9.2 - Production of Materials (1)

8/10/2019 9.2 - Production of Materials (1)

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HSC - Stage 6 2 Unit Chemistry

9.2 Production of Materials:

. Construct word and balanced formulae equations of all chemical

reactions as they are encountered in this module:

BASIC reactions to remember:

Acid reactions:

acid + base salt + water

acid + metal salt + hydrogen gas

acid + carbonate carbon dioxide gas + salt + water

Complete combustion :

hydrocarbon + oxygen water + carbon dioxide

Dis lacement reactions:

Y + !anion" + Y !anion"# where Y $ on activity series %

Alkene/alkane reactions:

Crac!in" o& pentane:

pentane ethylene + propane

C' H(2 !g" C2H) !g" + C*H !g"

#ydro"enation o& ethylene:

ethylene + hydrogen ethane

C2H) !g" + H2 !g" C2H6 !g"

#ydration o& ethylene:

ethylene + water ethanol

C2H) !g" + H2, !l" C2H' ,H !l"

#alo"enation !more speci&ically Chlorination " o& ethylene:

ethylene + chlorine ( 2-dichloroethane

C2H) !g" + Cl2 !g" C2H) Cl2 !l"

#ydrohalo"enation !more speci&ically #ydrofluorination " o& ethylene:

ethylene + hydrogen &l.oride &l.oroethane

Copyright / 2001# hmad Shah 3dil


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C2H) !g" + H4l !g" C2H' 4l !g"

5eaction o& cyclohe$ene with bromine water :

cyclohexene + bromine + water 2-bromo-(-cyclohexanol + hydrogen

bromideC6H(0 !l" + r 2 !a7" + H2, !l" C6H(0 r,H !l" + H r !a7"

Fermentation and other ethanol-based reactions:

Dehydration o& ethanol:

ethanol ethylene + water

C2H' ,H !l" C2H) !g" + H2, !l"

Combustion o& ethanol:

ethanol + oxygen carbon dioxide + water

C2H' ,H !l" + *, 2 !g" 2C, 2 !g" + *H2, !g"

%ermentation o& gl.cose:

gl.cose ethanol + carbon dioxide

C6H(2 , 6 !a7" 2C2H' ,H !a7" + 2C, 2 !g"

Electrochemistry:

Dis lacement o& copper &rom sol.tion d.e to 8inc:8inc + copper s.l&ate 8inc s.l&ate + copper

9n !s" + C.S, ) !a7" 9nS, ) !a7" + C. !s"

&onic equation o& this reaction:

8inc + copper!33" ion + s.l&ate ion 8inc!33" ion + s.l&ate ion + copper

9n + C. 2+ + S, ) 2- 9n 2+ + S, ) 2- + C.

'et ionic equation o& this reaction:

8inc + copper!33" ion 8inc!33" ion + copper 9n !s" + C. 2+ !a7" 9n 2+ !a7" + C. !s"

#alf(equations o& this e7.ation:

9n 9n 2+ + 2e

C. 2+ + 2e C.



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). %ossil fuels ro*ide both ener"y and raw materials such as ethylene+ for

the roduction of other substances:

RECALL:

n ;< => is a hydrocarbon with ,=;Y single bonds between the carbons%

n ;=> is a hydrocarbon with ( or ?,5> do.ble bonds between carbons%

Identify the industrial source of ethylene from the cracking of some of the

fractions from the refining of etroleum:

Petroleum !cr.de oil" is a complex mixt.re o& hydrocarbons consisting mainly o&

al@anes and smaller 7.antities o& other hydrocarbons s.ch as al@enes%

,thylene !systematic name: ethene" C2H) is one o& the most .se&.l s.bstances in

the petrochemical ind.stry and is in e!tremely high demand%

Crac!in" is the process o& Abrea@ingB large hydrocarbon molec.les into smaller

length chains .sing heat ! "%

,- : the crac@ing o& pentane into ethylene and propane:

Cr.de oil is separated into its di&&erent components .sing &ractional distillation%

5eason &or Crac@ing:

3n re&ineries the o.tp.t o& prod.cts D,>S =,E match the economic demand#

>EHY;>=> is in Fery high demand b.t it only ma@es .p a Fery small

percentage o& cr.de oil%

Eo match the demand &or ethylene low-demand long-chain hydrocarbons are

Acrac@edB and ethylene is prod.ced%

Ehere are two &orms o& crac@ing catalytic crac@ing and thermal crac@ing%



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Catalytic Crac!in" :

3n this process carried o.t in a Acat-crac@erB longalkane molec.les !C(' -

C2'" are bro@en into G.st two molec.les an al@ane and an al@ene%

Ehis &orm o& crac@ing .ses a C E ;YSE to brea@ the al@anes%Ehe catalyst .sed are "eolite crystals:

9eolites are al.minosilicates !compo.nds made o& al.mini.m silicon and

oxygen" with small amo.nts o& metal ions attached%

Ehe reaction is carried o.t at '00 C in the absence o& air with press.re G.st

aboFe atmospheric press.re%

Ehis process .ses less heat than EH>5? ; crac@ing b.t it cannot

decompose large molec.les com letely into ethylene so it is ins.&&icient inmeeting the demands o& the ind.stry%

hermal Crac!in":

lso called AsteamB crac@ing%

Ehis process does not .se a catalyst only Fery high temperat.res%

Ehe long-chain al@anes are passed thro.gh metal t.bes at temperat.res o&

100 C to (000 C at press.re aboFe atmospheric%

Ehe al@anes are decomposedcom letely into ethylene and other short chains%

Ehe .se o& steam is that is allows &or easy &low o& hydrocarbon gases it

dil.tes the mixt.re to create smooth reactions and it remoFes carbon deposits

in the metal t.bes%

Identify that ethylene# because of the high reactivity of its double bond# is

readily transformed into many useful roducts:

>thylene has a highly reactiFe do.ble-bond# 3t is a site o& Fery H3IH

>;>CE5,= D>=S3EY% ,ne o& the bonds readily brea@s creating two new bonding sites on the molec.le:



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#ydrohalo"enation: 3n this reaction a hydrohalogen !s.ch as HCl or H4l"

and ethylene react to &orm a halo-ethane%,- : H4l reacting with ethylene

&orms &l.oroethane%

Ehe ? 3= adFantage o& the do.ble bond is that ethylene can .ndergo

polymerisation a Fery important reaction that will be disc.ssed later%

Identify that ethylene serves as a monomer from $hich olymers are made:

Polymerisation is the chemical reaction in which many identical small molec.les

combine to &orm one Fery large molec.le%

Ehe small identical molec.les are called ?,=,?>5S and the large molec.le is

called a J,;Y?>5%

eca.se o& its reactiFe do.ble bond ethylene is able to .ndergo polymerisation#

ethylene a monomer &orms the polymer poly!ethylene"%

Identify olyethylene as an addition olymer and e! lain the meaning of

this term:

3n an addition olymerisation reaction no additional molec.les !e%g% water" are

prod.ced there is no gain or loss o& atoms the do.ble bond simply AopensB and

monomers attach%



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Jolyethylene is an addition polymer as the ethylene molec.les combine with each

other in the &ollowing way:

s can be seen no extra molec.les are prod.ced% more realistic representation

o& the polyethylene polymer !with nine repeating .nits" is:

%utline the ste s in the roduction of olyethylene as an e!am le of a

commercially and industrially im ortant olymer:

>thylene is a commercially and ind.strially important polymer%

Ehere are two methods &or its prod.ction:

#i"h Pressure Method: 3n this process ethylene is s.bGected to press.res o& (00-*00 ?Ja with temperat.re in excess o& *00 C% molec.le called the

initiator is introd.ced .s.ally a peroxide% Ehe initiator starts o&& a chain-

reaction creating the polyethylene macromolec.le%

Ehis process creates 5 =CH>D chains o& polyethylene that cannot be

pac@ed together tightly% Eh.s branched polyethylene is called low-density

polyethylene !;DJ>"%

/ie"ler('atta Process: Ehis process .ses only a &ew atmospheres o& press.re

and temperat.res o& abo.t 60 C% catalyst is .sed: it is a mixt.re o& titani.m

!333" chloride and a [email protected] compo.nd%

Ehis process creates U= 5 =CH>D chains o& polyethylene that can be

pac@ed together Fery densely% Eh.s .nbranched polyethylene is called

high-density polyethylene !HDJ>"%



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Ehe steps ta@en to prod.ce the polymer are the same in both methods b.t the

initiator molec.le is di&&erent:

3=3E3 E3,=: Ehe initiator molec.le is added to the ethylene container# in the

diagram below it is shown as a ero!ide radical !an oxygen compo.nd with a&ree electron"% Ehe initiator reacts with one ethylene molec.le brea@ing its

do.ble bond and attaches to only ,=> bonding site creating an ethylene-

initiator 5 D3C ;% Ehe KdotL represents a &ree highly reactiFe electron%

J5,J I E3,=: nother ethylene monomer attaches to this radical opening

another bonding site then another attaches and so on rapidly increasing the

length o& the chain% ,ne o& these reactions:

