Chemistry Notes Production of Materials
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Transcript of Chemistry Notes Production of Materials
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7/25/2019 Chemistry Notes Production of Materials
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Production of Materials
Contents1. Fossil fuels provide both energy and raw materials such as ethylene, for the
production of other substances............................................................................. 2
Identify the industrial source of ethylene from the cracking of some of the
fractions from the rening of petroleum.............................................................2
Identify that ethylene, because of the high reactivity of its double bond, is
readily transformed into many useful products..................................................!
Identify that ethylene serves as a monomer from which polymers are made.. ..!
Identify polyethylene as an addition polymer and e"plain the meaning of this
term....................................................................................................................!#utline the steps in the production of polyethylene as an e"ample of a
commercially and industrially important polymer..............................................!
Identify the following as commercially signicant monomers by both their
systematic and common names$........................................................................%
&inyl chloride...................................................................................................%
'tyrene............................................................................................................ %
(escribe the uses of the polymers made from the above monomers in terms of
their properties...................................................................................................%
2. 'ome scientists research the e"traction of materials from biomass to reduce
our dependence on fossil fuels..............................................................................)
(iscuss the need for alternative sources of the compounds presently obtained
from the petrochemical industry........................................................................ *
+"plain what is meant by a condensation polymer............................................*
(escribe the reaction involved when a condensation polymer is formed...........*
(escribe the structure of cellulose and identify it as an e"ample of a
condensation polymer found as a maor component of biomass........................*
Identify that cellulose contains the basic carbon-chain structures needed to
build petrochemicals and discuss its potential as a raw material.......................*
!. #ther resources, such as ethanol, are readily available from renewable
resources such as plants.......................................................................................
(escribe the dehydration of ethanol to ethylene and identify the need for a
catalyst in this process and the catalyst used....................................................
(escribe the addition of water to ethylene resulting in the production of
ethanol and identify the need for a catalyst in this process and the catalyst
used....................................................................................................................
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(escribe and account for the many uses of ethanol as a solvent for polar and
non-polar substances.........................................................................................
#utline the use of ethanol as a fuel and e"plain why it can be called a
renewable resource............................................................................................
(escribe conditions under which fermentation of sugars is promoted.............../
'ummarise the chemistry of the fermentation process....................................../
(ene the molar heat of combustion of a compound and calculate the value for
ethanol from rst-hand data.............................................................................../
0ssess the potential of ethanol as an alternative fuel and discuss the
advantages and disadvantages of its use.........................................................../
Identify the IP0 nomenclature for straight-chained alkanols from 1 to . 13
%. #"idation-reduction reactions are increasingly important as a source of energy
............................................................................................................................ 11
+"plain the displacement of metals from solution in terms of transfer of
electrons...........................................................................................................11
Identify the relationship between displacement of metal ions in solution by
other metals to the relative activity of metals..................................................11
0ccount for changes in the o"idation state of species in terms of their loss or
gain of electrons...............................................................................................11
(escribe and e"plain galvanic cells in terms of o"idation4reduction reactions.12
#utline the construction of galvanic cells and trace the direction of electron
5ow...................................................................................................................12
(ene the terms anode, cathode, electrode and electrolyte to describe
galvanic cells.................................................................................................... 12
). 6uclear chemistry provides a range of materials............................................1!
(istinguish between stable and radioactive isotopes and describe the
conditions under which a nucleus is unstable..................................................1!
(escribe how transuranic elements are produced...........................................1!
