jacqueline lai - module 1 - production of materials

7/17/2019 Jacqueline Lai - Module 1 - Production of Materials

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HSC

Chemistrv

Production

of

Materials

l. Fossil uels

provide

both energyand

raw materials

suchasethyleneo

or

the productionof othersubstances

o

Identi f ' rl rc i rrc lLrst, ia luurccol 'cthr lcne

l 'orr t l recnrckinsofl rcfract ionsfrourthcref in ingof

petfoleLlnr

Petroleum,

r crudeoil, is a mixtureof hydrocarbons

f varyingcarbon hain

ength

hat

mustbe

separatedsing ractional istillation. he

global

demand

or

lighter

ractions

uchasethene

s much

higher

han he demand or heavy

ractions.However, ractional

distillation

usually

gives

a

much

higher ield

of

heavy ractions. o meet

hedemands,hese eavy ractions ndergo racking, sing

heat

and/orcatalystso break hemdown nto shorter,more

useful

ractions.

There

are wo typesof cracking:

-

Breaks own

ongmolecules

sing

high

emperatures

f

around

00-900

C.

-

It can

decomposelkanesnto

ethylene

ompletely.

- A mixtureof alkanes

with steam s

passed

hrougha very

hot metal

ube n the absence f air

to decompose

healkanes

-

Long

alkanes

C

1

5-C25)arebrokendown

nto an alkaneandan

alkene.

- As its name

mplies,t

uses catalyst nown

as

zeolites

crystalline

luminoscilicates)nd

carried

out at a temperature

f around

500"C.

- This

process

equires

ess eatand

hus

energy

han

hermal racking, ut t

cannot

decomposearge lkanesntoethyleneompletely, o t is insufficient

lone.

crH

rr<r,

heat

zeolite

, CrH

orr,

CrHrrrl

Ethvlene

(CzHq),

r

commonly

known

as

ethene,

s always

a by

product

of the cracking. t

is

removed

rom

other

products

y fractional

distillation.Thus,

catalytic rackingof

petroleum

as

become

hemajor

ndustrialsource

f ethylene.

'

Idcnti f,r

hat

ethrlette.eci ir.rse

f thc'Ir igh

eactir i t lof i tscloLrbleond s readilv

ransfbrrned

intonranv

usefirl

roducts

'

ldenti l ,r ' thatthvlel ie

ervcs s

a monorrreriorl

lvhich

olvmels

re nade

In general, lkenes remuchmore eactive hanalkanes ecauseheypossessoublebondswith

highelectron

ensity.

hedouble

onds an

easily penup o createwo single onds,

llowing

additional

toms

o bond.This

ypeof reactions known

asaddition eaction.

Ethylene

anundergo

many ypes

f addition eaction,

ome re istedhere:

Process

Reactant

Catalyst Product

Hydrogenation

Ethylene

Hz Nickel,

palladium

Ethane

Halosenations

Iz

None Diiododoethane

Hydrohalogenation

HBr

HCI

None

l-bromoethane

l-chloroethane

Hydration

Water Dil .

Sulfuric cid

Ethanol



'

Identi l - r

o lvcthr, lenesanarld i t ion

olrrrel

ancl rp la in

he

treanins

f th is

ert l

Polvmersare

high

molecular

eightmaterialsormed

rom simple

molecules

alled

monomers.

Many

dentical

monomers ombine

o

form

a

polymer

n a

process nownas

polymerisation.ach

polymer

ontains

etween

ew hundredo thousandsf

monomer

nits.

Polymerisation

an

occur

naturally r syntheticallynd alls nto wo groups:

-

Additional

polymerisation:

hen unsaturated

onomers

orm a single

argemolecule

without

the

oss

of

anyatoms.

-

Condensational

olymerisation:

henunsaturated

onomers

orm a single

argemolecule

y

eliminating

mall

molecule, uchaswater.

Polvethvlene

s an additional

olymer

orm

ethylene

monomershat

oin

together

y opening

up

its

double

onds.

olyethylene

as

he

general

ormula

CH:(CHz)"CH3,

here

couldbe

a number

n

the

housandso

hundreds fthousands.

n

Outl ine

hc

steps

n tl ie

production

1'

pol l

cth-r ' lene

s ri l r

e arnple

of cotnttrercial l l

ttcl

inclustriaIf i rnporlartt

ol1 'rer

Polyethylene

s

one

such

polymer

hat

s

very

important

oth

commercially

nd

ndustrially

n our

society. hereare

several tepsnvolved n

producing olyethylene:

-

High molecular

eight ractions reextractedrom

petroleumhrough ractional

istillation.

- These

ractions henundergo atalytic racking o

produce

thylene s

a by

product.

-

Through

ddition

olymerisation,

any

ethylene

monomers rechemically

oined

o

produce

a

polymer.

In

polymerisation,

hereare3 stages:

l) Initiation: ethylene,

nderhigh emperatures mixedwith an

nitiator,

uchas

peroxides

o

produceree adicals.Radicalsareanatomor a groupof atoms hat hasan unpaired lectron,

they arehighly

reactive.

R-O-O-R

---+

2R-O.

Peroxide

Reactivefree adicals

Thesehighly reactive adicals eact with anotherethylene

monomer o

form a

monomer

radical

R-O.

+

CtHt

---+

R-O-CHzCHz.

Free Radical

+

Monomer

ActivatedMonomer

Radical

2) Propagation: he ethylene

monomer

adical eactswith

many

more

ethylene

monomerso

increasehe carbon

hain ength

and

orm

a

polymer

adical.

R-O-CHzCHz. + nlC2Hal ---+ R-O-[CH2]4CH2'

MonomerRadical

+

n monomers

Polymer

ree

radicals.

3) Termination: he

polymer

adicals

ollide

and

eact, orminga

longer arbon hain.

This s a

completely andom

process

o he ength

of the carbon

hains an

vary

greatly.

t1

t1/H

f.H

l-r H H.,H H.H

H

i

ii

I

l\

t

|

\i

I

R-O-C.-ci-g

C;c

c-c c;c c+c

-c-o

R

I

\ r l

, , , i

i

i

i ' , , ,

i

, . ,

I

HHHHHH}IHHHiIH

, , l

H,, ,

or mot*: tnrply

"*t

C

"j

{ , :

r:

v{ 'rv ta:{ i r , -

-} tcf l { . r

l r , . l

\

l-l

H

,/n



There

are

two

types

of

polyethylene

hat

can

be

produced

depending

n

the conditions

of

polymerisation,

oth

utilises

he

same

rocess soutlined

reviously.

1) Gas

Phase/Ilish

Pressure

Process

-

High

pressure

up

o

3000

atmosphere)

nd

high

emperatures

up

o

300"c)

-

Initiator

sed

s

peroxides,

compound

ontaining

-o-o-

group.

-

The reaction

must

be

keptcool

as

t

produces ignificant

eat.

-

The

polymer ormed

s called

Low

Densitv

Polvethvlene

LDPE).

-

It hassignificant

hain

branching,

hus

cannot

e

packed losely.

-

Weaker

dispersion

orces,

hus

lexible,

oft

and

ower

ensile

trength

-

Readily

melted

and

moulded

nto

plasticbags,

ottles

and

etc'

2)

Ziesler-Natta/Low

DensitvProcess

-

Low

pressure

20

atm)

and

ow temperatures

f

only

about

60oC'

- Initiator sed s a catalyst ontaining mixtureof titanium(lll) hloride TiCl3).

-

The

polymer ormed

s called

Hieh

Densitv

Polvethvlene

HDPE).

-

lt forms

unbranched

hains

hat

can

be

packed

losely

-

Stronser

dispersion

orces,

hus

harder,

enser

nd

stronger

ensile

strength

-

Chemically

esistant,

uitable

or

petrol

anks,

bins

and

pipes.

