hsc chemistry summary richard shaw

8/10/2019 HSC Chemistry Summary Richard Shaw

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Richard Shaw

Production of Materials

1. Fossil fuels provide both energy and raw materials such as ethylene, for the

production of other substances

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

refining of petroleum

Ethylene is the most versatile and widely used raw material in the petrochemical industry.

However, because very little ethylene is found in natural gas or crude oil, it must be produced from

other hydrocarbons by a process known as cracking. Cracking is the process of breaking

hydrocarbons of high molecular mass into ones of lower molecular mass. Cracking can occur

through catalytic cracking (used for C15 to C25) or steam cracking (used for natural gas).

Catalytic cracking occurs in a cat cracker at a temperature of approximately 500C and at pressures

somewhat above atmospheric. Catalytic cracking involves the use of crystalline aluminosilicates or

zeolites as catalysts for the process. Catalytic cracking alone is often insufficient to meet current

needs of these industrially important compounds and hence some fractions of crude oil are often

decomposed completely to produce ethylene in a process called steam cracking. Steam cracking

involves a much higher temperature of approximately 900C. In this process the hydrocarbons are

mixed as a gas with CO2present as an inert diluent that allows the process to operate at just above

atmospheric pressure. The mixture is then passed over a series of hot metal coils. The steam

removes carbon deposits from the coils while the heat from the coils causes the hydrocarbons to

crack into smaller molecules.

Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into

many useful products

Ethylene is readily transformed into many useful products such as the polymers LDPE and HDPE

as well as ethanol. This is due to the high electron density associated with the double bond. This

higher electron density at the double bond functional group of ethylene can induce numerous

reactions to occur (temporary dipole production and therefore readily reacts with diatomic halide

molecules such as Cl2).

Identify data, plan and perform a first-hand investigation to compare the reactivities of appropriate

alkenes with the corresponding alkanes in bromine water.

Aim:To compare the reactivity of cyclohexene with the corresponding alkane cyclohexane inbromine water.

Equipment: cyclohexene, cyclohexane, bromine water, 2 test tubes, fume cupboard, darkened room

Risk Assessment:The bromine water used in the experiment is corrosive and harmful so caution

must be taken to clean up spills immediately and avoid skin contact. Also, the chemicals used in

the experiment release harmful fumes so caution must be taken around them and a fume cupboard

should be used. Cyclohexene and cyclohexane are also highly flammable and care must be taken to

keep all naked flames away from these liquids. Keeping a working fire extinguisher close by also

minimizes this hazard.


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Method:

1)

Take two test tubes and fill one with 2mL of cyclohexane and the other with 2mL of

cyclohexene inside a fume cupboard. Ensure that the experiment is conducted in subduedlighting.

2)

Add 4 drops of bromine water to each test tube

3) Gently shake both test tubes to an equal degree

4) Record changes observed in reagents test tubes before and after shaking

Results:When the substances were mixed, two immiscible layers formed: a lower aqueous layer

and a hydrocarbon layer on top. Upon mixing, the cyclohexene decolourises bromine water from

reddish-orange to colourless. Meanwhile, the cyclohexane did not react as reailty and diluted the

bromine water.

Discussion:Bromine water exists as an equilibrium system,

The reaction of bromine water with cyclohexene is then,

This is an addition reaction which occurs readily due to the reactive double bond of the

cyclohexene. Meanwhile, the bromine water was only diluted in the cyclohexane as no reaction

occurred. Some bromine molecules actually dissolved in the cyclohexene layer; causing the lower

layer to slightly decolourise and the upper layer to take on the reddish colour of the bromine. It is

important that this experiment be conducted in subdued lighting as cyclohexane will eventually

react with bromine water in the presence of UV light via a substitution reaction.

Cyclohexene and cyclohexane were chosen as they are both colourless liquids at room

temperature, stable and corresponding alkenes and alkanes. They are also easily stored.

Conclusion:We were successfully able to compare the reactivity of cyclohexene with its

corresponding alkane cyclohexane in bromine water. We found that testing with bromine water


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was able to show that cyclohexene is more reactive than cyclohexane due to the presence of the

reactive double bond that caused cyclohexene to decolourise the bromine water.

Identify that ethylene serves as a monomer from which polymers are made

Polymerisation is a chemical reaction in which many identical small molecules combine togetherto form one large molecule. The small molecules are called monomers, and the large molecule is

called a polymer. Ethylene serves as a monomer and forms the polymer polyethylene.

Analyse information from secondary sources such as computer simulations, molecular model kits,

or multimedia resources to model the polym erisation process

Process did not show the random nature of the propagation and termination stages

Did not provide a true indication of the number of monomers in the polymer chains

Did not demonstrate the bonding between polymer chains

Did not demonstrate the role of the catalyst/initiator.

Identify polyethylene as an addition polymer and explain the meaning of this term

Polyethylene is an addition polymer, meaning that it is formed from monomers without the loss of

a small molecule. This achieved by the opening out of the ethylene double bond. The opening of

the double bond allows free electrons to covalently bond to neighboring monomer unit. Addition

polymerisation can only occur if the monomer has a double or triple bond.

Outline the steps in the production of polyethylene as an example of a commercially and

industrially important polymer

Both LDPE and HDPE are widely used commercially for items such as milk bottles, cling wrap,

kitchen utensils and garbage bins. Its inert nature and relatively cheap production costs has seen

polyethylene become an extensively used commercially and industrially important polymer.

Ethylene is the monomer used to produce polyethylene. The polymerization of ethylene can occur

in one of two ways, resulting in variations in the resultant polymer.

The gas phase process involves high pressure (1000 to 3000 atmospheric), high temperature (300C)

and an organic peroxide (or oxygen) initiator. The product has significant chain branching as some

hydrogen atoms are replaces by alkyl groups. Consequently, low density polyethylene is produced.

The newer Ziegler-Natta process uses pressures of only a few atmospheres and a temperature of

about 60C. Catalyzed by a mixture of titanium(III) chloride and triethyaluminium, this process

produces unbranched polyethylene molecules which are able to pack closely together and formhigh density polyethylene.

In both cases, the polymerization process begins with initiation whereby the initiator or catalyst is

broken into free radicals which then attack the double bond of an ethylene molecule to form an

activated monomer species. Another ethylene molecule then attaches itself to this activated

monomer, acting as the new activated species. This propagation continues and the polymer chain

continues to grow in a random fashion. Finally, termination occurs when two activated chains

collide and join to form a stable polymer or exchange a hydrogen atom to form two stable

molecules.


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Initiation:

Propagation:

Termination:

Identify the following as comm ercially significant monomers by both their systematic and

common nam es:

Vinyl chloride Chloroethene) and Styrene Phenylethene)

Describe the uses of the polymers made from the above monomers in terms of their properties

Polymer Properties Uses

HDPE Rigid and strong due to crystalline structure

achieved by linear chains and minimal chain

branching (more intermolecular forces)

Hardness is limited by absence of chainstiffening, cross-linking

HDPE is much harder, stronger and has a

higher melting point and greater tensile

strength than LDPE

Non-toxic, inert C-H bonds, waterproof

Kitchen utensils and

containers; non-toxic, inert

and has a high melting point

Plastic buckets; strong andrigid

Rubbish bins; strong and rigid

Tougher carry bags; high

tensile strength

LDPE Extensive chain branching, lack of stiffening

side groups and lack of cross-linkages gives

amorphous structure

Soft and flexible, low tensile strength

Non-toxic, inert C-H bonds, unreactive andwaterproof

Plastic bags; inert and flexible

Clingwrap; flexible, CO2,O2

permeable

Milk bottles; flexible and inert

PVC Rigid due to Cl chain stiffening

C-Cl is susceptible to U.V and must be

combined with an inhibitor (TiO2) before

outdoor use

Electronegative Cl causes dipole forces and

also ties up electrons, meaning it has a high

melting point and is an electrical insulator

and flame retardant

Plasticisers (dialkyl phthalates) make PVC

soft and flexible

Underground pipes; light,

tough and rigid

Electrical wires; insulator,

flame retardant, high melting

point

Garden hoses, raincoats,

shower curtains; flexible

Floor and carpet backing; soft,

insulator, fire and water

resistant

Polystyrene Phenyl group provides chain stiffening,

making polymer rigid, hard and strong

Very stable to heat and UV

Good thermal insulator

Crystalline, quite transparent

Can form light-weight sponge when gas is

Tool handles, CD cases, car

battery cases, modern

furniture, rigid cups; rigid,

tough, transparent

Foam cups; light foam and

thermal insulator


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bubbled through polymerisation Packaging; gas compressibility

2. Some scientists research the extraction of materials from biomass to reduce our

dependence on fossil fuels

Discuss the need for alternative sources of the compounds presently obtained from the

petrochemical industry

Petrochemicals have become a pivotal part of everyday life and their use has become a

necessity for the function of society. Yet currently, Australias petrochemical industry has

its chemicals derived from fossil fuels such as crude oil and natural gas.