5epeating this reaction many times giFes a general &orm.la:

E>5?3= E3,=: Ehe reaction stops !terminates" when two s.ch chains

collide and the two radicals react &orming a longer chain% Ehis is a random

process so the length o& polyethylene chains can Fary greatly% !Ehe peroxide

initiator is eFent.ally eng.l&ed by the reaction and so is no longer present at

termination":



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within ben8ene are not reactiFe# b.t the do.ble bonds in al@enes are

reactiFe%

3t &orms polystyrene%

Diagram o& polystyrene:

&escribe the uses of the olymers made from the above monomers in terms

of their ro erties:

ow(Density Polyethylene 3 DP,4:

Uses 5elated to Jroperties:

Jlastic cling wrap# beca.se it is &lexible clear and non-toxic%

Disposable shopping bags# beca.se it is cheap and relatiFely strong%

?il@ bottles# as it is non-toxic cheap .n-reactiFe and recyclable%

#i"h(Density Polyethylene 3#DP,4:



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Crystal Polystyrene:


CD cases and cassette tapes# .sed beca.se polystyrene is clear hard rigid

easily shaped and is a good ins.lator%Screw driFer handles and @itchen c.pboard handles# Fery d.rable and

strong hard and in&lexible%

,$ anded Polystyrene:


Jac@aging and disposable c.ps# it is light !&.ll o& air" cheap and it is a

thermal ins.lator%

So.nd-proo&ing# it is a shoc@ absorbent material light easily shaped% PRACTICAL ' Identify data# lan and erform a first-hand investigation to

com are the reactivities of a ro riate alkenes $ith the corres onding

alkanes in bromine $ater:

3n this experiment an al@ene !cyclohe!ene " and its corresponding al@ane

!cyclohe!ane " were placed in a sol.tion o& yellow bromine water%

5,16 : 3t was obserFed that cyclohexene t.rned the bromine water colo.rless

whereas the cyclohexane sol.tion remained yellow% Eh.s ,=;Y cyclohexene reacted with the bromine water and th.s the al@ene was

said to be more reactiFe than its corresponding al@ane# this is d.e to the do.ble

bond o& the al@ene%

5eaction:



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761 &%8 the method:

Cyclohexene and cyclohexane were .sed instead o& ethylene or propene

beca.se C( to C) are gases at room temperat.re and wo.ld be hard to

manage# cyclohexene is li7.id at room temperat.re%lso cyclohexeneOane was .sed instead o& hexeneOane beca.se cyclic

hydrocarbons are more stable than their linear co.nterparts%

&M& A & '1 o& the method:

Ehe al@ane reacted slightly as UN radiation ca.sed slow s.bstit.tion

reactions%

1A%, 8 preca.tions:

romine water is highly toxic i& ingested and is slightly corrosiFe%

Cyclohexene and cyclohexane are both poisono.s i& ingested and both giFe

o&& &.mes as they are highly Folatile and highly &lammable%

PRACTICAL ' Analyse information from secondary sources such as

com uter simulations# molecular model kits or multimedia resources to

model the olymerisation rocess:

3n this experiment molecular modellin" !its were .sed to show how

polyethylene is prod.ced thro.gh the polymerisation o& ethylene% Ehe class was diFided into gro.ps and each gro.p was proFided with a @it%

* ethylene monomers were created by each gro.p with black balls representing

carbons and smaller $hite balls representing hydrogen%

Ehen the monomers were ApolymerisedB: each gro.p combined their monomers

with eFery other gro.p .ntil a large chain was created a section o& polyethylene%

761 &%8 the method:

Ehe models created a *D representation o& the chemical process which led to

greater .nderstanding o& polymerisation%

Ehe .se o& ball-and-stic@ models depicting the do.ble-bond with &lexible

r.bber rods greater increased .nderstanding o& the process%




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Ehe model only proFided a Fery limited section o& a polyethylene molec.le as

there were limited n.mbers o& @its%

Ehe .se o& catalysts !s.ch as 9eigler-=atta catalysts" was not shown in the

process and th.s it was not completely acc.rate%



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2. 1ome scientists research the e$traction of materials from biomass to

reduce our de endence on fossil fuels:

RECALL:

Addition polymers &orm =, extra molec.les when their monomers Goin together%

Ehis type o& polymerisation reaction occ.rs d.e to a do.ble-bond opening

creating 2 new bonding sites%

&iscuss the need for alternative sources of the com ounds resently

obtained from the etrochemical industry:

Ehere is an oFerwhelming need &or alternatiFe so.rces o& compo.nds that are

presently deriFed &rom the petrochemical ind.stry !i%e%crude oil "%

Ehis is beca.se cr.de oil is a &ossil &.el and is hence a non-renewable reso.rce%

ased on c.rrent .sage statistics cr.de oil reserFes co.ld be completely .sed .p

within a &ew decades%

Compo.nds obtained &rom the petrochemical ind.stry haFe two .ses:

Ehe prod.ction o& ener"y : )P o& cr.de oil is .sed to prod.ce energy% Ehis

incl.des petrol and diesel &or cars heating oil Get-engine oil and ;JI%

Ehe prod.ction o& materials : Ehe other (6P is .sed to prod.ce polymers

pharmace.ticals and other extremely important chemicals% Some o& the materials created &rom cr.de oil cannot be deriFed by any other ways

!or wo.ld be m.ch too expensiFe to synthesise" so once cr.de oil is exha.sted

there will be no way to prod.ce them%

3t has been arg.ed that alternatiFe &.els be created so that cr.de-oil can be

reserFed &or .se by the petrochemical ind.stry to create materials%

Ehe increasing cost o& cr.de oil in this c.rrent day and age is another &actor%

lso many co.ntries that contrib.te a signi&icant portion o& the worldBs cr.de oil

are Fery economically and politically .nstable with &ragile in&rastr.ct.re and

s.pply &rom these co.ntries can be Fery erratic%

,ne o& the most appealing replacements &or cr.de-oil deriFed compo.nds is

cell.lose# this is beca.se it contains all the carbon-chain str.ct.res needed &or the

prod.ction o& materials and it is so remar@ably ab.ndant on >arth%



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E! lain $hat is meant by a condensation olymer:

condensation polymer is a polymer that prod.ces > E5 molec.les !.s.ally

water" when its monomers combine%

>xamples incl.de nat.ral polymers s.ch as cell.lose starch protein D= andman.&act.red polymer &abrics s.ch as sil@ polyester and nylon%

&escribe the reaction involved $hen a condensation olymer is formed:

3n condensation the monomers reactdifferently than in addition reactions%

Ehere is no do.ble-bond that opens !as in addition"# the 4U=CE3,= ; I5,UJS

o& the two monomers react together &orming a new bond and water%

,- ( Cell.lose:

Cell.lose is a nat.ral polymer &ormed thro.gh the polymerisation o& gl.cose-lucose C6H(2 , 6 is the monomer in this polymer%

Ehe reaction occ.rs between 2 hydroxyl gro.ps &orming a glycosidic bond:

s can be seen the reaction sites are the hydroxyl !,H -" gro.ps on the &irst

and &o.rth carbons !C-( and C-)"%

>ach gl.cose molec.le has 2 reaction sites# that is why it can polymerise%

,ne C-,H bonds to another C-,H &orming a C-,-C bond ! glycosidic bond "%

Ehe le&t oFer H+ and ,H - combine &orming water%

&escribe the structure of cellulose and identify it as an e!am le of a

condensation olymer found as a ma(or com onent of biomass:

Cell.lose is a nat.rally occ.rring condensation polymer !a bio olymer "

3t is the single most ab.ndant polymer on >arth ma@ing .p abo.t '0P o& the total

biomass o& the planet !biomass is the mass o& all organisms in a giFen area"%



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3t is long polymer chain made o& repeating gl.cose monomer .nits which 4;3J

&or eFery alternate gl.cose as can be seen in the aboFe diagram%

boFe the str.ct.re o& gl.cose is 7.ite cl.ttered% Eo demonstrate a section o& a

cell.lose chain a simpli&ied &orm o& gl.cose will be .sed% Il.cose# in short-&orm:

3t is ass.med that at

eFery corner there is a

carbon atom%

Hydrogen atoms are not

shown b.t are also

ass.med to be there and are ded.ced by @nowing that carbon ma@es ) bonds%

Hence the str.ct.re o& cell.lose can be shown as:

s can be seen it is a Fery linear molec.le d.e to its straight chains%

Identify that cellulose contains the basic carbon-chain structures needed to

build etrochemicals and discuss its otential as a ra$ material:

