CHEMISTRY Year 12

SHADDY HANNA EPPING BOYS HS

†

Chemistry

Shaddy Hanna

1 of 79

DISCLAIMER

The following set of notes has been compiled by Shaddy Hanna in the years 2012-2013.

These notes were intentionally written out for personal use and NOT as a teaching resource. For this reason,

bear in mind, that the quality of these notes were, and never have been, intended for publishing purposes.

Thus, due to the purpose of these notes, they are definitely not a full proof reference to the content covered

in the Board of Studies Higher School Certificate Syllabus for this subject, and should not be used as a point-

of-call reference. They were written as a personal reference and at times, ‘cheat sheet,’ to help with personal

memory. On this note, use them at your own discretion.

Along the same notion, these were never intended to be sold. If you have been sold these set of notes, please

contact the seller and ask for a refund.

Finally, all ideas and diagrams expressed in this sheet are not my own and have been adapted from the

references listed at the end of this document. For more thorough explanations on any of the topics covered

in this document, refer to these textbooks.

A PERSONAL WORD FROM ME (:

If you’re reading this, you’re probably a year 12 student about to sit their HSC this year. You may skip through

all this, and that doesn’t bother me, but if you haven’t, I hope this advice can be helpful.

The tip to succeeding in the HSC isn’t a high ATAR. The reality is, that ‘succeeding in the HSC’ comes down to

what you make out of this last year of high school, and every next one that follows. And that goes beyond the

ATAR you get. So what does make a successful year? Build your character. The rant will probably start about

now, just because I can since I’m writing this, and you’re choosing to read this, lol. By the way, please don’t

get offended by my use of Bible quotes to back up what I believe. I’m a proud Christian and profess that the

wisdom I’ve learnt in the last few years of my life are straight from the Bible. I don’t share them to arrogantly

‘bible-bash’ you. Again, remember, whether you choose to skip this or not, is up to you. So here goes:

Don’t be remembered as the kid who was competitive all year round, who screwed others to get themselves

ahead, or maybe, you didn’t actively screw others but you chose not to help them. I’m not trying to judge

you, believe me, I’m the last person to do this. I just want to give you advice I wish more people heard when

I was in high school. This quote from the bible well captures what I mean by the power of indifference:

So whoever knows the right thing to do and fails to do it, for him it is sin

Don’t be remembered as the kid who cared more about his ATAR then the people around them. Let me frame

it this way, if you were to die tomorrow, what would people remember you for? What legacy do you want to

leave behind? That you got a 99 ATAR? That you got a band 7 in Ext 2 Maths? Here’s another quote from the

bible which has often spoken truth into me:

Do not store up for yourselves treasures on earth, where moths and vermin destroy, and where

thieves break in and steal… For where your treasure is, there your heart will be also.

Don’t be remembered as the kid who never took anything serious. There’s a lot to reap from hard work which

extends beyond an ATAR. Hard work and diligence is what build character.

In Christ,

Shaddy Hanna

Chemistry

Shaddy Hanna

2 of 79

TABLE OF CONTENTS

GLOSSARY OF KEY TERMS 5

PRACTICAL SKILLS 6

VALIDITY, RELIABILITY, ACCURACY 6

TYPES OF EXPERIMENTAL ERROR 6

PRODUCTION OF MATERIALS 7

ETHYLENE, POLYMERS AND ETHANOL 7

COMMON REACTIONS 7

ETHYLENE BY THE CRACKING OF CRUDE OIL 7

ALKANES 8

ALKENES 8

INDUSTRIAL USE OF ETHYLENE 10

POLYMERISATION 10

ADDITION POLYMERISATION 11

EXTRACTION OF MATERIALS FROM BIOMASS 14

FOSSIL FUELS ARE A NON-RENEWABLE SOURCE 14

CONDENSATION POLYMERISATION 14

FUTURE OF BIOPOLYMERS 15

ETHANOL 16

DEHYDRATION TO ETHYLENE 16

ETHANOL AS A SOLVENT 16

ETHANOL AS A FUEL 16

FERMENTATION OF SUGARS 17

MOLAR HEAT OF COMBUSTION 19

ELECTROCHEMISTRY 21

DISPLACEMENT REACTIONS 21

ACTIVITY SERIES 21

OXIDATION STATES 21

GALVANIC CELLS 22

STANDARD POTENTIAL 22

COMPARISON OF CELLS 23

NUCLEAR CHEMISTRY 24

STABLE VS RADIACTIVE ISOTOPES 24

TRANSURANIC ELEMENTS 25

DETECTING RADIATION 25

Chemistry

Shaddy Hanna

3 of 79

THE ACIDIC ENVIRONMENT 26

INDICATORS 27

COMMON ACIDS/BASES 27

VARIOUS INDICATORS 27

ACIDIC/BASIC OXIDES 29

OXIDES 29

LE CHATELIER’S PRINCIPLE 30

ACID RAIN 32

ACIDS 34

COMMON ACIDS 34

THE PH SCALE 35

RELATIVE STRENGTHS OF ACIDS 36

ACIDS - MODERN DEFINITION 37

HISTORICAL DEVELOPMENT 37

BRONSTED-LOWRY THEORY 37

TITRATIONS 39

BUFFERS 41

ESTERIFICATION 42

ALKANOLS & ALKANOIC ACIDS 42

REACTION 42

COMMON ESTERS 43

CHEMICAL MONITORING AND MANAGEMENT 45

CHEMIST MONITOR REACTIONS AND MANAGE CONDITIONS 45

WORKING AS A CHEMIST 45

INDUSTRIAL CHEMIST 46

CHEMICAL PROCESSES REQUIRE MONITORING 47

AMMONIA 47

HABER PROCESS 47

PRODUCTS ARE ANAYLSED TO DETERMINE THEIR CHEMICAL COMPOSITION 49

IONS 49

ATOMIC ABSORPTION SPECTROSCOPY – AAS 52

THE ATMOSPHERE MUST BE MONITORED 53

COMPOSITION/STRUCTURE OF THE ATMOSPHERE 53

ALLOTROPES OF OXYGEN 55

CFCS (CHLOROFLUOROCARBON) 56

WATER IS CHEMICALLY MONITORED AND MANAGED 58

DETERMINING/COMPARING WATER QUALITY 58

FACTORS AFFECTING [IONS] IN SOLUTION IN NATURAL BODIES OF WATER 59

MASS WATER SUPPLIES 60

Chemistry

Shaddy Hanna

4 of 79

INDUSTRIAL CHEMISTRY 62

REPLACEMENTS FOR NATURAL RESOURCES 62

DISCUSS: ISSUES ASSOCIATED WITH SHRINKING WORLD RESOURCES – GUANO 62

EQUILIBRIUM REACTIONS 63

PRAC: MODEL AN EQUILIBRIUM REACTION 63

PRAC: ANALYSE AN EQUILIBRIUM REACTION 63

EXPLAIN: FACTORS WHICH EFFECT EQUILIBRIUM (LE CHATLIER’S PRINCIPLE) 64

INTERPRET: THE EQUILBRIUM CONSTANT 65

SULFURIC ACID 66

IDENTIFY AND DESCRIBE: SAFETY PRECAUTIONS WHEN USING CONC. 𝐻2𝑆𝑂4 66

OUTLINE: USES OF 𝐻2𝑆𝑂4 66

DESCRIBE: THE FRASCH PROCESS 67

DESCRIBE: THE CONTACT PROCESS 67

PRAC: REACTIONS OF 𝐻2𝑆𝑂4 AS AN OXIDISING AGENT AND DEHYDRATING AGENT 68

SODIUM HYDROXIDE (𝑵𝒂𝑶𝑯) 69

EXPLAIN: THE DIFFERENCE BETWEEN GALVANIC CELLS AND ELECTROLYTIC CELLS IN TERMS OF ENERGY REQUIREMENTS 69

EXPLAIN: THE PRODUCTS FROM ELECTROLYSIS OF AQUEOUS AND MOLTEN 𝑁𝑎𝐶𝑙 69

OUTLINE: STEPS IN THE INDUSTRIAL PRODUCTION OF 𝑁𝑎𝑂𝐻 FROM 𝑁𝑎𝐶𝑙 SOLUTION 70

SAPONIFICATION 73

DESCRIBE: SAPONIFICATION 73

ACCOUNT: FOR THE CLEANING ACTION OF SOAP BY DESCRIBING ITS STRUCTURE 74

EXPLAIN: SOAP ACTING AS AN EMULSIFIER WHEN IT FORMS AN EMULSION WITH WATER AND OIL 74

DISTINGUISH: BETWEEN SOAPS AND SYNTHETIC DETERGENTS 74

DISCUSS: THE ENVIRONMENTAL IMPACTS OF THE USE OF SOAPS AND DETERGENTS 75

THE SOLVAY PROCESS AND SODIUM CARBONATE 76

DESCRIBE: USES OF SODIUM CARBONATE 76

IDENTIFY: RAW MATERIALS AND PRODUCTS OF THE SOLVAY PROCESS 76

IDENTIFY: THE SEQUENCE OF STEPS USED IN THE SOLVAY PROCESS 76

DISCUSS: ENVIRONMENTAL ISSUES WITH THE SOLVAY PROCESS EXPLAIN: HOW THESE ISSUES ARE ADDRESSED 78

DETERMINE: CRITERIA USED TO LOCATE A CHEMICAL INDUSTRY (USING THE SOLVAY PROCESS) 78

Chemistry

Shaddy Hanna

5 of 79

GLOSSARY OF KEY TERMS

Account for State reasons for, report on. Give an account of: narrate a series of events or transactions

Analyse Identify components and the relationship between them; draw out and relate implications

Apply Use, utilise, employ in a particular situation

Assess Make a judgement of value, quality, outcomes, results or size

Calculate Ascertain/determine from given facts, figures or information

Clarify Make clear or plain

Classify Arrange or include in classes/categories

Compare Show how things are similar or different

Contrast Show how things are different or opposite

Define State meaning and identify essential qualities

Demonstrate Show by example

Describe Provide characteristics and features

Discuss Identify issues and provide points for and/or against

Distinguish Recognise or note/indicate as being distinct or different from; to note differences between

Evaluate Make a judgement based on criteria; determine the value of

Examine Inquire into

Explain Relate cause and effect; provide why and/or how

Extract Choose relevant and/or appropriate details

Extrapolate Infer from what is known

Identify Recognise and name

Interpret Draw meaning from

Investigate Plan, inquire into and draw conclusions about

Justify Support an argument or conclusion

Outline Sketch in general terms; indicate the main features of

Predict Suggest what may happen based on available information

Propose Put forward (for example a point of view, idea, argument, suggestion) for consideration or action

Recall Present remembered ideas, facts or experiences

Recommend Provide reasons in favour

Recount Retell a series of events

Summarise Express, concisely, the relevant details

Chemistry

Shaddy Hanna

6 of 79

PRACTICAL SKILLS

VALIDITY, RELIABILITY, ACCURACY

Definition Examples

Validity Validity is how appropriate the procedure and materials are to achieve a desired experimental result.

Fairly testing the hypothesis Keeping the variables to a minimum

Reliability Reliability is how repeatable the experiment is. Do you get very similar results every time?

Repeating several times and taking the average value Using computer simulation Include a range of frequencies

Accuracy Accuracy is how close the value calculated from the experiment is to the accepted true value.

TYPES OF EXPERIMENTAL ERROR

Random errors are caused by unknown and unpredictable changes in the experiment

o Repetition can reduce the effects.

To help reduce random errors:

Correctly take measurements

Take multiple measurements (repetition increases reliability!) take averages

Systematic errors are caused by errors in experimental equipment

o Limit accuracy

To help reduce systematic errors:

Instructions for the use of the instrument should be read and followed.

Corrections for instrument bias should be made (if necessary).

Chemistry

Shaddy Hanna

7 of 79

PRODUCTION OF MATERIALS

ETHYLENE, POLYMERS AND ETHANOL

COMMON REACTIONS

𝐴𝑐𝑖𝑑 + 𝑏𝑎𝑠𝑒 → 𝑠𝑎𝑙𝑡 + 𝑤𝑎𝑡𝑒𝑟

𝐻𝐶𝑙 + 𝑁𝑎𝑂𝐻 → 𝑁𝑎𝐶𝑙 + 𝐻2𝑂

𝐴𝑐𝑖𝑑 + 𝑚𝑒𝑡𝑎𝑙 𝑜𝑥𝑖𝑑𝑒 → 𝑚𝑒𝑡𝑎𝑙 𝑠𝑎𝑙𝑡 + 𝑤𝑎𝑡𝑒𝑟

𝟔𝐻𝐶𝑙 + 𝐹𝑒2𝑂3 → 𝟐𝐹𝑒𝐶𝑙3 + 𝟑𝐻2𝑂

𝐴𝑐𝑖𝑑 + 𝑚𝑒𝑡𝑎𝑙 → 𝑚𝑒𝑡𝑎𝑙 𝑠𝑎𝑙𝑡 + ℎ𝑦𝑑𝑟𝑜𝑔𝑒𝑛

𝟐𝐻𝐶𝐿 + 𝑍𝑛 → 𝑍𝑛𝐶𝑙2 + 𝐻2

𝐴𝑐𝑖𝑑 + 𝑐𝑎𝑟𝑏𝑜𝑛𝑎𝑡𝑒 → 𝑠𝑎𝑙𝑡 + 𝑐𝑎𝑟𝑏𝑜𝑛 𝑑𝑖𝑜𝑖𝑥𝑑𝑒 + 𝑤𝑎𝑡𝑒𝑟

𝐻2𝑆𝑂4 + 𝐶𝑎𝐶𝑂3 → 𝐶𝑎𝑆𝑂4 + 𝐶𝑂2 + 𝐻2𝑂

ETHYLENE BY THE CRACKING OF CRUDE OIL

The process of breaking down a hydrocarbon into smaller molecules.

THERMAL/STEAM

Non catalytic process where a mixture of alkanes are passed through hot metal tubes with steam at

very high temperatures (700° - 1000°) and pressures where hydrogen gas is a product

𝐶11𝐻24 → 𝟒𝐶2𝐻4 + 𝐶3𝐻6 + 𝐻2

𝐶2𝐻6 → 𝐶2𝐻4 + 𝐻2

𝐶3𝐻8 → 𝐶2𝐻4 + 𝐶𝐻2 + 𝐻2

CATALYTIC

Process where high molecular weight fractions from crude oil are broken down into low molecular

weight substances to increase the output of high-demand products, such as ethene

o Carried out at 500°C in the absence of air and above average pressures

Catalysts used are inorganic compounds called zeolites

o Highly porous, heterogeneous (different state to reactants) and have large surface area

𝐶5𝐻10 → 𝐶2𝐻4 + 𝐶3𝐻6

Chemistry

Shaddy Hanna

8 of 79

ALKANES

Saturated hydrocarbons with only single C-C bonds.

o Non polar molecules with only weak dispersion forces

o LBP are gases at room temp; HBP are liquids at room temp

𝐶𝑛𝐻2𝑛+2

REACTIONS

Combustion: Alkanes burn in air to form 𝐶𝑂2 and 𝐻2𝑂

𝐶3𝐻8 (𝑔) + 𝟓𝑂2(𝑔) → 𝟑𝐶𝑂2(𝑔) + 𝟒𝐻2𝑂 (𝑔)

Substitution: Alkanes react with chlorine and bromine when exposed to UV light

𝐶𝐻4 (𝑔) + 𝐶𝑙2 (𝑔) → 𝐶𝐻3𝐶𝑙 (𝑔) + 𝐻𝐶𝑙 (𝑔)

ALKENES

UNsaturated hydrocarbons- contain double C=C bonds (make them more reactive then alkanes)

𝐶𝑛𝐻2𝑛

REACTIONS

Combustion: Alkenes burn in air to form 𝐶𝑂2 and 𝐻2𝑂; same way as alkanes

𝐶2𝐻4(𝑔) + 𝟑𝑂2(𝑔) → 𝟐𝐶𝑂2(𝑔) + 𝟐𝐻2𝑂 (𝑔)

Addition: a chemical reaction in which a small molecule adds across a double or triple bond of a

hydrocarbon molecule.

o Hydrogenation:

heating of ethene with hydrogen

and a metal catalyst

𝐶2𝐻4 + 𝐻2𝑚𝑒𝑡𝑎𝑙→ 𝐶2𝐻6

o Halogenation: addition of bromine (halogen) liquid forms colourless compound

𝐶2𝐻4 + 𝐵𝑟2 → 𝐶2𝐻4 𝐵𝑟2

o Hydrohalogenation: adding hydrogen joined to halogen element

𝐶2𝐻4 + 𝐻𝐶𝑙 → 𝐶4𝐻5 𝐶𝑙

o Hydration: adding water and sulphuric acid catalyst

𝐶2𝐻4 + 𝐻2𝑂 𝐻2𝑆𝑂4→ 𝐶2𝐻6 𝑂

Prefix meth- eth- prop- but- pent- hex- hept- oct- non- dec-

# of C atoms 1 2 3 4 5 6 7 8 9 10

Chemistry

Shaddy Hanna

9 of 79

PRACTICAL EXPERIMENT

AIM

To compare the reactivity of cyclohexane and cyclohexene using bromine water

METHOD

Performed in a fume cupboard;

Add 1mL of cyclohexane into a test tube

Add 1mL of cyclohexene into another test tube

Add 1ml of bromine water to each of the test tubes

Stopper the test tubes and wait for 10 minutes to record observations

RESULTS

Name Formula Colour

(before) Colour (after)

Cyclo-1-hexene 𝐶6𝐻10 Clear Clear

Cyclo-hexane 𝐶6𝐻12 Clear Orange

DISCUSSION

Cyclo-x was used since it is at liquid at room temperature, and much less volatile then x

Further, hexane vs hexane was used due to the differing existence of a double bond

VARIABLES

Independent: o The reactivity of the substance

Dependent: o The presence of a double bond

Controlled: o Amount of bromine water, hexane used o Temperature o Exposure to light

SAFETY PRECAUTIONS

Can release toxic fumes perform in fume cupboard (well ventilated area

Hydrocarbons are extremely flammable keep from naked flames

Bromine water is corrosive use safety equipment (goggles, gloves, aprons etc)

Chemistry

Shaddy Hanna

10 of 79

INDUSTRIAL USE OF ETHYLENE

ETHYLENE WITH WATER

Hydration reaction to create ethanol. Uses of ethanol:

o Widely used as a reactant and solvent in the synthesis of products:

Pharmaceuticals

Perfumes

Varnishes

Plastics

Antiseptic

Catalyst: 𝐻2𝑆𝑂4

o Dehydration Concentrated

o Hydration Dilute

NAMING ALKANOLS

Delete the e of the parent alkane and add –ol

Add a number prefix to denote the position of the alcohol group (OH)

ETHYLENE WITH OXYGEN

Ethylene oxide is produced in the presence of a silver catalyst at higher temperatures

Ethylene glycol is used in large quantities for the manufacture of Automotive antifreeze

POLYMERISATION

Polymerisation: the chemical reaction in which many identical small molecules combine to form a

large molecule

o Monomer: the small molecules

o Polymer: the large molecules (macromolecule) produced

Chemistry

Shaddy Hanna

11 of 79

ADDITION POLYMERISATION

Forms by molecules adding together without the loss of any atoms

o Each double bond “opens out” to form single bonds with neighbouring monomers

o Essential are long alkane molecules: each

molecule containing 100s-1000s of

monomer units

MODELLING THE PROCESS

The polymerisation process may be difficult to visualise given the chemical equations

o Diagrams and models can be used to simplify understanding of the reactants and products

Benefits Limitations Provides physical representation of type/quantity of atoms in each molecule

Relative sizes/distance between atoms are unrealistic

Simple representation – easy to understand Dynamic nature of molecules and bonds not shown

STAGES IN PRODUCTION

Initiation

o A chemical called an initiator initiates the reaction by opening the double bond.

o The forms a monomer free radical

Has an unpaired outer shell electron, therefore is very active

Propagation

o Monomers begin to join the monomer free

radical, to form a chain

Termination

o Once both ends of the free radical

monomer chains combine, a complete

polymer is formed and the process then

terminates

As a result of this production, there is a distribution

of molecular weights in all polymer samples.