(escribe how commercial radioisotopes are produced....................................1%
Identify instruments and processes that can be used to detect radiation........1%
Identify one use of a named radioisotope$.......................................................1%
- in industry...................................................................................................1%
- in medicine..................................................................................................1%
(escribe the way in which the above named industrial and medical
radioisotopes are used and e"plain their use in terms of their chemical
properties.........................................................................................................1%
2
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1. Fossil fuels provide both energy and raw materialssuch as ethylene, for the production of other substances
Identify the industrial source of ethylene from the cracking
of some of the fractions from the rening of petroleum
atalytic cracking$
7igh molecular weight fractions 8alkanes9 are broken into lower
molecular weight fractions 8shorter chain alkanes and small alkenes
ethylene and propene9
onditions are$ :eolite catalyst 80luminosilicate9
)33o
0 few atm pressure
'team or thermal cracking
0lkanes are decomposed completely into smaller alkenes 8butane,
propene and ethylene9 also producing hydrogen gas. ;his is used
more often due to its higher concentration of products
onditions are$ ust above atm pressure
Identify that ethylene, because of the high reactivity of its
double bond, is readily transformed into many useful
products
+thylene?sreactive double bond allows it to be easily converted into other
products such as ethanol and starting materials for plastics
Identify that ethylene serves as a monomer from which
polymers are made
0 polymer is a large molecule composed of smaller molecules
8monomers9, about !33 = !333 units = ethylene 8monomer9 is polymerised
to form polyethylene
!
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Identify polyethylene as an addition polymer and explain the
meaning of this term
Polyethyleneis an addition polymer because it forms by ethylene
molecules adding together without any loss of atoms
utline the steps in the production of
polyethylene as an example of a
commercially and industrially important polymer
!ow "ensity
#olyethylene $b%
&igh "ensity #olyethylene
$a%#ressure 1333-!333 atm 0 few atm'emperatur
e
!33o 8high9 @*3o 8low9
Catalyst #rganic pero"ide
8Initiator9
:ieglar-6atta catalyst
#roperties 7ighly branched
Aow density
Aow MP
'oft
Aow crystallinity
nbranched
7igh density
7igh MP
7ard
7igh crystallinity6ote$ the denser the polymer, the closer the molecules are together which
results in stronger dispersion forces 8since non-polar9 thus higher melting
point
'teps in the process$
1. Initiation$ ;he pero"ide initiator produces radicals which activatessome monomers
Initiation:B-#-#-B -C 28B-#D9
Activation:B-#D E 7272-C B-#-72-72D
2. Propagation$ 0ctivated monomers react with other monomers to
increase the chain length
Propagation: B-#-72-72D E 7272-C B-#-72-72-72-72D
%
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'ometimes the chain will curl around and GbitebackH on the e"isting
chain, removing a hydrogen and having an unpaired electron where
branching may occur.
!. ;ermination$ ;he free radicals combine with each other to form a
neutral species and chain growth stops
Termination:B-#-72-72D E B-#-72-72D -C B-#-72-72-
72-72-#-B
'ince there is no uniform polymer chain length there is a distribution of
molecular weights hence the term average molecular weightis
commonly used.
Identify the following as commercially signicant monomers
by both their systematic and common names(
)inyl chloride
hains of chloroethene form polychloroethene or poly 8vinyl chloride9
8P&9
*tyrene
hains of phenylethylene form polyphenylethylene or polystyrene
"escribe the uses of the polymers made from the above
monomers in terms of their properties
*tructure #roperty
0verage molecular
weight
Melting point, hardness
hain branching rystallinity 8density, melting point, hardness and toughness9
6ote$ the more orderly the arrangement, the stronger the
dispersion forces
hain stiening 'tiness, rigidity 8does not J5op around?9ross-linking Bigidity or elasticity
)
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#olymer +ses #roperties
A(P+ Krapping materials
Lags
Fle"ible toysMilk bottles
'oft
Fle"ible
Aow melting point6ot strong
7(P+ itchen utensils
ontainers
Bigid toys
Pipes 8transporting natural gas9
7ard
7igh tensile strength
7igh melting point
Poly8vinyl chloride9,
P&
'oft
+lectrical
insulation
Narden hoses
Bigid
Nuttering
'ewage pipes
'oft or rigid 8can be
adusted9
Polystyrene ;ool handles
( cases
Foam packaging 1
&ery hard
Bigid
. *ome scientists research the extraction of materials
from biomass to reduce our dependence on fossil fuels
"iscuss the need for alternative sources of the compounds
presently obtained from the petrochemical industry
0s oil reserves diminish, there will be no source of the raw materials
needed to make plastics. It is important to obtain a new source to keep up
with the high demand to produce plastics.
