + 2H2O → CH3COOH + Cu2O + 4H+

Summary
-Primary and secondary alcohols can be oxidised to aldehyde, carboxylic acids and ketones by
using an oxidising agent such as acidified potassium dichromate (VI)

Cue
Identification of functional
groups

Notes

Mass spectroscopy – the
molecular ion

The peak with the highest mass/charge ratio will be normally due to the
original molecule that hasn’t fragmented (called the molecular ion)
...

High resolution mass spectrometry can be used to determine the
molecular formula of a compound from the accurate mass of the molecular
ion
-Can measure the mass to 5 d
...
This can help differentiate between
compounds that appear to have similar Mr
If a compound contains a chlorine or a bromine atom then two molecular
ion peaks will occur: A M and a M+2 peak will occur due to the two
naturally occurring isotopes of chlorine or bromine
...
When you shine a beam of
IR radiation through a compound, the bonds can absorb energy from it and
vibrate more; however, the bond can only absorb radiation with the same
frequency as its vibrations, so this frequency will be missing from the
leftover radiation
...
A beam of IR radiation containing a range of frequencies is passed
through a sample
2
...
The instrument plots a graph of the intensity of the radiation emerging
from the sample (called transmittance) against radiation frequency
4
...
UV light from the Sun absorbed by Earth's surface and re-radiated as IR
radiation
2
...
This either gives the gas particles more energy (meaning they react
more) or causes their energy to be released into the atmosphere, heating it

High resolution mass
spectroscopy

M + 2 peak

Basic principle of IR
spectroscopy

What happens in an IR
spectrometer?

The fingerprint region
Infrared absorption and
global warming

Summary
-High resolution mass spectrometry can be used to identify compounds with similar Mr values

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