It is estimated that Australia has petrol reserves to last 10 more years and natural gas

reserves to last 100 years.

95% of these resources are burned as fuel and cannot be retained. The other 5% is used by

the petrochemical industry and an even smaller fraction of this 5% is recycled.

A large number of jobs, directly and indirectly depend on the petrochemical industry and

continual production of compounds.

As crude oil supplies decrease, prices will increase and there is now pressure to reduce costs

through viable alternative methods.

Current processes are environmentally detrimental and cause large greenhouse gas

emissions, there is also pressure to reduce environmental impact through alternatives

Unfortunately, it appears that methods of extracting important compounds from other

sources would be more expensive than extracting them from crude oil, making manyreluctant to shift away from current fossil fuel sources.

It is clear that with diminishing fossil fuels and relatively low recycling rates that an

alternative source will be required for the petrochemical industry.

Note: The keyword is DISCUSS and so it is important to give at least one point AGAINST the use of

alternative compounds.

Use available evidence to gather and present data from secondary sources and analyse progress in

the recent development and use of a named biopolymer. This analysis should name the specific

enzyme s) used or organism used to synthesize the material and an evaluation of the use or

potential use of the polymer produced related to its properties.

Biopolymers are polymers that are made in large part by living organisms. Biopol is the commercial

name of one such biopolymer formed from the monomers 3-hydroxybutyrate and 3-

hydroxyvalerate.


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By fostering the growth of the bacteria cupriavidus metallidurans (alcaligenes eutrophus) in a high

glucose, high valeric acid environment and then creating a nitrogen deficiency, the bacteria begin

to store carbon in the desired 3-HB/3-HV co-polymer form. The polymer can then be isolated andextracted through the use of hot trichloromethane. This process is quite expensive and so, more

recent developments in genetic engineering has provided alternate pathways for the synthesis of

Biopol. The production of Biopol by genetically engineered E.coli has seen benefits over the

previous process such as better and faster growth, higher yields, less waste and faster bacterial

recovery. Also cheaper substrates can be used to grow the bacteria such as whey or molasses.

Despite this improvement, Biopol is still considerably more expensive than similar conventional

polymers such as polypropylene and also produces pungent waste that is difficult to dispose.

Nevertheless, Biopol does have ideal properties that have seen its application in areas where there

is often no commercial alternative. Biopol is insoluble in water, has high tensile strength, UV

resistant and is biodegradable, biocompatible and is produced from a renewable resource. Theseproperties have seen Biopol applied in medicine as well as nappy linings where biodegradability is

important. Surgical pins and sutures are often made from Biopol as it isnt rejected by the body

(being biocompatible) and is safely broken down in the body (being biodegradable). The stiff and

brittle nature of Biopol has been applied in bottles, laminated foils, fishnets and textile fibres.

Overall, it is clear that Biopol has both benefits and disadvantages over conventional polymers, but

with ever depleting fossil fuel reserves the demand for alternatives such as Biopol can only

increase. Since 2001, bio-technology development corporation Metabolix has been producing

Biopol by microbial conversion of natural sugars and is developing ways to produce Biopol in

transgenic plants. Despite its current cost of production and impracticality, further developments

such as those being made by Metabolix may see biopolymers such as Biopol become as extensively

used as current petroleum based polymers.

Another biopolymer Medicoatis a slippery product used to coat catheters so that bacteria cannot

get a hold and reproduce to cause infection. The polymer Elastinis being developed at USYD as an

artificial human skin useful in replacing skin for burns patients. Cyclodextrinis a toroid

(hydrophilic outside and hydrophobic inside) biopolymer formed from -amylase. It has

pharmaceutical applications in medicine absorption, fragrances, food products and environmental

protection.

Explain what is meant by a condensation polymer

Condensation polymers are polymers formed by the elimination of a small molecule when pairs of

monomers join together. In order for condensation polymerisation to occur, the monomer(s) must

contain a functional group at either end. Cellulose, starch, glycogen are all condensation polymers.

Describe the reaction involved when a condensation polymer is formed


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Describe the structure of cellulose and identify it as an example of a condensation polymer found

as a major component of biomass

Cellulose is formed through the condensation polymerisation of -glucose molecules which link

together via -1,4-glycosidic bonds with an alternating CH2OH group. Due to the alternatingglycosidic bond angles, and the geometry of the glucose rings, cellulose has a very linear and rigid

structure. Furthermore, the hydroxyl groups on neighbouring chains hydrogen bond with each

other forming very strong cellulose fibres and contributing to the linear structure.

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

and discuss its potential as a raw material

Advantages

Cellulose contains the basic C-C chains required to manufacture petrochemicals

Unlike fossil fuels, cellulose is a readily available raw material and the major constituent of

biomass (material made entirely or in large part by living organisms), making it a renewable

resource.

Cellulose can be broken down to glucose by acid digestion or through cellulase enzymes,

Once broken, glucose can be fermented to form ethanol, which is an industrially important

solvent, as well as being a useful fuel extender in vehicles.

Cellulose is biodegradable and can be used to develop biopolymers such as rayon,

cellophane and cellulose acetate.

Ethanol can be further reacted in a dehydration reaction to form ethylene, which is an

industrially significant monomer used to manufacture many petrochemicals.

Ethylene can then be used to form polyethylene or other important monomers such as vinyl

chloride and styrene.

It is this formation of ethanol and ethylene from cellulose that gives it the potential as a raw

material in the production of petrochemicals.

Disadvantages

Breaking cellulose by acid digestion or through cellulose enzymes are both time consuming

and expensive as the strong -1,4-glycosidic bonds of cellulose are difficult to break.

This process also requires a lot of energy most likely provided by fossil fuels, meaning that

this process could in fact require more non-renewable resources than before.

Cellulose based biopolymers are relatively costly and are not widely applied.

Loss of arable land: If large areas of land were devoted to the growth of biomass for

petrochemicals this would also cause environmental problems such as erosion and

deforestation.


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Discussion:

Advantages:

They model allowed us to represent the process of bond breakage and formation that occurs

in these two reactions They provided a visual representation of the reactions, rather than the linear chemical

equations that are usually written

Shows the shape of the reactants and products.

Disadvantages:

Model cannot perfectly re-create the shape of a molecule

Ball and stick models could not represent polarity

This model did not show the role of the sulfuric acid catalyst in the reaction

Conclusion:We were able to model the hydration of ethylene and the dehydration of ethanolusing molecular model kits.

Describe the addition of water to ethylene resulting in the production of ethanol and identify the

need for a catalyst in this process and the catalyst used

Hydration is a chemical reaction in which water is added from a compound. Ethylene is hydrated

by heating with dilute sulfuric acid as a catalyst. This process requires a dilute sulfuric acid catalyst

to lower the activation energy of the reaction by providing an alternate pathway (that also

increases the rate of reaction), and hence speeds it up to a sufficient and sustainable rate.

Process information from secondary sources to summarise the processes involved in the industrial

production of ethanol from sugar cane

1)

Sugar cane is ground and crushed before undergoing acid digestion for two hours at 100C.

This created a sugar and acid solution which is neutralized using calcium hydroxide.

2) The sugar is fermented with yeast to produce a dilute ethanol solution of (ideally) 15%.

3)

Distillation is used to produce greater concentrations. For an even higher concentration of

ethanol, a dehydration or absorption process is used.

However, this process is expensive, time consuming and not economically viable. A more effective

method of obtaining glucose for fermentation is the use of molasses. Molasses is syrup left over

when sugar cane is milled and is very high in sucrose content. Sucrose can be broken down toglucose by the action of the enzyme invertase which can then be fermented. Glucose can also be

obtained from unfermented xylose by the action of E.coli bacteria.

Describe and account for the many uses of ethanol as a solvent for polar and non-polar substances

Ethanol is an important solvent due to its ability to dissolve both polar and non-polar substances.