Chemistry

Shaddy Hanna

12 of 79

TYPES OF PRODUCTION

LDPE

o Conditions:

Peroxide catalyst

300°

3000 𝑎𝑡𝑚

o Amorphous structure branched chain polymers

Chains cannot pack close together

Low density (weaker dispersion forces) weaker and softer plastics

HDPE

o Zeigler-Natta conditions:

Use of catalyst

60°

3 𝑎𝑡𝑚

o Crystalline structure unbranched chain polymers

High density (greater dispersion forces) stronger, rigid plastics

PROPERTIES OF ADDITION POLYMERS

PHYSICAL

Average molecular weight

o Longer the chain = higher molecular weight = greater dispersion forces = higher melting

point

Arrangement of the chains

o Crystalline: High density = greater dispersion forces = High melting point and stronger

o Amorphous: Low Density = Less dispersion forces = Lower melting point and softer/flexible:

Chain stiffening from functional groups in the monomer units

o Polar functional groups on the monomers = increased intermolecular forces

o Hydroxyl (-𝑂𝐻) and amine (-𝑁𝐻2) groups = H bonding = stronger intermolecular forces

Cross-linking between polymer chains

o More rigid structure = less flexible

Inclusion of additives:

o Pigments to give desired colour

o Plasticisers to soften material

o Flame retardants to reduce flammability

o Stabilisers to increase resistance to decomposition by heat, UV etc

CHEMICAL

Solubility of addition polymers

o None of the polymers mentioned so far contain OH groups or expose O atoms therefore no

hydrogen bonding

o Despite polar C-CL bonds, there are many more non-polar bonds

Therefore they are insoluble in water and hydrophobic (water repelling)

Chemical stability

o Most of the bonds are strong C-C and C-H bonds, therefore they are fairly stable

o PVC C-CL bonds can be decomposed by sunlight, therefore need additives

Chemistry

Shaddy Hanna

13 of 79

COMMON POLYMERS AND ASSOCIATED USE

ETHYLENE

Systematic name: Ethene

IUPAC preferred name: Ethylene

Use:

o LDPE:

Disposable shopping bags: light and strong

Milk bottles: non-toxic and un-reactive

o HDPE:

Kitchen utensils and containers: strong and unreactive/non-toxic

Rubbish bins: hard/rigid.

VINYL CHLORIDE

An ethene molecule with one of its hydrogen atoms placed with a chlorine atom

Systematic name: Chloroethene

IUPAC preferred name: Vinyl chloride

Use:

o Underground piping—rigid and un-reactive (non-metal)

o Electrical wire coating—tough and insulating (since it is a non-metal)

STYRENE

An ethene molecule with one of its hydrogen atoms replaced with a benzene ring

o Benzene ring is a 6-carbon ring with alternating double bonds (not reactive)

Systematic name: Poly(ethenylbenzene)

IUPAC preferred name: Styrene

Use:

o Crystal Polystyrene: CD cases–clear and rigid

o Expanded Polystyrene: Disposable cups—light and a good insulator

Chemistry

Shaddy Hanna

14 of 79

EXTRACTION OF MATERIALS FROM BIOMASS

FOSSIL FUELS ARE A NON-RENEWABLE SOURCE

Crude oil is a non-renewable resource

o Will lead to greater cost in the future

o Greenhouse emissions

Cellulose is renewable source

o It is an example of biomass: the term used to describe organic matter

CONDENSATION POLYMERISATION

Polymers that form by the elimination of a small molecule (often water) to join pairs of monomers

Functional groups

o Alkanol: (𝑅 − 𝑂𝐻)

o Carboxylic acid: (𝑅 − 𝐶𝑂𝑂𝐻)

o Amine: (𝑅 − 𝑁𝐻2)

o Ester: (𝑅 − 𝐶𝑂𝑂 − 𝑅)

CELLULOSE

Naturally occurring monomer: Glucose

𝐶6 𝐻12𝑂6 𝑜𝑟 𝐻𝑂 − 𝐶6 𝐻10𝑂4 − 𝑂𝐻

𝑛(𝐶6 𝐻12𝑂6) → 𝑛(𝐶6 𝐻10𝑂5) + 𝐻2𝑂 (𝑛 − 1)

Straight, flat, rigid carbon structure (up to 10000 monomer units )

o Hydrogen bonding between chains S

Strong, yet decomposable (insoluble in water)

CELLULOSE AS A SOURCE OF CHEMICALS

Glucose is a C6 molecule, therefore it can be decomposed into petrochemicals like C2 and C3

Advantages Disadvantages

Renewable resource Production requires large areas of land and significant energy – also creates a lot of waste

Readily available Lengthy, difficult and expensive process

Carbon-based compound, as are petrochemical

Currently no viable way to decompose cellulose Industrial method (acidic hydrolysis) requires large amount of energy and cost

Chemistry

Shaddy Hanna

15 of 79

FUTURE OF BIOPOLYMERS

Biopol is the trade name for poly(hydroxybutaneoate) [PHB]

PRODUCTION

o The bacterium “Alcaligenes eutrophus” creates PHB

naturallyAE are fed supplies of nutrients (glucose and nitrogen) to encourage large growth

The supply of nutrients is then changed to be deficient in nitrogen

o Stops AE from multiplying

o Thus, they rely on forming PHB as an alternative food source

PHB is then isolated from AE through thermal decomposition of AE leaving pure PHB

USES RELATED TO PROPERTIES

The potential to be used due to its similar properties to polypropylene:

o Plastic bags due to its high tensile strength and biodegradability

o Stiches in the body due to its biocompatibility

Other useful properties

o Biodegradable - environment-safe

o Renewable resource – unlike polypropylene

EVALUATION

For the time being it is more expensive to produce than current polymers

As oil prices rise in the near future, large scale production of PHB may be a viable option

corresponding with research in the alternative bacteria E. Coli

Chemistry

Shaddy Hanna

16 of 79

ETHANOL

DEHYDRATION TO ETHYLENE

Hydration: addition of water

Dehydration: removal of water

o 𝐶𝑜𝑛𝑐. 𝐻2𝑆𝑂4 is needed to break the C-OH and C-H bonds

ETHANOL AS A SOLVENT

Why solvency works:

o When molecule A can develop greater intermolecular forces with molecule B than molecule

B can with its own molecules, molecule A becomes soluble in molecule B

Dissolving polar substances

o C-O and O-H bonds are polar

o Thus, H bonding occurs with other polar substances

o Water, Ammonia

Dissolving non-polar substances

o The ethyl end is non-polar

o Thus, dispersion forces between non-polar molecules

o Fuels (e.g. methane), fats

ETHANOL AS A FUEL

As ethanol completely combusts in air, it readily releases carbon dioxide, water and heat. Uses:

o It is a liquid, therefore is easily transportable. Can be used campers etc

o Fuel additives in automobiles, up to 20% ethanol

𝐶2𝐻5𝑂𝐻 (𝑙) + 3𝑂2 (𝑔) → 2𝐶𝑂2(𝑔) + 3𝐻2𝑂 (𝑔)

RENEWABLE SOURCE

Ethanol can be seen as a renewable resource since the glucose required to produce it is readily

replaced by nature.

Further, since the products of combustion (CO2 and H2O) are the reactants used by plants (which are

decomposed into ethanol) during photosynthesis, the reaction can be seen as greenhouse neutral.

o However, this is not entirely true since the energy input required in all steps of

fermentation comes from fossil fuels further carbon dioxide

POTENTIAL OF ETHANOL AS A FUEL

Ethanol can be incorporated into petroleum blends to reduce air pollution 10% in Australia

Advantages Disadvantages

Burns more cleanly in air, complete combustion Fuel lines and the engine needs to be modified for >10% ethanol

Reaction has a net greenhouse effect of zero (however, inputs in fermentation produce 𝑪𝑶𝟐)

The energy output per gram is lower than octane (less mileage per lire)

Could reduce the use of non-renewable fossil fuels

Chemistry

Shaddy Hanna

17 of 79

FERMENTATION OF SUGARS

Fermentation: is the process in which glucose is broken down to ethanol and carbon dioxide by the

act of enzymes present in yeast

Suitable conditions needed:

o Presence of glucose (fruit) mashed in water

o Presence of yeast

o The exclusion of air (an anaerobic environment)

o Warm temperature, 37 °𝑪

o Alcohol content less than 15%

CHEMISTRY PROCESS

Molasses is leftover sugar from sugar milling

o For this reason it is one of the most economical ingredients in fermentation

Enzymes in the mixture decompose cellulose into glucose

Yeast is then used to convert glucose into ethanol and carbon dioxide

𝐶6𝐻12𝑂6(𝑎𝑞) 𝑦𝑒𝑎𝑠𝑡→ 𝟐𝐶2𝐻5𝑂𝐻 (𝑙) + 𝟐𝐶𝑂2 (𝑔)

Fermentation process must end once ethanol reaches a concentration of 15%, or else alcohol will kill

the yeast.

Fractional distillation can then be used to produce up to 95% ethanol

Chemistry

Shaddy Hanna

18 of 79

PRACTICAL EXPERIMENT

AIM

To ferment a glucose solution and to monitor the mass changes involved.

METHOD

Place the following in a flask:

o 20g glucose

o 1g yeast

Allow a capillary tube to run from the rubber stopper into a separate beaker to act as a water trap

preventing air entering the fermentation flask, yet allowing 𝐶𝑂2 to escape

Place apparatus in a beaker containing 37°𝐶 water

After 30 min, remove apparatus and weigh again

RESULTS

𝑪𝟔𝑯𝟏𝟐𝑶𝟔(𝒂𝒒) 𝒚𝒆𝒂𝒔𝒕→ 𝟐𝑪𝟐𝑯𝟓𝑶𝑯 (𝒍) + 𝟐𝑪𝑶𝟐 (𝒈)

∴ 1 𝑚𝑜𝑙 ∶ 2 𝑚𝑜𝑙 ∶ 2 𝑚𝑜𝑙

∴ 0.076 𝑚𝑜𝑙 ∶ 0.152 𝑚𝑜𝑙 ∶ 0.152 𝑚𝑜𝑙

𝑚𝑎𝑠𝑠 𝑜𝑓 𝑓𝑙𝑎𝑠𝑘 = 𝑔 𝑚𝑎𝑠𝑠 𝑜𝑓 𝐶𝑂2 = 𝐺𝑙𝑢𝑐𝑜𝑠𝑒𝑏𝑒𝑓𝑜𝑟𝑒 − 𝐺𝑙𝑢𝑐𝑜𝑠𝑒𝑎𝑓𝑡𝑒𝑟

∴ 𝑚𝑜𝑙 𝑜𝑓 𝐶𝑂2 =𝑚

𝑀

∴ 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑡ℎ𝑎𝑛𝑜𝑙 = 𝑛𝑀

∴ % 𝑜𝑓 𝑒𝑡ℎ𝑎𝑛𝑜𝑙 =𝑚𝑒𝑡ℎ𝑎𝑛𝑜𝑙𝑚𝑠𝑦𝑠𝑡𝑒𝑚

∴ 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑔𝑙𝑢𝑐𝑜𝑠𝑒 = 𝑛𝑀

DISCUSSION

The mass of system being the same before and afterwards proves the Law of Conservation of Mass

o Therefore experiment is accurate since no gas has escaped

Reliability could be improved by repeating the experiment, setting controls on surrounding

VARIABLES

Independent: Mass of glucose used

Dependent: CO2 and ethanol produced

Controlled: Water temperature, air pressure, catalyst used

System Change in mass (g)

Before After Mass of flask 103

Mass of flask + glucose + yeast 149 142

Mass of glucose + yeast 46 39

Chemistry

Shaddy Hanna

19 of 79

ETHANOL FROM SUGAR CANE

MOLAR HEAT OF COMBUSTION

The heat liberated when one mole of the substance undergoes complete combustion with oxygen at

standard atmospheric pressure with the final products being carbon dioxide gas and liquid water

o It is minus the enthalpy change for the combustion process

Steps to calculating molar heat of combustion:

o Not that the ∆𝐻 is applied to the “system” (usually water)

Calculate ∆𝑇 (𝑓𝑖𝑛𝑎𝑙 𝑡𝑒𝑚𝑝 − 𝑖𝑛𝑡𝑖𝑎𝑙 𝑡𝑒𝑚𝑝)

Note mass of “system” (e.g. 250 g of water)

Therefore, ∆𝐻 = −𝑚𝐶∆𝑇 where 𝐶 = 4.18 × 103 (𝑓𝑜𝑟 𝑤𝑎𝑡𝑒𝑟)

Divide by 1000 to get kJ

o Note mass of ethanol burnt

𝑛 =𝑚

𝑀

∴,𝑚𝑜𝑙𝑎𝑟 ℎ𝑒𝑎𝑡 𝑜𝑓 𝑐𝑜𝑚𝑏𝑢𝑠𝑡𝑖𝑜𝑛 = 𝑘𝐽

𝑀

Figure 2 - Ethanol from other sources

Figure 1 - Ethanol from

Sugar Cane

Chemistry

Shaddy Hanna

20 of 79

PRACTICAL EXPERIMENT

AIM

To determine the molar heat of combustion of three alkanols

METHOD

Repeat for all three alkanols

o Record the mass of alkanol in their spirit burners

o Fill measuring cylinder with 100mL water and record temp.

o After 5 min, light the spirit burner

o Record temp. difference at 3.5 min

RESULTS

Due to the extra covalent bonds as C rises, more temp is need to overcome them.

DISCUSSION

Much lower than theoretical value of:

o 𝑀𝑒𝑡ℎ𝑎𝑛𝑜𝑙 = 890 𝑘𝐽𝑚𝑜𝑙−1 (10% error)

o 𝐸𝑡ℎ𝑎𝑛𝑜𝑙 = 1560 𝑘𝐽𝑚𝑜𝑙−1 (25% error)

o 𝑃𝑟𝑜𝑝𝑎𝑛𝑜𝑙 = 2220 𝑘𝐽𝑚𝑜𝑙−1 (29% error)

Heat loss due to surroundings

o Can be reduced by use of a thermally conductive can, or closing the lid

o Spirit burner can be placed higher, however ensure enough O for complete combustion

Reliability: could have been improved by repeating experiment, testing a variety of mass(es)

Variables:

Independent: The alkanol being used (#: C)

Dependent: The change in mass, temp etc

Controlled: Amount of water (C) Time for combustion

Alkanol Methanol Ethanol Propanol

𝑨𝒍𝒌𝒂𝒏𝒐𝒍 𝑭𝒐𝒓𝒎𝒖𝒍𝒂 𝐶𝐻3𝑂𝐻 𝐶2𝐻5𝑂𝐻 𝐶3𝐻7𝑂𝐻

𝑴𝒂𝒔𝒔 𝒐𝒇 𝒔𝒚𝒔𝒕𝒆𝒎𝒊𝒏𝒕𝒊𝒂𝒍 (𝒈) 247.27 176.50 211.80

𝑴𝒂𝒔𝒔 𝒐𝒇 𝒔𝒚𝒔𝒕𝒆𝒎𝒇𝒊𝒏𝒂𝒍 (𝒈) 242.84 171.85 210.49

∆ 𝒎 (𝒈) 4.38 1.65 1.31

𝑻𝒆𝒎𝒑 𝒐𝒇 𝒘𝒂𝒕𝒆𝒓𝒊𝒏𝒕𝒊𝒂𝒍 (℃) 24 24 24

𝑻𝒆𝒎𝒑 𝒐𝒇 𝒘𝒂𝒕𝒆𝒓𝒇𝒊𝒏𝒂𝒍 (℃) 51 57 57

∆𝑻 (℃) 27 33 33

Moles 𝑛 =𝑚

𝑀= 0.127 𝑚𝑜𝑙 𝑛 =

𝑚

𝑀= 0.036 𝑚𝑜𝑙 𝑛 =

𝑚

𝑀= 0.022 𝑚𝑜𝑙

Heat of Combustion ∆𝐻 = −𝑚𝐶∆𝑇 = −11.286 𝑘𝐽

∆𝐻 = −𝑚𝐶∆𝑇 = −13.794 𝑘𝐽

∆𝐻 = −𝑚𝐶∆𝑇 = −13.794 𝑘𝐽

Molar Heat of Combustion ∆𝐻

𝑛= −88.87 𝑘𝐽𝑚𝑜𝑙−1

∆𝐻

𝑛= −383.17 𝑘𝐽𝑚𝑜𝑙−1

∆𝐻

𝑛= −627 𝑘𝐽𝑚𝑜𝑙−1

Chemistry

Shaddy Hanna

21 of 79

ELECTROCHEMISTRY

DISPLACEMENT REACTIONS

A reaction in which a metal converts the ion of another metal to the neutral atom

o As a result, the metal will lose electrons and become a positive ion

o The metal ion will gain these electrons and became a stable element

This is called a redox reaction, involving the transfer of electrons

E.g. If an iron nail is placed in a blue copper salt solution, some of the iron dissolves and the blue

copper solution decolourises as a dark coating appears on the nail.