Uses

Related o

Properties:

-

Plastic

ling

wrap;because

t is flexible,

clear

and

non

oxic

-

Shopping

ags;

t is cheap

and

lexible

- Milk bottles, ixpack ings;non oxic,cheap' nd ecyclable

-

Kitchen

utensils:

trongdispersion

orces,

greater

trength

-

Bowls,

buckets

nd

bins:

igid,

hardand

nflexible

-

Pipes,

uilding

materials:

igid,

hardand

unreactive

.

Identi t-r '

he

bl lor.r ' ing

scommercial l l

igni l icant

nonomers:

-

Vini

chlor ide

-

Styrette

By

both heir

vsternatic

tlcl olr lnon

alnes

, Describeheuses 1'the olrmersnaclel 'onrhe rboveloltolt lersn terlns f theirpfoperties.

Common

ame:

inyl chloride

Molecular

ormula:

C

Hr:61-ta

Structure:

inyl chloride

s an ethylene

molecule

n which

a

hydrogen

atom

is

replaced

by

a

chlorine tom.

HHHHHHHT-I

(:.

(--

+

(-

t-'

P0Yrl*rrsa:r'.,r

../

'\

.r'

\

H

(-l

H

t- l

i , inyi

h lnr id*

H

{- H

(-

c r loroethene

1-rr : r ly ' r i r ry l r

r ior ide

l

pyrr_

i

HSC Chemistry

Module 01



Common

ame: tyrene

Molecularormula:CHz:CHCoHs

Structure:

tyrene

s an ethylene oleculen whichoneof

its hydrogen

atoms s replaced

ith a benzene

ing.A

benzene

ing is a 6 carbon ing

with alternatingouble onds. hedouble ondsn benzenerenot

reactive

ike heones n ethylene.

i:

li

n

l .51r i t : r r :

HHHH

' \ , t t ' . , tHHH

I r - '

1-.

.-.

T

r-.

'-

-.

'.

t-riynr*ri-r*iicl'

| |

'

\,

s. '

\

{-.

-

(:

(-

-

(- '

H

{-e

H., H

i l rH:

| |

t tyrer l *

H

(-1rH5

H

i-

6H1

elhenyf bef izrr rP

,-ro lvr tvrenF

UsesRelated

o Properties:

-

CD cases

ndcassetteapes:

ransparent,ard, igid, easilyshaped nd

good

nsulator

-

Styrofoam ups: t is light

anda

good

hermal

nsulator

s

ts ull

of air

- Water

pipes, uttering:

eryrigid

and

hard,

asily haped ndcanbe UV

resistant

- Garden

oses:

lexible, urable,

anbe softened ith

plasticisers

ndmadeUV

resistant ith additives

Vinyl Chloride Styrene

Hardness

High

due o the

argemolecular

weishtof chlorine toms

Higherdue o the

even arger

molecular eishtof benzene

inss

Flexibilitv

Low due to the large molecular

weight of chlorine atoms.But

can be

varied

bv

introducins

additives.

Low

due

o the argemolecular

weight

of benzene

ings

Limitations

C-Cl bond s vulnerableo UV light,

PVC materials ustbe

used

ndoors

unless

UV

stabilisers

addedo

prevent

ecomposition

C-C andC-H bond

s resistanto UV

light andheat,

permitting

useboth

outdoorsnd

ndoors.

Heat tolerance

Low,decomposesnderUV light.

High,

styrene

s

produced

y blowing

gas hrough iquidpolystyrene.he

gases

rapped

n the

foammakes t a

excellent shtwei

ht

insulator

Other

Properties

Water esistant, oesnot

conduct

electricityor heat, lame esistant,

unreactivendeasily haped.

anbe

made

ofter sing

plasticisers.

Excellent eat,

cold

andelectrical

insulator. ewcrystals, anbe

made

transparent

Common

uses

RigidPVC:water

pipes, uttering,

electrical onduit loor

iles.

FlexiblePVC:

garden

ose,

ottoms

thatholdoil andorsanicmaterials

Disposablensulating ups,Styrofoam

cups, skies, ore

of surfboards, D

cases ndaudiocassettes

if

crvstallised nd

made

ransoarent)

HSC Chemistry

Module 01



2. Some cientists

esearch

he extraction

of

materials

rom biomass

o

reduceour dependence

n fossil

uels

.

Discr.rsshc

neeclbl r l ternati \c or.rrces

1-t l reornpounJs

rcs' :nt l r

btainecl

l r rrn

he

petrochcmcal nclrrstr '1

Petrolchemicalsrechemicalserivedrompetroleum,heyare he aw materialshatare equired

for

the

production

f

polymers,

uchas ethylene

nd

propenewhich

forms he starting

material

or

many

products

nd

ndustries. owever,

etroleum

ndcrude

il are

non

enewableesources,

hich

meansheywilleventually

un

out.

t hasbeen orecastedhat

world supply

f crude

il will runout

mid

century.

heeffectof

petrol

hortage

s

already

vident

n its significant

ncrease

n

price

over

the

past

decade.

n alternate ource

s neededo cope

with

the

world

demand

or

various

polymers

once

hesupply fpetroleum

unsout.

Af

so,

oughly95%of crudeoil

is

used s

uel.The

combustion

f

somuch uel

eleases

ollutants

into

the

atmosphere,eading o enhanced

reenhouseas

effect

andacid

ains.

By

developing n

alternativeource f fuel,morecrude ilcan beused o produce etrochemicalso creatematerials.

.

Hrplairr 'hat

s meant r a condensatior-rolvnrer

Condensation

olymers

re

polymers

hat orm by theelimination

f a small

moleculemostly

water,

when

pairs

of

monomermolecules

oin

together.

ellulose

s

anexample

f a condensation

olymer

andalsomanynatural

polymers

uchas starch.

rotein

and

DNA.

'

Describehestructure

l 'cel lulose

nd

denti l f t

asanexample

l 'aconclensation

oll 'mel ' l i l r"rnci

asa nrajor

ornponent

f hiomass

'

Describehe eactionnvolveclvhen condensation

oly'nrcr

s brmed

Celluloses a naturallyoccurring ondensationolymer,alsoknownasa

bjgp y 11q.

The monomer

that

orms

celluloses

glucose.

nstead f

having

bonds

penup,

he unctionalgroup f the

monomerseact ogether,ormingnew

bondandexpelling

water.There

are

wo

types

of

glucose:

glucose

nd

B

glucose. glucose

orms

starch nd

B

glucose

ormscellulose.

11

s up

t--1

Twtr

-dtnr

ers tonal st.r-ucture

I

-?

I

oH

rr-glucose

/ l ' -g lucose

Glucose as hemolecularormulaCoHrzOo

r

HO-CoHroO+-OH.ondensation

olymerisation

occurs y eliminatinghe watermolecules

etween

airs

of

glucose

molecules.

ach

glucose

monomer xpels heir unction

group

hydroxyl)

on

its

either

end,which

ormswater.

-( . . . , l l l , , t i l - [ . ] i1

i l i l - ( ."111

,t i r - t) ] .1

I l : i l - t i . l { r ,r(}+-[ ' r f ]

I l ( ]- t1,,1.. l , , , i l r -

n(C

6HnO)

--+...

(C

6H cO),...

+ nH

20

,{

OH,

(/

l5 down

CH

OII

I

jl

I

I alr-]

ou

T'

I

CH OH

J

il

| ..f

t

l \ , l . .1u

o'H\"

T

ta

ca

'r.