This is a consequence of its structure. The hydroxyl group is polar in nature (due to the high

electro-negativity of the oxygen-carbon bond) so there it can dissolve polar substances through


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dipole-dipole interactions of hydrogen bonding. The alkyl group is non-polar so it is able to

dissolve non-polar substances through dispersion forces along the alkyl tail.

Due to its ability to dissolve both polar and non-polar substances, ethanol has a wide range of uses

as a solvent including:

Cosmetics (perfumes, deodorant, aftershave etc)

Food colouring and preservatives

Medical preparations (antiseptics)

Cleaning agents

Pharmaceutical products

Outline the use of ethanol as a fuel and explain why it can be called a renewable resource

Ethanol combusts with oxygen in an exothermic reaction that releases large amounts of heat:

Ethanol has been used as a fuel extender in cars, planes and trucks

Ethanol has also been commonly found in camping stove fuels

Ethanol can be produced by the fermentation of the naturally occurring sugar glucose. Glucose is

part of cellulose, which is the major constituent of biomass and a renewable resource. Since

ethanol can be produced from a renewable resource, it too is a renewable fuel source.

Process information from secondary sources to summarise the use of ethanol as an alternative car

fuel, evaluating the success of current usage

Ethanol was used as a petrol extender during WWII (and more recently) in concentrations

of 10-20%.

During the 1970s and 1980s Brazil used pure ethanol as the major fuel for cars. Sugar cane

was grown specifically for this purpose and engines were modified accordingly. The

program was subsidized by the Government, and was designed to address a trade imbalance

and reduce the consumption of non-renewable fossil fuels. The program was initially very

successful that by the mid 1980s 94% of new vehicles ran exclusively on ethanol. However

the use of ethanol was challenged in the 1990s by lower oil prices and the use of ethanol

was eventually phased out; however it has experienced resurgence in recent years following

record world oil prices and the release of flex-fuel cars in 2003. In Brazil, ethanol fuel iscurrently cheaper than petrol.

Ethanol is currently used as a fuel additive in many Brazilian cars. 30% of Brazilian cars use

a fuel blend containing 25% ethanol. This is more cost effective and improves octane rating

and the higher flash point is easily met due to higher temperatures in Brazil. However car

modifications are still required to use such high percentages of ethanol.

Ethanol is used in USA (called gasohol) and Canada (where ethanol is required by the law to

be added to fuels) at approximately 10% with some success as it doesnt require engine

modifications and improves octane rating. However in colder states, some cars have had


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trouble starting (due to ethanols higher flash point) and it has been criticized for

consuming food crop.

In Australia, governments are encouraging 10% ethanol blends such as E10 by providing

subsidies for petrol suppliers that use it. Despite this, ethanol still costs more to produce.There is some question as to whether using ethanol as a fuel additive at 10% still causes engine

corrosion. Nevertheless, the use of ethanol as a fuel extender seen currently has been reasonably

successful, particularly in Brazil where it has reduced the nations dependency on fossil fuels.

Describe conditions under which fermentation of sugars is promoted

Anaerobic

37C

Yeast (zymase enzyme is biological catalyst for fermentation) and glucose solution

Solve problems, plan and perform a first-hand investigation to carry out the fermentation of

glucose and monitor mass changes

Aim:Monitor mass changes occurring during the fermentation of glucose

Equipment:250mL vacuum flask with rubber stop and side arm, 500mL beaker, 50mL measuring

cylinder, large test tube, 20mL glucose solution (10% w/v), 1g sodium dihydrogen phosphate (yeast

nutrient), limewater, thermometer, electronic balance.

Method:

1) Weigh out 1g of yeast and add it to the vacuum flask

2) Measure 20mL of glucose solution using a measuring cylinder and add to the flask

3) Insert the rubber stop and weight the apparatus and record exactly the initial mass.

4) Place the reaction apparatus in a 500mL beaker containing water held at approximately

37C

5) Over successive days, re-weight the flask and record any mass changes that have occurred.

6) Connect the rubber hose to a glass test tube containing limewater. Observe and record any

changes in appearance.


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Results/Observations:

The initial yeast solution was milky yellow in colour. It was opaque and its smell

resembled chicken broth.

After 1 day, a creamy layer was on top of the mixture. An odour resembling that of

wine was noted.

After 2 days, the wine odour was much stronger. When the flask was swirled, the

creamy substance on top of the mixture dissolved. Sediment was observed at the

bottom of the flask.

The lime water went cloudy

Discussion:There were several assumptions made in this experiment: The first was that all the mass change was due to the escape of CO2and not due to

evaporating water or air entering.

We assume all the glucose was completely fermented

Some sources of experimental error include:

Lack of sensitivity of electronic scales

Difficulty of maintaining anaerobic conditions and a temperature of 37C

The entering of air into the vessel and the evaporation of water

The fermentation is limited as the yeast will die once ethanol concentration reaches 15%.

Due to the small amounts of glucose used, the mass changes are small and so there is a large

percentage of error.

Conclusion:We were successfully able to conduct an investigation to monitor mass changes in the

fermentation of glucose.

Summarise the chemistry of the fermentation process

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

the action of enzymes present in yeast. Fermentation can only produce ethanol concentrations of

15% before the yeast die. Higher concentrations can only achieved by fractional distillation.

Sucrose is broken into its monosaccharide components by the enzyme invertase present in yeast:

Fermentation can then occur through the action of zymase in yeast:

The positive result for the release of carbon dioxide can be confirmed by passing the gas through

limewater, which then turns milky if carbon dioxide is present:


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Present information from secondary sources by writing a balanced equation for the fermentation of

glucose to ethanol

Define the molar heat of combustion of a compound and calculate the value for ethanol from first-

hand data

The molar heat of combustion of a substance is 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 and liquid water only.

Assess the potential of ethanol as an alternative fuel and discuss the advantages and disadvantages

of its use

Advantages

Ethanol can be produced by the fermentation of glucose, making it a more desirable fuel

source as it can be produced from renewable resources.

The presence of oxygen in the molecule means that combustion is almost always complete,

meaning a reduction in polluting forms such as CO and soot.

The presence of the oxygen also means that toxic additives such as MTBE

(methyltertiarybutylether) that help petrol burn evenly by providing oxygen do not need to

be added to fuel.

Ethanol also has the potential to be carbon neutral as the products of its use are exactly

those required for its production by photosynthesis.

Ethanol has already been successfully applied as a fuel extender without engine damage.

Ethanol has a high flash point, meaning it is safer to use on camping stoves as it is less likely

to accidentally ignite.

Ethanol has a higher RON or octane rating than petrol meaning it burns smoother in high

compression performance engines.

Ethanol contains no impurities such as sulfur and so produces no polluting SO2

Ethanol is easily transportable and can be easily incorporated into fuel blends

Disadvantages

Ethanol is far more expensive to produce than hydrocarbons used for fuel such as octane

Ethanol has a lower heat of combustion, so more ethanol would be required to travel the

same distance as when using petrol.

Ethanol has a high affinity to water making it corrosive to fuel lines and engines. The

process of distillation is thus very expensive


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Large areas of land would be needed to grow biomass needed to produce ethanol. This can

cause environmental problems such as soil erosion, land clearing and deforestation as well

as result in losses of large amounts of arable land.

Ethanol is corrosive to engines and fuel lines, and using ethanol in concentrations above10% would require engine modifications.

The smelly waste products of fermentation are difficult to dispose of.

Ethanol has a higher flash point that normal petrol, meaning a greater temperature is

required for combustion to occur.

Overall, ethanol is currently not viable as a stand-alone fuel source, and can currently only be used

a fuel additive/extender at concentrations of 10%. However, with ever increasing need for

renewable fuel sources as oil supplies dwindle, ethanol may become an important fuel alternative

of the future.

Identify data sources, choose resources and perform a first-hand investigation to determine and

compare heats of combustion of at least three liquid alkanols per gram and per mole.

Aim:To perform an experiment to determine the heat of combustion of a series of alkanols

Risk Assessment:Since alkanols are being burned there is exposure of a naked flame and a

flammable hazard. Care must be taken to ensure that any spills are cleaned up immediately and

safety goggles should be worn. A fire extinguisher should also be kept close by for emergencies.

Equipment:Electronic balance, aluminium can, thermometer, retort stand, clamp, boss head, spirit

burners (ethanol, propanol and butanol), measuring cylinder.