Half equations:

𝐹𝑒 (𝑠) → 𝐹𝑒2+(𝑎𝑞) + 2𝑒−

𝐶𝑢2+(𝑎𝑞) + 2𝑒− → 𝐶𝑢 (𝑠)

Overall net equation:

𝐹𝑒 (𝑠) + 𝐶𝑢2+(𝑎𝑞) ↔ 𝐹𝑒2+(𝑎𝑞) + 𝐶𝑢 (𝑠)

ACTIVITY SERIES

The more reactive metal is the one which will displace the other metal from a solution of its ions

o Reactivity of metals can be found on the data sheet

Metals at the top are the most reactive, metals at the bottom are the least

The further metals are from H, the more vigorous their reactions

OIL RIG

o Oxidation involves the loss of electrons

Occurs with the more reactive metal

Reducing agent (reductant)

AN OX: Oxidation occurs at the Anode

o Reduction involves the gain of electrons

Occurs with the more reactive metal [ions]

Oxidising agent (oxidant)

RED CAT: Reduction occurs at the Cathode

OXIDATION STATES

A number (in roman numerals) given to an atom to indicate the number of e- it has lost or gained

Group Oxidation State

Monatomic Ions charge on the ion

Stable Elements 0

Oxygen (with peroxides)

−𝐼𝐼 −𝐼

Hydrogen (with metals) (with non-metals)

−𝐼 +𝐼

𝑜𝑣𝑒𝑟𝑎𝑙𝑙 𝑐ℎ𝑎𝑟𝑔𝑒 = ∑(𝑜𝑥𝑖𝑑𝑎𝑡𝑖𝑜𝑛 𝑛𝑢𝑚𝑏𝑒𝑟𝑠)

Chemistry

Shaddy Hanna

22 of 79

GALVANIC CELLS

WIRE

The wire that connects the two electrodes allows for a transfer of electrons

The electrons flow from the anode to the cathode (electrodes)

The voltage (electrode potential) is measured by a Voltmeter connected across the wires

ELECTRODES

The electrodes are the two pieces of metal partially placed in the solution

o The anode is the negative terminal

o The cathode is the positive terminal

ELECTROLYTES

The electrolytes provide a supply of charge carriers (ions) and the cations for the reduction cell

SALT BRIDGE

The salt bridge allows transfer of ions – usually 𝑲𝑵𝑶𝟑

o Ions migrate through the cell to maintain electrical neutrality

NOTATION

Salt bridge is denoted by the double vertical lines ||

Anode on the left-hand side, Cathode on the right hand side

𝑍𝑛 | 𝑍𝑛2+ || 𝐶𝑢 | 𝐶𝑢2+

STANDARD POTENTIAL OF CELLS

Measured relative to the standard Hydrogen electrode

Each half-equation is written as reduction

𝐸° = 𝐸°𝑟𝑒𝑑𝑢𝑐𝑡𝑖𝑜𝑛 + 𝐸°𝑜𝑥𝑖𝑑𝑎𝑡𝑖𝑜𝑛

Standard potentials are measured under standard conditions (RTP):

o 25 ℃

o 100 kPa

o Using 1𝑀 electrolytes

o Electrodes must be completely immersed into

← 𝑵𝑶𝟑− 𝑲+ →

Chemistry

Shaddy Hanna

23 of 79

COMPARISON OF CELLS

DRY CELL (LE CLANCHE CELL)

Type of Reaction Species Reaction

Anode (-) Oxidation 𝑍𝑛(𝑠) → 𝑍𝑛2+(𝑎𝑞) + 2𝑒

−

Cathode (+) Reduction 𝑀𝑛4+(𝑎𝑞) + 𝑒− → 𝑀𝑛3+(𝑎𝑞)

Redox Complete 𝑍𝑛(𝑠) + 𝑀𝑛4+(𝑎𝑞) → 𝑍𝑛

2+(𝑎𝑞)+ 𝑀𝑛

3+(𝑎𝑞)

Electrolyte Aqueous paste of Ammonium Chloride, Zinc Chloride

BUTTON CELL

Type of Reaction Species Reaction

Anode (-) Oxidation 𝑍𝑛(𝑠) → 𝑍𝑛2+(𝑎𝑞) + 2𝑒

−

Cathode (+) Reduction 𝐴𝑔2𝑂(𝑠) + 𝐻2𝑂 (𝑙) + 2𝑒− → 2𝐴𝑔(𝑠) + 2𝑂𝐻

−(𝑎𝑞)

Redox Complete 𝑍𝑛(𝑠) + 𝐴𝑔2𝑂(𝑠) + 𝐻2𝑂 (𝑙) → 𝑍𝑛2+(𝑎𝑞) + 2𝐴𝑔(𝑠) + 2𝑂𝐻

−(𝑎𝑞)

Electrolyte Porous medium saturated with concentrated Potassium Hydroxide

COMPARISON

Implications Dry Cell Button Cell

Diagram

Cost and Practicality

Cheap Expensive

Short shelf life Long shelf life

Small Even smaller

Non-rechargeable Rechargeable

Impact on Society

Torches Watches

TV Remotes Hearing AIds

Impact on Environmental

Ammonia can expand and leak into waterways

Silver (toxic heavy metal) can leak out and into waterways

Chemistry

Shaddy Hanna

24 of 79

NUCLEAR CHEMISTRY

Nuclear reactions: involve changes in the nucleus

Chemical reactions: involve loss, gain, & sharing of e-

𝐸𝑍𝐴

𝑨 = 𝑎𝑡𝑜𝑚𝑖𝑐 𝑚𝑎𝑠𝑠 𝑛𝑢𝑚𝑏𝑒𝑟

(𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑟𝑜𝑡𝑜𝑛𝑠 + 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑛𝑒𝑢𝑡𝑟𝑜𝑛𝑠)

𝒁 = 𝑎𝑡𝑜𝑚𝑖𝑐 𝑛𝑢𝑚𝑏𝑒𝑟

(𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑟𝑜𝑡𝑜𝑛𝑠) ∴ 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑛𝑒𝑢𝑡𝑟𝑜𝑛𝑠 = 𝑍 − 𝐴

STABLE VS RADIACTIVE ISOTOPES

Radioactive isotopes occur when either size of the nucleus or ratio of neutrons to protons is too high

o Isotope is a form of an element (same # of protons & electrons, but different mass number)

o Radioactive decay: when they emit radiation as they release energy

(Z<20); stable isotopes have a ratio of neutrons to protons of about 1:1

(Z=50); stable isotopes have a ratio of neutrons to protons of about 1:1.3

(Z>80); stable isotopes have a ratio of neutrons to protons of about 1:1.5

HALF-LIFE OF RADIOACTIVE ISOTOPES

Half-Life’s are a measure of the stability of radioisotopes

o The time required for half the atoms in a given sample to undergo radioactive decay

o Dependent on a logarithmic scale

TYPES OF RADIATION

Alpha radiation:

o Low penetration ability

o High ionising ability

Beta radiation:

o Medium penetration ability

o Medium ionising ability

Gamma radiation:

o High penetration ability

o Low ionising ability

o Associated with the emission of alpha and beta particles

Radiation Cause of instability Mechanism Mass Charge

Alpha (𝜶) Too many protons Emission of 𝐻𝑒24 4 +2

Beta (𝒆− 𝒐𝒓 𝜷−) Too many neutrons 𝑛 → 𝑝 + 𝑒− tiny -1

Positron (𝒆+ 𝒐𝒓 𝜷+) Not enough neutrons 𝑝 → 𝑛 + 𝑒+ tiny +1

Gamma (𝜸) Excess energy Emission of 𝛾 radiation 0 0

Chemistry

Shaddy Hanna

25 of 79

TRANSURANIC ELEMENTS

Elements that have come after element 92 (Uranium) on the periodic table are radioactive isotopes

These elements are not natural, and need to be made in nuclear reactors (transmutation)

o Neutrons are shot into the nucleus of atoms (increasing atomic number=new element)

o Beta decay then often occurs, forming transuranic elements

RECENT DISCOVERY OF ELEMENTS (2012)

Livermorium, 116 protons, was made by smashing Ca, 20 protons, into Cm targets, 96 protons.

o This element almost immediately decayed into Flerovium, 115 protons

𝐶𝑎2048 + 𝐶𝑚96

248 + → 𝐿𝑣116296 → 𝐹𝑙115

289 + 2 𝑛01

DETECTING RADIATION

Geiger-Muller tube

o Consists of a sealed tube filled with argon gas and a high voltage b/w the cathode/anode

o When radiation enters the tube, it ionises the argon gas, exciting electrons to the anode

and thus completing the circuit.

This signal is then converted into sound and amplified so a tone is heard

Photographic film

o Darkens when exposed to radiation according to intensity and length of exposure

Scintillation counter

o Contains solids which give off EMR (scintillate) when exposed to radiation.

This light is then amplified by a photomultiplier and measured

Chemistry

Shaddy Hanna

26 of 79

COMMERICAL RADIOISOTOPES

NUCLEAR REACTORS

Controlled nuclear fission (splitting the atom)

o Neutrons bombard atoms and cause them to split into two roughly equal fragments

o Gives off a lot of energy

CYCLOTRONS

Positive particles (𝛼 𝑜𝑟 𝑒+) are accelerated by passing through alternative positive/negative fields.

o When very high speeds are reached they collide with atoms of the target substance

RADIOACTIVE ISOTOPES

Implications Medicine (Iodine-131) Industry (Cobalt-60)

Radiation Beta Beta and Gamma

Half-life 8 days

o Minimizes exposure to radiation – safety

5.3 years o Radiation does not need to

be replaced - durable/cheap

Use

Diagnosis for Thyroid Cancer o Iodine is Thyroid-specific o Higher detection of

radiation is emitted in cancerous cells

Treatment for Thyroid Cancer o Beta radiation kills

cancerous cells

Thickness Gauge o Measures amount of

radiation penetrating through a material by photographic film

Defects o Higher concentration of

radiation in cracks (due to build-up)

Benefits Can perform diagnostic

procedures non-invasively

Therapy can treat cancer

Ability to more precisely and reliably monitor equipment

Examine structural faults in planes and buildings

Problems Radiation can cause other

cancers or genetic damage in the patient or doctors

Requires special disposal and storage of radioactive waste

Can damage healthy tissue and cause cancers – risky for technicians

Chemistry

Shaddy Hanna

27 of 79

THE ACIDIC ENVIRONMENT

INDICATORS

COMMON ACIDS/BASES

GENERAL PROPERTIES

Feature Acids Bases*

Definition A substance which produces hydronium ions in solution

a substance which produces hydroxide ions in solution

OR contains oxide ions, 𝑂2−

Ions Produced 𝐻+ 𝑜𝑟 𝐻3𝑂+ 𝑂𝐻−

Taste Sour Bitter

Feel Sting/burns skin Soapy

Electrical Conductivity Good in solution Good in solution

Corrosiveness High Low

pH <7 >7

*NOTE: Alkalis are just a type of base: an alkali is a base which is soluble

CHEMICAL EXAMPLES

Acids Bases Neutral

Acetic acid Sodium hydrogen carbonate Distilled Water

Hydrochloric acid Sodium hydroxide Table Salt (NaCl)

Citric acid Detergent

Stomach juices Soap

VARIOUS INDICATORS

An indicator is a natural or synthetic dye that shows colour change depending on how acidic or basic

the solution is.

Chemistry

Shaddy Hanna

28 of 79

HOW INDICATORS WORK

Upon disassociation, the indicator molecule has a colour and the anion it forms is another colour.

o Accordingly, when an acid is added to the mixture (with the indicator inside), the system

will shift to the left to decrease the hydrogen ions and forming colour 1

o More so, when excess acid is added the reverse reaction shifts the completion so that the

only colour produced is colour 1.

𝐻𝐼(𝑎𝑞) ⇌ 𝐻(𝑎𝑞)+ + 𝐼(𝑎𝑞)

− 𝐜𝐨𝐥𝐨𝐮𝐫 𝟏 𝐜𝐨𝐥𝐨𝐮𝐫 𝟐

USES

Testing acidity/basicity of soil

o Some flowers, such as hydrangeas, require certain acidity to form different colours

Checking pH of the water in swimming pools

o 𝑊𝑎𝑡𝑒𝑟 = 𝑎𝑐𝑖𝑑𝑖𝑐 = 𝑖𝑟𝑟𝑖𝑡𝑎𝑡𝑖𝑜𝑛𝑠 𝑡𝑜 𝑒𝑦𝑒 𝑎𝑛𝑑 𝑠𝑘𝑖𝑛

o 𝑊𝑎𝑡𝑒𝑟 = 𝑏𝑎𝑠𝑖𝑐 = 𝑔𝑟𝑒𝑒𝑛 𝑎𝑙𝑔𝑎𝑙 𝑠𝑐𝑢𝑚 𝑔𝑟𝑜𝑤𝑖𝑛𝑔 𝑖𝑛 𝑝𝑜𝑜𝑙

Waste water monitoring

o Alkaline solutions must be neutralised before discharging into sewer

PRACTICAL EXPERIMENT: PREPARING A NATURAL INDICATOR

AIM

To extract an indicator solution from red cabbage and use it to test the acidity/basicity of a range of

substances.

METHOD

1. Gather red cabbage leaves as the natural indicator and slice them into small strips

2. Place the strips and 300mL of water into a beaker

3. Set up apparatus so as to boil the water in the beaker

4. Stir beaker continuously and leave to boil until cabbage leaves lose their pinkish colour

5. Draw up extracted indicator solution using a pipette into a new beaker

6. Set up 3 test tubes with HCl, distilled water and NaOH

7. Add a few drops of the indicator to each test tube

8. Repeat steps 6-7 five times

9. Record results

RESULTS

Red cabbage indicator turned:

o Pink in the presence of acidic solutions

o Purple in the presence of neutral solutions

o Green in the presence of basic solutions

Chemistry

Shaddy Hanna

29 of 79

ACIDIC/BASIC OXIDES

OXIDES

ACIDIC OXIDES

Are oxides of non-metals

React with bases to form salts

𝐴𝑐𝑖𝑑𝑖𝑐 𝑂𝑥𝑖𝑑𝑒 + 𝐵𝑎𝑠𝑒 → 𝑆𝑎𝑙𝑡 +𝑊𝑎𝑡𝑒𝑟

𝑆𝑂2 (𝑔) + 2 𝑁𝑎𝑂𝐻(𝑎𝑞) → 𝑁𝑎2𝑆𝑂3 (𝑎𝑞) + 𝐻2𝑂(𝑙)

React with water to form an acid or;

𝐴𝑐𝑖𝑑𝑖𝑐 𝑂𝑥𝑖𝑑𝑒 + 𝑊𝑎𝑡𝑒𝑟 → 𝐴𝑐𝑖𝑑

𝐶𝑂2 (𝑔) + 𝐻2𝑂 (𝑙) → 𝐻2𝐶𝑂3 (𝑎𝑞)

BASIC OXIDES

Are oxides of metals

Reacts with acids to form salts

𝐵𝑎𝑠𝑖𝑐 𝑂𝑥𝑖𝑑𝑒 + 𝐴𝑐𝑖𝑑 → 𝑆𝑎𝑙𝑡 +𝑊𝑎𝑡𝑒𝑟

𝐶𝑢𝑂(𝑠) + 𝐻𝐶𝑙(𝑎𝑞) → 𝐶𝑢𝐶𝑙2 (𝑎𝑞) + 𝐻2𝑂(𝑙)

Some react with water to form base

𝐵𝑎𝑠𝑖𝑐 𝑂𝑥𝑖𝑑𝑒 + 𝑊𝑎𝑡𝑒𝑟 → 𝐵𝑎𝑠𝑒

𝐶𝑢𝑂(𝑠) + 𝐻2𝑂(𝑙) → 𝐶𝑢(𝑂𝐻)2 (𝑎𝑞)

POSITION ON PERIODIC TABLE

Metals close to the bottom left corner are more basic since they have greater metallic properties

Non-metals close to the top right corner of the table are more acidic

Oxides of some elements in between are amphoteric

Noble gases do not form oxides

Chemistry

Shaddy Hanna

30 of 79

LE CHATELIER’S PRINC IPLE

DEFINITION

If a closed system at equilibrium is subjected to a change in conditions, the system will readjust

itself to minimise the disturbance

FACTORS WHICH EFFECT EQUILIBIRUM

CONCENTRATION

Increasing the concentration of a substance will cause the system to favour the direction that will

decrease the concentration of that substance

Changing the concentration of a solid or liquid species has no effect

PRESSURE (CHANGE IN VOLUME)

Increasing the pressure of a system will cause the system to favour the direction with less gas

molecules. The converse is also true

TEMPERATURE

𝐴 + 𝐵 + ℎ𝑒𝑎𝑡 → 𝐶 + 𝐷 ∆𝐻 = (+𝑣𝑒)

Endothermic reaction: Heat is a reactant

o Increase in temperature will cause the system to favour the forward reaction

𝐴 + 𝐵 → 𝐶 + 𝐷 + ℎ𝑒𝑎𝑡 ∆𝐻 = (−𝑣𝑒)

Exothermic reaction: Heat is a product

o Increase in temperature will cause the system to favour the reverse reaction

STANDARDS FOR VOLUME OF GASES

𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 = 𝑣𝑜𝑙𝑢𝑚𝑒

𝑚𝑜𝑙𝑎𝑟 𝑣𝑜𝑙𝑢𝑚𝑒

Thus, 𝑛 = 𝑉

𝑉𝑛

Chemistry

Shaddy Hanna

31 of 79

SOLUBILITY OF CARBON DIOXIDE

𝐶𝑂2 (𝑔) ⇌ 𝐶𝑂2 (𝑎𝑞)

Dissolved 𝐶𝑂2 reacts with water to form a weak acidic solution (carbonic acid):

𝐶𝑂2 (𝑔) + 𝐻2𝑂(𝑙) ⇌ 𝐻2𝐶𝑂3 (𝑎𝑞) ∆𝐻 = −57𝑘𝐽

Carbonic acid establishes equilibrium with the hydrogen-carbonate and carbonate ions:

𝐻2𝐶𝑂3 (𝑎𝑞) ⇌ 2𝐻+(𝑎𝑞) + 𝐶𝑂3

−(𝑎𝑞)

Concentration

o When concentration of carbon dioxide increases, reaction 1 shifts to the right and thus

more carbon dioxide is dissolved

o When concentration of carbonic acid increases, reaction 2 shifts to the left and thus less

carbon dioxide is dissolved

Temperature

o If temperature is increased, reaction shifts to the left.