I

,l

1.. . / '

}

I

OH

Gff iG

@

"-,j

G .. ff '1

HSC Chemistry

Module 01



Due o thestructure

f

B

glucose,

veryalternatingunit of

glucose

lips.

|

- ,-

i.

i

i-l

Lj

- ' - - i

- rr

L.-

:

I

ti

a\l i | |

\ t t t

\ t I t

i -E i r

tt

ti

r-

'-l

-i

Pronerties

of Cellulose:

-

Despite

he hydrogen

onding,

ts

structures

so

arge

hat ts insoluble n water

-

Every

second nit

of

glucose

lips,creating

linear tructure o

t has

highdensity nd

strength

-

It is found

abundantlyn nature,making

up 50o/o f the

otal biomass n Earth

- Commonly ound n

plant

cell walls

-

Used

ndustriallyn

the

manufacture

f

fibres

uchascotton nd

paper

'

ldenti l 'r

hat

el lLrloscoti taitrsltc

blsiccai[ron-chain

trrrcirrr---.

ree,lcel

o

bLri ld

ctrr-r lclrc-i tr ical:

andcl iscirss

ts

rotcntial

sa ra\\ n-raterial

Thebasic

carbonchain

structures eeded

o build

petrochemicals

reethylene,

ropene

nd

butene,

whichhave

a carbon

hain ength f

two, hree

nd our.Glucose,

hebasicmonomer f cellulose,

has

a carbon

hain

ength

f 6.

Hence,

heoreticallylucose

molecules

an

be ransformednto he

basic ompounds

hat

are

presently

btainedrom petrochemicals.

Celluloses

a major

component

f biomass. iomass

s a renewableesource,

ormed

when

green

plants

se

carbon ioxide,

waterand

solarenergy

or

photosynthesis.

n theory,

ellulose an

provide

infinite

amount

f

renewable

aw materials

ut

with

the

known

echnologiest is

yet

oo

expensive

and

nefficient

o do so

on a mass cale.

Problems

associated

ith Cellulose:

r

It is

difficult o

break

ellulosento

glucose.

his s

because

he

ong

chains f cellulose re

bonded

o each

ther hrough ydrogen

onding

o

form

very

compactibres.Thismakest

difficult or

chemicals

o

get

between

hese

lucose-glucose

inks.One

solutiono this s using

strong, oncentratedulfuric cid,but his s expensive.

'

Fossil

uels

arecurrentlymuch

cheaper

o

produce

han

biomass

uels.

After

celluloses broken

down

o

glucose,

t

mustbe ermented

nto

ethanol

nd hendehydrated

ntoethylene.

his

s

a

Iong

and

expensive

rocess

'

Fertile

and

s required

o

grow

crops

o use

asan energy

ource. owever,

hese

ands

ave

more

important

oles n

growing

rops

sa source

f food.

Clearingorestsor

landcanalso ead o

destruction

f animal

habitats

ndenvironmental

oncerns

uchassoil

erosion

In

conclusion,

ellulose

asa

great

otentialas

replacement

o crude il

asa source f fuel. t is

renewable

ndenvironmentally

riendly.

However,

urther esearch

ust

beconducted

o find more

efficient nd ow-costing ethods f usinscellulose sa source f fuel.

i

r :-.r l

:

r

- .-

: 4,.--

r- , , ' i - i

i

|

"

, l i , , ,-,H ;

L

;

i F

i l \ , t

I

i i i \ l

{ '

i

ii

- ' re- i_;

il

i i . l i

, - ,

l

_______. i

:_

_..i,.i-;:l

'

----

-i

f i

,1...

H

y. { lH :

IEiT

ll

.'l

il

'l

i - - -----

, - , , t

i

ta' -' l

il

i r -

I rr- l

, . ' ]

i '

i - iL l i r

i ' : ' ' ; - iH

F

r

ir . ,n,r

iL t /

L,.,

|

'r-L)

r l

i J ' ,

:

l l ' ,c]Hi:

HSC Chemistry

Module 01



'

E,valuatehe

use

r the

potential

se f

a

named

iopolvrner

roducedn

relation

o i ts

propcrtics.

Polyhyd oxvbutanoate

PHB)

Production:

PHB

s

a naturally

ccuming

iopolymerhat s

produced

rom

a typeof

bacteria alledAlcaligenes

eutrophus.

These

acteria recultivated n large

colonies ndare

allowed o reproduceapidlyon a

nutrient ich diet.

At

which

point

an

mportant

utrient uchas

glucose

s taken

away.

hebacteria

begin

o

produce

PHB

as

a

source f energy.The bacteria

re

henharvestedor its PHB.

Properties

and Uses

-

It is a renewableesource

-

Biodegradable.isposable

ontainers

or

shampoo,

everagestc.will naturally

ecompose

so t saves pacesn landfills.

-

It will

also

decomposeaturally

n human

odies

o

t is used

s

sutures

o

no surgery

s

necessaryo remove t afterwards.

-

Biocompatible.t will funct ion

normally n

a

human

body

meaning t has

potential

o be used

as

surgicalmplants

-

Similar

structure

o

polypropylene

o

t can eadily eplacemany

petrochemical lastics

Advantages

and Disadvantases

In

the

medicine,

hedevelopment

f

PHB

s very mportant

s t can eplaceraditional utures,

allowing t to

decompose aturally n human

bodies,

voidinganother urgery o

remove

hem

afterwards.ts biocompatibility

lso

means t

hashighly suitable,for urgical

mplants.

Commercially,t is still moreexpensiveo producehanpetrochemicalshichhavehinderedts

development ndhence t is not

mass

produced.

urthermore, HB is

brittle

and

cannot

handlehigh

impact.Also, PHB would

obviouslybe

unsuitable

or areas

where

he

materialmustnot

decomposeo

suchaswater

pipes.

However,

s andfills

ecomemore

strained,

HB's

biodegradability

akes t

muchmoreattractive

ndenvironmentallyriendly.

Also,

as

ossil

uelsupplies

windle,

ocietywill

be

ncreasingly

eliant n PHB

andotherbiopolymers

or its enewability

nd

t's increasing

economically

fficiency s

he

prices

f fuel

rises

ue

o demands.

Recent

Development

Recently,

cientists avebeen

able o

genetically

ngineer bacterium

nown

as

pglito

produce

PHBby transferringhegenes f Alcaligenesutrophushatproduces HB.Thismethod s more

efficient sscientists

remore amiliarwith

E.coli's

physiology

o t is easy or

us

o manipulate

ts

growth

and

production

ateo

llowinghigher

nd aster

ields

of PHB.

This

s

n

comparison

uch

more

efficient

han

Alcaligenes

utrophus,

f which

scientisti nown ittle about. his helps o make

PHB

more

economicallyiable.However,

he

use

of

transgenic

lants

s a

controversial

ssue

mong

society,aisingmany

questions

mong

eligious

roups.

HSC Chemistry

Module 01



3.

Other resources,

uchas

ethanol,

are

readily

available

rom

renewable

resources uchas

plants

.

I )csrr i t ' ,c l i , " ' i lc i r l t i r i i t ion

r"r1 'c i i i . r r l l

, r c i l l ) lcr rc ant l ic lcr t t i l r

t l tc t tecr i b i 'calnlrst

in t l i is

plocess

l t i t ( l l lc e l t t l t l . r

' i

t t : r t i

.

I )cscr ibe t l rc addi t i , r l t

r l l ' \ \ i i tcr t ( )

cth\1cn, ' r 'estrl i i rg

in th.

prot l t t r - . l r , t tr ietharrol

and

icigt t i l r thc

nccci i r r " r ta l r r l

i r r h is

prr \ (ess

al tc l

l :c c l t l l t l . r : .1tset i

Ethanol

s

a

member f thealkanol

homologous eries.

lkanols

ave he

generalormula

CnHzn*rOH.

thanol

as he

molecularormula

CzHsOH.

Ethylene an be

producedrom ethanolthrough

y@:

Ethanol

conc'HtSoo

,

ethylene

*

water

C

2HsoH

(t

Je :'-rc)

C

rH o,

t

+ H

2o1r1

The

catalyst

equired n dehydration f ethanol

s

concentrated

ulfuric

acid.