Method:

1) Weight the aluminium can and record its mass

2) Measure 300mL of water and pour it carefully into the can

3) Insert a thermometer into the can and record the initial temperature of the water

4)

Place the can in the clamp on the retort stand

5) Weigh the capped ethanol spirit burner and record the mass

6) Light the burner and heat the water until the temperature rises by 20C

7)

Extinguish the flame and cap the burner. Stir the water gently and record the maximum

temperature reached.

8)

Reweigh the spirit burner and determine the mass difference9) Repeat the process for propanol and butanol.


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Discussion:

The main source of error on this experiment was the calorimeter as much of the heat was lost

to the surroundings. This could have been improved by using a better insulated calorimeter or a

wind break to minimize heat loss.

Incomplete combustion occurred as seen by the presence of black soot on the bottom of the can

Failure the keep the thermometer in the middle of the can

Heat absorption by the aluminium can, would not necessarily have been completely transferred

to the water.

Conclusion: We successfully measured the heat of combustion of a series of alkanols.

Identify the IUPAC nomenclature for straight-chained alkanols from C1 to C8

4. Oxidation-reduction reactions are increasingly important as a source of energy

Explain the displacement of metals from solution in terms of transfer of electrons

A metal displacement reaction occurs when one metal converts the ion of another metal into a

neutral atom through the transfer of electrons. This occurs because of a transfer of electrons

between the ions. While one metal loses electrons, the other metal gains electrons.

Perform a first-hand investigation to identify the conditions under which a galvanic cell is

produced

We found that a strong electrolyte is required

The electrodes cannot be touching and must be in contact with an electrolyte solution

between them

A salt bridge is required

A potential difference between the electrodes is required (i.e. the electrode cannot be the

same metal)

Identify the relationship between displacements of metal ions in solution by other metals to the

relative activity of metals

At the conclusion of a displacement reaction, the more reactive metal will be in the form of an ion

(in solution) while the less reactive metal is a neutral atom (solid form).

Perform a first-hand investigation and gather first hand information to m easure the difference in

potential of different combinations of m etals in electrolyte solution

Sand each of the metals before use, EXCEPT for lead as it is toxic and poses health risks.

Discussion: The cell voltages obtained were lower than the theoretical value because of a number

of reasons.


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We used low quality voltmeters which created a load on the circuit causing the voltage to

drop significantly

The concentrations of electrolyte solutions used were 0.1M and not 1M as required.

We could not ensure other standard conditions such as temperature and pressure. The metals may still have had impurities in them, particularly lead electrodes.

The salt bridge may have begun to dry out as it was used.

Account for changes in the oxidation state of species in terms of their loss or gain of electrons

When elements lose of gain electrons, they undergo a change in oxidation states. Whether a

species is oxidised or reduced can be determined by examining their oxidation states.

The rules of oxidation states are:

The oxidation state of an element alone is 0

The oxidation state of an ion is equal to its charge

The sum of oxidation states of all atoms in a neutral molecule must add to 0 Oxygen has an oxidation state of -2 unless in the form of a peroxides where it is -1 and in

F2O where it equals +2.

Hydrogen has an oxidation state of +1 unless in the form of a metal hydride (-1)

Gather and present information on the structure and chemistry of a dry cell or lead-acid cell and

evaluate it in comparison to button cell, fuel cell, vanadium redox cell, lithium cell, liquid junction

photovoltaic device.

The lead-acid cell is the cell in the common motor car battery. Six such cells are joined together in

series to make a car battery. In the one cell the positive and negative electrodes each consists of

several plates joined together to maximise the area of contact between electrode and electrolyte

which allows the cell to deliver a large current. The electrode plates are close together: this also

increases the current the cell can deliver.

Lead-Acid cell Silver-Oxide Button Cell

Chemistry Anode:

Cathode:

Overall:

Electrolyte: 4M Sulfuric Acid

Voltage: 2V

As the reaction proceeds, the electrodes

are coated with insoluble lead sulfate and

the concentration of sulfuric acid

Anode:

Cathode:

Overall:

Electrolyte: KOH

Voltage:1.5V

This cell delivers a very constant voltage

throughout its lifetime, because as it operates

there is no change in concentration of the


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Richard Shaw

decreases. However the reaction can be

reversed and driven so that the cell is

restored to its original condition, by

applying a high voltage. Therefore the leadacid cell is rechargeable.

electrolyte solution. This cell also delivers a high

voltage for its small size. This cell is not

rechargeable.

Cost and

Practicality

Relatively cheap and suitable

for situations where large bursts

of current are needed (e.g. car

batteries). It is however,

expensive compared to other

smaller cells

Rechargeable, this means it has

a long lifespan and is more cost

effective

Low maintenance, reliable

Heavy duty casing makes it

robust and durable

Its large size constrains its use in

smaller applications

Voltage drops as lead sulfate

gradually precipitates out; needs

to be recharged when thisoccurs

Very practical: very small and

portable so can be used in small

appliances such as watches, hearing

aids and pace makers.

Steady voltage delivered over life

space as all reactant and products are

solids and are not depleted.

Long shelf life as the electrolyte is not

used up

More expensive than an ordinary dry

cell

Impact on

Society

Used to electrically star cars and

heavy machinery which use

petrol and diesel engines

Allows development of starters

in cars and trucks, allowing

them to become an efficient

method of transport-unlike

previous manually started cars

Impacted on societydemographics, allowing for

urban sprawl with transport

becoming efficient

Has increased the portability and

miniaturization of electronics

Has been extremely important in a

number of specialist areas such as in

hearing aids and pace makers which

have greatly improved the quality of

life for these people.


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Richard Shaw

Lead Acid Cell

Silver-Oxide Button Cell

Impact on the

Environment

Materials used are potentially

damaging to the environment:

Pb is a heavy toxic metal (can

cause anaemia and affect brain)and sulfuric acid is corrosive

Explosive hydrogen gas is

released on recharging

Silver is a precious, expensive metal

and needs to be recycled

KOH electrolyte solution is caustic

No highly toxic materials that willsignificantly harm the environment.


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Richard Shaw

Describe and explain galvanic cells in terms of oxidation/reduction reactions

Outline the construction of galvanic cells and trace the direction of electron flow

Define the terms anode, cathode, electrode and electrolyte to describe galvanic cells

Electrodes:The combination of conductor and associated ion solution through which electrons

enter or leave a cell

Anode:The electrode at which oxidation occurs

Cathode:The electrode at which reduction occurs

Electrolyte:A substance which in solution or molten state conducts electricity.

5.

Nuclear chemistry provides a range of materials

Distinguish between stable and radioactive isotopes and describe the conditions under which a

nucleus is unstable

Radioactive isotopes are those that have an unstable nucleus and spontaneously emit radiation in

the form of , or radiation. Stable isotopes have a nucleus that remains unchanged over time

and do not emit radiation.

In order for a nucleus to be stable, it must lie within the zone of stability. In order for this to

occur, the nucleus cannot be too large as it must have an atomic number less than (or equal to) 83.

It must also have a suitable neutron to proton ratio. For Z


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Richard Shaw

In 1994 they produced darmstadtium and roentgeium by bombarding a nickel-64 nucleus into lead

and bismuth respectively.

Since 1982 at total of 6 transuranic elements have been produced, all through the use of the GSIs

Universal Linear Accelerator capable of producing 20MeV per nucleon. Although these elements

are now established, they usually have extremely short half-lives and are produced in extremely

small quantities. In the case of darmstadtium, the required reaction only takes place at a very

specific velocity of the nickel-64 nucleus, and the produced darmstadtium decayed in a thousandth

of a second. These recently developed elements are still nothing more than a novelty, but with

continuing development and research they may one day be applicable in society.

Describe how transuranic elements are produced

Transuranic elements are non-naturally occurring elements and have an atomic number

greater than 92 and they are produced through various means such as neutron

bombardment, linear accelerators, cyclotrons and synchrotrons.

Neutron Bombardment:

Bombardment with high speed positive particle:

Use available evidence to analyse benefits and problems associated with the use of radioactive

isotopes in identified industries and medicine

Benefits:


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Richard Shaw

Medical Imaging: new range of non-invasive diagnostic methods which are more efficient

and effective at detecting abnormalities such as tumours. This allows cancer to be detected

earlier and hence allowing for medical intervention.

Radiotherapy: Isotopes such as I-123 and C0-60 can be used to treat tumours and cancerouscells more effectively that other available methods

Food sterilization: irradiation of food and medicine by radioisotopes results in increased

shelf life and indirect health benefits in not consuming diseased/decaying food

Product quality testing: non destructive way for testing for cracks and damage. Sr-90 can be

used to gauge the thickness of paper while Na-24 is used to detect pipe leakage. Ir-192 used

in gamma radiography. Such monitoring equipment is sensitive, precise, efficient and

reliable.