Ehe S3C carbon-chain str.ct.res that are .sed to ma@e petrochemicals are

short-chained al@enes s.ch as ethylene !2C" ro ene !*C" and butene !)C"%

Il.cose the basic str.ct.re in cell.lose is a 6C molec.le%

Hence it has to potential to be trans&ormed into the aboFe compo.nds%

Ehe Jotential o& Cell.lose as a 5aw ?aterial:

ltho.gh theoretically cell.lose can proFide limitless amo.nts o& renewable

raw materials this is c.rrently too expensiFe and impractical%

Ehis is beca.se in order to deriFe ethylene etc% &rom cell.lose &irstly

cell.lose m.st be bro@en into gl.cose !.sing either bacterial digestion or



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acidic decomposition" then &ermented !with yeast" into ethanol and then

dehydrated !.sing H 2S, ) " into ethene# this is a lengthy and expensiFe process%

Hence cell.lose has great potential b.t is c.rrently not economical%

REPORT ' )se available evidence to gather and resent data from secondary sources and analyse rogress in the recent develo ment and use

of a named bio olymer* +his analysis should name the s ecific en"yme,s

used or organism used to synthesise the material and an evaluation of the

use or otential use of the olymer roduced related to its ro erties:

'ame of io olymer : iopolQ

3t is made o& olyhydro!ybutyrate !JH " and olyhydro!yvalerate !JHN"%

r"anism 6sed :

lcaligenes e.troph.s !a bacteri.m"%

Production :

3n ind.strial prod.ction % >.troph.s is grown in an enFironment favourable

to its gro$th to create a Fery large pop.lation o& bacteria !s.ch as high

nitrates phosphates and other n.trients"%

Rhen a s.&&iciently large pop.lation has been prod.ced the enFironment is

changed to one that is high in glucose high in Faleric acid and low innitrogen %

Ehis .nnat.ral enFironment ind.ces the prod.ction o& the polymer by the

bacteri.m# the polymer is act.ally a nat.ral &at storage material created by the

>.troph.s in adFerse conditions%

;arge amo.nts o& a chlorinated hydrocarbon s.ch as trichloromethane are

added to the bacteriaOpolymer mix# this dissolFes the polymer%

Ehe mixt.re is then &iltered to remoFe the bacteria%Ehe polymer is extracted &rom the hydrocarbon solFent as a powder which is

then melted or treated &.rther to create a .sable polymer%

Pro erties:

3t is 3,D>I5 D ;> and 3,C,?J E3 ;>



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3t is non-toxic insol.ble in water permeable to oxygen resistant to UN light

acids and bases high melting point high tensile strength%

6ses in 5elation to Pro erties:

3t has many medical applications !e%g% biocompatible stiches that dissolFe or are absorbed by the body"%

Disposable containers &or shampoo cosmetics mil@ bottles etc% as it only

ta@es 2 years to decompose bac@ into nat.ral components%

Disposable ra8ors c.tlery r.bbish bags plastic plates etc%

Ad*anta"es:

3t is biodegradable .nli@e polyethylene and other petrole.m deriFed plastics

and so will help to red.ce leFels o& r.bbish in land&ills%

3t is compatible with organisms !biocompatible"# it is not reGected by the

bodyBs imm.ne system and so can be .sed sa&ely%

3t is a renewable reso.rce%

Disad*anta"es:

3t is c.rrently Fery expensiFe and c.rrently the demand is not high eno.gh &or

it to be economically Fiable%

%uture De*elo ments:

5ecently the gene &or prod.cing iopol polymer strands &rom the lcaligenes

>.troph.s bacteria was extracted and implanted into >% coli .sing genetic

engineering techni7.es% >% coli bacteria are m.ch easier to grow than other

bacteria and th.s are cheaper%

=.trient so.rces are starting to be deriFed &rom waste materials s.ch as

molasses and other agric.lt.ral wastes% Ehis greatly red.ces costs%



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;. ther resources+ such as ethanol+ are readily a*ailable from renewable

resources such as lants:

RECALL:

J,; 5 coFalent bond is a bond where one o& the atoms in it is more

electronegatiFe than the other and so the bond has a slight charge%

,lectrone"ati*ity is the ability o& an atom to attract electrons# the more electro-

negatiFe an atom the stronger it will hold onto electrons in a chemical bond %

Ehe order o& electronegatiFity &rom most electronegatiFe to least &or releFant

atoms is: fluorine o!ygen chlorine nitrogen carbon and then hydrogen*

4or example a bond between oxygen and hydrogen is a polar

bond beca.se oxygen holds onto negatiFe electrons stronger#th.s in this bond oxygen is slightly negatiFe%

1olubility 5ules:

Jolar s.bstances dissolFe other polar s.bstances: Ehis is beca.se the slightly

negatiFe end is attracted to the slightly positiFe end o& another polar bond

&orming a slight intermolec.lar bond%

=on-polar s.bstances dissolFe other non-polar s.bstances: Ehis is d.e to Fery

wea@ dispersion &orces between molec.les%

&escribe the dehydration of ethanol to ethylene and identify the need for a

catalyst in this rocess and the catalyst used:

Ehe dehydration o& ethanol is the chemical process

whereby a water molec.le is remoFed &rom ethanol

&orming ethylene%

Dehydration o& ethanol:

ethanol ethylene + water

C2H' ,H !l" C2H) !g" + H2, !l"

n acid catalyst !concentrated s.l&.ric acid" is needed

beca.se the acid brea@s the C-,H and C-H bonds allowing the &ormation o& a

do.ble-bond and water !it also red.ces the actiFation energy"%



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S.l&.ric acid is the chosen acid beca.se it is also a power&.l dehydrating agent%

&escribe the addition of $ater to ethylene resulting in the roduction of

ethanol and identify the need for a catalyst in this rocess and the catalyst

used: Ehe hydration o& ethylene is the chemical process

whereby a water molec.le is added to ethylene

&orming ethanol%

#ydration o& ethylene:

ethylene + water ethanol

C2H) !g" + H2, !l" C2H' ,H !l"

3n this case the acid catalyst !concentrated

phosphoric acid" opens the do.ble bond allowing

water to attach &orming ethanol%

&escribe and account for the many uses of ethanol as a solvent for olar

and non- olar substances:

See RECALL aboFe%

Ethanol is able to act as a solFent &or polar non-polar and some ionic s.bstances

d.e to its .ni7.e molec.lar str.ct.re:

s can be seen ethanol is not completely polar or completely non-polar:

Ehe # ( gro.p: Ehis section is polar and as a res.lt can &orm polar bonds

with other polar s.bstances s.ch as water%



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Ehe C# *C# 2< gro.p: C-H and C-C bonds are non-polar and hence this

section is non-polar% 3t can share dispersion &orces with other non-polar

s.bstances and dissolFe them# &or e%g% heptane%

Hence it is a widely .sed solFent &or per&.mes dyes pharmace.ticals etc% %utline the use of ethanol as a fuel and e! lain $hy it can be called a

rene$able resource:

Combustion is the reaction whereby a hydrocarbon reacts with oxygen to &orm

carbon dioxide and water Fapo.r releasing energy%

>thanol is able to .ndergo comb.stion so it can be .sed as a &.el:

C2H' ,H !l" + *, 2 !g" 2C, 2 !g" + *H2, !g"

Despite its short chain ethanol is a li7.id !d.e to strong polar bonds"% Ehis ma@es it an easily transportable &.el and th.s has been .sed &or many years

&or o.tdoor camping hi@ers etc%

3t has also been .sed as a &.el-additiFe in a.tomobiles .p to abo.t 20P ethanol%

s a renewable reso.rce:

>thanol can be a renewable reso.rce beca.se it can be deriFed &rom non-&ossil

&.el so.rces s.ch as the &ermentation o& gl.cose%

Ehis gl.cose can be deriFed &rom bacterial decomposition o& cell.lose !a

renewable Fery ab.ndant material" or &rom starch !mainly &rom corn crops"%

Assess the otential of ethanol as an alternative fuel and discuss the

advantages and disadvantages of its use:

Jotential o& >thanol:

0P o& the worldBs demand &or transportation &.els is petrole.m deriFed%

HoweFer as the price o& petrole.m contin.es to rise the concept o& other

&.els as alternatiFes becomes more attractiFe%pproximately million Fehicles worldwide r.n on ethanolOpetrol blends%

*0P o& ra8ilian a.tomobiles r.n on at least 2'P ethanol &.els%

?any other co.ntries s.ch as China and So.th &rica are inFesting money in

researching the potential o& ethanol as a &.el%



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3n .stralia s.gar cane and wheat haFe been &ermented to prod.ce ethanol

b.t here it is c.rrently an .neconomic proposition%

DN =E I>S o& ethanol:

3t is a rene$able reso.rce%3t is Kgreenho.seLneutral # that is the C, 2 absorbed by the crop !e%g% corn"

can match the C, 2 prod.ced by comb.stion !i& Fery e&&icient"%

eca.se ethanol has less carbon than octane !the maGor component o& petrol"

as well as the &act it already contains an oxygen atom it re7.ires less oxygen

to com letely comb.st# hence it is a C;> =>5 and ?,5> >443C3>=E &.el%

Jrod.ces only carbon dioxide and water as a by-prod.ct%

D3S DN =E I>S o& ethanol:>ngines m.st be modified to r.n on &.el containing more than 20P ethanol%

>ngines $ear do$n &aster d.e to the need &or higher engine compression

ratios needed &or ethanol comb.stion%

;arge areas o& land are re7.ired to grow crops that will be harFested &or

ethanol prod.ction# land that can be .sed &or other p.rposes%

Disposal o& &ermentation wastes presents maGor enFironmental iss.es%

.rocess information from secondary sources to summarise the use of ethanol as an alternative car fuel# evaluating the success of current usage:

Ehere are a &ew &orms in which ethanol can be .sed as an alternatiFe car &.el#

these incl.de ethanol/ etrol mi$tures very ure ethanol fuels and ethanol-

o$ered fuel cells :

>thanolOJetrol ?ixt.res: Signi&icant 7.antities o& (0P ethanol are sold in

some parts o& .stralia# howeFer there has not been m.ch s.ccess as the

p.blic holds s.spicions abo.t the e&&ect o& ethanol on their engines%

HoweFer in other co.ntries ethanolOpetrol mixt.res are Fery s.ccess&.l%

3n the United States many states re7.ire a minim.m o& (0P ethanol in all &.el

sold% 3n Sweden 'P ethanol mixt.res are common% ra8il re7.ires that ;;

car engines are able to accept at least 2'P ethanol% Eh.s in certain co.ntries

.se o& ethanol as a &.el is 7.ite s.ccess&.l%



24/52


J.re >thanol 4.els: KJ.reL ethanol is ethanol with E ?,SE (P water% 3t is a

Fery clean &.el% >ngines m.st be modi&ied to deal with s.ch high leFels o&

ethanol% 3t is c.rrently being .sed in ra8il and rgentina as a complete

alternatiFe to gasoline% 7.arter o& all ra8ilian cars r.n on p.re ethanol% 3thas proFen to be a Fery e&&icient &.el%

>thanol 4.el-Cells: Ehis is still in an experimental stage# it is the proposition

that &.el cells be .sed to r.n cars# s.ccess o& s.ch a scheme is still not @nown%

&escribe the conditions under $hich fermentation of sugars is romoted:

%ermentation is the biochemical process in which glucose is t.rned into ethanol

and carbon dioxide by the action o& en8ymes prod.ced by microbes !esp% yeast"%

Ehe conditions .nder which &ermentation is promoted are:Jresence o& s.itable grain or &r.it made into a p.lp with water%

Jresence o& yeast c.lt.res%

Ehe excl.sion o& air !anaerobic enFironment"%

Ehe temperat.re is @ept at abo.t *1 C%

.resent information from secondary sources by $riting a balanced e uation

for the fermentation of glucose to ethanol:

%ermentation o& gl.cose:

Summarise the chemistry of the fermentation rocess:

Yeast is added to mashed grain and water%



25/52


Ehe yeast and other microbes brea@ down the large carbohydrates !e%g% starch or

s.crose" into simple s.gars !gl.cose or &r.ctose" which are then &ermented%

s.crose + water gl.cose + &r.ctose

C(2H22, (( !a7" + H2, !l" C6H(2 , 6 !a7" + C6H(2 , 6 !a7" 3n an oxygen-&ree atmosphere the yeast .se their en8ymes to brea@ down the

s.gars &orming ethanol and C, 2 as prod.cts%

C6H(2 , 6 !a7" 2C2H' ,H !a7" + 2C, 2 !g"

Rhen ethanol concentration reaches ('P the yeast die and &ermentation SE,JS%

Distillation is .sed to obtain higher ethanol concentrations ! '-(00P"%

.rocess information from secondary sources to summarise the rocesses

involved in the industrial roduction of ethanol from sugar cane: Ehe industrial roduction o& ethanol &rom s.gar-cane .ses a &ew more chemicals

!some o& which are toxic" and processes compared to ethanol prod.ced &or

cons.mption# also s.garcane is higher in simple s.gars compared to corn starch%

Ehis is a s.mmary o& the process:

Ehe s.gar-cane crop is harFested# the whole plant is then cr.shed and grinded

to create a cell.loseOs.gar p.lp%

Ehe p.lp is heated to (00 C and dil.te s.l&.ric acid is added% Ehis hydrolysesthe cell.lose and s.crose into gl.cose molec.les%

Ehe mixt.re is &iltered to separate the gl.cose sol.tion &rom the solid resid.es

o& lignin and .nbro@en cell.lose%

Ehe solids resid.e is &.rther hydrolysed with stronger acids and &iltered again%

Calci.m hydroxide is added to the s.gar sol.tion remaining to ne.tralise the

s.l&.ric acid# an insol.ble salt !precipitate" o& calci.m s.l&ate is &ormed%

Ehe sol.tion is &iltered again to remoFe solid calci.m s.l&ate particles%

Ehe sol.tion is then placed in an oxygen-&ree tan@ warmed to *1 C and

s.itable yeast c.lt.res are added%

&ter ('P concentration is reached the sol.tion is distilled to prod.ce high

concentration ind.strial grade ethanol%



26/52


&efine the molar heat of combustion of a com ound and calculate the value

for ethanol from first-hand data:

Ehe molar heat of combustion is the heat energy released when one mole o& a

s.bstance .ndergoes complete comb.stion with oxygen at a press.re o& (0(%* @Ja!or ( atmosphere" with the &inal prod.cts being C, 2 and H2,%

4orm.la &or change in heat:

4or the calc.lation o& the molar heat o& comb.stion o& ethanol the &ollowing &irsthand Fal.es were .sed !&rom 200( HSC T(1":

3n this case the &orm.la &or H is applied to the water !the KsystemL":



27/52


E M ' ( M )0 <

m M 2'0 g M 0%2' @g

C M )%( x (0* @g-( < -( !Ehis Fal.e is a constant# giFen in exams"

Ehere&ore: H M -0%2' x )%( x (0* x )0 M -)( 00 Go.les ! "

M -)(% @iloGo.les !@ "

.t the change in mass o& the b.rner was 2%* grams there&ore only 2%* grams o&

ethanol was comb.sted%

?oles M mass O molar mass M 2%* O )6 M 0%0' mol

Ehere&ore -)(% @ O0%0' mol M - *6 @ Omol

Hence the experimental molar heat o& comb.stion o& ethanol is(=;> !7?mol %

Identify the I).AC nomenclature for straight-chained alkanols from C0 to

C1:

Al!anols are a gro.p o& al@anes where one or more hydrogens haFe been replaced

by the hydro!yl !,H" &.nctional gro.p

Rhen naming al@anols there are speci&ic r.les:

Ehe n.mber o& carbons determines the pre&ix o& the name:

@C s ( 2 * ) ' 6 1Prefi$ methane- ethane- propane- b.tane- pentane- hexane- hepane- octane-

3& there is only ,=> hydroxyl gro.p the KeL is dropped &rom the pre&ix and

the s.&&ix K(olL is added% Ehe carbon the hydroxyl is on m.st also be stated#

this is written be&ore the pre&ix with a KdashL% Ehe carbons depending on how

long the chain is are n.mbered &rom ( to %

,.-. Ehis al@anol has ' carbons b.t only one

hydroxyl so its pre&ix is Kpentan-L and its s.&&ix

is K-olL% lso the hydroxyl is on the 2nd carbon!the n.mber is ta@en either &rom the le&t ,5 the right# the S? ;;>5

n.mber m.st be ta@en"% H>=C> this al@anol is2( entanol

3=C,55>CE naming wo.ld be )-pentanol%

3& there is more than one hydroxyl gro.p the s.&&ixes are !(-)":



28/52


'o. of # s ( 2 * )1uffi$ -ol -diol -triol -tetraol

4or more than one carbon the KeL at the end o& the pre&ix is =,E dropped%

Ehe positions o& the ,H gro.ps m.st be stated% 3& there are 2 hydroxyls on the

same carbon then the n.mber is written twice with a comma in between:

,.-. Ehis al@anol has 6 carbons and *

hydroxyl gro.ps so its pre&ix is Khexane-L and

its s.&&ix is K-triolL% lso one hydroxyl is on

the ( st carbon while the other 2 are on the * rd carbon% H>=C> the 3UJ C

name &or this al@anol is)+;+;(he$anetriol %

3=C,55>CE naming wo.ld be ) ) 6-hexanetriol%

PRACTICAL .rocess information from secondary sources such as

molecular model kits# digital technologies or com uter simulations to model

the addition of $ater to ethylene and the dehydration of ethanol:

Molecular modellin" !its were .sed to model:

the addition o& water to ethylene !hydration"%

the remoFal o& water &rom ethanol !dehydration"%

K all-and-stic@L @its were .sed whereblack balls represented carbons smaller

$hite balls representing hydrogen and red balls represented oxygen%

4irstly and ethylene molec.le was created and a water molec.le created:

Ehen the water molec.le was split into a H + ion and an ,H - ion%

Ehe do.ble-bond o& ethylene was opened and the ions were attached where

there were &ree bonding sites# the res.ltant molec.le was ethanol%

Secondly a separate ethanol molec.le was created:

Ehe hydroxide gro.p !,H -" and a hydrogen was remoFed &rom the ends%

Ehey were combines and water was &ormed# the two open bonding sites o& the

ethanol were Goined and ethylene was &ormed%

761 &%8 the method:

Ehe models created a *D representation o& the chemical process which led to

greater .nderstanding o& dehydration and hydration processes%



29/52


Ehe .se o& ball-and-stic@ models depicting the do.ble-bond with &lexible

r.bber rods greater increased .nderstanding o& chemical reactions%


oth were seFerely simpli&ied representations o& chemical processes whichhad many m.ltiple steps and consisted o& a series o& a7.eo.s !dil.te s.l&.ric

acid" or solid catalysts%

PRACTICAL Solve roblems# lan and erform a first-hand investigation

to carry out the fermentation of glucose and monitor mass changes:

3n this experiment sucrose sol.tion was &ermented to &orm ethanol and carbon

dioxide% Ehe yeast cells &irst split s.crose into two gl.cose molec.les .sing the

invertase en8yme % 2'0 m; side-arm conical &las@ with a

r.bber stopper was .sed% plastic hose was

connected to the side arm and the end o&

the hose was placed in another conical &las@

in a sol.tion o& lime$ater % =o gas was

allowed to escape the apparat.s:

(00 ml o& 0%(' ? sucrose sol.tion was

placed in the conical &las@% ,=> gram o&active yeast was placed into the s.crose

along with a pinch o&sodium bi hos hate !=a 2HJ, ) " as a yeast n.trient% Ehis

was mixed thoro.ghly%

Ehe stopper &irmly p.t on and the &las@ was R>3IH>D with an electronic scale%

Ehe apparat.s was then set .p as shown with the yeast bea@er in a water bath at a

constant temperat.re !*1 C"%

oth &las@s were weighed daily &or ' days%

5,16 1:Ehe yeast &las@ t.rned &oamy and smelt clearly o& alcohol while the limewater

t.rned clo.dy# this proFed that C, 2 and ethanol were prod.ced and that

&ermentation occ.rred%



30/52


Ehe mass o& the yeast &las@ also steadily decreased by abo.t hal& a gram each

day# this is d.e to the carbon dioxide escape# the limewater &las@ also gained

approximately the same mass%

761 &%8 the method: KclosedL system !where no gas was allowed to escape" was .sed to ens.re

an acc.rate experiment%

;imewater was employed to proFe C, 2 was prod.ced%

Ehe water bath ens.red that the most optimal &ermentation occ.rred%

&M& A & '1 o& method:

Ehe combined masses o& both &las@s steadily decreased as well# this was d.e

to ineFitable lea@ages o& gas%Ehe atmosphere in the &las@s was not anaerobic !oxygen-&ree" and this co.ld

haFe hampered the &ermentation process%

PRACTICAL ' Identify data sources# choose resources and erform a first-

hand investigation to determine and com are heats of combustion of at least

three li uid alkanols er gram and er mole:

Ehe * al@anols .sed were: methanol ethanol and)( ro anol

>ach al@anol was placed in a spirit b.rner# the original mass recorded and thenwas .sed to heat 200 m; o& water !at 2' C" in a tin can%

thermometer was .sed to stir the water as well as meas.re the temperat.re

,nce the temperat.re rose by (0 degrees !


31/52


=,E>: Ehis is not beca.se o& the extra bonds in longer hydrocarbon

chains b.t rather more bonds need to be created in the prod.cts !H 2, and

C, 2"# recall that:

creatin" bonds releases energy% brea!in" bonds absorbs energy%

761 &%8 the method:

tin can was .sed as it is a better thermal cond.ctor than a glass bea@er%

?ethanol ethanol and (-propanol were .sed as they are the shortest al@anols

and th.s are the most li@ely to .ndergo complete comb.stion%

&M& A & '1 o& method:

?olar heat o& comb.stion re&ers ,=;Y to complete comb.stion# the yellow&lames and soot &ormed indicated that the comb.stion was incomplete% Eh.s

the experimental data gathered is inacc.rate%

lso m.ch heat was lost to the air as there was not (00P e&&iciency o& heat

trans&er &rom &lame to tin can%

Heat was also radiated &rom the can to the air# ins.lation wo.ld red.ce this%

B. $idation(reduction reactions are increasin"ly im ortant as a source of

ener"y: RECALL:

&onic e7.ations are chemical e7.ations where the ionic compo.nds are split into

their ions displaying their charges# e%g%salts and acids can be split%

,-: Ehe reaction between s.l&.ric acid and magnesi.m:

Chemical e uation: H2S, ) !a7" + ?g !s" ?gS, ) !a7" + H2 !g"

Ionic e uation : 2H+ + S, ) 2- + ?g ?g 2+ + S, ) 2- + H2

s can be seen the ionic compo.nds s.l&.ric acid and magnesi.m s.l&ate weresplit% Hydrogen gas is C,N ;>=E so it cannot be split%

Ehe states !solid li7.id etc%" do not need to be written &or ionic e7.ations%

', ionic e7.ations are ionic e7.ations where the s ectator ions are remoFed#

spectator ions are ions !.s.ally polyatomic ions" that remain .nchanged

thro.gho.t the reaction%



32/52


;oo@ing at the aboFe acid-metal reaction the s.l&ate ion !S, ) 2-" is the same on

both sides o& the e7.ation# it remains .nchanged hence:

2et ionic e uation: 2H+ + ?g ?g 2+ + H2

E! lain the dis lacement of metals from solution in terms of transfer of electrons:

dis lacement reaction is a reaction in which a more reactiFe metal changes a

less reactiFe metalBs 3,=S into solid E,?S% Ehat is the less reactiFe metalBs

ions are KdisplacedL o.t o& sol.tion and ne.tralised into atoms%

,-: Rhen "inc metal is placed in co er s.l&ate sol.tion the 8inc will displace

the copper ions &orming 8inc s.l&ate and solid copper:

Chemical e uation: 9n !s" + C.S, ) !a7" 9nS, ) !a7" + C. !s" Ionic e uation : 9n + C. 2+ + S, ) 2- 9n 2+ + S, ) 2- + C.

2et ionic e uation : 9n + C. 2+ 9n 2+ + C.

Displacement reactions are act.ally >;>CE5,= E5 =S4>5 reactions where

one s.bstance donates electrons to another# howeFer this is not clear .ntil yo.

loo@ at thehalf-e uations o& the reaction%

#alf(equations are another way o& displaying chemical reactions# the net ionic

e7.ation is split into two KhalFesL !.s.ally b.t not always the same element &rom both sides o& the net ionic e7.ation is ta@en on its own as a hal&-e7.ation"%

4rom aboFe the two hal& e7.ations are:

9n 9n 2+

C. 2+ C.

H,R>N>5 these are incomplete as the electrical charges on both sides o& the

e7.ation are not balanced% Hence a tr.e depiction o& the 2 hal&-reactions:

9n 9n 2+ + 2e

C. 2+ + 2e C.

,$ lanation : 4or 8inc to ionise it has to giFe .p 2 electrons &rom its o.ter shell%

.t &or the copper ion to solidi&y !ne.tralise" it has to gain 2 electrons% Hence the

net reaction is that 8inc D,= E>S !or Atrans&ersB" 2 electrons to copper%

Ehere&ore displacement reactions are electron trans&er reactions%



33/52


&DA & ' V 5,D6C & ' :

%!idation and reduction reactions !or 5>D, reactions" are the scienti&ic

way o& saying Aelectron-trans&er reactionsB%

Ehe terms KoxidationL and Kred.ctionL re&er to the two separate hal&-e7.ationso& a redox reaction# in one hal& oxidation occ.rs and red.ction in the other%

Eo identi&y whether a hal&-reaction is oxidation or red.ction:

&DA & ' 5,D6C & 'Iain o& , YI>= ;oss o& , YI>=

;oss o& HYD5,I>= Iain o& HYD5,I>=WW ;oss o& >;>CE5,=S WW WW Iain o& >;>CE5,=S WW

3ncrease in , 3D E3,= SE E> Decrease in , 3D E3,= SE E>

' , : %!idation states $ill be e! lained later3

T.ic@ way to memorise which is which# remember the & (5&- :

xidation &s oss 5 ed.ction &s - ain o& >;>CE5,=S%

Hence the 2 hal&-e7.ations aboFe can be labelled as oxidation or red.ction%

9n 9n 2+ + 2e !,xidation# 8inc ;,S>S electrons"