Sulfuricacid works by breaking he C-OH bond and C-H bonds,allowing he

formation

of a doublebond

andwater. t is

alsoa

powerful

dehydration

gent.

Theopposi teofth isproceSSisknownashydrat ion,the.catalyst is@,which

breaks

he doublebond o form ethylhydrogen

ulfate

hat

reactswith water

o form ethanol,

reproducingulfuric

cid

n

the

process.

s a catalystt does

ot

ake

part n theend eaction

Hydration of ethylene:

CrHo*nr+

H2o11y

dit' Il2so4

>CrH5oHlrt

.

[)cscribe

rrcl ccorint

br

he

nauruses

f cthanol sstl l rent

irr

polar

nd tcltt

olalsubslatrccs

Ethanols used xtensivelysan ndustrial

nd

pharmaceutical

olvent,

uchasmethylatedpirits,

solvent ased

aints,

nks,

perfumes

nd

antiseptics.his s because

thanol an

dissolve

oth

polar

andnon

polar

substances.

his

unique

roperty

s

due o

its structure,

t has:

-

A

polar

hydroxyl

OH) group,

which

can

brm dipole-dipolettraction,

on dipoleor

hydrogen ondingwith other

polar

molecules

uch

s

water,

lucose

ndsucrose

-

A non

polar

ethyl

CzHs) roup,

which

can

orm dispersion

orceswith other

non

polar

substancesuch s odine.

theralkanes

nd

alkenes.

Thisdual-dissolvingature f ethanols onlypossible ecauset is a smallmolecule, here he

attraction ue o

polar

andnon

polar

sectors

aveequal

power

against ach

other.For larger

moleculesuchasoctanol,heattraction

ue o alky

group

s muchstrongerhan

ts

OH

group

and

hencet does annot issolve

olar

substances.

rl

t t

8*C C

Li

l t

t l

t1

HH

i iG)

HH

I

I

,o,

,/

HH

'u'

H

'H

HSC Chemistry

Module 01



n

Out l ine

he useo1-ethanolsa l i re lancl xpla inn 'hr i t canbe cal lcc la en*r 'able

csoLl rces

.

Asscss

he

potor t iu l

o1 'c thanol s an al tcrnr t i lc i rc l ancl iscLrssheaclvantagesnd

cl sa. l rut t i l es

' l - i l r

L lse

Ethanol is consideredas a renewable

esource

because t is derived from

glucose.

Despite ts

short

chain,ethanol s a

liquid

and hus t

is

commonly

used

as

portable

uel for

campingand as biogas

n

car engines. t also considered

fuel

becauset readily

undergoes

ombustion:

C

2H sOH

(D

* 3Oztst ------+2CO2r

rt

t 3H

rOtt,

Advantages f usingEthanolas

a

fuel:

-

80y'

of the

world's

demandor fuel s

petroleum

ased. hesupply f

petroleum

il l

eventually windleand ts

price

will rise,making

ethanol moreattractive ndcostefficient

source f fuel.

-

It

is a

@,

it can

bederived

rom

glucose.

-

Theoretically,

t

is

greenhouse

eutral:

Photosynthesis:6COz1*1+

HzOtl l ---+CoHrzOo

uq)

consumes

moles

f

COz]

Fermentation

f Glucose:

C6H12O6

aq)

2CzHsOH(tl+

COzlry

releases

moles

of

CO2]

Combustion f

ethanol:

2CzHsOH1rl

602

@------+4COzre)*

HzO(g)

releases

molesof

COzl

From

hese quations,

henetamount

f

carbon ioxide eleaseds zero.However,n reality

it is not,

but still muchmore

environmentally

riendly

hancombustion f

petrol.

- Ethanol

undergoesomplete

ombustion

moreefficiently

hanoctane,he majorcomponent f

petrol.

This

s

due o

its

shorter arbon

hain ength

and he fact hat t

already ontains n

oxygenatom,so ess

oxygen s required

or

the combustion. his

produces

leaner uel with

fewerpollutants

uchassootandcarbon

monoxide.

2CrH,rt t + 25O2G)--+18 H 2O,,, l6COr1*1 Requires2.5molof oxygen]

Disadvantages

f usingEthanol

as a fuel:

- Currently, t is

still muchcheaper

o

produce

uel through

combustion f

petrol

-

Produces

ess

energy

er

mole

hanoctane

- Carengines

anonly useup

o l5%o

f ethanol

sadditive

o

regular

etrol,

nownas

"gasohol".

ny more

han 5%oequires

nginemodification,

which ncurs conomic

nd

financial

ssues

uch

as

he ailure

of Brazil

n the 1970s.

-

Large

areas f arable and

mustbe

dedicated

o

growing

suitable rops o be

harvested

or

fermentation.

hese

andsmay

already

e used

o

grow

food

crops

and

clearingany

new and

can

cause nvironmental

roblems

uch

as soil

erosion, eforestation

ndsalinity.

-

Disposal

f the arge

amounts

f smelly

waste ermentation

iquors

after

emovalof

ethanol

canbeenvironmentally

amaging

Future Research:

Future

esearch

f ethanol s

concentrated

n

making t more

economically

iableby increasingts

production

ate

and

yield.

Oneway

to do this

is by

genetically

ngineering

east

ho increase

he

concentration

f

alkanol

roduced

n fermentation

o higher

han he l5%

possible

t

hemoment.

Another

method

s developing

mechanism

o

decompose

ellulosento

glucose

conomically,

r

maybe venproducing thanol irectly romcellulose

HSC Chemistry

Module 01



o

Dcscl ibc t i tc cr . rnt lt ior . i

u i i , - ict

r

r ic l r

t l i r tcnle ni ; . i i ion

r i -sr . l i i r ' :

r

l l i r ' i l t r , r icr l

Theconditions

equired

or

fermentation

re :

- Presencef

grain

or

fruit mashed

p with water

- Presencefyeast

-

Anaerobic onditions

absence

f air)

- Temperatureeptaround ody emperature,.e. 37'C. Too ow and hereaction ouldbe

slower nd

oo

hish

veast

will not

survive

t

St t t t i tn l i l

ise t l r . c l tcnt i>i | r rr i l re f l ' t t - le111ai i()n

l) l r rrr : r :

In the ermentation

f

glucose,

east

s nitially

addedo

mashed

rain

andwater.Any oxygen

present

ill beabsorbed

y the

growing

and

eproducingeast

ellsand

heconditions hange

o

anaerobic.

When

yeast

s deprived

f air, t will

respire ndbreak own

he stored

lucose

o obtain

energy nd n the

process

orming

ethanolas

product

f cellular espiration

CuHrrOu,rtl2C2H

sOH

ont

2COrtrt

As fermentationontinues,ubbles f carbon ioxideescapesrom hemixture.Whenethanol

concentrationeaches 5Yo,the

ermentationrocess

tops

sanyalcohol oncentrationigher

han

thiswill killthe

yeast.

o obtain igher

oncentration

f

ethanol,

ractional istillation

s

used,which

obtains p o 95o/o

thanol.

'

[ )e

l l tc l ic r lo lar l ic r tt

f conthi rs l ion

1-a

:or l l loui tL]

nd

i r lcLi

atc

hc tn lLrc i r l

e thar io l

l t r r r i

l l rst-hancJ

ata

Molar heat

of combustio n s

the amount

of energy

eleased hen

one

mole

of a compoundunder

goes

combustion under

standard oom

temperature

and atmospheric

pressure.

The molar heat

of

combustionof ethanol

s l360kJ/mol.