Biochemistry studies: Cl-36 can be used to monitor methods of ion transport around a plant,

leading to further understanding of the roles of certain nutrients

Safety assessments: identifying cracks in bridges, planes and large scale machinery allowsprevention of serious accidents. Am-241 used in smoke detectors can potentially save lives

Problems

Health issues: tissue damage, immediate skin burns, nausea, sicknesses such as leukemia and

lung cancer and eventually death

Genetic mutation

Enzyme denaturing, disruption of protein synthesis

Radioisotopes are expensive and difficult to store as they continuously emit radiation

Potential for large scale nuclear disaster from nuclear reactors.

Describe how commercial radioisotopes are produced

Commercial radioisotopes are usually formed by neutron bombardment, in cyclotrons or as

by-products of fission reactions. Neutron bombardment produces neutron rich isotopes

whereas cyclotrons generally produce neutron poor isotopes.

Linear accelerators are not used to produce commercial radioisotopes as they are extremely

large and powerful and their use is restricted to scientific study purposes

Example:cobalt-60 is produced by neutron bombardment of cobalt-59 and technetium-99m is

produced by the decay of molybdenum-99 which is obtained as a fission product of uranium-235 or

from neutron bombardment of molybdenum-98. Fluorine-18 (used for PET) is obtained by

bombarding nitrogen with a helium nucleus.

Identify instruments and processes that can be used to detect radiation

Photographic film/Dosimeter: when exposed to radiation the film darkens and indicates the

level of exposure and is used in dosimeters by laboratory workers.

Geiger-Muller Counter: Metal tube filled with argon gas. Radiation ionises the gas particles

and a high voltage accelerates the charged particles. The free electrons are accelerated

towards a central electrode. The electrons progressively gain energy and cause further

ionisation so that a cascade of electrons reaches the electrode. This movement of charge


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Richard Shaw

generates a current which is recorded. The size of the current indicates the incident

radiation and is thus used to detect and measure its magnitude.

Scintillation Counters: Radiation causes a scintillating substance such as zinc sulfide to

produce a light pulse when struck by radiation. These flashes of light are counted

electronically using a photomultiplier and indicate the amount of incident radiation

Wilson Cloud Chamber: Super saturated ethanol or water is cooled by dry ice. Radiation

ionises the vapor causing the formation of liquid droplets on the ions so that the radiationpath is visible. The different types of radiation leave different sized tracks and curve in

different directions under the influence of electric plates.

Identify one use of a named radioisotope in:

Industry Sodium-24 and Medicine Technetium-99m

Describe the way in which the above named industrial and medical radioisotopes are used and

explain their use in terms of their chemical properties

Sodium-24

Formed by deuteron bombardment of Sodium-23, Na-24 has greatly enhanced the industrial means

of leak detection in water and oil pipelines. Sodium-24 is reactive with a lot of elements and this

allows it to be combined into soluble compounds before being released safely into pipelines.

Sodium-24 is chemically non-toxic leaving the pipes contents safe for human and animal use.

Sodium-24 is a beta and low intensity gamma radiation emitter. No radiation from this radioisotope

will be detectable if there is no leak present in the pipe. But if a leak is present, then sodium-24will leak into the pipes surroundings and radiation can then be detected. Sodium-24 has a

relatively short half-life of 15hrs meaning that the radioactivity of the pipes contents quickly

decays and the products of this decay pose no threat to humans or animals. Without the use of

sodium-24, leak detection was both expensive and time consuming as entire piping systems had to

be unearthed. Sodium-24 has improved this industrial process significantly in terms of efficiency,

precision, sensitivity and reliability.

On the other hand, as with the use of any radioisotope, sodium-24 also poses some problems.

Sodium-24 is a non-naturally occurring radioisotope, relying on the commercial production of the


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Richard Shaw

substance in a nuclear reactor. This poses the threat of possible large scale nuclear disaster (i.e.

Chernobyl). The short half-life of Na-24 also means that the pipeline area to be tested must be

reasonably close to a nuclear reactor. And as with any radioisotope exposure for

technicians/industrial workers can cause biological damage such as tissue damage or even cancer.

Technetium-99m

Technetium is produced by the neutron bombardment of molybdenum-98 to form molybdenum-

99 which then slowly decays to form Tc-99m, a meta-stable form of Tc-99. Chemically Tc-99m is

quite reactive and has multiple oxidation states; this property is beneficial as it allows Tc-99m to be

bound to different compounds for a variety of purposes. Combined with a tin compound it can

bind to red blood cells, allowing the circulatory system to be mapped and bleeding/clot sites to be

detected. When combined with a pyrophosphate ion Tc-99m sticks to calcium deposits in damaged

heart tissue, allowing for myocardial perfusion imagery. Sulfur colloid can also be combined with

Tc-99m to be taken up by the liver or spleen, making imaging of these organs easier. Tc-99m emitslow energy gamma radiation, minimizing the damage to healthy tissue and the high penetrative

ability of gamma radiation even at low intensity allows the radiation to be detected outside the

body. Tc-99m has a half life of 6hrs, this is also beneficial as there is minimal exposure to radiation

for the patient. However, such a short half-life also means the source of the radioisotope must be

very close to the hospital or produced on site with a cyclotron. As with any commercial

radioisotope its production using a nuclear reactor or cyclotron poses a risk for a potentially large

scale nuclear disaster. Its use also poses risks for technicians, scientists, medical staff and the patient

if they are subject to prolonged exposure. Gamma radiation can cause considerable tissue damage,

genetic mutation, enzyme denaturing and disruption to protein synthesis. Tc-99m exposure is kept

to a minimum when not in use by storing in a lead case. Although care must be taken in its use, Tc-

99m has greatly enhanced diagnostic techniques in medicine.


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Richard Shaw

Color Red Purple Violet Blue Blue-Green Greenish Yellow

Conclusion: We were successfully able to prepare and test a natural red cabbage indicator.

Identify that indicators such as litmus, phenolphthalein, methyl orange, and bromothym ol blue

can be used to determine the acidic or basic nature of a material over a range, that the range is

identified by change in indicator colour

Identify data and choose resources to gather information about the colour changes of a range of

indicators

Identify and describe some everyday uses of indicators including testing of soil acidity/basicity

Testing Soil

1.

Moisten soil with water and add universal indicator

2.

Place some BaSO4power onto the soil surface

3. The white powder absorbs the soil water and the indicator colour can be readily seen

against the white background.

Some plants like azaleas need acidic soils while most flowering plants and vegetables need neutral

or slight basic soils

Pool Testing

1.

Take a small sample of the water in a test tube and add an indicator such as phenol red

or universal indicator

2.

Place and compare against a white background to easily identify the colour and thenrefer to a colour chart

If pH is above 7.4 then green algal scum will form

If pH is below 7 then water will irritate eyes. Hypochlorite salts manage pool pH

Waste from laboratories must be monitored as the waste must be in the acceptable pH range so as

to minimize environmental harm and meet regulations. Photographic film waste is almost always

highly alkaline and must be neutralized.


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Richard Shaw

7. While we usually think of the air around us as neutral, the atmosphere naturally

contains acidic oxides of carbon, nitrogen and sulfur. The concentration of these

acidic oxides have been increasing since the Industrial Revolution

Identify oxides or non-meals which act as acids and describe the conditions under which they act

as acids

An acidic oxide is one which either:

Reacts with water to form an acid or

Reacts with bases to form salts (or does both)

A basic oxide is one that:

Reacts with acids to form salts but

Does not react with alkali solutions

Oxides that react with acids to form salts, but also react with alkalis are known as amphoteric

oxides. Neutral oxides are those that do not react with acids or bases.

Identify data, plan and perform a first-hand investigation to de-carbonate soft drink and gather

data to measure mass changes involved and calculate the volume of gas released at 25C and 100kPa

Aim: To de-carbonate a soft drink and gather data to measure the mass changes involved and

calculate the volume of as released at 25C and 100kPa

Equipment:electronic scales, 375mL can of unopened soft drink, empty 800mL bottle with lid,

filter funnel

Method:

1)

Measure the mass of the empty 800mL bottle and lid using the electronic scale

2) The 375mL can of soft drink was opened and poured into the 800mL bottle using the filter

funnel.