Thus more 𝐶𝑂2 is released; concentration of 𝐻2𝐶𝑂3decreases = a “flat” taste

o If temperature is decreased (e.g. when refrigerated), reaction shifts to the right.

Thus more 𝐶𝑂2 is dissolved; concentration of 𝐻2𝐶𝑂3 increases = a “sharp” taste

Pressure

o If pressure is decreased (removing lid) reaction favours side with more gas moles

Thus shifts to reverse reaction, 𝐶𝑂2is released as a gas

o If pressure is increased (lid back on) reaction favours side with less gas moles

Thus shifts to forward reaction, 𝐶𝑂2is dissolved into 𝐻2𝐶𝑂3

Acidity

o If acid is added, [𝐻+] increases and the reaction will shift to the left, producing more 𝐻2𝐶𝑂3

o If a base is added, [𝑂𝐻−] increases, and thus [𝐻+] increases, and the reaction will shift to

the right, reducing the amount of 𝐻2𝐶𝑂3

Chemistry

Shaddy Hanna

32 of 79

ACID RAIN

SOURCES OF SULFUR/NITROGEN OXIDES

NATURAL SOURCES

Sulfur Dioxide

o Combustion of organic matter; bushfires

o Bacteria decomposition of organic matter to produce 𝐻2𝑆 which oxidises to form 𝑆𝑂2

2𝐻2𝑆 (𝑔) + 3𝑂2 (𝑔) → 2𝑆𝑂2 (𝑔) + 2𝐻2𝑂 (𝑙)

Nitrogen Oxides

o 𝑁𝑂: Reaction of 𝑁2 (𝑔) and 𝑂2 (𝑔) in the atmosphere due to high temp; lightning strikes

𝑁2 (𝑔) + 𝑂2 (𝑔) → 2𝑁𝑂 (𝑔)

o 𝑁𝑂2: Reaction of 𝑁𝑂 (𝑔) and 𝑂2 (𝑔) in the air

2𝑁𝑂 (𝑔) + 𝑂2 (𝑔) → 𝑁𝑂2 (𝑔)

INDUSTRIAL SOURCES

Sulfur Dioxides: Smelting of metal ores

𝐹𝑒𝑆 (𝑠) + 𝑂2 (𝑔) → 𝐹𝑒(𝑠) + 𝑆𝑂2 (𝑔)

Nitrogen Oxides

o 𝑁𝑂: Combustion engines. Reaction of 𝑁 and 𝑂 in air.

𝑁2 (𝑔) + 𝑂2 (𝑔) → 2𝑁𝑂 (𝑔)

o 𝑁𝑂2: Combustion engines providing enough heat to spur reaction

2𝑁𝑂 (𝑔) + 𝑂2 (𝑔) → 𝑁𝑂2 (𝑔)

INCREASES OF OXIDES IN ATMOSPHERE

Quantitative Evidence – quite accurate

o Measurement of carbon isotopes in old trees

o 25% increase in atmospheric concentration of oxides from ancient air trapped in ice sheets

of Antarctica

Qualitative Evidence – not very accurate

o Increased incidence of acid rain

o Photochemical smog- direct indicator of excessive nitrogen oxide in atmosphere

o Sulfur oxides are greenhouse gases thus due to increased climate change, increased

oxides of sulfur can be suggested as a cause

Difficulties

o Oxides are present in very small concentrations (0.001 ppm)

o Instruments capable of testing atmospheric concentration only available since 1970’s

o Oxides form ions that are soluble in water

Chemistry

Shaddy Hanna

33 of 79

CONCERNS OF OXIDES IN ATMOSPHERE

Form acid rain when dissolved in rain (danger to living organisms, buildings, society)

NOx contribute to formation of photochemical smog – ozone in the lower atmosphere as a pollutant

FORMATION OF ACID RAIN

Unpolluted rain is slightly acidic due to 𝐶𝑂2 dissolved in water forming acidic 𝐻2 𝐶𝑂3

𝐶𝑂2 (𝑔) + 𝐻2𝑂(𝑙) → 𝐻2𝐶𝑂3 (𝑎𝑞)

Acid rain: defined as rain with pH < 5 o Sulfur readily oxidises in air to form sulfur trioxide

2𝑆𝑂2 (𝑔) + 𝑂2(𝑔) → 2𝑆𝑂3 (𝑔)

o Sulfur oxides react with rain in atmosphere to produce acid rain

𝑆𝑂2 (𝑔) + 𝐻2𝑂(𝑙) → 𝐻2𝑆𝑂3 (𝑎𝑞)

𝑆𝑂3 (𝑔) + 𝐻2𝑂(𝑙) → 𝐻2𝑆𝑂4 (𝑎𝑞)

o Nitrogen oxides react with rain in atmosphere to produce acid rain

2𝑁𝑂2 (𝑔) + 𝐻2𝑂(𝑙) → 𝐻𝑁𝑂2 (𝑎𝑞) + 𝐻𝑁𝑂3 (𝑎𝑞)

EFFECTS OF ACID RAIN

Can damage pH sensitive environments o Fish eggs can’t hatch, adult fish may die at low pH’s o Reduction in fish population disrupts food chain o Acid dissolves nutrients and minerals important for plant growth

Can damage industrial buildings, structures, statues (corrosion) o Sulfuric acid in rain corrodes limestone and marble buildings

As water evaporates into rock crevices, calcium sulfate crystallises out causing rocks to crumble

𝐶𝑎𝐶𝑂3 (𝑠) +𝐻2𝑆𝑂4 (𝑎𝑞) → 𝐶𝑎𝑆𝑂4 (𝑠) + 𝐶𝑂2 (𝑔) + 𝐻2𝑂(𝑙)

Chemistry

Shaddy Hanna

34 of 79

ACIDS

An acid donates H+ ions

o H+ ions are protons; therefore acids can be defined as proton donors

o The ionisation in water can be summarised as the dissociation of a substance into its ions

o When an acid is placed in water, it ionises and releases a proton forming a negative ion

𝐻𝐶𝑙(𝑎𝑞) + 𝐻2𝑂(𝑙) ⇌ 𝐻3𝑂 +(𝑎𝑞)

+ 𝐶𝑙−(𝑎𝑞)

Acids ultimately ionise to form hydronium ions

o Monoprotic: Can only donate one 𝐻+

o Diprotic: Can only donate two 𝐻+

o Triprotic: Can only donate three 𝐻+

COMMON ACIDS

Strong Acid Weak Acid

Hydrochloric acid (𝑯𝑪𝒍) Acetic acid (𝐶𝐻3𝐶𝑂𝑂𝐻)

Ethanoic acid

Sulfuric acid (𝑯𝟐𝑺𝑶𝟒) Citric acid (𝐶6𝐻8𝑂7)

2-hydroxypropane-1,2,3-tri-carboxylic acid

Nitric acid (𝑯𝑵𝑶𝟑) Carbonic acid (𝐻2𝐶𝑂3)

FOOD ADDITIVES

Enhance flavour of food Citric acid

Increase nutritional value Ascorbic acid

Prevent “spoilage” micro-organisms from producing by reducing pH Ethanoic acid

NATURALLY OCCURING ACIDS/BASES

Citric acid (2-hydroxypropane-1,2,3-tricarboxylic acid)

o Occurs naturally in citrus fruit

Lime (𝐶𝑎𝐶𝑂3)

o Naturally present in limestone and marble

Chemistry

Shaddy Hanna

35 of 79

THE PH SCALE

PH MEASURED AS A TEN-FOLD CHANGE

The way pH is calculated is through an equation related to H+ concentration

𝑝𝐻 = − log10[𝐻+]

∴ [𝐻+] = 10−𝑝𝐻

o Therefore a change in pH of 1 = a ten-fold change of [H+]

o Furthermore, the pH depends on how protic the acid is

USING PH METERS

pH Meters are electronic devices which function by measuring [H+]

o Are accurate to 0.01 pH units (compared to 1 pH unit accuracy of indicators)

o Must be calibrated and rinsed in water to neutralize before use

COMPARING ACIDS VS BASES

Auto ionisation of water

o 2𝐻2𝑂(𝑙) ⇌ 𝐻3𝑂+(𝑎𝑞) + 𝑂𝐻

−(𝑎𝑞)

Ionisation constant for water at 25 °

o 𝐾𝑊 = 1.0 × 10−14 molL−1 = [𝐻+][𝑂𝐻−]

Acidic solution: [𝐻+] > 1.0 × 10−7 molL−1 (𝑝𝐻 < 7)

Basic solution: [𝑂𝐻−] > 1.0 × 10−7 molL−1 (𝑝𝐻 > 7)

Chemistry

Shaddy Hanna

36 of 79

RELATIVE STRENGTHS OF ACIDS

Acids are also describes according to the amount of acidic moles in solution

o Concentrated: [𝐻𝑋] > 1M

o Dilute: [𝐻𝑋] < 1M

Acids are described according to their degree of ionisation

o 𝐷𝑒𝑔𝑟𝑒𝑒 𝑜𝑓 𝑖𝑜𝑛𝑖𝑠𝑎𝑡𝑖𝑜𝑛 (%) =[𝐻+]

[𝐻𝑋]

[𝐻+] refers to the concentration of hydrogen ions

[𝐻𝑋] refers to the concentration of the whole solution

STRONG ACIDS

Completely ionize to produce 𝐻+ ions in aqueous solution

o 𝐻+ ions released join with produce 𝐻2𝑂 to form 𝐻3𝑂 + ions

Do not form equilibrium with intact molecule and its ions

o Only forward reactions occur till completion

WEAK ACIDS

Only partially ionize in water

Establishing an equilibrium between intact molecules and ions

o Equilibrium lies to the left as very little molecules ionise

Chemistry

Shaddy Hanna

37 of 79

ACIDS - MODERN DEFINITION

HISTORICAL DEVELOPMENT

LAVOISIER (1780S)

Acids were non-metal compounds that contained oxygen

However, there were many acids which did not contain oxygen

DAVY (1815)

All acids contained a replaceable hydrogen

However, some non-acidic substances also contained replaceable hydrogen e.g. sugar

ARRHENIUS

An acid is a substance which produces H+ ions in solution

A base is a substance which produces OH- ions in solution

However, many bases do not contain OH-

Strong acids completely ionise in aqueous acids

Only applicable to aqueous solutions

Did not address relative strengths and amphoterism

BRONSTED-LOWRY THEORY

Acid-base reactions involve a transfer of protons from the acid to a base. Explaining acid-base

reactions without a solvent.

o An acid is a proton donor.

o A base is a proton acceptor. Explains the behaviour of bases not containing the OH- group

Further, if a substance has greater tendency to give up protons than the solvent, then it is an acid in

the solvent. The converse also being true. Explaining amphoterism and the relative strengths of

acids

AMPHIPROTIC SUBSTANCES

Amphoteric: substances which can act both as acids and bases

Amphiprotic: accept or donate protons (thus act as acid or base)

o Must contain a H+ atom (proton) to donate

EXAMPLES

Water (H2O)

o Acid: 𝑁𝐻3 (𝑎𝑞) + 𝐻2𝑂(𝑙) ⇌ 𝑁𝐻4 +(𝑎𝑞)

+ 𝑂𝐻−(𝑎𝑞)

o Base: 𝐻𝐶𝑙(𝑔) +𝐻2𝑂(𝑙) ⇌ 𝐻3𝑂+(𝑎𝑞) + 𝐶𝑙

−(𝑎𝑞)

Hydrogen-carbonate ion (HCO3)

o Acid: 𝐻𝐶𝑂3−(𝑎𝑞)

+ 𝐻2𝑂(𝑙) ⇌ 𝐻3𝑂+(𝑎𝑞) + 𝐶𝑂3

2−(𝑎𝑞)

o Base: 𝐻𝐶𝑂3−(𝑎𝑞)

+ 𝐻3𝑂+(𝑎𝑞) ⇌ 𝐻2𝐶𝑂3(𝑎𝑞) + 𝐻2𝑂(𝑙)

Amphoteric

Amphoteric

Chemistry

Shaddy Hanna

38 of 79

PRODUCTION OF SALTS

𝐴𝑐𝑖𝑑 + 𝐵𝑎𝑠𝑒 → 𝑆𝑎𝑙𝑡 + 𝑊𝑎𝑡𝑒𝑟

Neutral salts: ion does not react with water

o 𝑆𝑡𝑟𝑜𝑛𝑔 𝐴𝑐𝑖𝑑 + 𝑆𝑡𝑟𝑜𝑛𝑔 𝐵𝑎𝑠𝑒 → 𝑁𝑒𝑢𝑡𝑟𝑎𝑙 𝑆𝑎𝑙𝑡

o 𝑊𝑒𝑎𝑘 𝐴𝑐𝑖𝑑 +𝑊𝑒𝑎𝑘 𝐵𝑎𝑠𝑒 → 𝑁𝑒𝑢𝑡𝑟𝑎𝑙 𝑆𝑎𝑙𝑡

Basic salts: ions react with water to form hydroxide ions

o 𝑊𝑒𝑎𝑘 𝐴𝑐𝑖𝑑 + 𝑆𝑡𝑟𝑜𝑛𝑔 𝐵𝑎𝑠𝑒 → 𝐵𝑎𝑠𝑖𝑐 𝑆𝑎𝑙𝑡

Acidic salts: ions react with water to form hydronium ions

o 𝑆𝑡𝑟𝑜𝑛𝑔 𝐴𝑐𝑖𝑑 +𝑊𝑒𝑎𝑘 𝐵𝑎𝑠𝑒 → 𝐴𝑐𝑖𝑑𝑖𝑐 𝑆𝑎𝑙𝑡

CONJUGATE PAIRS

Acids give up protons to form a conjugate base

o Strong acids will have a weak conjugate base

Bases accept protons to form a conjugate acids

o Strong bases will have a weak conjugate acid

NEUTRALISATION REACTIONS

Neutralisation reactions are those that occur between acids and salts

o Involve transfer of protons

𝐻+(𝑎𝑞) + 𝑂𝐻−(𝑎𝑞) → 𝐻2𝑂(𝑙) + 𝐡𝐞𝐚𝐭 ∆H = −57 kJmol

−1

o Therefore the reaction is exothermic

o This is how we gain the ionic product of water (KW)

NEUTRALISATION OF CHEMICAL SPILLS

Acids/bases are corrosive and can cause irritations to eyes and skin

In the case of an acid spill; a weak base is used to neutralize it and form a salt and water

o E.g. 𝐻𝐶𝑙(𝑎𝑞) + 𝑁𝑎𝐻𝐶𝑂3 (𝑎𝑞) → 𝑁𝑎(𝑎𝑞) + 𝐶𝑂2 (𝑔) + 𝐻2𝑂(𝑙)

𝐻+(𝑎𝑞) +𝐻𝐶𝑂3−(𝑎𝑞)

→ 𝐶𝑂2 (𝑔) + 𝐻2𝑂(𝑙) ⇌ 𝐻2𝐶𝑂3(𝑎𝑞)

In the case of a base spill, a weak acid is used to neutralize it

o E.g. 𝑁𝑎𝑂𝐻(𝑎𝑞) + 𝑁𝑎𝐻𝐶𝑂3 (𝑎𝑞) → 𝑁𝑎2𝐶𝑂3 (𝑎𝑞) + 𝐻2𝑂(𝑙) + 𝑁𝑎(𝑠)

𝑂𝐻− (𝑎𝑞) + 𝐻𝐶𝑂3−(𝑎𝑞)

→ 𝐶𝑂3 2−

(𝑎𝑞)+ 𝐻2𝑂(𝑙)

Advantages Disadvantages

Stored and transported easily (since it is stable)

Exothermic reaction: can cause severe burns if carried onto skin

Amphiprotic: allowing it to be used to neutralize acids and bases

Relatively cheap

Forms a gas when reaction indication of when the reaction has stopped

Chemistry

Shaddy Hanna

39 of 79

TITRATIONS

Titrations are a volumetric analytical technique used to determine the concentration a solution by

reaction it with a solution of known concentration (standard solution)

o Volumes of the reactants at the endpoint are measured and by using knowledge of v and c

of original solution; c of unknown can be calculated

STANDARD SOLUTIONS

Standard solution: solution of accurately known composition/concentration

o High purity to produce accurate results

o Chemical stability so they don’t react violently with water solvent

o Non-hygroscopic so they don’t absorb/release water; affecting concentration

o High solubility to dissolve completely into solutions

o Large molar mass to minimize weighting/calculation errors

Primary standard: used directly for preparation of standard solutions

o Acidic primary standard: anhydrous sodium carbonate, 𝑁𝑎2𝐶𝑂3

NOTE: 𝑁𝑎2𝐶𝑂3 is for primary standard; 𝑁𝑎𝐻𝐶𝑂3 is for neutralisation

o Basic primary standard: hydrated oxalic acid, 𝐻2𝐶2𝑂4. 2𝐻2𝑂

Secondary standard: sometimes used as an intermediary standard solution

o Prepared by being standardised by the primary solution

o Usually is used since the preferred titrant is hygroscopic etc.