The

formula

for calculatins

heatof combustion

s:

LH

-

-t?l{Af

\\:here:

lH

=

heat

.-.I c'urtrustirrnkJ:

l l t

=

It la55 L-af

" 'ater

(.ql

c

=

specii-ic eat capacit"'i- { 8

tbr

rlater

)

-lf

=

change n

ter:rlrerature

:C

)

The

molarheat

of combustion

anbe ound

by

dividing he otal

heat f combustion y thenumber

of moles

f fuel burnt.

However,

n reality t

is hard

o obtain

his esult

n an

experiment.his s due

o several

actors:

- Heat romspiritbumerdissipatednto heenvironment

-

Heat

escaping

he

container

olding

hewater

-

Lack

of oxygen eading

o incomplete

ombustion,ndicated

y formation

f sootand

yellow

lames

HSC Chemistry

Module 01



4. Oxidation-reduction

eactions re ncreasingly

mportant

as a source

of

energy

r

Erplain

hecl

sl t lace

rcnt

l ' rnctnls

l lnt

solLtt i t ) i r5i r cr 'nr i f t ' ' l tnsle

o1'clcrt t" , , t ts

A displacement

eactions a

reactionn whicha more

reactive

metal

ransfers

lectrons

o a

q

reactivemetal's on to convert t to an atomby neutralisinghe charge.Reactionshat nvolve he

transfer f electrons

recollectively

nown

as

Redox eactions.

edox eactions

lways

onsist

f

an oxidation

and eduction eaction, r

two half equations.

o

Oxidation

s he ossof electrons

.

$[@

is

the

gain

of electrons

Forexample, henzincmetal

s

placed

n copper

ulfur

solution,

hezincwill

give

2 electrons

o the

negative opper on,

ormingzinc

sulfur

andsolid

copper

.

Chemical

quation:

n

61-r

uSO+

uq)

ZnSOqluq;Cu

1r ;

r

Net

ionic

equati n',

n

+

Cu2*

-------+

nz*

+

Cs

Thenet onicequation

s

thensplit

nto wo halfequations:

.

Zn

-----+

Zn"- 2e This s oxidation s

zinc oses

lectrons

.

Cu2* 2e

--------+

Cu

This is reduction scopper

gains

electrons

o

Thespecie

hat

s oxidiseds he

@,

i.e.

zinc

r

Thespeciehat

s reduced

s heoxidant/oxidisine

gent, .e.

copper

r

Identi fvhe clatiolrslr ipetvvccnisplacernent

f 'metal

r ins n solr,rt ion

r

other

tctalso

thc

relatir,e

ctivi t l

of rne'tals

In displacementeactions,

nly

a more eactivemetalcandisplace

less

eactivemetal. n the

previous xample, incdisplacedopper ecauset wasmore eactive.f copperwasplacedn a zinc

sulfate, o reaction

will

take

place.

The relativities

f

metals

are

epresentedn the

Agl yi$@:

K tsa

I-i

}la

{ ln

I'lu Al Zn I;c litt []l-r

H

{.-lrr

Aq I}t Arr

Metals

on

the eft

are

more reactive

while

metals

on the

right are ess eactive. herefore,

metal

n

theseries andisplace solution

ontaining

nymetalon ts right,but

cannot

isplace

nysolution

containingmetalson its left. n

general:

-

Metalson

he

eft

are

very eactive nd ose

electrons,

r oxidises,

ery

easily

-

Metalson the

right

areunreactive ut in ion form they canelectrons, r reduce,

ery easily

I

Describc nderplain alr. 'arric

el ls

n

terrlsol 'oxidation/recluction

eactiolrs

r

OLrtl ine

ire onstrLrctiorrf

salranic

e ls

anclface hedircction l 'electron

lol

'

Deflne he erms nocle.athocle.lectrode

ncl lectrol l ' teo clescribe

alvanic

e-l ls

A

salvanic

cell is a device

hat utilise

he

chemical nergy eleased y

a spontaneousedox

eaction

to

perform

electrical

work.

.

A

galvanic

ell

consist

wo

@ fu q

connected y a copper

wire and

a salt

bridge.Each

half

cell consists f a

solution f

an electrolyte

ndan

electrode.

.

An

electrolvte

s

a substancehich n aqueous

r

molten tate onducts lectricity.

. An electrodes a solidconductingerminal onnectedo theexternal ircuit.Thematerial f

theelectrodes usually hesolidstate

f

electrolyte. .g.Cu is used

or CuNOg.

HSC Chemistry

Module 01



There

re

2 typesof electrodes

n

termsof charge:

-

1s 9:

thenegative lectrode hereoxidation

ccurs

-

Cathode:

he

positive

lectrode here

eduction ccurs

There realso

2 types f electrodesn termsof

material:

-

I&lalelectrodes

suchascopperandsilver

- Inert electrode uchasplatinumdo notreact

A salt bridee s a U-tube

illedwith a solution, sually

otassium

itrate

KNO3).

ts

purpose

is o allow he

misration f ions o

neutralise

hecharse

f the wo

half

cells.

Apparatus,:l a Gah'attic

:ell

In this

galvarrir

rell- the uei ic,nit e{rlrt i*l i

rrf he reactiorrs:

{ .

- r t

s ' r

-

- r \g '

i , rq

r

(

.Lt l

' ,1 . j

-

Jr \g

I

The oridation equaticn s.

( , . , t t

. " '

( . . , t1- ' t , iy

- - . -

E

N

- ' i

: ' l ' i

{t s

ejectron

lor'.,

The reductic'n

quatiorr

s:

t

- r -

1

- \ f

' r ' /1

:

-

4

'

;L-;

The atiove celtr

arralsc. re represerrted

s:

L

"rl Lr]. L 11-

.L

i

J:

.

\fhere

Zu Zrr:-represents uretr.l rletal

ou

.

The doutrleliue represerlts ire salt trridge

In

thisexample,

opper

isplacedilverbecause

t is more

eactive. he

anode s hecopper

nd he

cathodes the

silver.Oxidation occurs

at

the anodewherecopper oses n

electron.

Sinceelectrons

flow towards hepositive erminal, here s a net electron low towards he cathode.Whenelectrons

arrive

at the cathode

t reacts

with the silvercations n

the electrolyte

nd orms

solid silver

on the

silverelectrode,

rocess

nown as

4g 41 g.

At the same ime he copper

s

losing

massas t is

oxidised.Thiscanbeconfi rmedbyweighing.Thisreact ionproduces1.lVandis@

meaning

t can

continue n

ts

own

without

external elp. f

a

negative oltage

s shown, he

eaction

is not spontaneous

hichoccurs hena less

eactivemetal ries o displace more eactive

metal's

ions.Such eaction

equires xtemalpower

upply o startand hroughouthe

reaction.

Reading

he Standard PotentialTable:

o

Going

down and eft of the ist, reactivity

and he endency

o be reduced

oxidant)

ncrease

o Goingup and ightof the ist, eactivity

nd endencyo beoxidised

reductant)

ncrease

o

OIL RIG:

oxidisation

s ost

of

electrons),eductions

gain of

electrons)

o

More

eactivemetal

up

he ist)oxidises,

ess eactivemetal

down

he

ist) educes

t-, t

-l

ir i

lr ,

li :

tl

t ,- -

. r . , , +

,^.11 t t . l F

uu

.

tr*\J3

HSC Chemistry

Module 01



Half

Equation

Potential

Difference

Zn'* +2e-

^

Znr",

-0.76V

Cu'* +2e-

--Cur,,

0.34V

Potential

DifferenceCalculations

To calculate

he

potential

ifference

n the

galvanic

ell above,

we mustuse he

ableof standard

potentials.

he

values

n this ableare

calculated ith

respecto a hydrogen

lectrode 0V.