3) Re-weigh the 800mL bottle

4) Seal the bottle and shake vigorously for 10 seconds.

5) Re-open the bottle slowly to allow any gases to escape

6)

Re-weigh the 800mL bottle

7) Repeat until a constant mass is measured

8) Calculate the amount of CO2released from the change in mass.


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Richard Shaw

Discussion:Shaking the bottle increases the movement of the particles and hence their kinetic

energy. This in turn causes an increase in temperature. Since the dissolution of CO2is an

exothermic equilibrium reaction, by Le Chateliers Principle the equilibrium will shift so as to

minimise the disturbance, that is, minimise the change in temperature. Hence, the backwardendothermic reaction will be favoured, shifting the equilibrium to the left and reducing the

solubility of the CO2. The loss in mass throughout the experiment is due to the loss of CO2escaping

from the bottle.

Droplets of water lost during the experimental method means that the apparent mass

of CO2is larger than the actual case. This is minimised by opening the lid slowly

Decimal rounding on the electronic balance created inaccuracy

The small mass of CO2lost means that there is a large percentage of error

Validity is reduced as the conditions were strictly kept at 25C and 100kPa.

Conclusion: We successfully de-carbonated a soft drink and measured the mass changes.

Analyse the position of these non-metals in the Periodic Table and outline the relationship

between position of elements in the Periodic Table and acidity/basicity of oxides

Acidic oxides are generally oxides of non-metals:

These are mostly covalent compounds and form covalent bonds with oxygen gas

They are located towards the right-hand side of the periodic table and are concentrated in

the top right-hand corner of the periodic table with the exception of noble gases

Basic oxides are generally oxides of metals:

They are mostly ionic compounds

They are located towards the left-hand side of the periodic table and increase in character

towards the bottom-left corner as the metallic character of the metals increases

Amphoteric oxides are generally oxides of semi-metals and are located near the borderline between

metals and non-metals.

Analyse information from secondary sources to summarise the industrial origins of sulfur dioxide

and oxides of nitrogen and evaluate reasons for concern about their release into the environment

Oxides of sulfur and nitrogen are a reason for concern due to the adverse effects they have on the

environment and its inhabitants, including humans. Sulfur dioxide and nitrogen dioxide are

respiratory irritants and at concentrations as low as 1ppm can cause breathing difficulties,

aggravating asthma and emphysema. Prolonged exposure to sulfur dioxide can also lead to increasesusceptibility to bronchitis, and nitrogen dioxide can cause other lung infections and tissue damage.

Nitrogen dioxide is also harmful to vegetation and damages plant foliage. Oxides of nitrogen also

lead to the formation of photochemical smog when sunlight acts upon NO2to form ozone. This is

both visually unattractive and a health hazard.


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Richard Shaw

Another major concern for the release of oxides of nitrogen and sulfur into the environment is that

they lead to the formation of acid rain. Acid rain damages plant leaves, changes acidity of lakes and

rivers killing fish eggs and pH sensitive plants and animals. Soil pH is also affected which leads to

the biological magnification of heavy and toxic metals such as aluminium as well as the leeching ofminerals. Direct evidence in the form of quantitative analysis of Antarctic ice cores by the CSIRO

and indirect evidence through the increased occurrence of acid rain both indicate increasing

concentrations of oxides of sulfur and nitrogen in the air. With these increasing concentrations, it

is clear that such oxides are a concern to the environment and its inhabitants as it has numerous

adverse effects.

Define Le Chateliers principle

If a closed system at equilibrium is disturbed, then the equilibrium will shift so as to minimise the

disturbance.

Identify factors which can affect the equilibrium in a reversible reaction

Factors affecting the equilibrium of a reversible reaction:

Temperature

Pressure (partial)

Concentration

Describe the solubility of carbon dioxide in water under various conditions as an equilibrium

process and explain in terms of Le Chateliers principle

If the concentration (pressure) of CO2is increased, then some CO2goes into solution as

H2CO3to try to counteract the increase; the equilibrium shifts to the right. If the pressure of

CO2decreased, then some H2CO3decomposes to CO2and comes out of solution to try and

counteract the decrease, and the equilibrium shifts to the left.

If the total pressure of the reaction system is increase, the equilibrium moves in the

direction that tends to reduce pressure. Some CO2dissolves, the equilibrium shifts right.

The formation of carbonic acid from carbon dioxide and water is exothermic. This means

that as it proceeds from left to right, heat is liberated, and conversely as it goes from right to

left heat is absorbed. Thus, if we increase the temperature of this reaction the equilibrium

will move to the left in order to counteract the increase in temperature.A word of caution is needed about the effect of increasing the total pressure of the system. If we

had increased the total pressure by pumping in some nitrogen or argon into the vessel, this would

have had no effect upon the equilibrium because it would not have changed the pressure of CO2.

Another way of increasing CO2solubility is to make the solution alkaline. If there is OH-in the

solution, then carbonic acid reacts with it, effectively removing the product from the reaction of

water with carbon dioxide. The equilibrium then moves to try and counteract this, so more CO2

dissolves to form H2CO3which in turn reacts with OH-and so on. This illustrates an affective

method of forcing an equilibrium reaction to completion-remove the product as it form.


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Richard Shaw

Identify natural and industrial sources of sulfur dioxide and oxides of nitrogen

Natural Sources Industrial Sources

Sulfur Dioxide

0.001ppm)

Volcanoes and geothermal hot

springs

Burning of sulfur containing fossil fuels

Metal extraction from their sulfide ores,

such as the smelting of ZnS

Nitric Oxide High localized temperatures

provided by lightning strikes

Formed due to high temperatures in

combustion chambers, such as at power

stations and motor vehicles.

Nitrogen Dioxide

0.001ppm)

Oxidation of NO Formed due to high temperatures in

combustion chambers, such as at power

stations and motor vehicles.

Nitrous Oxide The action of bacteria on

nitrogenous materials in soils

Increased uses of nitrogen based

fertilizers has increased the amount of

nitrous oxide released.

Describe, using equations, examples of chem ical reactions which release sulfur dioxide and

chemical reactions which release oxides of nitrogen

Assess the evidence which indicates increases in atmospheric concentration of oxides of sulfur and

nitrogen

Despite there being no evidence for a global increase in the concentrations of these oxides there is

both direct and indirect evidence suggesting the atmospheric concentrations of oxides of sulfur and

nitrogen have been increasing in localized areas. Qualitative analysis of Antarctic ice cores by the

CSIRO has shown a steady increase in concentrations of these oxides in the past few decades. Also,

while the averages in cities has not increased significantly, the number of days where

concentrations have exceeded safety levels has been increasing. Such quantitative evidence is

slightly unreliable as the levels of these oxides are below 0.01ppm and hence it is difficult to

measure their concentrations to a sufficiently high degree of accuracy. Also, before the 1950s is no

reliable data, and it wasnt until the 1970s with the development of infra-red spectroscopy that


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Richard Shaw

more accurate measurement could be made. Sulfur dioxide and nitrogen dioxide can be washed out

of the atmosphere, reducing direct evidence reliability.

On the other hand, indirect evidence also suggests increasing concentrations of these oxides in

localized regions. The increasing incidence of acid rain as well as the increasing incidence ofpollution and photochemical smog both suggest increasing concentrations of oxides of sulfur and

nitrogen. However, this evidence is also flawed as it is indirect, and hence is affected by various

other variables that reduce its validity. Overall, although we do not have evidence to suggest a

global increase in the concentration of these oxides, there is an increasing amount of quantitative

and qualitative data that suggest the localized concentrations of oxides of sulfur and nitrogen have

been increasing since the industrial revolution.

Explain the formation and effects of acid rain

Rain is naturally acidic due to the dissolution of carbon dioxide forming weak carbonic acid. Acid

rain refers to rain that has a higher hydrogen ion concentration than normal-higher than about 10-5mol/L. Acid rain occurs due to the dissolution of acidic oxides in the atmosphere. Sulfur dioxide is

one such acidic oxide which is produced by natural means such as volcanoes and geothermal hot

springs and industrial processes such as the burning of sulfur containing fossil fuels and metal

extraction from sulfide ores.

Burning of fossil fuels:

Burning of Zinc Sulfide:

The other major acidic oxide that contributes to the formation of acid rain is nitrogen dioxide.

Nitric oxide is formed in high localized temperatures created by lightning strikes and naturally

reacts in the atmosphere to produce nitrogen dioxide. Nitrogen dioxide is also produced in the hightemperatures of combustion chambers of power stations and motor vehicles.