-xplain what is meant by a condensation polymer
0 condensation polymer is a polymer formed by the removal of a small
molecule 8often water9 when monomers are oined
1 Khen gas is bubbled during polymerisation, a lightweight foam is formed andsolidies
*
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"escribe the reaction involved when a condensation polymer
is formed
0 number of monomers are oined together to form a long chain but in the
process, water molecules are eliminated between each pair
"escribe the structure of cellulose and identify it as an
example of a condensation polymer found as a maor
component of biomass
ellulose consists of alternating inverted glucose units and forms a very
linear molecule. It is a
maor component in plantmaterial or biomass
8material produced by
living organisms9.
ellulose cannot be
digested by humans
however the similar in
structure biopolymer starch can be digested.
Identify that cellulose contains the basic carbon/chain
structures needed to build petrochemicals and discuss its
potential as a raw material
Nlucose units, in cellulose, contain * carbon atoms which can be regarded
as able to make the starting molecules for petrochemicals. 7owever, to
break cellulose into glucose it reOuires a lot of energy coming from oil inthe rst place. (eveloping ecient ways to allow cellulose as an
alternative source of chemicals, other than oil, is underway.
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0iopolymers
Poly8Q-7ydro"ybutyrate9 or P7L is a biopolymer having similar propertiesto polypropylene and also is biodegradable. Microorganisms called
Alcaligenes eutrophusare fed nutrients to multiply and grow. ;he diet is
then restricted 8such as 6itrogen9 so it produces P7L storing energy for
later use. ;he amount of P7L produced is from !3R to 3R of its own dry
weight. ;he P7L is separated out for use. 0lthough much more e"pensive
to produce than oil-based polymers, there is a growing demand for
biodegradability for applications such as disposable nappies and
packaging 8bottles, bags and wrapping lm9.
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. ther resources, such as ethanol, are readily
available from renewable resources such as plants
"escribe the dehydration of ethanol to ethylene and identify
the need for a catalyst in this process and the catalyst used(ehydration is a reaction where water is removed from a compound.
+thanolcan be dehydrated to form ethylenewith heat 8123oC9 and the
use of a catalyst$ concentrated sulphuric acid or phosphoric acid
27)#7 27%E 72#
"escribe the addition of water to ethylene resulting in theproduction of ethanol and identify the need for a catalyst in
this process and the catalyst used
7ydration is the addition of water to a compound. +thylene is hydrated to
form ethanol using heat and a catalyst$ dilute sulphuric acid
27%E 72# 27)#7
;he diagram below shows how the catalyst is involved in the hydration ofethylene$
/
concentrated
dilute
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"escribe and account for the many uses of ethanol as a
solvent for polar and non/polar substances
+thanol contains ends which are polar as well as can form hydrogen bonds
8#79 to dissolve polar substances. 7owever, it contains alkyl groups 8ethyl
27)9 which are non-polar thus it can also dissolve non-polar substances.
'ince o"ygen atoms are more electronegative than hydrogen and carbon
an electric dipole is formed thus it is polar. +thanol is a common solvent
in$
osmetics
Food colouring and 5avourings
Medicinal preparations
'ome cleaning agents
utline the use of ethanol as a fuel and explain why it can
be called a renewable resource
+thanol is a liOuid which can readily burn. ;here is already petrol
containing 13R ethanol which any engine can run on without
modications.
It is called a renewable resource because there is a cycle$ when ethanol is
burnt, it produces #2and 72# which are the raw materials for
photosynthesis forming glucose which can be broken down into ethanol
and thus the cycle repeats
"escribe conditions under which fermentation of sugars is
promoted
'uitable grain or fruit is mashed up with water
Seast is added
0ir is e"cluded
Mi"ture is kept at around !