But as

zinc undergoesxidation,

e

must

lip

theequation

oundwhichalso

lips

he

potential

difference:n,",-Zn:*

+2e-

(0.76V)

Adding hevaluesogether,he

galvanic

ell

hasa

potential

ifference

f 1.10Vwith respecto the

anode, opper. verycouple f electrolytes

roduces

he

same

oltage, o matter ow

manymoles

ofeach substance re

present

Purpose

f the Salt Bridge

As oxidationoccurs

at the anode,

radually

herewill be an excess f

positive

ons

such

as

copper

ions n the

above

xample).

imilarly,

n

the

other

half

celltherewillbe

an

excess

f negativeons

(nitrate

ons)as

moresilver ons

become olid

silver.

This

would

cause n

mbalance

f

positive

nd

negative hargesn

the system

nd he

Redox

eaction eases.

The

salt

bridge's urpose

s

to comnlete he circuit

and

allow

he

migration f ions o maintain

electricalneutralitv in

bothhalf

cells.

n

the

above

example, itrate

ons

rom the salt

bridge

moves

into the coppernitrate

solution

o

neutralise

he

excess f

positive

charges

rom copper ations.

Meanwhile,

otassium

ationsrom

hesaltbridge

moves

nto

he silver

nitrate olution. his

balanceshe charges

n both cells.KNO3

s commonly

used

because

t's

q g[ g

r

Accountbr

changesn the

oxicl i i t ior-rtate

f specicsn ternrs f their

oss

r

gainof

electrons

The oxidation

stateof an element s its

valency. t is definedas he charge

f an element

n

a

compoundwhenall its bonded

tomsand

electron

airs

are

emoved.

The oxidation

state:

-

of atoms n

elementalorm

is 0, suchas

H2andPa

-

of ions

reequal

o

heircharge,

.g.OH-: -1,PO+: -3,NH+* l ,SOq2': 2

For

example,heoxidation

umber

f manganese

n

permanganate

on

(MnOa-)

s:

Total

charge

charge foxygen

charge

fmanganese

Charge

f

manganese

-l

+

8:7

In

general

-

Oxidation s INCREASE

n oxidation

state,

orresponding

o

a

loss

of electrons

-

Reductions

DECREASE

n oxidation

tate,

orrespondingo a

gain

of

electrons

HSC Chemistry

Module 01



.

Gather ncl

resgrt

rr lbrmation

n the structurc

hemistrr

of a

dr1 cel l

evaluate

t

in

contparison

o the br-rt tonel l

i rr ert-ns

f: c l ienristrr" .

ost

or-r ocietr.

crt t lotrntental

mpaet

Drv Cell

of ' leacl-acid

el l and

ancl

pract ical i t l ' .

mpact

Voltase

1.5V

Anode

(-)

Zinc

Anode

half

equation

Znur-------+Zn'* 2e-

Cathode

+)

Mans.anesexide

MnOr)

andcarbon

Cathodehalf equation

2AInO2(n LNH

4clk,t,

+ 2e-

--) MnrOrt,,,

2NH

r(or)

H

rOrq

+ 2Cl

-

Electrolyte

Aqueous

aste

f ammonium

hloride

Overall equation

Zfl

,,,

r 2MnOr,

",

+ 2N H

4C

@n,

----)

MnrOr(,

t

* Zn(N H.), C1.,

H

20

Costand

practicality

Materials re nexpensive ndcheap

o replace

Not rechargeable

Low energydensity

output

o size atio)

Shonbattery ife

Leaks aused y zinccasing xidising

uringdischarge

Robust, asy

o storeand

portable

Cannotdeliverhish currents

Impact on

society

-

Widelyused n low current ppliances

uchas orches, alculators

nd

remote ontrols

-

Firstcommercially vailable attery,

made

portable

dvices

ossible

Impact

on environment

-

Ammonium

saltsandcarbon

renon oxic

-

Manganese(lll)xide eadily xidises

o insolublemanganese(lV)

xide

Voltase

l .6v

Anode

(-)

Zinc

Anode half

equation

2n,.,+ 2OH- ----+ Zn(OH),

+ 2e-

Cathode

+)

Graphite and silver oxide

oaste

Cathode half equation

AgrO,,,

+ H

rO,,,

+

2e-

12Agc,

+ 2OH-

Electrolvte KOH

paste

Overall

equation

Znle

+ AgrO

+

ZnO,,,+ 2Ag,

",

Cost and practicality veryexpensiveue o silver

verysmalland

ponable

provide

arge mounts

f

electricity

long

battery

ife

not rechargeable

steel asedoesnot

take

part

n reaction o eaksareunlikely

Impact

on

society

Due

o

its

smallsizeandhighconstant

oltage t is widelyused

n

smaller ppliances

uchas

watches, alculators,igitalcameras.

Good or appliances

hat

require

mall

batteryand ong battery

ife

Impact

on environment -

All

materials

are

non

toxic

-

KOH is

a stronsbaseand can causeburns

f

battery

s damaged

HSC Chemistry

Module 01



Visual

Comnarison

f the two

cells

Evaluation:

-

In termsof chemistry,hebutton ell

s

able

o

produce larger oltage s

silverasa higher

reduction

otential

hanmanganese.t

alsohasa moreconstant upply

ue o

its

alkaline

tate.

-

In

termsof cost

and

practicality,

he

dry cell s more

practical

n

most

situations

s t

is

much

cheaper nd

used

by many

more

appliances.

ry cellsare

also

cheaper,

he silver

n button ells

areexpensive.

owever,

he button ell s more

useful n situations

hat equire mall

cellswith

long

battery

ife. t is

alsomore eliable s

t doesn't eak

easily,while he

zinccasings

gradually xidised. Iso,dry cell'svoltage rops ver ime andmaybe oo ow for some

applicationsespite ot being lat

yet.

-

In

termsof

impact

on society, he

significance

impact

on society han he more

ecent

button

invented

nd

used

n a

large

cale.

-

In

termsof environmentalmpacts,

oth

have

more

polluting

ellssuch

as

ead

acid.

of the dry cell's

historymeans

t

hada

far

greater

cell. t allowed

or

portable

lectrical eviceso be

very ittle negative ffectsandare

preferred

ver

r

Analr 'sctt l i t rmationr"() ln

econclar ' - \ 's()rrrcer

uclr

s

colr lputcr

imrr lut ions.rolccLr lar

noclel

i i i ls o rnocielhepolvnrcrisatiorr

r()cess

Computersimulations reuseful n studyinghepolymerisationrocess.t allowsus o see learly

the

elationship

etweenhestructure

f

the

monomer

nd hestructure

f the

polymer.

Also t

shows

visually

how andwhichbonds

rebroken uring nitiation

y an

nitiator ndhow bonds re

ormed

during

propagation.

omputer

imulationslso

allow bondangleso

beaccurately

ortrayed

nd he

moleculeso be

rotated

ndaltered

uickly.

Whennecessary,t is a dynamic

model

hat

allowsus o

see he nteraction f the

catalystwith the reactants.

Molecularmodels re

used

o

model he

polymerisationrocess

s t hasmanyadvantageshan

writingequations

n

paper.

t

shows

he

hree

dimensional tructure nd

shapes f molecules, here

andhow hebonds onnect

toms hroughout

hemolecule. his s mportant s he bonding

nd

structure

f

themolecule

irectly nfluence

hechemical nd

physical

roperties

f the molecules.

Dry Cell

Silver

Button

Cell

I

:

:

1 '" ,

-

7t

t i - ) ,

rr l i , r

-_ i t

i

-i

i i l l l r l t

it{-)H n R

Fiit.::r-;':

a;

i-1.