Formation of Nitrogen Dioxide:

Both sulfur dioxide and nitrogen dioxide are acidic oxides and react with water to form acids.

Sulfur dioxide reacts with water to form sulfurous acid.

Substances in the upper atmosphere then catalyse the reaction between sulfurous acid and oxygen

to from sulfuric acid.

Similarly, nitrogen dioxide reacts with water to form a mixture of nitric acid and nitrous acid.

Substances in the atmosphere then catalyse the reaction between nitrous acid and oxygen causing

the formation of more nitric acid.

Both sulfuric acid and nitric acid are soluble in water and are the major acids present in acid rain.

As this rain forms and falls onto the Earths surface, these strong acids are also brought to the

surface causing harmful effects on the built and natural environment.

Acid rain damages plant leaves and has cause mass defoliation of pine forests in Europe and USA.

Acid rain changes acidity of lakes and rivers killing fish eggs and pH sensitive plants and animals.


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Richard Shaw

Soil pH is also affected which leads to the biological magnification of heavy and toxic metals such

as aluminium as well as the leeching of minerals vital to the survival of flora. Acid rain also causes

damage to concrete, marble, limestone and sandstone buildings and statues (Notre Dame).

It is clear that acid rain has a wide range of negative effects on the natural and built environment.

It is only through the regulation of release of acidic oxides such as SO2and NO2that acid rain can

be minimised.

8. Acids occur in many foods, drinks and even within our stomachs

Define acids as proton donors and describe the ionisation of acids in water

According to the Bronsted-Lowry theory of acids and bases, an acid is a proton donor while a base

is a proton acceptor. In water, an acid will donate a proton to the water molecule to form its

conjugate base. Also, water is acting as a proton acceptor, that is, water is acting as a base and

forming its conjugate acid.

Solve problems and perform a first-hand investigation to use pH meters/probes and indicators to

distinguish between acidic, basic and neutral chemicals

Aim:To use pH meters/probes and indicators to distinguish between acidic, basic and neutral

chemicals.

Equipment:litmus paper, methyl orange, phenolphthalein and bromothymol blue indicators, pH

meter, spot plate, test tubes, 0.1M solutions of HCl, acetic acid, citric acid, NaOH, ammonia and

distilled water.

Risk Assessment:Acids and bases are corrosive and caustic and so caution must be taken to avoid

contact with skin, eyes and clothing. Safety goggles should be worn.Method:

1) 5mL of each solution was poured into a separate test tube

2) The pH meter was removed from its storage solution and the sensitive glass probe was

washed with distilled water and then patted dry

3) The probe was immersed in the HCl and the reading was recorded

4) This was repeated for all solutions, taking care to re-wash, dry and calibrate with each

reading.

5) Using dropper bottles, 4 drops of each indicator was placed on the spot plate.

6) Using a dropper bottle, 3 drops of each of the solutions was added to the indicators and the

resultant colour changes were recorded.Conclusion: We were able to use pH metres and indicators to distinguish between acidic, basic and

neutral chemicals.

Identify acids including acetic ethanoic), citric 2-hydroxypropane-1,2,3-tricarboxylic),

hydrochloric and sulfuric acid


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Richard Shaw

Acetic Acid Citric Acid Sulfuric Acid

Plan and perform a first-hand investigation to measure the pH of identical concentrations of strong

and weak acids

Aim: To measure and compare the pH of identical concentrations of hydrochloric acid, acetic acid

and citric acid

Equipment:pH meter, 0.1M solutions of HCl, acetic and citric acids, 3 test tubes, test tube rack

Risk assessment: Acids and bases are corrosive and caustic and so caution must be taken to avoid

contact with skin, eyes and clothing. Safety goggles should be worn.

Method:

1)

10mL of each solution was pipetted into a separate test tube on the test tube rack.



3) The probe was immersed in the HCl and the reading was recorded


reading.

Discussion:The pH of HCl was 1. The pH of acetic acid was 2.9. The pH of citric acid was 2.1.

Conclusion: We were able to measure and compare the pH of identical concentrations of strong

and weak acids.

A pH meter is an instrument that directly measures the pH of a solution. The sensing device

consists of a pair of electrodes. The measuring electrode consists of a thin glass membrane which

develops and electrical potential which depends on the pH. The other electrode is a reference

electrode. When these electrodes are immersed in a solution they form a galvanic cell, and the

EMF of this cell is converted in a pH reading. Using a pH meter is a non-destructive testing method

as it does not alter the chemical equilibrium involved and leaves the solution unchanged.

Describe the use of the pH scale in comparing acids and bases


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Richard Shaw

Gather and process information from secondary sources to write ionic equations to represent the

ionisation of acids

Describe acids and their solutions with the appropriate use of the terms strong, weak, concentrated

and dilute

Use available evidence to model the m olecular nature of acids and simulate the ionisation of strong

and weak acids

Identify pH as log

10

[H

+

] and explain that a change in pH of 1 means a ten-fold chan ge in [H

+

]

Note: The number of significant figures in the hydrogen ion concentration determines the number

of decimal places of the pH and vice versa.

Gather and process information from secondary sources to explain the use of acids as food additives

Acids are often added to food during manufacturing or processing. There are several reasons for

this:

Acids lower the pH of the food and its container which has the effect of killing

microorganisms such as bacteria that are responsible for the spoiling of food.

Acids acts as anti-oxidants and so prevent spoilage by slowing the oxidation of oils

Acids may be added to improve taste by adding a certain tangy or tartness flavour

The common acids used for such purposes are acetic acid, citric acid and occasionally phosphoric

acid. Propanoic acid is often used as a preservative in bread.

Compare the relative strengths of equal concentrations of citric, acetic and hydrochloric acids and

explain in terms of the d egree of ionisation of their molecules

Hydrochloric acid is a strong acid and has a degree of ionisation of 100%

Citric acid is a weak acid and has a degree of ionisation of 7.94%

Acetic acid is a weak acid and has a degree of ionisation of 1.26%

Identify data, gather and process information from secondary sources to identify examples of

naturally occurring acids and bases and their chemical compositon

HClis produced by glands in the lining of our stomachs to form an acidic environment for the

efficient operation of enzymes that break some complex food molecules into easily transportablesmall molecules that are absorbed into the blood stream when they pass into the intestine.

Acetic Acid present in vinegar which is commonly made from the natural oxidation of the ethanol.

Citric Acid occurs in citrus fruits, and is also made industrially and widely used as a food additive.

Ascorbic Acidoccurs widely in fruits and vegetables and essential to our health and well being.

Formic Acidis a naturally occurring acid in ant and bee stings.

Ammoniapresent in the stale urine of humans and other animals. Formed by the anaerobic decay

of organic matter.


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Richard Shaw

Amineshave a strong fishy smell and are weak bases that are also formed in the anaerobic

decomposition of organic matter.

Metallic oxides occur naturally in the lithosphere

Hydrogen Carbonatea naturally occurring base in the blood.

Describe the difference between a strong and w eak acid in terms of an equilibrium reaction

between the intact m olecules and its ions

A weak acid exists in equilibrium between the intact molecules and its ions. A strong acid does not

exist in equilibrium and all the molecules are disassociated and exist as ions in solution.

Process information from secondary sources to calculate pH of strong acids given appropriate

hydrogen ion concentrations

9. Because of the prevalence and importance of acids, they have been used and studied

for hundreds of years. Over time, the definitions of acids and bases have been refined

Outline the historical development of ideas about acids including those of:

- Lavoisier

- Davy

- Arrhenius

Originally, an acid was a substance that had a sour taste and which reacted with certain metals. In

1776, Antoine Lavoisier proposed that acids were substances that contained oxygen. While this is

clearly wrong due to the existence of many acids lacking the presence of oxygen such as HCl andHBr, Lavoisiers proposal was significant as it was the first attempt to classify acids by their

chemical properties/structure.

In 1815 Humphrey Davy attempted to rectify Lavoisiers proposal by studying hydrochloric acid

and hydrogen cyanide. Their obvious lack of oxygen led to Davy proposing that all acids contained

replaceable hydrogen-hydrogen that could be partly or totally replaced by metal ions. When acids

reacted with metals, they formed salts and bases were substances that reacted with acids to form

salts and water. Davy provided the first working definition of an acid and base, but was still unable

to justify why many substances contained replaceable hydrogen but were not acidic, and why

substances with acidic properties did not contain hydrogen such as SO2and NO2. He was alsounable to explain how both acids and bases could conduct electricity.