PREPARING THE SOLUTION

1. Weigh the exact amount of solid on watch glass on analytical

balance

2. Transfer to beaker dissolved in distilled water

3. Using a funnel, transfer to volumetric flask

4. Wash out beaker with water and transfer to volumetric flask

5. Make up volume using distilled water till calibration mark

6. Stopper the flask and invert to ensure thorough dissolving

EQUIPMENT

Volumetric flask: holds an accurate volume (250 mL) indicated by the calibration mark

o Used to prepare the standard solution

Pipette: used to deliver an accurate volume (25 mL) into the conical flask

o Do not shake out the last drop; pipette is calibrated to account for this

Burette: used to deliver accurate variable volumes of solution into the conical flask

o Reading is accurately estimated to ±0.05 mL

Pipette and burette should be rinsed with water and then rinsed with the solution to ensure the

calibrations droplets do not dilute the solution when titrating

Chemistry

Shaddy Hanna

40 of 79

DEFINITIONS

Indicator: substances which signals the end point of a titration by the change in colour

Equivalence point: point which reaction has completely occurred

o When the equal moles of H+ ions and OH- are present to form water and a salt

End Point: point when indicator changes colour

Titrant: the standard solution of known concentration and composition

Titre: The volume of the standard solution (delivered from burette)

Analyte: the substance which needs to be analysed

TITRATION PROCEDURE

1. Rinse burette with water and then with titrant solution

2. Set up burette with retort stand

3. Carefully pour titrant solution into the burette using funnel

4. Rinse pipette with water and then with analyte solution

5. Fill the 25 mL pipette with the analyte solution

o The solution should be poured from the volumetric flask into a clean beaker and then

drawn from the clean beaker so the whole analyte solution is not contaminated by material

in the pipette

6. Wash a conical flask with water

7. Empty the analyte solution from the pipette into the conical flash and add 3 drops of indicator

8. Position conical flask under burette

9. Using burette, slowly add titrant solution, whilst swirling flask until colour changes

10. Record amount of titrant solution used up in burette

11. Repeat previous steps 3 times for a total of 1 rough titration and 3 precise titration

NEUTRALISATION CURVES – CHOOSING APPROPRIATE INDICATOR

Bromothymol Blue

Methyl Orange Phenolphthalein

Chemistry

Shaddy Hanna

41 of 79

BUFFERS

A buffer is a solution that resist rapid change to pH when an acid or base is added

o Composed of roughly equal molar amounts of a weak acid and its conjugate base

o Often made by mixing a weak acid with its salt

THE CARBONIC ACID SYSTEM

𝐶𝑂2 (𝑔) + 𝐻2O (𝑙) ⇌ 𝐻2𝐶𝑂3 (𝑎𝑞)

𝐻2𝐶𝑂3 (𝑎𝑞) ⇌ 𝐻+(𝑎𝑞) + 𝐻𝐶𝑂3

−(𝑎𝑞)

The system occurs naturally in the human body to maintain the pH of blood for metabolic processes

o When an acid is added, [𝐻+] increases, shifting the equilibrium to the left to decrease [𝐻+]

o When a base is added, [𝑂𝐻−] reacts with [𝐻+] to form neutral water, decreasing [𝐻+] and

thus shifting the equilibrium to the right, producing more [𝐻+]

Chemistry

Shaddy Hanna

42 of 79

ESTERIFICATION

ALKANOLS & ALKANOIC ACIDS

ALKANOLS

Hydroxyl functional group

o Polar due functional group

o Thus, soluble in water

𝐶𝑛𝐻2𝑛+1𝑂𝐻

ALKANOIC ACIDS

Carboxyl functional group

o More polar than alkanols

o Thus; soluble in water

Acidic since Hydrogen can disassociate to form H+ ions in a solution

𝐶𝑛𝐻2𝑛+1𝐶𝑂𝑂𝐻 (𝑤ℎ𝑒𝑟𝑒 𝑛 = 𝑛 − 1)

DIFFERENCES IN MELTING/BOILING POINTS

Alkanes, alkenes, alkynes are not polar

o Only have weak dispersion forces

o Lower boiling points

Alkanols have 2 polar bonds (C-O and O-H)

o Form dipole and hydrogen forces

o Higher boiling points

Alkanoic acids have 3 polar bonds (C-O; O-H and C=O)

o Form dipole and hydrogen forces

o Even higher boiling points than alkanols

REACTION

Esterification involves the reaction of an acid with an alkanols

o When the acid is an alkanoic acid, the product is known as a carboxyl ester

o Condensation reaction (Endothermic )

Chemistry

Shaddy Hanna

43 of 79

NAMING - IUPAC NOMENCLATURE

𝑎𝑙𝑘𝑎𝑛𝑜𝑙 + 𝑎𝑙𝑘𝑎𝑛𝑜𝑖𝑐 𝑎𝑐𝑖𝑑 → 𝑎𝑙𝑘(𝒚𝒍) 𝑎𝑙𝑘𝑎𝑛𝑜(𝒂𝒕𝒆) + 𝑤𝑎𝑡𝑒𝑟

The alkanol loses its ending “-anol” and “yl” is added

The alkanoic acid loses its ending “-ic” and “ate” is added

CATALYST - 𝐶𝑜𝑛𝑐. 𝐻2𝑆𝑂4

Speeds up the rate of reaction

o Allows point of equilibrium to be reached faster

Increases the yield of the reaction since acts as a dehydrating agent

o Absorbs water encouraging the forward reaction

REFLUX

Esterification is an endothermic reaction

o Thus increase in temperature will push equilibrium to right

o Thus high temp = great yield of ester

Refluxing is the process of heating a reaction mixture in a vessel with a cooling condenser attached

in order to prevent any loss of any volatile reactants or products

o Prevents the volatile reactants from escaping before the system has reached equilibrium

o Prevents flammable, toxic reactants from escaping into the lab

o Performing the experiment in a closed system would lead to a dangerous build-up of gas

COMMON ESTERS

OCCURRENCE

Occur naturally in nature to form scents

o Can be found in flowers and fruits

o Often have pleasant smells

Orange flavour: Octyl Ethanoate

Banana flavour: Pentyl Ethanoate

PRODUCTION

Identify the chemical constituents of the naturally occurring flavour

Synthesise it with esters

Usually cheaper to produce than natural extracts – also don’t pose any known health risks

USE

Flavours in processed foods - Octyl Ethanoate - Orange flavour:

Perfumes in cosmetics - Ethyl Ethanoate - Nail polish remover

Industrial solvents - short esters - e.g. Ethyl Ethanoate

Plasticisers (to soften hard plastics) – larger esters (make them up, lol)

Chemistry

Shaddy Hanna

44 of 79

PRAC: PREPARATION OF AN ESTER (USING REFLUX)

AIM

To prepare an ester using reflux

METHOD

1. Place the following into a 50 mL conical flask:

o 10 mL of 1-pentanol

o 10 mL of glacial acetic acid

Anhydrous shifts the reaction to the

right

o 1 mL of concentrated sulfuric acid

o Few boiling chips (not marble chips)

2. Assemble reflux apparatus as shown in diagram

3. Heat water bath with Bunsen Burner for 30 minutes

4. Remove flask and pour contents into a separate flask.

5. Add 15 mL of 1M sodium carbonate solution.

6. Stopper the funnel and shake. Allow layers to separate and

discard of the lower aqueous layer

7. Carefully smell ester and describe the smell

RESULTS

A dark brown precipitate formed on the wall of the flask.

o Eventually the whole solution turned dark brown colour

𝐶5𝐻11𝑂𝐻(𝑙) + 𝐶𝐻3𝐶𝑂𝑂𝐻 (𝑙) ⇌ 𝐶𝐻3𝐶𝑂𝑂𝐶5𝐻11(𝑙) + 𝐻2𝑂(𝑙)

CONCLUSION

Ester produced was 1-pentyl ethanoate.

o Banana flavour

Chemistry

Shaddy Hanna

45 of 79

CHEMICAL MONITORING AND MANAGEMENT

CHEMIST MONITOR REACTIONS AND MANAGE CONDITIONS

WORKING AS A CHEMIST

VARIETY OF CHEMICAL OCCUPATIONS

Industrial chemists research into development of petrochemicals, detergents etc.

Environmental chemists monitoring water/air samples for pollutants

Polymer chemist produces synthetic fibres and manages polymerisation processes

NEED FOR COLLABORATION BETWEEN CHEMISTS

Different specialists chemists require collaboration between other chemists to solve problems

Compare analysis results from tests done by other chemists – confirming validity

Discussion of results/conclusions with other professionals

Sharing of the usage of equipment, scheduling of test to be completed etc.

Keeping up to date with new developments in the field

MONITORING CHEMICAL PROCESSES - COMBUSTION

In cars, chemical reactions such as combustion, form different products under different conditions

(levels of oxygen) and thus needs monitoring:

𝐶3𝐻8 (𝑔) + 𝟓𝑂2 (𝑔) → 𝟑𝐶𝑂2 (𝑔) + 𝟒𝐻2𝑂 (𝑔)

o Complete combustion occurs when sufficient oxygen is supplied to the reaction

As a result the products are carbon dioxide and water

𝐶3𝐻8 (𝑔) + 𝟕𝑂2 (𝑔) → 𝟔𝐶𝑂(𝑔) + 𝟖𝐻2𝑂 (𝑔)

o Incomplete combustion occurs when insufficient oxygen is supplied to the reaction

As a result the products are carbon monoxide and water

Less energy is released per unit of fuel used (compared to complete combustion)

Carbon monoxide is toxic

Build-up of soot can cause mechanical problems

o However, when excess oxygen is supplied, it is more likely to react with nitrogen present in

air to yield nitrogen oxides

𝑁2 (𝑔) + 𝑂2 (𝑔) → 𝟐 𝑁𝑂(𝑔)

𝑁2 (𝑔) + 𝟐 𝑂2 (𝑔) → 𝟐 𝑁𝑂2 (𝑔)

In the car, the mixture ratio of fuel and air is constantly monitored is vital to ensure maximum

energy yield, efficiency and safety.

Chemistry

Shaddy Hanna

46 of 79

INDUSTRIAL CHEMIST

Named industry: Plastics industry

Branch of chemistry: Industrial Chemistry

Role: designing chemical processes for the manufacture of a chemical product – to ensure efficiency

o Monitoring work practices to ensure safety and efficiency

CHEMICAL PRINCIPLE – ADSORBTION: GAS CHROMATOGRAPHY

A sample to be analysed is injected into a stream of inert carrier gas (e.g. helium)

As the mixture flows through the Chromatography Column, different molecules adsorb to the

coating according to polarity, size and shape.

Thus, each substance moves at different rates so each fraction emerges separately and is picked up

by a sensitive detector

Chemistry

Shaddy Hanna

47 of 79

CHEMICAL PROCESSES REQUIRE MONITORING

AMMONIA

INDUSTRIAL USES

Used to produce nitrates via the Ostwald Process

o Nitrates are used to produce fertilisers to grow crops and as explosives for war

SYNTHESISATION

𝑁2 (𝑔) + 3𝐻2 (𝑔) ⇌ 2𝑁𝐻3 (𝑔) ∆𝐻 = −92 𝑘𝐽𝑚𝑜𝑙−1

Reversible reaction

o Reaches equilibrium

o Exothermic

REACTANTS

Nitrogen: obtained by purifying air

Hydrogen: obtained by the electrolysis of salt water or extracted from natural gas

HABER PROCESS

Chemistry

Shaddy Hanna

48 of 79

BALANCING ACT

Many factors affect the yield and rate of the reaction

o Thus a balance of conditions must be used

TEMPERATURE

Rate of reaction

o Increased by higher temps – particle theory

As particles are moving faster they collide more frequently

Thus particles collide more often, forming more ammonia

Yield of product

o Lower temps will shift the equilibrium to the right (LCP)

Producing greater yield of ammonia

USE OF CATALYST – MAGNETITE (𝐹𝑒3𝑂4)

Lowers the activation energy

PRESSURE

Increased pressure will shift equilibrium to the right (LCP)

o Produce more ammonia

Puts more stress on the pipes

o Pipes will need to be thicker to withstand high pressure

o Constructing/maintaining the system becomes more expensive/hazardous

COMPROMISE CONDITIONS

Temperature: 400°C -500°C

Pressure: 200 atm

MONITORING NEEDED

Continuous monitoring of the reaction vessel is required for safety and optimal yield

o Maintaining temperature of 400°C -500°C

o Maintaining optimal pressure

o Mixing efficient ratio of reactant gases

o Levels of contaminating gases which could poison the catalyst – causing the iron to rust

HISTORICAL SIGNIFICANCE

In the early 1900s, there was great demand for nitrates due to:

o Increasing world population and the need for greater agricultural output

o Development of explosives during WWI

Thus, since guano (non-renewable) was the main source of nitrates then, the development of the

Haber Process could be used in conjunction with the Ostwald process to produce nitrates from a

much more cost-effective and renewable source

Chemistry

Shaddy Hanna

49 of 79

PRODUCTS ARE ANAYLSED TO DETERMINE THEIR CHEMICAL COMPOSITION

IONS

CATIONS

The cations in solution can be identified by testing the formation of precipitates and using flame

tests

ANIONS

The anions in solutions can be identified by testing the formation of precipitates

Cation Flame tests

Barium Green-Apple

Calcium Brick-Red

Copper Blue

Sodium Yellow

Cation Other tests

Iron II Decolourises KMnO4

Iron III Scarlet red solution with SCN-

Chemistry

Shaddy Hanna

50 of 79

NEED TO MONITOR THE LEVELS OF LEAD IN SOCIETY

Monitoring of lead is essential to protect people and the environment from harm of lead poisoning

since it can impact all organisms in the food chain by bioaccumulation

Lead is a neurotoxic (heavy metal) bioaccumulative

o Dangerous even in very low levels accumulates in the body until it reaches toxic levels

Can cause permanent brain damage in children

Leads to chronic neurological disease in adults

Sources:

o Old paints which contained a very high percentage of lead

o Leaking of lead-acid batteries

Chemistry

Shaddy Hanna

51 of 79

PRAC: MEASURE THE SULFATE CONTENT OF LAWN FERTILISER

Aim: To use gravimetric analysis to measure the sulphate content of a lawn fertiliser

METHOD

1. 1g of the lawn fertiliser was weighed out and transferred to a 250 mL beaker to dissolve the crystals

o HCl is added to react with PO4/CO3 to ensure they do not precipitate out with Ba

2. A hotplate was used to heat the mixture to near boiling, then BaCl2 was slowly added to the mixture

by a burette until no more BaSO4 precipitated out

3. A hotplate was used to re-heat the mixture again for 30 min, and then cool to room temperature

4. The solution was filtered through a weighted filter, washed with warm water, and then dried in oven

5. Filter paper was then weighed again to determine the mass of the precipitate

RESULTS

Item Weight (g)

Original fertiliser sample 0.76

Filter paper 2.54

Filter paper + precipitate 4.18

(𝑁𝐻4)2𝑆𝑂4 (𝑠) + 𝐵𝑎𝐶𝑙2 (𝑎𝑞) → 𝟐 𝑁𝐻4𝐶𝑙(𝑎𝑞) + 𝐵𝑎𝑆𝑂4 (𝑠)

𝑛(𝐵𝑎𝑆𝑂4) =𝑚(𝐵𝑎𝑆𝑂4)

𝑀(𝐵𝑎𝑆𝑂4)=

1.64

233.37= 0.00703 𝑚𝑜𝑙

𝐵𝑎𝑆𝑂4 (𝑠) ⇌ 𝐵𝑎(𝑎𝑞)2+ + 𝑆𝑂4 (𝑎𝑞)

2−

∴ 𝑛(𝑆𝑂4) = 𝑛(𝐵𝑎𝑆𝑂4) = 0.00703 𝑚𝑜𝑙 𝑚(𝑆𝑂4) = (0.00703)(96.07) = 0.675𝑔

∴ (𝑆𝑂4)% =𝑚(𝑆𝑂4)

𝑚(𝑓𝑒𝑟𝑡𝑖𝑙𝑖𝑠𝑒𝑟)=0.675

0.76= 88.8%

𝑆𝑂4 (𝑎𝑞)2− ⇌ 𝑆(𝑎𝑞)

8+ + 𝟒 𝑂(𝑎𝑞)2−

∴ 𝑛(𝑆) = 𝑛(𝑆𝑂4) = 0.00703 𝑚𝑜𝑙 𝑚(𝑆) = (0.00703)(32.07) = 0.225𝑔

∴ (𝑆)% =𝑚(𝑆)

𝑚(𝑓𝑒𝑟𝑡𝑖𝑙𝑖𝑠𝑒𝑟)=0.225

0.76= 29.6%

RISK ASSESSMENT

BaCl2is toxic and HCl is corrosive

o Avoid contact with skin and eyes wear safety glasses and lab coat

Have NaHCO3 available in case of spills for neutralisation

Be wary of the naked flames

DISCUSSION: SOLUTIONS TO THE PROBLEMS ENCOUNTERED DUE TO RELIABILITY

Since the sample size was so small, it is not a very reliable representation of the entire mixture

o Larger samples could be used (however would require more Barium Chloride – safety issue

The experiment was only performed once (no repetition)

o Could be performed multiple times

The BaSO4 precipitate is very fine and easily passes through school-grade filter papers

o A finer-grade filter paper could be used – may much longer

Chemistry

Shaddy Hanna

52 of 79

ATOMIC ABSORPTION SPECTROSCOPY – AAS

Extremely sensitive instrument to measure metals

o Measures concentrations of metal ions in solution at ppm or even ppb levels

HOW IT WORKS

Cathode lamp: emits a wavelength of light (specific to the material being measured)

Nebulizer: Vaporises the substance to a thin, aerated mist (allowing light to pass through)

Flame: provides the heat required to vaporize the sample

In the flame, ions present absorb the EMR so that an absorbance measurement is detected at the

detector. When calibrated correctly, this is then accurately reflected as a measure of concentration.