Agr

:it

e

rl

t i

l't't

HSC Chemistry

Module 01



Lead

Acid Cell:

Voltase

1.92V

Anode

(-)

Lead

Anode

half equation

Pbu, + HrSOoront----->PbSOo6l

r

2H*

+ 2e-

Cathode

+)

Lead(IV)

oxide

Cathode

half equation

PbOz(

n

+

2H* + H

rSO

r^

* 2e-

------+

P

bSO

4@

2H

rO,

Electrolyte

Sulfuricacid

Overall equation

Pb*",+ P

bOrf,,

+ 2H

rSO

@r)

2P

bSO

4(n

+ 2H

2OU)

Cost

and

practicality - Materials reexpensive ue

o

leadcontent

-

Rechargeable,an ast

many

years

-

Low energy ensity

output

o

size

atio)of any

echargeableatteries

-

Battery

s

very heavyand

arge,hard o

handleand store

-

Not subject o

memory, an eavecharging

or

prolonged

ime

-

Low maintenance

s

no electrollte

needs o be

filled

-

Rechargesery slowly

Impact on society

-

Widely used n automobiles,orklifts and

argeuninterruptable

ower

supplysystem

-

First

commercially vailable

echargeable

atteryandstill the mostused

rechargeable

attery

Impact on environment

-

High leadcontent

ndsulfuric

acid s a environmental

azard f not

disposed orrectly.

- Leadcancause naemian humans

Ca*pde

Pb/Sn

grid

Pb&

HrS&

Por.ous

SePeretsr

HSC Chemistry

Module 01



5. Nuclearchemistry

rovides

range

of

materials

o

Dist i r rguish

ctr icc-n

table

nt l

' ; . r t l i r r l ic t i rc

: r , l t i l tc . '

r r r r i lc :u ' i l - .cl ic

c, - ' r tc l i t ic ,ns

rnt lcr

h ich

a

t t t tc lst t .

i r

t t i t .1 ; tb l t '

Isotopes re

atoms f

thesame lement ut

with differentmass umber. ome lements avestable

and

adioactivesotopes uchascarbon.Radioactive

sotopes r

4 ljglgglgpg

are

hose

hat

spontaneously

mit adiation

rom

ts

nucleus.

here re3

types

of radiation:

Alpha Decav:heliumnucleiareejectedrom

heunstable ucleibecauset

is

too

heavy. or

example:

he

decay

f uranium-238

: ' ,

11-

.

=i l ,

-

l ' -

l ' l i

Beta

Decav:electrons reejected

rom

the nucleus

ue

o

n:p

ratio

oo

high. For this o occur,a

neutronn thenucleusmust

decompose

o

form

proton

andelectron:

ln-lp*

-1,"

The

nucleusoses neutron

ut

gains

ne

proton,

enceheelements different ut samemass

number.

or

example

he

beta ecay

f cobalt-60:

- , . , ,

'_ ' l

.

- : , \ i

Gamma

Radiation:gamma

ayemission

ccurs suallywith betaand

alpha

ecay.

hey

are

high

energy

electromagnetic aves hat havehigh

penetrating

ower.

There

are

2

conditions o

predict

whether

an atom s radioactive:

l. If the

atomic

number

(Z)

is

greater

han83, hen

heatom

s radioactive.

2.

lf

proton-neutron

ratio is

outside:

-

l f Z

<

20,

atio s

I

:l

- lf Z is around 0, atio

s about : 1.3

- l f Z

is

around 0, atio s

about : 1.5

If theno. of neutron nd

proton

areplotted, here s a

naruow and

called he

zone

of stabilitv,

anything

hat

':

"

l ies

within hiszone s

stable.

H

".

b"

o

E

:: ,

E

=

u,

z

: : -+, : , t , : E: - i ' :

f.lunlbFr

i

protonr

Properties

of Alpha, Beta and

Gamma decay

Radioactive

decay

Identity

Charge

Penetrating

power

Ionising

power

Electric ield

deflection

Magneticield

deflection

Alpha

Heliumnucleus

TL

Lo w

High To negative Yes

Beta Electron

- l

Medium

Medium

To

positive

Yes

Gamma ay EMR

0

High

Low None No

HSC Chemistry

Module 01



u

[)csel ' i t ' r r ' l t t ] \ \

{ t ' i t t t \ t l i , l t i i ' ,

r . i i " i t r r . i i :

i l t i

l l j i ) r i t tca{1

Transuranicelements re

artificial lements ith

atomic

number

reater

han 92

(uranium,

he

heaviest aturally

ccurring lement). ransuranic

lements

re

not ound

n

nature,

heyare

artificialand

reonly

ound n nucleareactors. here re wo methods

f

producing

ransuranic

elements.

i. NeutronBombardment n NuclearReactors

Nuclear ission

s

a

process

here n

atom

s

bombarded

ith neutrons

hich

causehe

atom o

break

own ntosmaller lements.hisoften

occurs n nuclear

eactors. owever,

or some sotopes

suchasuranium-238,heyareunstable henneutrons

reabsorbednd

undergoe eta

decay o form

a

newelement, p:

Tu

*

in-';lu

----

_1"*Twp

Neptunium rapidly decays o

plutonium

Pu

which is much more stable

Ttup---t

_lle

-'i'^ru

*

NuclearFusion

n ParticleAccelerators

In this

process,

lighter

atom's

rucleus

s

srnashedntoa heavier tom's

nucleus. or example,

plutonium-239

s bombarded ith helium

o form

curiumandneutron.

'il

P, +

|

He

------>'ficm

ln

Atoms

heavier han heliurn

can also

be usedsuch

bornbardins

raniurnwith carbon o

form

californiurn:

u,)u

*'tc

---'l\cf

+a(ln)

When bombardingheavy

nuclei with high

speed

positiveparticles

ike the examplesabove,we first

need o

acceleratehese

positive

particles

o

a

high

speed

o overcome he repulsionbetween he

positiveparticle

and

he nuclei so

hat hey fuse

ogether.

Particle

Accelerators

*

Cyclotron

A cyclotron

consists f two

@

with

alternating

positive

and

negative ields

causedby an AC

power

source.A

proton

s

passed

hrough

he

cyclotronwhich is kept n a spiral

path

using

a strong

magnetic

field. The frequency

of AC

is in

phase

with the speed

of the

proton

so that

when

the

proton

passes

hrough

he

gap

between he

two

Dees,

he

voltagesalternate o hat the Dee t's

going

into is

now negative

and will

attract he

proton.

After

many revolutions t

acquires igh speedand

strikesa

target.Cyclotronsusuallyusechargedparticles uchas electrons, rotonsand smallnuclei

\ \ : r : l+; t : i :=

ir i . j i \

i : I - : . ; i=: :

'1- . . l . "

l : :+1, ' .

'=r,1l '+

; : . ' : i : : ,

r : '

i1

; ,1ql ;

J

-'

111

11ji *l 11irl',,i

;r 11r-l ,r'1,-r',','

ir:

f i . i ' ,

: , i t r ' ; r i , : : , t ' f t l ' - . [ ] i . .

HSC Chemistry

Module 01



{.

Linear

accelerator

In

a linear

ccelerator

ons

of

elements

re

accelerated

n

a straight

ine

of

a series

f cylinders.

hese

cylinders

ave

alternate

charge;

a negative

lways

ollows

a

positive,

o

hat

particles

re

always

being

epelled

y

a

positive

ylinder

while pulled

orward

by

a

negative

ylinder.

As the

speed

becomes

aster,

he

cylinders ets

onger

so

hat

he on

stays

he

same

mount

of time

in

each

cylinder. hese

ccelerators

re

usually

more

han

a kilometre

n lensth

lon

source

L*ant1tE.

ickel.64

i'tAC

sc'urce

l'

r. '

Hollow

tubes

Trrget

elenrent

l*on;

pi*:

brsnruth-

.0?

i

lon

beanr

slrkes

arget

.