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"ene the molar heat of combustion of a compound and
calculate the value for ethanol from rst/hand data
;he molar heat of combustion is the amount of heat liberated when one
mole of a substance undergoes complete combustion
4ssess the potential of ethanol as an alternative fuel and
discuss the advantages and disadvantages of its use
+thanol is a potential as an alternative fuel due to its alternative source
other than oil however currently the processes to obtain ethanol produce
a lot of greenhouse gases anyway.
0dvantages$
Benewable resource
Beduce greenhouse gas emissions
(isadvantages$
Aarge areas of land would be needed to grow suitable crops
(isposal of waste fermentation liOuors
#btaining glucose 8to ferment into ethanol9 from cellulose is not
very ecient due to the energy for machinery and keeping atconstant temperatureto digest the cellulose by either$
ellulase enTymes$ 6a#7 is added to nely grounded
cellulose materials used to open up bres for the enTymes to
produce glucose 'trong acids$ moderately concentrated 72'#%is added a
suspension of cellulose 8with wood chips9 producing glucose
Identify the I+#4C nomenclature for straight/chained
alkanols from C1 to C2
G-olH su" 6umber to denote location of #7 at a certain carbon atom
Neneral formula$ n72nE1#7
1. Methanol2. +thanol!. Propanol%. Lutanol). Pentanol*. 7e"anol
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5. xidation/reduction reactions are increasingly
important as a source of energy
-xplain the displacement of metals from solution in terms of
transfer of electrons0 displacement reaction is when a metal converts another metal ion to a
neutral atom. ;his is done by the transferring of electrons e.g.
u donates electrons to form u2E8o"idation9
0gEreceives electrons to form 0g 8reduction9
Identify the relationship between displacement of metal ions
in solution by other metals to the relative activity of metals
;he more reactive metal is the one which will displace the other metal
from a solution of its ions
;he metals on the left are more reactiveU easily o"idised than compared to
the right
4ccount for changes in the oxidation state of species in
terms of their loss or gain of electrons
0n o"idation state is the valence of the atom e.g. for monatomic ions the
o"idation state is the positive or negative charge on the ion
If there is an increase in o"idation state, the atom has lost electrons
8o"idation9
If there is a decrease in o"idation state, the atom has gained electrons
8reduction9
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"escribe and explain galvanic cells in terms of
oxidation6reduction reactions
Nalvanic cells are devices which uses chemical reactions to produce
electricity. ;his is done by splitting up the o"idation and reduction
reactions in dierent locations. 0s seen in the picture, the u loseselectrons 8o"idation9 and 5ows through the wire to give 0gEions electrons
8reduction9.
utline the construction of galvanic cells and trace the
direction of electron 7ow
0 u strip is placed in a beaker of u86#!92solution connected with a wire
to a 0g strip in another beaker of 0g6#!. ;he 5ow of electrons goes from
the u to 0gU where the o"idation reaction occurs to where the reductionreaction occurs.
0 salt bridge is used to maintain neutrality in both beakers and keep the
reactions continuing i.e. the concentration of u2E increases as well as 6#!-
in the left beaker as 6#!-ions 5ow from the right beaker to the left beaker
which also balances the 6#!-concentration with the decreasing
concentration of 0gE. ;he substances used in the salt bridge must not
react with the ions i.e. form precipitates.
"ene the terms anode, cathode, electrode and electrolyte
to describe galvanic cells
0node$ the electrode where o"idation occurs
athode$ the electrode where reduction occurs
1!
