chemistry notes production of materials

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


3/18

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

!


4/18

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

%


5/18

'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

)


6/18

#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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7/18

"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.


8/18

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.


9/18

. 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


10/18

"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 !


11/18

"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


12/18

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

12


13/18

"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!


14/18

+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%


15/18

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)


16/18

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*


17/18

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

1


18/18

"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

chemistry notes production of materials

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