In 1884 Svante Arrhenius proposed that an acid was a substance that produces hydrogen ions in

solution, and a base produced hydroxide ions in solution. This allowed Arrhenius to explain and

generalize acid-base reactions by the net ionic equation:

Arrhenius went further and classified acids as strong or weak depending on their degree of

ionisation in solution (strong acids ionised completely, weak acids do not). The shortcomings of


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this definition lie in the fact that it does not give due recognition to the solvent as the degree of

ionisation is dependent not only on the acid but also the solvent. For example, HCl is a strong acid

in water but when dissolved in diethyl ether is quite weak. Also, acid-base reactions often do not

require hydrogen or hydroxide ions to be produced. HCl and react with ammonia to formammonium chloride salt without needing to be ionised in solution.

Finally, in 1923 Johannes Bronsted and Thomas Lowry independently proposed a new, and

currently accepted definitions of acids and bases. The Bronsed-Lowry theory defines an acid as a

proton donor and a base as a proton acceptor. Bronsted-Lowry theory explained the inadequacies

of previous definitions as it allowed neutralization to proceed by direct proton transfer reactions

and gave recognition to the role of the solvent in the ionisation process.

Note: You may need to go on to talk about conjugates and the relationships between and possibly

mention this theories impact on the pH of salts.

Gather and process information from secondary sources to trace developments in understanding

and describing acid/base reactions

Choose equipment and perform a first-hand investigation to identify the pH of a range of salt

solutions

Aim:To identify the pH of a range of salt solutions

Equipment: pH meter, 5 large test tubes, test tube rack, 0.1M solutions of potassium sulfate,

ammonium chloride, sodium acetate, sodium chloride and ammonium nitrate.

Risk Assessment:Acidic and basic substances are corrosive and caustic and so caution must be

taken to avoid contact with skin, eyes and clothing. Safety goggles should be worn.

Method:

1) Place 15mL of each solution into a separate test tube on the test tube rack



3) The probe was immersed in the NaCl solution and the reading was recorded


reading.

Discussion:

0.1M Solution pH Reading

Potassium Sulfate 7.1

Ammonium Chloride 6.2

Sodium Acetate 8.2

Sodium Chloride 7.1

Ammonium Nitrate 6.1

Conclusion: We were able to identify the pH of a range of salt solutions.

Outline the Brnsted-Lowry theory of acids and bases


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In 1923 Johannes Bronsted and Thomas Lowry independently proposed a new, and currently

accepted definitions of acids and bases. The Bronsed-Lowry theory defines an acid as a proton

donor and a base as a proton acceptor. Bronsted-Lowry theory explained the inadequacies of

previous definitions as it allowed neutralization to proceed by direct proton transfer reactions andgave recognition to the role of the solvent in the ionisation process.

Note: You may need to go on to talk about conjugates and the relationships between and possibly

mention this theories impact on the pH of salts.

Perform a first-hand investigation and solve problems using titrations and including the

preparation of standard solutions, and use available evidence to quantitatively and qualitatively

describe the reaction between selected acids and bases

Aim: To determine the concentration of sodium hydroxide

Equipment list:volumetric flask, funnel, electronic scales, retort stand, clamp, burette, pipette,

conical flask, oxalic acid (anhydrous), sodium hydroxide, phenolphthalein indicatorRisk Assessment:Acids and bases are corrosive and caustic and so caution must be taken to avoid

contact with skin, eyes and clothing. Safety goggles should be worn.

Method:

Part 1-Preparing a Primary Standard

1)

2.25g of oxalic acid was weight out using an electronic balance and transferred into a clean

beaker. The oxalic acid was dissolved by adding a suitable amount of demineralised water.

2) Using a funnel, the oxalic acid solution was transferred to a clean 250mL volumetric flask

3) The volumetric flask was filled with demineralised water until the bottom meniscus was

level with the 250mL graduation mark.

4)

The flask was stoppered and gently inverted, before being labeled 0.1M oxalic acid.

Part 2-Titration

1) A Pipette was filled with 25mL of the oxalic acid solution and transferred to a conical flask,

that had previously been rinsed with water

2) 3 drops of phenolphthalein indicator was then added to the conical flask

3) The burette was filled with NaOH until the bottom of the meniscus reached the 0mL mark.

The burette was set up over the conical flask using a retort stand and clamp

4)

The NaOH was slowly run into the conical flask as the flask was swirled. A rough titre was

performed and then steps 1-4 were repeated to obtain 3 consistent titre volumes (within0.1mL)

5)

The concentration of the NaOH could then be calculated

Conclusion:We were successfully able to create a standard solution and conduct a titration using

this standard solution to determine the concentration of NaOH.

Describe the relationship between an acid and its conjugate base and a base and its conjugate acid

An acid donates a proton to form its conjugate base while a base accepts a proton to form its

conjugate acid.


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Identify a range of salts which form acidic, basic or neutral solutions and explain their acidic,

neutral or basic nature

Perform a first-hand investigation to determine the conc entration of a domestic acidic substance

using computer-based technologies

A titration of acetic acid can be made easier using a pH probe and data logger to generate a curve of

pH as the volume of acid added is increased. From this titration curve, the equivalence point and

volume acid needed to reach this point can be determined.

Identify conjugate acid/base pairs

Identify amphiprotic substances and construct equations to describe their behaviour in acidic and

basic solutions

Analyse information from secondary sources to assess the use of neutralisation reactions as a safety

measure or to minimise damage in accidents or chemical spills

Neutralisation is a reaction between an acid and a base and is an exothermic process that involves

the transfer of protons. Many acids and bases pose a health hazard as they are often highly


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corrosive, and hence it is important to neutralize any spills that occur as fast as possible. In addition

sewage authorities put strict limits on the pH of laboratory and factory effluents discharges to

sewers. The acid/base used in the neutralization process must be chosen carefully, being acids or

bases themselves they too pose a health hazard. An ideal substance to use will react quickly toneutralize a spill, will not cause harm if excess is used and is safe to handle. A weak acid or base

that is also cheap is ideal. Sodium hydrogen carbonate is an ideal substance often used in the

neutralization of spills as it is amphiprotic and hence can be used to neutralize both acid and base

spills. Furthermore, it is easy and safe to handle, cost effective and poses no threat if excess is used.

The utilization of neutralization has greatly helped in minimizing damage of accidents or industrial

waster. Despite some neutralization substances being a hazard themselves, their use has greatly

minimised the damage of acidic and basic chemicals.

Note: Neutralization is exothermic and thus cannot be used for body spills as it can cause burns

Identify neutralisation as a proton transfer reaction which is exothermic

Describe the correct technique for conducting titrations and preparation of standard solutions

Titration and Standard Solution Technique

Volatalisation of HCl and HNO3and absorption of water by H2SO4makes them unsuitable

primary standards. Similarly, NaOH and KOH both absorb moisture from the air and also

react with CO2and are thus not a suitable primary standard.

Anhydrous sodium carbonate, sodium hydrogen carbonate or oxalic acid (C2H2O4) is a

suitable primary standard.

Preparing a Standard Solution

1. Ensure that the substance being used as a primary standard is as pure as possible and

particularly that it is free of moisture (dry in oven, cool in dessicator)

2. Weigh as accurately as possible on electronic balance

3. Ensure volumetric flask has been thoroughly cleaned with pure water

4. Carefully transfer all solute from the measuring beaker into the volumetric flask

5. Ensure that the solute is completely dissolved before filling flask with water. The bottom of

the meniscus should sit on the graduation mark

6.

Final solution should be gently inverted or shaken to ensure uniform mixing

Using a pipette

To fill a pipette after rinsing with some of the solution first, the solution is drawn in using the

pipette filler until the solution is well above the graduation mark. The solution is then carefully

run out until the meniscus sits exactly on the mark. To do this it is essential that the pipette is held

at eye level to avoid parallax errors. The solution is then run out of the pipette into the conical

flask by gravity (not by blowing) and finally, the pipette is held with its tip in contact with the wall


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of the receiving flask or beaker. It is important that the final portion of liquid in the pipette is not

blown out as the pipette is already calibrated to take this into account.

Using a burette

Before filling a burette, it is rinsed with a portion of the solution to be dispensed. It is then

overfilled and the excess run out. During this procedure, care is taken to e

hsc chemistry summary richard shaw

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