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+lectrode$ the conductors of a cell which are connected to the e"ternal
circuit
+lectrolyte$ a substance which in solution or molten state conducts
electricity
!eclanche Cell $"ry Cell%
0node reaction$
:n 8s9 :n2E
8aO9E 2e-
athode reaction$
Mn#28s9E 67%E
8aO9E 72#8l9 E e- Mn8#79!8s9E 67!8aO9
706N+
6ote$ the anode and cathode must 6#; touch each other otherwise theredo" reaction will occur and will short circuit the battery
0attery Cost and #racticality Impact on
*ociety
-nvironmental
Impact(ry cell heap
6on rechargable
(oes not store a lot of
charge
Produces 1.)&
ould potentially leak
Portable power
source
Powers small
electrical devices
Improves Ouality of
life
Inert manganese o"ide
compounds
1%
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0utton cell0node reaction$
:n 8s9E 2#7-8aO9 :n#8aO9 E 72# 8l9E 2e
-
athode reaction$
0g2# 8s9E 72#8l9E 2e- 20g8s9E 2#7
=8aO9
0attery Cost and #racticality Impact on
*ociety
-nvironmental
ImpactLutton
cell
+"pensive
6on rechargeable
Produces 1.)&
onstant, stable
voltage
Powers very small
devices 8e.g.
hearing aids and
heart pace makers9
= improves life
e"pectancy andOuality of life
#7 is caustic
'ilver needs to be
recycled 8e"pensive
material from mining9
6o highly to"ic
materials
1)
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8. 9uclear chemistry provides a range of materials
"istinguish between stable and radioactive isotopes and
describe the conditions under which a nucleus is unstable
Badioactive isotopes are isotopes spontaneously emitting radiation and
stable isotopes do not.
Nenerally, the nucleus is unstable if the atomic number is greater than !
or if the ratio of neutrons to protons places it outside the Tone of stability
8red9.
"escribe how transuranic elements are produced
ertain isotopes are not ssile i.e. does not split when hit by a neutron but
instead it forms a new element. ;he neutron will Jdecompose? releasing
beta radiation 8electrons9 and adding a proton to the nucleus thuschanging its atomic number.
1*
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6uclei can also be bombarded with positive particles using linear
accelerators orcyclotrons.
"escribe how commercial radioisotopes are produced
6uclear reactors$ a source of neutrons e.g. cobalt-)/ captured a neutron
to form cobalt-*3 or to obtain molybdenum-// 8technetium-//m is then
obtained from this9 from ssion of uranium.
yclotrons$ small positive particles 8such as helium and carbon9 bombard
the target nucleus to obtain isotopes such as 5uorine-1. ;he particle
goes through alternating magnetic elds so it is pulled and pushed to
accelerate it to high speeds.
Identify instruments and processes that can be used todetect radiation
Photographic lm$ lm darkens when e"posed
loud chamber$ contains supersaturated water or alcohol vapour
Neiger-Muller counter$ uses ionisation of gas particles to detect
electrons 'cintillation counter$ certain substances emit a 5ash of light when
e"posed
Identify one use of a named radioisotope(
/ in industry
Iridium-1/2
Industrial radiography 8non-destructive testing9
/ in medicine
;echnetium-//m
Badioactive tracer 8cancer diagnosis9
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"escribe the way in which the above named industrial and
medical radioisotopes are used and explain their use in
terms of their chemical propertiesIndustry$ radioisotopes emit radiation through the material which absorbs
some it and a detector picks up the remaining. ;he thicker the material
the less radiation the detector will receive which is connected to the
controller which adusts the rollers to the thickness reOuired. ;he
radioisotope has to emitlow energy radiation and have a long half
life.
Badioisotopes can also be used to detect leaks in pipes using a radio
tracker. If radiation is detected in the area, there is a leak in the pipe. It
might have ashort half life to prevent contamination of water.
Badiation can kill micro-organisms and bacteria to sterilise eOuipment and
minimise spoilage in food. 'he energy must not be too high otherwise
it could make the food radioactive and the source must have a long half
life to minimise replacement.
Medical$ radioisotopes 8such as cobalt-*39 emit gamma rays which are
used to kill cancer cells and its half life is suitable to be stored for a
while but short enough to emit suitable amounts of radiation.
#ther radioisotopes 8such as technetium-//m9 can be distributed
throughout the bloodstream to observe clotting, constrictions or disorders
and also assess the heart. It hasashort half life thus causing minimal
damage to the patient.
1