USE

AAS is used to regularly measure catchment water for the presence of lead (Pb) ions.

AAS is also used to checking for metals in engine oil. The concentrations of metals will determine

the amount of wear in an engine.

IMPACT ON SCIENTIFIC UNDERSTANDING OF THE EFFECTS OF TRACE ELEMENTS

Has allowed for essential trace elements to be detected that would otherwise go undetected

o E.g. Lead, a bioaccumulative neurotoxic heavy metal – detrimental to brain health.

Scientists have also become aware that minute quantities of certain elements may have significant

effects within biological systems

EVALUATE: ITS EFFECTIVENESS IN POLLUTION CONTROL

As such, this has heavily increased the sensitivity of pollution monitoring since AAS can measure

even minimal amounts of pollutant materials in a solution effectively, as well as the trace elements

which may have not been considered.

Chemistry

Shaddy Hanna

53 of 79

THE ATMOSPHERE MUST BE MONITORED

COMPOSITION/STRUCTURE OF THE ATMOSPHERE

Composition:

o 80% nitrogen

o 20% Oxygen

o 1% Argon

o 0.03% Carbon Dioxide

o Other gases + pollutants

Structure:

o Troposphere: 0-15km above sea level

Tropopause: slow rate of gas transfer

o Stratosphere: 15-50km above sea level

Warm due to the absorption of UVR

o Mesosphere: 50-80km above sea level

o Thermosphere: 80-400km above sea level

Very hot due to the absorption of high freq radiation

MAIN POLLUTANTS IN LOWER ATMOSPHERE

Pollutant Source

Nitrogen oxides Formed in internal combustion engines

Hydrocarbons and Volatile organic compounds (VOC)

Incomplete combustion

Solvents and paints

Sulfur dioxide Burning fossil fuels

Lead Old paints

Particulates Incomplete combustion

Dust storms

Carbon monoxide Incomplete combustion

Ozone Combination of oxygen molecules and free radicals

Chemistry

Shaddy Hanna

54 of 79

OZONE IN THE ATMOSPHERE

LOWER ATMOSPHERE – POLLUTANT

In the lower troposphere, ozone can cause respiratory distress in human.

o Further, it can increase the severity of asthma and induce fatigue and the onset of

headaches

o Photochemical smog: when UV reacts with motor car exhaust gases

UPPER ATMOSPHERE – UV RADIATION SHIELD

When in the stratosphere, ozone works to absorb UV radiation, using its energy to decompose

𝑂3 (𝑔)𝑈𝑉 𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛→ 𝑂2 (𝑔) + 𝑂 ∙ (𝑔)

Oxygen free radicals combine to form oxygen gas which in turns absorbs UV radiation to decompose

𝑂 ∙ (𝑔) + 𝑂 ∙ (𝑔) → 𝑂2 (𝑔)

𝑂2 (𝑔)𝑈𝑉 𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛→ 2 𝑂 ∙ (𝑔)

Oxygen free radicals also combine with oxygen gas to reform ozone, completing the cycle

𝑂2 (𝑔) + 𝑂 ∙ (𝑔) → 𝑂3 (𝑔)

Consequently, this cycle continues, absorbing UV radiation from the sun

Chemistry

Shaddy Hanna

55 of 79

ALLOTROPES OF OXYGEN

COORDINATE COVALENT BOND

A coordinate covalent bond is a covalent bond in which one atom provides both the shared electrons

o Consequently, the species with a full valence shell can still covalently bond with another

species to fill that one’s outer shell of electrons

OXYGEN VS OZONE

Property 𝑶𝟐 𝑶𝟑 Explanation

Melting point ( °𝑪) -220 -200 Ozone has greater dispersion forces between molecules, thus resulting in higher melting and boiling pts. Boiling point ( °𝑪) -180 -100

Density Less dense than

air More dense than

air

Ozone has a larger molecular mass, and hence greater dispersion forces. Thus, molecules pack much closer together than 𝑂2

Solubility in water Sparingly soluble Relatively soluble

Oxygen is non-polar. Ozone is a polar molecule and thus forms dipole-dipole forces with water, increasing solubility.

Stability Very stable Very instable Due to the coordinate covalent bond, ozone is extremely reactive and easily decomposes

Chemical reactivity (oxidising strength)

Reactive Very reactive

OXYGEN/OZONE VS OXYGEN FREE RADICAL

The oxygen free radical is much more reactive than 𝑂2/𝑂3 due the desire to fill its outer shell

The oxygen free radical conducts in aqueous form, contrasting to 𝑂2/𝑂3

Chemistry

Shaddy Hanna

56 of 79

CFCS (CHLOROFLUOROCARBON)

NAMING CFCS

Isomers: different structural forms of the same molecular formula

o Allotropes: different molecular formulas of the same compound/element

o Isotopes: different forms of the same element – same atomic number, different mass

Chlorofluorocarbon (CFCs): haloalkanes where all H atoms have been replaced with Cl and Fl

o Haloalkanes: alkanes with at least one halogen (group 7) atom - HFCs/HCFCs

o Halons: haloalkanes where all H atoms have been replaced with Cl, Fl and Br. – CFCs

o Numbering:

First digit is the number of carbon atoms minus 1

Second digit is number of hydrogen atoms plus 1

Third digit is number of fluorine

Remaining atoms are chlorine

TIP: add 90 to the number given, and you can just remember C H F

o IUPAC naming:

Halogens prefixes are positioned in alphabetical order

The numbering of halogens follows to give the lowest possible summation

For official IUPAC Nomenclature refer to the following document:

http://www.raci.org.au/document/item/1012

ORIGINS OF CFCS AND HALONS IN THE ATMOSPHERE

CFCs were initially used in refrigerants and propellants

Halons were initially used in fire extinguishers

PROBLEMS WITH THE USE OF CFCS - REMOVAL OF THE OZONE

Removal of the ozone:

o CFCs in the upper atmosphere are decomposed by UV radiation, creating a 𝐶𝑙 ∙ which reacts

with ozone and oxygen radicals to decompose ozone into oxygen

𝐶𝐶𝑙2𝐹2𝑈𝑉 𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛→ 𝐶𝐶𝑙𝐹2 ∙ + 𝐶𝑙 ∙

𝐶𝑙 ∙ + 𝑂3 → 𝐶𝑙𝑂 ∙ + 𝑂2

𝐶𝑙𝑂 ∙ + 𝑂 ∙ → 𝐶𝑙 ∙ + 𝑂2

As such, the presence of CFCs decompose the ozone, creating “holes” in the ozone layer :

𝑂 ∙ + 𝑂3𝐶𝐹𝐶𝑠→ 𝟐 𝑂2

The decreased concentration of ozone in the upper atmosphere thus allows increasing UV radiation

to penetrate the atmosphere, with severe consequences:

o Danger of global warming as temp. increases slightly

o Increased risk of skin cancer and eye cataracts due to UV radiation

o Crop damage due to skin cancer

Chemistry

Shaddy Hanna

57 of 79

EFFECTIVENESS OF STEPS TAKEN TO ALLEVIATE PROBLEMS

Montreal Protocol (1987): drafted to restrict the production and use of various haloalkanes in

purpose of preserving the ozone layer.

o This has proven effective since the ozone hole has decreased slightly since

Further, some nations have created trade agreements for the purpose of restricting trade of

substances dangerous to the ozone layer

EFFECTIVENESS OF ALTERNATIVE CHEMICALS USED TO REPLACE CFCS

Hydrochlorofluorocarbons (HCFCs) – similar to CFCs, yet containing hydrogen

o Still pose a threat to the ozone layer, and have thus been phased out

Hydrofluorocarbons (HCFs) – compounds containing carbon, hydrogen and fluorine

o Contain no chlorine or bromine, thus do not destruct ozone

o Used widely as a replacement for CFCs

o More costly however, and less efficient

Overall, the replacement of CFCs with HCFs has been a reasonably valid and effective strategy

INFORMATION INDICATING CHANGES IN ATMOSPHERIC OZONE CONCENTRATIONS

Information about the thickness of the ozone is obtained from ground-based instruments which

function by measuring the intensity of light received from the sun at the wavelength usually

absorbed by ozone and then at other wavelengths the ozone does not absorb.

o Thus, by comparison of the intensity of differing wavelengths (which should be equal) the

total column ozone (total ozone per unit area measured in Dobson Units, DU) can be

calculated and compared to other locations.

o Further, Total ozone mapping spectrophotometers (TOMS) is another method of measuring

ozone levels by satellites above the Earth

Information collected by these devices have illustrated that the concentration of ozone has been

decreasing since industrial revolution. However, since the introduction of the Montreal Protocol, the

concentration of ozone has slightly increased.

It is important to note though, that the lifetime of CFCs are very long in the atmosphere since they

are repeatedly recycled. Thus, scientists predict it will be a while until the ozone is completely

replenished, however it should happen gradually over time

Chemistry

Shaddy Hanna

58 of 79

WATER IS CHEMICALLY MONITORED AND MANAGED

DETERMINING/COMPARING WATER QUALITY

Qualitative analysis: determining which ions are present in the water sample

Quantitative analysis: determining the amount of ions present in the water sample

Consideration Importance Testing procedures

Qualitative Quantitative

Concentrations of common

ions

High concentrations of common ions decrease the quality of the water

May be toxic

Flame test

Precipitation test

Atomic Absorption Spectrometry (AAS)

Total dissolved solids (TDS)

Mass of solids dissolved in a unit volume of water

High amount of TDS may be harmful to drink

Gravimetric analysis

o Filtering then evaporating

Hardness

Hardness is due to calcium or magnesium ions forming an insoluble scum o Reduces the ability of

soap to lather

Add water: o Hard water turns milky o Soft water bubbles

Precipitation test

Flame Test

Volumetric analysis o EDTA titration

Gravimetric analysis o Precipitating ions

out and filtering o Add the molarity

of Mg and Ca o Multiply by molar

mass of 𝐶𝑎𝐶𝑂3 (100.1)

Turbidity

Turbidity is the measure of suspended solids in the water o High turbidity

“milky” water o Low turbidity

Clear water

Secchi disk o The length of the string

when a quadrant is visible gives a relative measure of the turbidity of the water.

Gravimetric analysis o Filtering then

evaporating

Acidity Affects the ability of water

to support life and be drunk Litmus indicator pH meter

Dissolved oxygen (DO)

A measure of the concentration of oxygen dissolved in 1 litre of water

Visual inspection of the water quality

Oxygen sensor probe

Volumetric Analysis o The Winkler

Titration Biochemical

oxygen demand (BOD)

A measure of the concentration of DO consumed by the decay of organic matter

Measured by the change in DO over 5-day period

Measuring the amount of organic matter in the water

Chemistry

Shaddy Hanna

59 of 79

FACTORS AFFECTING [IONS] IN SOLUTION IN NATURAL BODIES OF WATER

Soil type

o Greater prevalence of ions in the earth’s crust greater concentration of ions

o Water that flows through a limestone area will pick up dissolved salts

Proximity to farms

o Fertiliser can seep into the soil and leak into the water bodies (more phosphates/nitrates)

Water Temperature

o Increased temperature generally increases the solubility of solids

Rate of evaporation

o In extended period of sunlight, rate of evaporation can be very high

Thus the concentrations of ions in solution increase, as water volume decreases

Frequency of rainfall (floods/droughts)

o Excessive rain can dilute water reducing the concentration of ions

o Absence of rain build of the concentration of ions

HEAVY METAL POLLUTION

Caused by the presence of high levels of heavy metals in water bodies:

o Lead is a bioaccumulative neurotoxin which leads to nerve, brain and kidney damage

Bioaccumulation: when metals accumulate in organisms and flow up the food

chain

o It may end up in water bodies as a result of run-offs from industrial wastes and agriculture

MONITORING HEAVY METAL POLLUTION

Atomic Absorption Spectrometry (AAS)

Mass spectrometry

Flame test and precipitation test

EUTROPHICATION

Eutrophication is when the presence of nutrients enriches waterways.

o These typically promote excessive growth of algae.

o As the algae die and decompose, high levels of organic matter and the decomposing

organisms deplete the water of available oxygen, causing the death of other organisms

o Due to increased fertilizers and detergents in the water bodies, eutrophication has sped up.

MONITORING EUTROPHICATION

Eutrophication is monitored by measuring Biological Oxygen Demand.

o BOD is measured by the change in dissolved oxygen over 5 days

o Greater BOD corresponds to more microorganisms in the water which have grown (most

likely) due to excess phosphates and nitrates feeding them.

Chemistry

Shaddy Hanna

60 of 79

MASS WATER SUPPLIES

METHODS TO PURIFY AND SANITISE WATER

The purpose of water treatment is to remove colour, odour, suspended solids and pathogens from

water

1. Screening – The removal of large debris

2. Aeration – Water is sprayed into the air

o Increases dissolved oxygen conc., since oxygenated water tastes better

3. Flocculation – The coagulation of colloidal and particulate matter to form flocs

o Coagulants such as 𝐹𝑒𝐶𝑙3 are added to the water where flocs form and settle to

the bottom as colloids clump together.

4. Sedimentation – Water is left to stand allowing flocs to settle and form a sludge

5. Filtration – The removal of substances causing turbidity and colouration

o Water is filtered through granulated filters: beds of charcoal, sand and gravel

o Membrane filters may be used Effective (due to pore size), yet more expensive

6. Chlorination – The disinfecting of water using chlorine to kill microorganisms

o Can bleach coloured compounds in water

o Removes tastes and odours produced by some algae

o Hypochlorous acid (𝐻𝑂𝐶𝑙) produced kills bacteria and microorganisms

𝐶𝑙2 (𝑔) + 𝐻2𝑂(𝑔) → 𝐻𝑂𝐶𝑙(𝑎𝑞) + 𝐻𝐶𝑙(𝑎𝑞)

7. pH adjustment – acid or base neutralising agents are added to raise/lower the water pH

8. Fluoridation – adding of fluoride for dental health reasons

Although the introduction of technology such as membrane filters would provide even higher quality

water the high costs cannot be justified with the currently sufficient methods used to purify and

sanitise mass water supplies.

Chemistry

Shaddy Hanna

61 of 79

MICROSCOPIC MEMBRANE FILTERS

Allows for the removal of particles of subcellular size and molecules of relatively small size

DESIGN AND COMPOSITION

A membrane filter is a thin film of a synthetic polymer with pores of fairly uniform size (0.5 𝜇m

depth)

The microscopic size of the polymers act as

microscopic pores

o However, they can be easily clogged by

particles blocking pores reducing flow

o This is prevented by the use of course filters

prior to filtration

PURIFICATION TECHNICQUE

Pressure (developed by a vacuum, gravity or pump) is used to force the water through the filter

In doing so, all particles, bacteria and even viruses that are greater than the size of the pores are

trapped outside the filter.

LOCAL TOWN WATER SUPPLY – WARRAGAMBA DAM

Warragamba dam is Sydney’s main storage dam with a catchment of area of approx. 9000km2

Possible sources of contamination:

o Fertiliser run-offs from nearby agricultural zones

o Chemical run-offs from nearby residential zones (leakage of sewerage and rubbish)

Chemical tests available to measure levels and types of contaminants:

o AAS

o Precipitation tests

o pH tests

o Filtration and gravimetric analysis

Processes used to purify water:

o Physical: screening, filtration and sedimentation

o Chemical: flocculation, pH adjustment

Chemical additives in the water – reasons for their presence

o Chlorine: kills bacteria and viruses to sanitise water

o Fluoride: added to water for dental health reasons

Chemistry

Shaddy Hanna

62 of 79

INDUSTRIAL CHEMISTRY

REPLACEMENTS FOR NATURAL RESOURCES

A natural product is that is used with little modification

DISCUSS: ISSUES ASSOCIATED WITH SHRINKING WORLD RESOURCES – GUANO

Guano is bat and bird droppings which were once used for the production of nitrates

o Guano is a non-renewable resource

o Was only produced in Chile, and thus other countries had to have it shipped for use

Due to increasing population in the early 1900s, there was greater demand for nitrates for use in

fertiliser to boost agriculture.