C. 2+ + 2e C. !5ed.ction# copper I 3=S electrons"

Ehe species that is oxidised is the red.ctant !th.s 8inc is the red.ctant"

Ehe species that is red.ced is the oxidant !th.s copper is the oxidant"

Ehere are many types o& redo! reactions a &ew o& which are:

Dis lacement reactions# e%g% magnesi.m and silFer nitrate:

?g !s" + 2 g=, * !a7" ?g!=, *"2 !a7" + 2 g !s"

?g + 2 g + + 2=, *- ?g 2+ + 2=, *- + 2 g

?g + 2 g + ?g 2+ + 2 g !2=, *- is the spectator ion"

?g ?g 2+ + 2e !,xidation"

2 g+

+ 2e

2 g

!5ed.ction"Acid?Metal reactions# e%g% s.l&.ric acid and 8inc:

H2S, ) !a7" + 9n !s" 9nS, ) !a7" + H2 !g"

2H+ + S, ) 2- + 9n 9n 2+ + S, ) 2- + H2

2H+ + 9n 9n 2+ + H2 !S, ) 2- is the spectator ion"



34/52


9n 9n 2+ + 2e !,xidation"

2H+ + 2e H2 !5ed.ction"

Metal?'on(metal reactions# e%g% reacting sodi.m and chlorine gas:

2=a !s" + Cl2 !g" 2=aCl !s"

2=a + Cl 2 2=a + + 2Cl - !=o spectator ion in this case"

2=a 2=a + + 2e !,xidation"

Cl2 + 2e 2Cl- !5ed.ction"

Al!ali metal?water reactions# e%g% reacting potassi.m and water:

2< !s" + 2H2, !l" 2


35/52


36/52


?n + )!-2" M -(

?n M ( M 1

Ehere&ore manganese has an oxidation state o& +1 in


37/52


cond.cting wire and salt bridge connects the two hal&-cells and completes the

circ.it# as electrons haFe to &low &rom the oxidation cell to the red.ction cell a

&low o& electrons is prod.ced in the wire and hence electricity is prod.ced%

IalFanic cells are explained in more detail belowX %utline the construction of galvanic cells and trace the direction of electron

flo$:

s galvanic cells .se a redox reaction to ma@e electricity the metal displacement

reaction o& 8inc and copper s.l&ate can be .sed as an example ! again X"

Ehe two hal&-e7.ations o& the reaction are:

9n 9n 2+ + 2e !,xidation"

C.2+

+ 2e

C. !5ed.ction" Ehis is the set-.p o& a galvanic cell .sing these 2 reactions:

Ehis type o& galFanic cell is also called a Daniell Cell%

I ;N =3C C>;; S>E-UJ:

Ehere are two cells each containing a sol.tion o& the metal-s.l&ate# one cell

contains "inc sulfate the other cellco er sulfate %3n the 8inc s.l&ate there is a solid inc electrode connected by a wire to a

solid co er electrode which is in the copper s.l&ate sol.tion%

salt bridge soa@ed in otassium nitrate sol.tion connects the two cells%

Ehe CH>?3C ; 5> CE3,=S:



38/52


3n the 8inc-s.l&ate cell o$idation is occ.rring as S,;3D 8inc is oxidised to

8inc 3,=S which then &low into the 8inc s.l&ate sol.tion% Ehe electrons that

are released &low into the wire:

9n 9n2+

+ 2e

!,xidation"3n the copper-s.l&ate cell reduction is occ.rring as copper 3,=S are red.ced

to S,;3D copper when then b.ild .p on the copper electrode% >lectrons are

receiFed thro.gh the wire which then red.ce the ions:

C. 2+ + 2e C. !5ed.ction"

=,E>: Ehe oxidation and red.ction cells can be on the le&t ,5 the right it does

not matter altho.gh oxidation is conFentionally on the right%

s the "inc is slowly oxidised and more 8inc ions b.ild-.p the 8inc s.l&ate

sol.tion b.ilds .p in J,S3E3N> charge !more 9n 2+ than S, ) 2-"%

Similarly as the co er ions are red.ced the copper s.l&ate sol.tion b.ilds in

=>I E3N> charge !more S, ) 2- than C. 2+"%

HoweFer this will a&&ect the &low o& electrons# electrically ne.tral sol.tions are

needed &or optimal electricity prod.ction% Hence the role o& the salt bridge:

Ehe salt brid"e completes the circ.it b.t also has another &.nction%

Ehe salt bridge maintains electrical neutrality # this means that it @eeps the

charges in both the hal&-cells at 8ero by allowing the &low o& ions%

Ehe salt bridge is soa@ed in otassium nitrate sol.tion: Eh.s as the positiFe

charge b.ilds .p in the le&t cell =>I E3N> nitrate ions migrate towards the

cell to ne.tralise the charge# as the negatiFe charge b.ilds .p in the right cell

the J,S3E3N> potassi.m ions moFe towards the cell to ne.tralise it as well%

&efine the terms anode# cathode# electrode and electrolyte to describe

galvanic cells:

n >;>CE5,D> is anything thro.gh which electrical c.rrent passes# in the

context o& galFanic cells they are the metal cond.ctors placed in the electrolytes %

n >;>CE5,;YE> is any sol.tion that can cond.ct electricity# all salt sol.tions

are electrolytes !b.t not all salts are sol.ble"%



39/52


Ehe terms anode and cathode re&er to the electrodes that are placed in the

sol.tion# to identi&y which is the anode and which is the cathode:

A' node is , 3D3S>D !it is the KnegatiFeL side"%

5,D CA Cathode is 5>DUC>D !it is the KpositiFeL side"% Hence the 8inc was the anode and the copper was the cathode%

3n galFanic cells electrons &low &romanode to cathode %

Solve roblems and analyse information to calculate the otential E

re uirement of named electrochemical rocesses using tables of standard

otentials and half-e uations:

Ehe total *olta"e !or >?4# electromotiFe &orce" a galFanic cell can prod.ce is

determined by the s.bstances ta@ing part in the redox reaction% Ehe aboFe cell can also be represented as: 9n Z 9n2+ ZZ C.2+ Z C. [:

Rhere 9n Z 9n 2+ represents a metalOmetal ion co.ple%

Ehe do.ble line ZZ represents the salt bridge%

>lectrodeOelectrolyte co.ples haFe a 43 >D Foltage no matter how many moles

o& each s.bstance is present%

Ehis K&ixed FoltageL is termed thestandard reduction otential !or > " and is

giFen in a table in the exam% 4or example in s.ch a table it has:9n 2+ + 2e 9n ! (E.F>0 "

C. 2+ + 2e C. ! E.;B0 "

HoweFer in the cell the 8inc reaction is: 9n 9n2+ + 2e thereverse o& the

aboFe reaction# so the S3I= o& > is % &PP,D % Hence &or o.r reaction the >

&or 9n Z 9n2+ is +0%16N !not -0%16N" and the > &or C.2+ Z C. is 0%*)N%

EHUS the total > Fal.e &or this cell is the s.m which is 0%*) + 0%16 M (%( Folts%

PRACTICAL ' .erform a first-hand investigation to identify the conditions

under $hich a galvanic cell is roduced :

galFanic cell was prod.ced in the lab in the same set-.p as aboFe# that is in the

&orm o& a D =3>;; C>;;%



40/52


2 cm strip o& inc and co er were c.t &rom metal strips% Using wire leads and

crocodile clips the 8inc strip was connected to the =>I E3N> terminal o& a

Foltmeter and the copper strip connected to the J,S3E3N> terminal%

Ehe 8inc was then placed in '0 m; o& (? sol.tion o& inc sulfate and the copper in '0 m; o& (? sol.tion o& co er sulfate.

strip o& &ilter paper was soa@ed inotassium nitrate # the two cells were then

connected .sing this Asalt bridgeB%

5,16 1 : Ehe Foltmeter showed a reading o& 0%) Folts% Rhen more electrolyte

was added the Foltage stayed at 0%) Folts# th.s the Foltage is determined ,=;Y

by the metals .sed and has nothing to do with the amo.nt o& copper or 8inc%

761 &%8 the method:

Copper and 8inc were .sed as they are readily aFailable non-toxic metals%

(? sol.tion was .sed as the ratio o& moles o& the salts was (:(

potassi.m nitrate salt bridge was .sed as potassi.m and nitrate ions do not

react with 8inc copper o& s.l&ate ions%

PRACTICAL ' .erform a first-hand investigation and gather first-hand

information to measure the difference in otential of different combinations

of metals in an electrolyte solution:

Ehe same experiment aboFe was per&ormed again except a range o& di&&erence

electrode electrolyte co.ples were .sed%

5,16 1:

9n Z 9n2+ ZZ C.2+ Z C. [: E,E ; Foltage M 0%) N

?g Z ?g 2+ ZZ C.2+ Z C. [: E,E ; Foltage M 0% ' N

l Z l*+ ZZ C.2+ Z C. [: E,E ; Foltage M 0%2 N

4e Z 4e2+ ZZ C.2+ Z C. [: E,E ; Foltage M 0%' N

REPORT ' 4ather and resent information on the structure and chemistry

of a "inc-carbon dry cell and evaluate it in com arison to a silver-o!ide



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button cell in terms of: 1. Chemistry 2. Cost and racticality 3. Im act on

society and 4. Environmental im act:

he D58 C, !or ;eclanch\ Cell":

SE5UCEU5>:Ehe dry cell is made o& acarbon rod

s.rro.nded by a mixt.re o&

man"anese3&04 o$ide and carbon

!in the &orm o& gra hite "# this is the

cathode% Ehis is then s.rro.nded by

a paste o& ammonium chloride

which acts as the electrolyte% ll o& this is contained in a inc shell which is the anode%

CH>?3SE5Y:

Ehe complete chemical e uation is shown as:

9n !s" + 2?n, 2 !s" + 2=H ) Cl !a7" 9nCl 2 !a7" + ?n 2, * !s" + 2=H * !a7" + H2, !l"

Ehe ionic e uation is:

9n + 2?n )+ + 2, 2- + 2=H ) + + 2Cl- 9n 2+ + 2Cl - + 2?n *+ + *, 2- + 2=H * + H2,

.t there is also another reaction: 2=H ) + 2=H * + 2H+

Ehis occ.rs on the le&t hand side# hence 2=H * and 2Cl - are spectator ions:

Eh.s the net ionic e uation is:

9n + 2?n )+ + 2, 2- + 2H+ 9n 2+ + 2?n *+ + *, 2- + H2,

Splitting this into redox half(cells :

, 3D E3,=: 9n 9n 2+ + 2e

5>DUCE3,=: 2?n )+ + 2, 2- + 2H+ + 2e 2?n *+ + *, 2- + H2,

/n is oxidised: !0 +2" and Mn is red.ced: !+) +*"%

Ehe S3?J;343>D galFanic cell representation is:

9n Z 9n2+ ZZ ?n)+ Z ?n*+ [

C,SE and J5 CE3C ;3EY:



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Ehe dry cell is relatiFely cheap%

3t is Fery practical to man.&act.re as there is little wastage o& materials# all

the materials !incl.ding the casing" ta@e part in the reaction%

3t is light and portable and can be .sed in small appliances%3t has a short shel&-li&e howeFer as the acidic =H) + slowly corrodes the

8inc%

3?J CE on S,C3>EY:

3t was the &irst commercially prod.ced battery and so it had a HUI>

impact on society# it made portable deFices s.ch as torches radios and

cloc@s possible%

3t is Fery widely .sed as it is a cheap portable so.rce o& steady electricity%>=N35,=?>=E ; 3?J CE:

Nery minimal enFironmental impact%

Ehe manganese!333" prod.ct is readily oxidised bac@ to manganese!3N"

which is stable and insol.ble# it is harmless%

mmoni.m salts and carbon are also harmless# small 7.antities o& 8inc

pose no enFironmental ris@%

he 1il*er( $ide 6 ' C, :SE5UCEU5>:

Ehe silFer-oxide b.tton-cell is made o& layers o& chemicals within a steel

case% Ehere is powderedsil*er3&4 o$ide at the bottom# this is the cathode%

t the top is powdered inc# this is the anode% Ehey are separated by a

paste o& al@aline otassium hydro$ide which acts as the electrolyte and a

catalyst% Ehe steel case does not ta@e part in the reaction%



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CH>?3SE5Y:

Ehe oFerall chemical e uation is:

9n !s" + g 2, !s" 9n, !s" + 2 g !s"

HoweFer this ignores the role o& the potassi.m hydroxide# a more

complete chemical e7.ation !with a7.eo.s DUCE3,=: 2 g + + , 2- + H2, + 2e 2 g + 2,H -

5 : g 2, + H 2, + 2e

2 g + 2,H-

/n is oxidised: !0 +2" and A" is red.ced: !+( 0"%

EHUS D galFanic cell representation is:

9n Z 9n2+ ZZ g+ Z g [

C,SE and J5 CE3C ;3EY:

SilFer oxide b.tton cells are Fery e$ ensi*e d.e to the high cost o& silFer%HoweFer eFen small cells are able to proFide large amo.nts o& electricity

with a Fery constant Foltage &or a long period o& time# so the bene&its

balance o.t the costs o& the silFer%

3t is non-rechargeable%



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Ehe steel case does not ta@e part in the reaction and there is Fery little

chance o& lea@age%

3?J CE on S,C3>EY:

Ehe Fery small si8e o& the cell and high constant Foltage allows it to haFemany applications s.ch as in wristwatches !where they last &or many

years" calc.lators and digital cameras%

>=N35,=?>=E ; 3?J CE:

>nFironmental impact is minimal%

Ehe "inc "inc o!ide# silver and silver o!ide are all stable insol.ble and

non-toxic compo.nds%

.otassium hydro!ide is strongly al@aline# howeFer it is in 7.ite a dil.te&orm as an electrolyte and small amo.nts are not harm&.l%

,0A 6A &'- the dry-cell in relation to the b.tton cell:

3n terms o& chemistry the dry-cell and the b.tton cell haFe Fery similar

reactions# howeFer the b.tton cell is able to prod.ce larger and more constant

Foltage s.pply in relation to si8e# this is beca.se sil*er has a higher red.ction

potential than man"anese3&04 % lso the al@aline enFironment o& the b.tton

cell enco.rages the reaction to occ.r at a constant rate &or long periods%

3n terms o& cost and practicality the dry cell is more practical in most

sit.ations as it is cheaper% HoweFer some sit.ations re7.ire smaller cells that

are able to last m.ch longer than the short li&e o& the dry cell s.ch as in

watches% lso the b.tton cell is m.ch less li@ely to lea@ and th.s is a more

reliable battery%

3n terms o& impact on society the dry cell has had a &ar greater impact than the

b.tton cell% Ehis is d.e to the historical signi&icance o& the ;eclanch\ cell the

&irst battery eFer prod.ced% Ehe dry cell made portable electrical deFices

possible# howeFer the b.tton cell has allowed the si8e o& electrical deFices to

red.ce greatly as some deFices these days are eFen smaller than dry cells%

oth cells haFe Fery minimal enFironmental impact and hence are adFisable

to be .sed oFer other more poll.ting cells s.ch as merc.ry cells%



45/52




46/52


G. 'uclear chemistry ro*ides a ran"e of materials:

RECALL:

&soto es are atoms o& the same element with di&&erent n.mbers o& =>UE5,=S#

b.t they haFe the same n.mber o& J5,E,=S% 3n nuclear chemistry !chemistry dealing with n.clear reactions" isotopes are

shown in the &ollowing &orm:

>%I% chlorine-*' is written as*'

Cl and r.bidi.m- ' as'

5b Ehere are three types o& radiation: H !alpha" I !beta" and J !gamma" radiation:

Al ha Decay : lpha radiation is made o& Aheli.m n.cleiB !2 protons and 2

ne.trons" that are eGected &rom .nstable large n.clei !too heaFy"% 4or example

the decay o& .rani.m-2* :

eta Decay : eta radiation is made .p o& electrons eGected &rom an .nstable

n.cle.s !too many ne.trons"# UE n.clei do not contain electrons% Hence the

.nderlying reaction is the decomposition o& a neutron :

Rhen a ne.tron decomposes it &orms an electron which is immediately

eGected as beta radiation and a roton !Ahydrogen n.cle.sB" which is

capt.red by the n.cle.s% Eh.s beta decay res.lts in an increase in atomic

n.mber !3?J,5E =E"% 4or example the beta decay o& cobalt-60 res.lts in

an increase o& atomic n.mber creating nic@lel-60:



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Ehere is no s.ch thing as K "amma decayL# gamma radiation high energy

electromagnetic waFes are emitted in addition to some beta or alpha decays%

&istinguish bet$een stable and radioactive isoto es and describe the

conditions under $hich a nucleus is unstable: 5adioacti*ity is the spontaneo.s emission o& 5 D3 E3,= &rom certain atoms

4or some elements !e%g% carbon" some o& their isotopes are stable !s.ch as

carbon-(2" and others are radioactiFe !s.ch as carbon-()"%

Ehere are 2 conditions .sed to predict whether an atom will be radioactiFe:

tomic =.mber: ll atoms !incl.ding all their isotopes" with more than *

protons ! / K =; " are radioactiFe% Ehat is all atoms with atomic n.mber greater

than bismuth are radioactiFe and .ndergo decay%Jroton-=e.tron 5atio: Ehe ratio o& protons to ne.trons determines whether an

atom will be stable or not% nything outside the ratios below is radioactiFe:

/ L 2E the stable ratio o& protons to ne.trons is ):)

ro.nd / ;E the stable ratio is abo.t ):).;

ro.nd / =E the stable ratio is ):).G

&escribe ho$ transuranic elements are roduced:

ransuranic elements are elements with atomic n.mbers greater than .rani.m#that is 9 $ 2 !more than 2 protons"%

ll trans.ranic elements are arti&icially prod.ced%

Erans.ranic elements are prod.ced in two ways:

'eutron ombardment !in n.clear reactors": 3n n.clear reactions the &ission

chain-reaction !o& .rani.m-2*' or other elements" prod.ces large amo.nts o&

ne.trons% Rhen atoms are placed inside the reactor they are bombarded by

these ne.trons% ,ccasionally the atom S,5 S one o& these ne.trons#howeFer it is .nstable and .ndergoes beta decay !see aboFe"% Hence the

proton n.mber increases and a trans.ranic element can be created%

,-: Urani.m-2* is not &issile !it can not .ndergo the n.clear chain-

reaction"# when it is placed in the reactor the &ollowing reaction occ.rs:



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Eh.s nept.ni.m-2* the &irst trans.ranic element is &ormed%

Ehis method is .sed to prod.ce the &irst &ew o& the trans.ranic elements%%usion 5eactions !in particle accelerators": Ehe prod.ction o& larger

trans.ranic elements is achieFed by colliding heaFy n.clei with high-speed

positiFe particles !s.ch as heli.m or carbon n.clei"% Ehe positiFe particles

need to be at Fery high speeds to oFercome the positiFe rep.lsiFe &orce o& the

heaFy n.clei and &.se with them% Jarticle accelerators are .sed to bring these

particles to the high speeds re7.ired%

,-: Urani.m-2* is &.sed with a carbon n.cle.s:

s a res.lt cali&orni.m-2)6 a large trans.ranic element is &ormed%

.rocess information from secondary sources to describe recent discoveries

of elements:

4o.r new elements haFe been discoFered in the 2( st cent.ry% Ehey are listed

below% =ote that their strange names are G.st temporary .ntil the 3UJ C decides

on permanent names:

6nunhe$ium : lso @nown as [email protected] element ((6 was synthesised

in December 2000 by the oint 3nstit.te &or =.clear 5esearch !D.bna

5.ssia"% 3t was prod.ced thro.gh the &.sion o& c.ri.m-2) and calci.m-) %

Ehe atom decayed ) milliseconds later%

6nun entium : lso @nown as [email protected] element ((' was synthesised in

4ebr.ary 200) by the scientists &rom the oint 3nstit.te &or =.clear 5esearch!D.bna 5.ssia" and the ;awrence ;iFermore =ational ;aboratory ! merica"%

3t was prod.ced thro.gh the &.sion o& americi.m-2)* and calci.m-) % Ehe

atom then .nderwent ;JH decay &orming element ((* a new element%



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6nuntrium : lso @nown as [email protected] element ((* was also synthesised

in 4ebr.ary 200) thro.gh the alpha decay o& unun entium %

6nunoctium : lso @nown as Ke@a-radonL element (( is the most recently

prod.ced and the heaFiest element @nown to man% 3t was prod.ced by the&.sion o& cali&orni.m-2) atoms and calci.m-) %

&escribe ho$ commercial radioisoto es are roduced:

Commercial radioisotopes are isotopes that are prod.ced on a reg.lar basis &or

medical ind.strial or other .se%

?any are prod.ced by ne.tron bombardment within n.clear reactors as explained

aboFe# at the ucas #ei"hts n.clear reactor in Sydney the .stralian =.clear

Science and Eechnology ,rganisation ! A'1 " prod.ces a range o& ne.tron-richisotopes &or commercial .se:

+echnitium-55m !an important medical radioisotope" is prod.ced by ne.tron

bombardment o& molybden.m- %

Cobalt-67 !.sed in ind.stry and medicine" is prod.ced by ne.tron

bombardment o& the stable cobalt-' %

Americium-890 !a domestically .sed isotope# in smo@e alarms" is prod.ced by

ne.tron bombardment o& pl.toni.m-2)(%

,ther isotopes are prod.ced in particle accelerators s.ch as the 'ational

Medical Cyclotron near the 5oyal Jrince l&red hospital% Jarticle accelerators

accelerate n.clei to incredible speeds and which are then collided with heaFy

n.clei% Ehis prod.ces ne.tron-de&icient radioisotopes% inear Accelerators

accelerate particles in a straight line while cyclotrons accelerate particles in a

spiral% 5adioisotopes prod.ced incl.de:

Iodine-0;0 !.sed to diagnose thyroid disorders"%

Carbon-00# nitrogen-0;# o!ygen-0< !all .sed in J>E scans"%

Identify instruments and rocesses that can be used to detect radiation:

-ei"er(MNller Counter:

Ehis deFice consists o& a metal t.be &illed with argon gas connected to a DC

power s.pply%



50/52


s radiation enters it ionises the gas splitting the atoms into electrons and

positiFe n.clei that complete the circ.it within the metal t.be# the stronger the

radiation the more ionisation that occ.rs%

Ehe ampli&ier releases a series o& clic@s or displays an electronic reading tosigni&y that radiation is present% Ehe co.nter th.s display a n.mber in terms o&

intensity o& radiation%

Photo"ra hic %ilm :

Jhotographic &ilm is a sheet o& plastic coated with silFer halide salts%

Ehese salts are sensitiFe to electromagnetic radiation !e%g% light or -rays"

and dar@en when they are exposed to radiation%

Jeople who wor@ with radioactiFe materials o&ten wear badges containing

photographic &ilm# the amo.nt o& dar@ening shows how m.ch they haFe beenexposed to radiation%

1cintillation Counter:

Some s.bstances giFe o&& light when they are str.c@ by high-energy radiation%

photo-receptor cell senses these &lashes o& light that occ.r and &rom this

meas.res the n.mber o& decay eFents that are occ.rring%

Identify one use of a named radioisoto e in industry and in medicine:

&ndustry: Cobalt-60 is .sed to irradiate &ood to prolong its shel&-li&e% Medicine: Eechneti.m- m can be .sed to identi&y the location o& t.mo.rs%

&escribe the $ay in $hich the above named industrial and medical

radioisoto es are used and e! lain their use in terms of their chemical

ro erties:



51/52


Cobalt(>E:

US>: Ehe irradiation o& &ood materials%

CH>?3C ; J5,J>5EY: 3t is chemically inert and hence it can be sa&ely

ho.sed within machinery witho.t &ear o& any .nwanted reactions s.ch asoxidation or red.ction% 3t is also a strong gamma emitter%

H,R 3E R,5?3C ; J5,J>5EY: Eechneti.m- m can be changed to a n.mber o&

oxidation states% Ehis allows &or the prod.ction o& a wide range o& biologically

actiFe chemicals# it can be chemically bonded to an organic s.bstance s.ch as

gl.cose and inGected into the body% 3t emits low energy gamma rays%

H,R 3E R,5


52/52


dFantages: 3t has a Fery short hal&-li&e o& 6 ho.rs and hence ca.ses minimal

damage to the patients tiss.es% 3t emits low energy gamma radiation that can

be pic@ed .p by machinery b.t does not damage cells to a great extent% 3t is

7.ic@ly eliminated by the body% Ec- m is relatiFely reactiFe and can be Goined to many compo.nds%

DisadFantages: s it has s.ch a short hal&-li&e it m.st be contin.o.sly made%

Healthy cells may also @illed%

)se available evidence to analyse benefits and roblems associated $ith the

use of radioactive isoto es in identified industries and medicine:

>=>43ES o& radioisotopes:

&ndustrial bene&its incl.de the ability to ma@e monitoring e7.ipment that ismore sensitiFe precise and reliable than preFio.sly possible% 3t allows &or

more e&&icient processes !s.ch as sterilisation and &ood irradiation" and

preFio.sly impossible things !examining &a.lts in constr.ction and

machinery"%

Medical bene&its incl.de a new wide range o& non-inFasiFe diagnostic

techni7.es that wo.ld not be possible on sensitiFe organs !brain etc"%

5adiation therapy is also a greatly positiFe new treatment%

J5, ;>?S with radioisotopes:

'uclear reactors which are the so.rce o& ne.trons prod.ce considerable

amo.nts o& n.clear waste which we haFe no way o& disposing sa&ely and

which last &or tho.sands o& years%

Ehe storage o&radioacti*e material presents a problem as they m.st be @ept

in shielded containers to preFent radiation lea@ages%

Doses o& radiothera y m.st be extremely care&.lly controlled to balance

between the bene&its o& @illing cancer cells and the ris@ o& harm%

=.clear technicians and other wor@ers m.st be contin.ally rotected and

aFoid any &orm o& irradiation as disease s.ch as cancer or radiation poisoning

9.2 - Production of Materials (1)

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Transcript of 9.2 - Production of Materials (1)