Describe

olr

cornntercial

adioisotopes

rc

producecl

I

lclenti f lv

ne

Llse

1'a

anted

adioisorope

- In

inclustr_r

- ln

medicine

'

Describe

he

'r 'av

n

r"lr ich

he

abol 'e

arled

nclustrial

ncl necl ical

.acl ioisotopes

fe

usecl

'ci

explain

heir

use

n

enns

l-their

roperties

Commercial

adioisotopes

re

usually

produced

n

nuclear

reactors

and

particle

accelerators.

he

difference

s

that nuclear

eactors

roduce

eutron

ich

isotopes

hereas

cceleratorsroduce

neutron

eficient

sotopes.

*

Radioisotope

n

Medicine:

Technetium-99m

Production:

Technetium-99m

s produced

y

bombarding

molybdenum-98

ith

a neutron

o form

Molybdneum-99:

liiut"

+

in---+

noltwo

+

y

Molybdneum-99

hen

undergoes

eta

decay

o form

technetium-99m

]lu"+'ni:Tt+

_0,"

This

can

also

be done

hrough

particle

accelerators.

n

isotope

f hydrogen,

euterium,

s

accelerated

nd

bombarded

t

Molybdenum-98

reating

Technetium-99m

nd

an

excess

f neutrons.

Uses:

echnetium

s

used

xtensively

n

the

medical

ield

as

racers

or

diagnosis.

mall

amounts

re

injected

nto

the

bloodstream

nd

hrough

ts

distribution

n

the

body

we

can

detect

blood

clots,

constrictions

nd

brain

umours.

.g.

Tc-99m

s

combined

ith

tin

and

njected

nto

he

blood

where

it

attaches

tself

o red

blood

cells,

ccumulating

t

any

blood

clots.

The

advantages

f this

method

are

hat t

can

examine

patient

without

significant

arm

and t

also

allows

apid

diagnosis.

Properties:

echnetium-99m

s

useful

or

medical

iagnosis

ecause

t

has

a

short

half

life

of 6

hours.

This

allows

t

to

decay

apidly

n

human

odies

o

hat ts

radiation

auses

inimal

damages.

However,

ts

radiation

eleased

nside

hebody

still

has

he

potential

o kill healthy ells.Also,due o

its

short

half

ife,

t

must

be

produced

ear

where

t's

used.

echnetium-99m

s

alsovery

expensive

to

produce

nd

t

will

alsogenerate

adioactive

aste

HSC Chemistry

Module 01



.i.

Radioisotope

n Industry:

Cobalt-60

Production:

obalt-60s

produced

y bombarding

obalt-59

ith

neutronsohich

are

absorbed

y

thenucleus.

obalt-60

s radioactive

nd

begins

o undergo

eta

and

gamma

ecay:

]ico+

r-

flco+y

fico----+ ili +_1"y

@:

cobalt-60 s

used

n

gausing

metal

thickness

and inding

aults

within

objects

uchas

metal

pipes,

oth ely

on he

detection

f

gamma

ay

emission.

source

f cobalt-60

s

placed

n

oneside

of the metal

heets nda

photographic

ilm

is

placed

n

theotherside.

Variationsn

the hickness

f

the metal

sheets an

be dentified

by

the consistency

n

the evelof

radiation

etected

y the

photographic

ilm. If

the

adiation

evels

re oo

high,

t indicates

hat

he sheets

too hin

and

didn't

absorbenoughradiation.

shielcJecl

r*.f,toac1 ve

scLlrr :e

.,.

shee1

ot

f i l r t t

of nrater

al

' - l

b*irrg c,r'nred

- 'detector

.

an'roLrnt

f racliatiorr

r l r tnrhrr l hr r c l rooi

trY

rrr

rr

?r

cleperrd= i i i ts

hickne:rs

Properties:

obalt-60 as

ow

energy

mission

o hat

hemetal

heets

an

absorb

significant

portion

of it.

Low

energy

emission

lsomeans

t is

safer.

t alsohas

a long

half

life of

5.J

years

so

that t

doesnot

need

requent

eplacement.

owever,

t

is

always

emitting

adiation

o t

must

always

be monitored,

sed

cobalt-60

s

difficult

to disposed

nd

hence

an

present

environmental

nd

health

hazard.

Note:

half

life is

the

ime

taken

or

half

of the

radioisotopes

n the

given

sample

o decay.

'

Process

nfortnation

'rotl

secontlar) '

r)urces

o tlescribe

ecent

l iscoveries

f elentents

Most

ecent

ransuranic

lements

re

created

y

accelerating

smallnucleus

ithin

a

particle

accelerator

o collide

with

a heavier

ucleus.

ew

elements

re

hard

o verify

as hey

only

exist

or

a

fraction

f

a second

ometimes.

ome

ecently

iscovered

lements

re :

'."

Darmstadtium:

iscovered

n

Darmstadt.

Germany

andpreviously

nown

as ununnilium.

Darmstadtium

as

a

atomic

number

of

I l0

and

s

produced

y

bombarding ead-208

with

Nickel-64

' i

pn

+

gNt

--4

iil

nr

+

,

t?'

Americium:

iscovered

n

1944

n

University

f California,

t is

produced

y bombarding

u-

239

with

neutrons

wice

and

hen

rom

the

unstable

Pu-241's

ubsequent

eta

decay.

Often

used n

smoke

alarms

T]P"

+ 2

n

--->'llp"*-)

,llz*

*

_0,€

Jacqueline Van Lai HSC Chemistry

Module 01

James Ruse Agriculture

High School MMIX



o

iCiCt l i i l - t i i t - r ' i i t ; : , . i11.

. : t ; r1i , , , , , ' , ' - - .

i i , .

r

l t i r

i , i

l r , . : r - i

i i ,

t1, i . ' , r ; i . l l i i i l l

ii

Thereare

our

ypes f

detectingadiationrom

radioisotopes:

a)

Photoeraphic

ilm

When

photographicilm comesn contactwith

radiation,he silver

halide ecomposes

nd he

film

darkens.

his

s

commonly sed

s adiation adges

or

people

hatwork

with radioisotopes

to monitor heamount f

radiation

hey

eceive

b) ScintillationCounter

Scintillation ounter etects

ow

energy on-ionising

adiation.Whenceftain ubstances

re

irradiated ith alpha, eta

or

gamma

ay,

hey

give

off

light.

When

excited

lectrons

ump

to

higher

energy hells senergy

s

absorbed,

hey

give

off

light

as

hey eturn o

their

ground

tate.

This ight s then

passed

hrough

photomultiplier hich n tum emitsan electrical

ulse

hat

can

be recorded.

c)

Cloud

Chamber

This

nstrumentonsists f anair space ith supersaturatedateror alcohol.When

adiation

passes

hrough he nstrument,

ir

becomes

onised.

heseonsactas

he

nucleus hich

vapours

forms

droplets.

n

this

way he

path

of the

adiation

ecomesisibleas

clouds'.Alphaparticles

travel n straight ines,beta

particles

eave

a zig-zag

path

and

gamma

ay

leaves faint rack.

d)

Geieer-Muller

Counter

The

Geiger-Muller ounter etectsonising adiation

nd

hence

articularly

ffective

n detecting

betaparticles.Radiation nters hrougha thin windowat the endof the ube illed with argongas

andas

t

hitsargonmolecules,t ionisest

by knocking lectrons ut.

High

voltage ccelerates

these lectronsoward he

central lectrode,ittingmoreargonmolecules long he way and

ionising

hem.This low

of electronsormsan electrical

ulse

t he

central

lectrode.

his

pulse

is amplified

ndused o

generate

licks

n

an audioamplifier r by anelectronic

igitalcounter.

The

positive

rgon

ons

moveslowly owlds

the

negative

:ase.to

omplete

he

circuit.

rr"\

'1

,

1

r', if.1

,

rtt--"---iF,

,l- '

{r

io,

C:

I

E"'

.... .

o-'

f-1

i.

i

r\

r_,

Lj

HSC Chemistry

Module 01

jacqueline lai - module 1 - production of materials

Documents