Also, corresponding with WWI, there was greater need for nitrates in the production of explosives.

IDENTIFY: REPLACEMENT MATERIALS USED

Consequently, the Haber process was developed to produce ammonia from nitrogen and hydrogen

which can then be used in the Ostwald Process to develop nitrates.

o This eliminate the need to use guano as fertiliser and explosives.

o The process involves reacting nitrogen gas with hydrogen gas under compromise conditions

to efficiently produce a maximum yield of ammonia.

EVALUATE: PROGRESS MADE TO SOLVE THE ISSUES

With the efficient and inexpensive creation of ammonia by the Haber process, the need for Guano, a

shrinking world resource, became redundant.

Chemistry

Shaddy Hanna

63 of 79

EQUILIBRIUM REACTIONS

PRAC: MODEL AN EQUILIBRIUM REACTION

Setup:

o Two buckets used as the reaction vessel

One holds the reactions

One holds the products

o The rates of chemical reactions are represented by the size of two other beakers which

transfer the reactants and products between buckets

Initially:

o 1L of water in reactant bucket

Beaker used to represent forward reaction rate is larger

o 0L of water in product bucket

Beaker used to represent reverse reaction rate is smaller

During:

o As the system reacts, the forward reaction beaker will draw lots of water (higher rate) then

the reverse reaction (slower rate) which has no water to draw from its vessel of products

o As the conc. in the product bucket increases, the reverse reaction rate will also increase.

Similarly, as the conc. in the reactant bucket decreases, the forward reaction rate will also

decrease.

Equilibrium:

o However, at one point when the rate of the reverse reaction is finally equal to the rate of

the forward reaction, the system will be at equilibrium. Here, both reactions will continue

whilst keeping the concentration of the buckets the same

Factors:

o An increase in temperature for an exothermic reaction will result in an increase in the

reverse reaction rate. Thus, a greater beaker is used to present this rate, affecting the

equilibrium constant (K).

o If the pressure is changed (or volume), the concentration of both systems decrease, and

thus the reaction rates remain the same

o The use of a catalyst will increase the reaction rate of both the forward and reverse rates at

the same time.

PRAC: ANALYSE AN EQUILIBRIUM REACTION

Method: A nitrogen dioxide sample was prepared and placed in a sealed glass tube.

Results: Nitrogen dioxide readily reacts to form di-nitrogen tetroxide at room temperature

𝟐 𝑁𝑂2 (𝑔) ⇌ 𝑁2𝑂4 (𝑔) ∆𝐻 = (−𝑣𝑒)

[𝑑𝑎𝑟𝑘 𝑏𝑟𝑜𝑤𝑛] [𝑐𝑜𝑙𝑜𝑢𝑟𝑙𝑒𝑠𝑠]

o When heated, the solution goes brown (shifting to the left)

o When cooled the solution turns colourless (shifting to the right).

Safety assessment: both gases are toxic experiment should be reacted in a fume cupboard

Chemistry

Shaddy Hanna

64 of 79

EXPLAIN: FACTORS WHICH EFFECT EQUILIBRIUM (LE CHATLIER’S PRINC IPLE)

If a chemical system at equilibrium is subjected to change in conditions, the system will readjust

itself to minimise the disturbance

2𝐴(𝑔) + 𝐵(𝑔) ⇌ 𝐶(𝑔) + 𝐷(𝑔) ∆𝐻 = (−𝑣𝑒)

PRESSURE (CHANGE IN VOLUME)

If the pressure of a system is increased, the system will react in such a way to minimise disturbance

and decrease pressure by shifting to the side with the least gas molecules

o Thus, shifting the equilibrium to favour the forward reaction

CONCENTRATION

If the concentration of one species in a system is increased, the system will react in such a way to

minimise disturbance and decreasing the concentration of that species by reacting it.

o Thus, if [A] in the above equation increased, the system would shift to decrease [A], shifting

the equilibrium to favour the forward reaction

TEMPERATURE

If the temperature of a system increased, the system will react in such a way to minimise

disturbance and decrease temperature by shifting the equilibrium towards the side which reduces

heat in the system

o Thus, in the above exothermic reaction (where heat is a product), if temp was increased,

the equilibrium would shift to favour the reverse reaction

Chemistry

Shaddy Hanna

65 of 79

INTERPRET: THE EQUILBRIUM CONSTANT

𝑎𝐴 + 𝑏𝐵 ⇌ 𝑐𝐶 + 𝑑𝐷

Assuming the above equation (where a, b, c, d are the respective molar ratios of A, B, C, D); a relative

value for the equilibrium can be assumed using the following expression:

𝐾 =[𝐶]𝑐 × [𝐷]𝑑

[𝐴]𝑎 × [𝐵]𝑏

NOTE: P.O.R.K Products over Reactants = K

The constant, K, can reveal how far towards equilibrium a react is at.

o Smaller values of K; i.e (𝐾 < 10−4) – more reactants and less products

o Large values of K; i.e (𝐾 > 104) – less reactants and more products

When the reaction is not at equilibrium, Q replaces K in the expression.

o If 𝑄 < 𝐾; [A] and [B] are too high and thus [C] and [D] must increase to reach equilibrium

o If 𝑄 > 𝐾; [C] and [D] are too high and thus [A] and [B] must increase to reach equilibrium

o If 𝑄 = 𝐾; the system is at the point of equilibrium

a : b : c : d

[A] [B] [C] [D]

I (initial) ia ib 0 0

C (consumed) a B c d

E (equilibrium) ia + a ib + b c d

Using the ICE table:

o The C (consumed) will always react in the mole proportions

o Contrastingly, I (initial) and E (equilibrium) are given and found using:

𝐼 + 𝐶 = 𝐸

∴ 𝐼 = 𝐸 − 𝐶

IDENTIFY: TEMPERATURE CAN CHANGE THE VALUE K

In an exothermic reaction; heat is product

As temp increases, the forward reaction rate is slowed and the reverse reaction rate sped up.

o Thus, when the system finally does re-achieve equilibrium, it is at a new position and

explains the

Chemistry

Shaddy Hanna

66 of 79

SULFURIC ACID

IDENTIFY AND DESCRIBE: SAFETY PRECAUTIONS WHEN USING CONC. 𝐻2𝑆𝑂4

Personal protection equipment (PPE):

o Wear safety goggles: contact with eyes can cause permanent damage

o Wear protective gloves and a lab coat: sulfuric acid is extremely corrosive to skin

Work near a supply of running water to wash off or dilute splashes

Have a supply of sodium hydrogen carbonate to neutralise any spills (since its amphiprotic)

When diluting conc. sulfuric acid; slowly add the acid to the water (A W)

o Since the dilution reaction is exothermic, heat will dissipate better over water

RELATE: SAFETY PRECAUTIONS FOR 𝐻2𝑆𝑂4 TRANSPORT AND STORAGE TO

PROPERTIES

Transportation of concentrated sulfuric acid:

o Since conc. sulfuric acid is virtually all molecular; it does not react with metals

o Therefore, it can be safely transported in steel containers

Transportation of dilute sulfuric acid:

o Since dilute sulfuric acid contains ions; it will vigorously react with metals to produce a salt

and explosive hydrogen gas

o Therefore, it is safely transported by glass or plastic containers

OUTLINE: USES OF 𝐻2𝑆𝑂4

Dehydrating agent

o Conc. sulfuric acid is hydrous (has a very strong affinity for water – absorbing water from

mixtures such as moist air)

o In addition conc. sulfuric acid can remove hydrogen and oxygen from compounds such as

water (e.g. dehydration)

Fertiliser production - Superphosphates o Sulfuric acid removes converts insoluble rock phosphate into mixtures that are soluble in

water and thus can be used as fertiliser for plants

Catalyst for many reactions due to its large surface area

Used in lead-acid car batteries

Chemistry

Shaddy Hanna

67 of 79

DESCRIBE: THE FRASCH PROCESS

The Frasch Process: is the processes used to extract sulfur from mineral deposits

A. Superheated water is pumped down the outer pipe into the sulfur deposit

Sulfur turns into its molten state since it has a low melting point

B. Compressed air is pumped down the inner tube into the sulfur deposit

Sulfur is easily forced upwards through the middle tube since it has a low density

C. Molten sulfur flowing up the middle tube is easily separated from water since it is insoluble

Potential environmental issues:

o Thermal pollution: superheated output water (from molten sulfur mixture) must be

disposed of into the ocean. This can damage aquatic environments increase the solubility

of carbon dioxide increases pH

o Earth subsidence: extracting of sulfur deposits results in holes which must be back-filled

o Oxidation of Sulfur to S02 in high temperatures: This gas then forms acid rain, etc etc.

o Impurities in output water: the superheated water may dissolve other unwanted impurities

(and heavy metals) into the water before discharged into natural waterways

DESCRIBE: THE CONTACT PROCESS

OUTLINE: STEPS AND CONDITIONS NECESSARY FOR THE CONTACT PROCESS

The contact process is used to manufacture of sulphuric acid from elemental sulfur

1. Production of 𝑆𝑂2

o Liquid sulfur produced by the Frasch process is burned in 𝑂2 to produce 𝑆𝑂2

𝑆(𝑠) + 𝑂2 (𝑔) → 𝑆𝑂2 (𝑔) ∆𝐻 = (−𝑣𝑒)

2. Production of 𝑆𝑂3

o 𝑆𝑂2 is burned in 𝑂2 to produce 𝑆𝑂3 (𝑔)

𝟐 𝑆𝑂2 (𝑔) + 𝑂2 (𝑔) ⇌ 𝟐 𝑆𝑂3 (𝑔) ∆𝐻 = (−𝑣𝑒)

3. Production of 𝐻2𝑆𝑂4

o 𝑆𝑂3 reacts with 𝐻2𝑆𝑂4 to produce 𝐻2𝑆2𝑂7 (oleum)

𝑆𝑂3 (𝑔) + 𝐻2𝑆𝑂4(𝑙) → 𝐻2𝑆2𝑂7(𝑙)

o 𝐻2𝑆2𝑂7 (oleum) then reacts with 𝐻2𝑂 to produce 𝐻2𝑆𝑂4

A

B

C

Chemistry

Shaddy Hanna

68 of 79

𝐻2𝑆2𝑂7(𝑙) + 𝐻2𝑂(𝑙) → 𝟐 𝐻2𝑆𝑂4(𝑙)

DESCRIBE: REACTION CONDITIONS NECESSARY

Step 1. The reaction occurs in a furnace, at higher temperatures to increase the reaction rate

Step 2. Since the reaction is an equilibrium; there are many considerations:

o Catalyst: 3 beds of 𝑉2𝑂5 (Vanadium Oxide) increases reaction rate due to large SA

Temperature varies from 550 400 400 to increase yield.

Yield increases from 70% 97% 99%

o Temperature: A compromise temperature of 450°𝐶 − 600 °𝐶 is used

Higher temperatures increases reaction rate yet decrease the yield (LCP)

Lower temperatures decrease the rate of reaction yet increase the yield (LCP)

o Pressure: although high pressures increases the yield, the above conditions are sufficient

enough to allow the process to operate at normal atmospheric pressure reducing cost

o Excess oxygen: is used to shift the equilibrium to yield more products

Step 3. The production of 𝐻2𝑆𝑂4 involves producing oleum as an intermediary product

o This occurs since the reaction of 𝑆𝑂3 gas with water forms a fog of 𝐻2𝑆𝑂4 droplets which

is too difficult to work with.

DESCRIBE AND EXPLAIN: THE EXOTHERMIC NATURE OF 𝐻2𝑆𝑂4 IONISATION

𝐻2𝑆𝑂4 (𝑎𝑞) → 𝐻3𝑂(𝑎𝑞) + + 𝐻𝑆𝑂4 (𝑎𝑞)

−

𝐻𝑆𝑂4 (𝑎𝑞) − ⇌ 𝐻3𝑂(𝑎𝑞)

+ + 𝑆𝑂4 (𝑎𝑞) 2−

The ionisation of sulfuric acid is exothermic, releasing a lot of heat

o This occurs since conc. sulfuric acid is almost 100% molecular

o Although, the ionization of sulfuric acid is endothermic, the coordinate covalent bonds

water creates with the ionized hydrogen ions are greatly exothermic.

o Thus, the net enthalpy change is greatly exothermic

𝐻2𝑆𝑂4 (𝑎𝑞) ⇌ 𝟐 𝐻3𝑂(𝑎𝑞) + + 𝑆𝑂4 (𝑎𝑞)

2− ∆𝐻 = −(𝑣𝑒)

PRAC: REACTIONS OF 𝐻2𝑆𝑂4 AS AN OXIDISING AGENT AND DEHYDRATING AGENT

Method:

o Pour 60mL of sucrose into a 250mL beaker

o Place the beaker in a fume cupboard

o Pour 25mL of conc. sulfuric acid into the beaker and move 1m away

Results:

o The sucrose is replaced by a much larger carbon structure, as sulfuric acid is dehydrated.

𝐶12𝐻22𝑂11 (𝑠) → 𝟏𝟐 𝐶(𝑠) + 𝟏𝟏 𝐻2𝑂(𝑙)

o Next, the carbon is oxidised to form carbon dioxide, sulfur dioxide and water demonstrating

sulfuric acid as an oxidising agent

𝐶(𝑠) + 𝟐 𝐻2𝑆𝑂4 (𝑙) → 𝐶𝑂2 (𝑔) + 𝟐 𝑆𝑂2 (𝑔) + 𝟐 𝐻2𝑂(𝑙)

Chemistry

Shaddy Hanna

69 of 79

SODIUM HYDROXIDE (𝑵𝒂𝑶𝑯)

EXPLAIN: THE DIFFERENCE BETWEEN GALVANIC CELLS AND ELECTROLYTIC CELLS

IN TERMS OF ENERGY REQUIREMENTS

Galvanic cells convert chemical energy into electrical energy

o The anode (where oxidation occurs) is negative

o The cathode (where reduction occurs) is positive

o The reaction is spontaneous, producing energy

o Sum of the Standard Half Cell Potential (𝐸0) is negative

Electrolytic cells convert electrical energy into chemical energy

o The anode (where oxidation occurs) is positive

o The cathode (where reduction occurs) is negative

This is explained since electrons are pushed by the external circuit on the cathode

so that the solution in this area is reduced and oxidations occurs at the anode

o Energy is provided to the cell to produce a reaction

o Sum of the Standard Half Cell Potential (𝐸0) is positive

EXPLAIN: THE PRODUCTS FROM ELECTROLYSIS OF AQUEOUS AND MOLTEN 𝑁𝑎𝐶𝑙

In an aqueous sodium chloride solution:

o The sodium ion is more stable than water, and as such, water is reduced instead

o At the anode, since chloride and water have comparable ease of oxidation, the one with

greater concentration is oxidised. Thus, in a :

Concentrated solution;

Anode: 𝟐 𝐶𝑙− → 𝐶𝑙2 + 𝟐 𝑒−

Cathode: 𝟐 𝐻2𝑂 + 𝟐 𝑒− → 𝐻2 + 𝟐 𝑂𝐻

−

Full equation: 𝟐 𝑁𝑎𝐶𝑙(𝑎𝑞) + 𝟐 𝐻2𝑂(𝑙) → 𝟐 𝑁𝑎𝑂𝐻(𝑎𝑞) + 𝐻2 (𝑔) + 𝐶𝑙2 (𝑔)

Aqueous solution

Anode: 𝟐 𝐻2𝑂 → 𝑂2 + 𝟒 𝐻+ + 𝟒 𝑒−

Cathode: 𝟐 𝐻2𝑂 + 𝟐 𝑒− → 𝐻2 + 𝟐 𝑂𝐻

− (𝟒 𝐻2𝑂 + 𝟒 𝑒

− → 𝟐 𝐻2 + 𝟒 𝑂𝐻−)

Full equation: 𝟔 𝐻2𝑂(𝑙) → 𝑂2 (𝑔) + 𝟐 𝐻2 (𝑔) + 𝟒 𝑂𝐻(𝑎𝑞)− + 𝟒 𝐻(𝑎𝑞)

+

In a molten sodium chloride solution:

o Water is not available, only the sodium ion, which is thus reduced:

Anode: 𝟐 𝐶𝑙− → 𝐶𝑙2 + 𝟐 𝑒−

Cathode: 𝑁𝑎+ + 𝑒− → 𝑁𝑎

Full equation: 𝟐 𝑁𝑎(𝑙)+ + 𝟐 𝐶𝑙(𝑙)

− → 𝟐 𝑁𝑎(𝑙) + 𝐶𝑙2 (𝑔)

Electrolytic cell

Galvanic cell

Chemistry

Shaddy Hanna

70 of 79

OUTLINE: THE PRODUCTS FROM ELECTROLYSIS (SIMPLE)

PRAC: IDENTIFY THE PRODUCTS OF THE ELECTROLYSIS OF 𝑁𝑎𝐶𝑙

Aim: To identify the products of the electrolysis of sodium chloride

Method:

1. A U-tube was set up (as in diagram).

2. 100mL of sodium chloride solution (with universal indicator) was then poured into the tube.

3. 2 graphite compounds (connected to a power pack of 6v) were placed in the solution.

4. All colour changes and observations were recorded

Results:

Observations pH Colour

Anode Gas produced which smelled like bleach Red

Cathode Gas bubbles emerged Violet

o As such, it was obvious hydrogen gas formed at the cathode and chlorine gas at the anode

OUTLINE: STEPS IN THE INDUSTRIAL PRODUCTION OF 𝑁𝑎𝑂𝐻 FROM 𝑁𝑎𝐶𝑙 SOLUTION

A solution known as brine (concentrated NaCl solution) is electrolysed.

o The brine solution is obtained from sea water

The first part of the process involves removing impurities.

The second part of the process is the electrolysis of NaCl to produce NaOH

o Anode: chlorine ions are oxidised to form chlorine gas since it has the highest ease of

oxidation (other than water which is being reduced)

𝟐 𝐶𝑙− → 𝐶𝑙2 + 𝟐 𝑒−

o Cathode: water is reduced (as opposed to sodium ions) since it has the highest ease of red.

𝟐 𝐻2𝑂 + 𝟐 𝑒− → 𝐻2 + 𝟐 𝑂𝐻

−

o Net ionic equation: 𝟐 𝐶𝑙(𝑎𝑞)− + 𝟐 𝐻2𝑂(𝑙) → 𝟐 𝑂𝐻(𝑎𝑞)

− + 𝐻2 (𝑔) + 𝐶𝑙2 (𝑔)

o Full equation: 𝟐 𝑁𝑎𝐶𝑙(𝑎𝑞) + 𝟐 𝐻2𝑂(𝑙) → 𝟐 𝑁𝑎𝑂𝐻(𝑎𝑞) + 𝐻2 (𝑔) + 𝐶𝑙2 (𝑔)

The final part of the process is to separate the products (𝑁𝑎𝑂𝐻,𝐻2, 𝐶𝑙2)

o Chlorine gas can be sold and used by other industries (producing PVC, cleaning products)

o Sodium hydroxide is obtained for use as a soap, in detergents etc

o Hydrogen gas is sold to other industries for the production of Hydrochloric acid

Chemistry

Shaddy Hanna

71 of 79

DISTINGUISH: BETWEEN THE ELECTROLYSIS METHODS USED TO EXTRACT 𝑁𝑎𝑂𝐻

DIAPHRAGM PROCESS

Electrodes:

o Anode: Titanium

o Cathode: Iron Mesh

Chemical Reactions:

o Anode: 𝟐 𝐶𝑙(𝑎𝑞)− → 𝐶𝑙2 (𝑔) + 𝟐 𝑒

−

o Cathode: 𝟐 𝐻2𝑂(𝑙) + 𝟐 𝑒− → 𝐻2 (𝑔) + 𝟐 𝑂𝐻(𝑎𝑞)

−

Separator: Asbestos diaphragm

o Asbestos is a porous material which allows ions to migrate between solutions whilst

separating the gaseous, spontaneous products (chlorine gas/hydrogen gas)

o Due to the migration of chloride ions, not only does NaOH form, but also NaCl

This must then be filtered out by drying the solution (since NaOH has a higher solubility,

NaCl will crystallise out)

MERCURY PROCESS

Electrodes:

o Anode: Titanium

o Cathode: Liquid Mercury

Chemical reactions (split up into two sections):

o Electrolysis and Separator:

Anode: 𝟐 𝐶𝑙(𝑎𝑞)− → 𝐶𝑙2 (𝑔) + 𝟐 𝑒

−

Cathode: 𝟐 𝑁𝑎(𝑎𝑞)+ + 𝟐 𝑒− + 𝟐 𝐻𝑔(𝑙) → 𝟐 𝑁𝑎/𝐻𝑔(𝑙)

Here, although sodium has a lower ease of reduction than water, it is

preferentially discharged, forming an amalgam (an alloy of mercury and

other metals)

o Decomposer:

𝟐 𝐻2𝑂(𝑙) + 𝟐 𝑁𝑎/𝐻𝑔(𝑙) → 𝟐 𝑁𝑎𝑂𝐻(𝑎𝑞) + 𝐻2 (𝑔) + 𝟐 𝐻𝑔(𝑙)

Here, the amalgam reacts with water to produce hydrogen gas, a very

pure sodium hydroxide solution and mercury (which is recycled)

Chemistry

Shaddy Hanna

72 of 79

MEMBRANE PROCESS

Electrodes: same as diaphragm cell

Chemical Reactions: same as diaphragm cell

Separator: PTFE (polytetrafluoroethylene) membrane – also called an ion exchange membrane

o It incorporates anionic groups (negative charges) to prevent anions in the solution from

travelling across the cell and thus the production of NaCl

COMPARING THE CELLS

Process Technical Difficulties Environmental Difficulties Voltage required

Purity of NaOH

Diaphragm Process

The final solution is not very pure at all

Abestos is used –carcinogenic agent (causes cancer) ClO— ion is a strong oxidant

Low 12%

Mercury Process

Lots of mercury is lost (mercury is $$$)

Releases mercury– toxic, heavy, bioaccumulative metal which can lead to biomagnification

High 50%

Membrane Process

High initial cost (price of membranes)

N/A Low 30%

Chemistry

Shaddy Hanna

73 of 79

SAPONIFICATION

DESCRIBE: SAPONIFICATION

Saponification is the conversion of fats or oils (by heating them in a basic solution) to

glycerol and salts of fatty acids (soaps)

o Fats and oils are esters of glycerol (1,2,3-propanetriol)

Fats have 3 saturated hydrocarbons attached to the hydroxide

Oils have 3 unsaturated hydrocarbons attached to the hydroxide

o For this reason, oils exist in liquid form at room temperature whereas fats are solids

𝑓𝑎𝑡/𝑜𝑖𝑙 + 𝑏𝑎𝑠𝑒 → 𝑠𝑎𝑙𝑡 (𝑠𝑜𝑎𝑝) + 𝑔𝑙𝑦𝑐𝑒𝑟𝑜𝑙

IDENTIFY: A RANGE OF FATS AND OILS USED FOR SOAP-MAKING

Fats:

o Lard – produces a mild soap derived from pig fat which is used for laundry

o Tallow – produces a yellow soap derived from the sold fat of beef cattle

Oils:

o Avocado Oil – produces a soap used in cosmetics

o Castor Oil – produces a relatively mild soap

o Olive Oil – produces a durable and hard soap

DESCRIBE: THE CONDITIONS OF SAPONIFICATION IN THE SCHOOL LAB VS INDUSTRY

School lab:

o Produced by heating a relatively pure fat/oil with excess NaOH with a reflux condenser

o Precipitated by adding saturated brine solution and is collected, washed and dried

Industry:

o Produced by heating fat residues from butchers with apt, measured amount of NaOH (since

NaOH it is expensive)

o Glycerol is recovered since it can be resold and brine is reused

o The raw soap is then carefully washed, dried and blended with perfumes/colouring agents

PRAC: CARRY OUT SAPONIFICATION AND TEST THE PRODUCT

Method:

1. 30mL of NaOH, 10mL of olive oil and a few boiling chips were placed in a 250mL beaker

2. The solution was boiled using a Bunsen burner until the oil layer disappeared

3. The beaker was then cooled using a water bath

4. Next, 40mL of a brine (saturated NaCl) solution was added

5. The mixture was filtered using filter paper, the residue washed, dried and weighed.

Results: An off white spongy mass of soap was collected

Test: Use the soap with hard water and with tap water

o With hard water: the solution does not later

o With tap water: the solution lathers

Chemistry

Shaddy Hanna

74 of 79

ACCOUNT: FOR THE CLEANING ACTION OF SOAP BY DESCRIBING ITS STRUCTURE

Soap is a surfactant (Surface Active Agent) – it decreases the surface tension of water, dispersing dirt

and grease as small particles throughout it

Structure: Soap has a polar end and a non-polar end

o The polar end (with the anion) is hydrophilic since it is water soluble

o The non-polar end (containing the hydrocarbon chain) is hydrophobic

Cleaning action:

o The non-polar chain attaches to non-polar dirt while the polar head is dissolved in water

This forms a micelle which has an overall net negative charge

o Since the particles are negatively charged, they repel each other and are dispersed

throughout the solution.

o As a result, the surfactant floats such particles off fabrics, fibres or skin.

EXPLAIN: SOAP ACTING AS AN EMULSIFIER WHEN IT FORMS AN EMULSION WITH

WATER AND OIL

An emulsion occurs when an insoluble material is broken up into smaller particles and dispersed

throughout water

Soap acts as an emulsifier when mixed with oil and water since it breaks down large drops of oil into

very small droplets dispersed throughout the solution

PRAC: DESCRIBE THE PROPERTIES AND USES OF A NAMED EMULSION

Mayonnaise is an emulsion of vegetable oil and egg yolk

o Here, the egg yolk acts as an emulsifier

Property Use

It does not separate into its component liquids even when stored for long periods of time

Used as a food product since it stays edible for long periods of time in storage

Has a creamy feeling, not feeling oily Has a pleasant taste as a food product

PRAC: DEMONSTRATE THE EFFECT OF SOAP AS AN EMULSIFIER

Method:

1. Fill a 25mL test tube with 10mL of water

2. Add 5mL of oil, stopper the test tube, shake, and observe results

3. Add 5mL of soap, stopper the test tube and shake it and observe results

Results:

o When oil is initially added, the water and oil are separated, forming separate layers

o Upon addition of soap, the oil and water form an emulsion with soap as an emulsifier

non-polar end

polar end

Chemistry

Shaddy Hanna

75 of 79

DISTINGUISH: BETWEEN SOAPS AND SYNTHETIC DETERGENTS

A soap is made of one compound from natural resources like animal fat

A detergent is a mixture of compounds: surfactants and builders

o The surfactants can be: anionic, cationic or non-ionic

o The builders (e.g. phosphates) are added to assist the effectiveness of the surfactants

Removes cations, and thus prevents precipitation of surfactants with cations.

Anionic Cationic Non-ionic

Features Soap Synthetic Detergents

Anionic Cationic Non-ionic

Effect in hard water

Soap anions form ppts with cations

Does not precipitate with cations in hard water

Chemical Composition

Tail: Hydrocarbon chain

H E A D

Carboxylate Benzene sulfonate Alkyl ammonium Alcohol function

group

Properties

Biodegradable

Chains do not remove natural body oils

Much more effective, however, can thus remove natural body oils

Act as disinfectants to kill microorganisms

The tail sticking out prevents static and fibre tangling

Do not lather or foam up

Uses

Personal hygiene

Industrial detergents

Hand-washing liquids

Hair conditioner

Fabric softener

Laundry/ Dishwashing detergents

DISCUSS: THE ENVIRONMENTAL IMPACTS OF THE USE OF SOAPS AND DETERGENTS

Advantages Disadvantages

Soaps Biodegradable

(produced by animal fats)

Can contain chemical additives which can harmfully lead into waterways

Detergents

Keep us clean, decreasing the transmission of disease

Are not biodegradable (since they are synthetic) leading to the foaming up on waterways o This was fixed by creating unbranched chains as

opposed to branched chain detergents

Contain phosphates as builders which lead to eutrophication

Contain chemical additives which can leak into waterways

Cationic detergents are biocides which kill many organisms

Chemistry

Shaddy Hanna

76 of 79

THE SOLVAY PROCESS AND SODIUM CARBONATE

DESCRIBE: USES OF SODIUM CARBONATE

Glass manufacture: Sodium carbonate is combined with silica and other ingredients to produce glass

Base: It is a cheap alkali which can be used for neutralising acids in labs

Detergents: Used to soften water by precipitating out with Calcium ions

IDENTIFY: RAW MATERIALS AND PRODUCTS OF THE SOLVAY PROCESS

Raw materials:

o Sodium chloride (NaCl) – from seawater (brine)

o Calcium carbonate (CaCO3) – from limestone – an abundant rock

o Ammonia (NH3) is purchased – although it is expensive, it is recycled therefore zero net

usage

Products:

o Sodium carbonate (Na2CO3) – the desired product

o Calcium chloride (CaCl2) – a useless product (no value)

Net reaction:

CaCO3 (𝑠) + 𝟐 NaCl(𝑎𝑞) → CaCl2 (𝑎𝑞) + Na2CO3 (𝑎𝑞)

IDENTIFY: THE SEQUENCE OF STEPS USED IN THE SOLVAY PROCESS

Chemistry

Shaddy Hanna

77 of 79

IDENTIFY: THE SEQUENCE OF STEPS USED IN THE SOLVAY PROCESS

1. Brine purification

o The main source of brine is from sea water and underground salt deposits

o The brine must be concentrated to at least 30% NaCl in water.

o Impurities are removed by precipitation so they do not precipitate with NaHCO3

Ca(𝑎𝑞)2+ + CO3 (𝑎𝑞)

2− → CaCO3 (𝑠)

Mg(𝑎𝑞)2+ + OH(𝑎𝑞)

− → Mg(OH)2 (𝑎𝑞)

Flocculants may be added so that precipitates group together for easy removal

2. Hydrogen carbonate formation

o The brine is the saturated with ammonia

o Limestone is decomposed in a lime kiln under high temperatures to produce CaO (for use in

ammonia recovery) and CO2 (for use in the Solvay tower)

CaCO3 (𝑠)ℎ𝑒𝑎𝑡→ CO2 (𝑔) + CaO(𝑠)

o CO2 is then bubbled through the brine solution to form weak carbonic acid

CO2 (𝑔) + H2O(𝑙) ⇌ H2CO3 (𝑎𝑞)

o This weak acid then reacts with ammonia (a weak base)

H2CO3 (𝑎𝑞) + NH3 (𝑎𝑞) ⇌ NH4 (𝑎𝑞)+ + HCO3 (𝑎𝑞)

−

o Sodium hyd-carbonate is then formed by the reaction of sodium(brine) with hyd-carbonate

Na(𝑎𝑞)+ + HCO3 (𝑎𝑞)

− ⇌ NaHCO3 (𝑠)

o Ammonium chloride is then formed by the reaction of ammonium and chloride (brine)

NH4 (𝑎𝑞)+ + Cl(𝑎𝑞)

− ⇌ NH4Cl(𝑎𝑞)

o Net reaction:

NaCl(𝑎𝑞) + NH3 (𝑎𝑞) + CO2 (𝑔) + H2O(𝑙) ⇌ NH4Cl(𝑎𝑞) + NaHCO3 (𝑠)

3. Formation of sodium carbonate

o Sodium hydrogen carbonate is decomposed into sodium carbonate

𝟐 NaHCO3 (𝑠)ℎ𝑒𝑎𝑡→ CO2 (𝑔) + H2O(𝑙) + Na2CO3 (𝑠)

o Carbon dioxide is collected and recycled into the Solvay tower

4. Ammonia recovery

o Calcium oxide produced by the lime kiln is combined with water in the slaker to form CaOH

CaO(𝑠) + H2O(𝑙) → Ca(OH)2 (𝑎𝑞)

o The Ca(OH)2 solution is then mixed with the NH4𝐶𝑙 solution to recover ammonia for re-use

Ca(OH)2 (𝑎𝑞) + 𝟐 NH4Cl(𝑎𝑞) → CaCl2 (𝑎𝑞) + 𝟐 NH3 (𝑔) + 𝟐 H2O(𝑙)

Chemistry

Shaddy Hanna

78 of 79

PRAC: CARRY OUT A CHEMICAL STEP INVOLVED IN THE SOLVAY PROCESS

Aim: To model the production of NaHCO3 as in the Solvay Process

Safety Assessment:

o Safety goggles must be worn to prevent ammonia from entering eyes

o Experiment must be conducted in a fume cupboard to prevent toxic gas from releasing

Method:

1. 200 mL of ammoniated brine was added to a 500mL conical flask

2. A spoonful of dry ice (CO2 source) was added to the flask and the fume cupboard closed

3. Observations were recorded

Results: NaHCO3 crystals were formed

Difficulties associated with modelling:

o Oversimplifies the model

o Only a small amount of crystals were actually formed

o The experiment was hard to see since it was performed in a fume cupboard

DISCUSS: ENVIRONMENTAL ISSUES WITH THE SOLVAY PROCESS

EXPLAIN: HOW THESE ISSUES ARE ADDRESSED

Thermal pollution:

o Exothermic reactions (lime kiln and ammonium chloride) require cooling

o This cooling can be provided by water bodies

However, the increase in temperature in these water systems can decrease the

solubility of gases and thus reduce DO and increase pH.

o Also, some inland plants do not have access to large water bodies

o Resolution: plants must consider the construction of pools within the tower

Release of Ammonia:

o Ammonia is an air pollutant which poses a possible health threat to marine ecosystems

o Resolution: Industry must carefully monitor and design the process

Disposal of Calcium Chloride: The Solvay process produced lots of Calcium chloride as waste

o Calcium Chloride is close to useless in Australia, thus it must be disposed safely

o Resolution: It is dumped into oceans or underground

NOTE: If disposed into rivers/lakes, the increase in Cl— can be catastrophic

DETERMINE: CRITERIA USED TO LOCATE A CHEMICAL INDUSTRY ( USI NG T HE S O LVA Y PR O CE S S)

Factor Reasoning Env. Eco. Soc.

Land The site of the plant must be of reasonable size, whilst as inexpensive as possible

Raw Materials Areas were brine and limestone are abundant and cheap to source

Labour Near cities so that there is an available workforce, which should be inexpensive without compromising quality and skill of workers

Transportation Should be of close proximity to suppliers and buyers

Water supply Should be of close proximity to a water source for the disposal of Calcium Chloride and excess heat

Government Regulations

Areas where the government regulations correspond with the industry’s desired usage of resources

Chemistry

Shaddy Hanna

79 of 79

Pollution Preferably in rural areas to minimize the disturbance to cities

REFERENCES

Slade, Roger, and Maureen Slade. HSC chemistry. 2013 ed. Port Melbourne, Vic.: Cambridge University Press,

2013. Print.

Stamell, Jim. Excel HSC chemistry. Glebe, N.S.W.: Pascal Press, 2008. Print.

Tregarthen, Linden. HSC chemistry. South Yarra, [Vic.: Macmillan Education Australia, 2003. Print.