Production of Materials Dennis Mok

1. Fossil fuels provide both energy and raw materials such as ethylene for the production of other substances

Fossil fuels are energy-rich substances having been formed in the Earth’s crust millions of years ago. Under intense heat and pressure, organic remains were gradually converted into petroleum.

We can extract and refine these fossil fuels to provide the energy requirements for machinery and to produce other forms of energy such as electricity. In addition, the basic building blocks of these chemicals can be used to create a multitude of more complex materials with different properties and uses.

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

Petroleum is a mixture of hydrocarbons. It consists of the liquid crude oil and the natural petroleum gas.

Both physical can chemical properties can be used to separate out the various compounds.

Fractional distillation: Liquid crude oil can be separated into a series of fractions containing molecules of roughly similar molecular weight.

Less useful larger molecules can be broken up into smaller and more useful molecules by cracking. This is achieved by breaking the covalent bonds within the larger compounds.

Steam/Thermal Crackingo High temperature (800oC)o Uses steam – inert dilatanto Absence of airo Just above atmospheric pressureo Keeps the concentration of gases low enough so it can flow

through the tubeso E.g. C3H8 → C2H4 + CH4

Catalytic crackingo Crack high molecular weight hydrocarbons to lower

molecular weights to increase the output of high demand products (e.g. octane and ethylene)

o Lower temperatures (500oC) o The catalysts commonly used for catalytic cracking are

silicon and aluminium oxides, or powdered zeolite.

o E.g. C10H22 → C8H18 + C2H4

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

Unsaturated hydrocarbons are quite reactive compared to the relatively inert saturated alkanes

The double bond in ethylene allows it to react readily with other molecules, thus making it useful as a starting point for many polymerisation reactions

The double bond means it readily undergoes addition reactions

Alkanes, on the other hand, undergo substitution reactions only under UV light

Addition: adding H2O into ethylene forms ethanol, adding HCl produces chloroethene, vinyl chloride, etc.

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

The double bond in the ethene molecule can be broken, and when this repeats hundreds and thousands of times, a polymer (polyethylene) is formed

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

Polyethylene consists of many ethene molecules joined together to form long chains of hydrocarbons

The double bond is broken and ethylene radicals are added onto it

An addition polymer is a formed by joining molecules together without the loss of any atoms, i.e. the double bond is simply opened and connects with neighbouring molecules

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

There are mainly two types of polyethylene produced: low density polyethylene and high density polyethylene

Steps in making polymers in generalo Initiation → Propagation → Terminationo Initiation: an initiator, e.g. peroxide

Low Density Polyethylene (LDPE)o Uses temperatures, around 300°C, and at very high

pressures, around 3000 atmospheres

o This does not use a catalysto An initiator such as oxygen, or an organic peroxide which

contains a –O-O- bond is usedo Both long and short chains are produced, and at some

carbons, the hydrogen is replaced by the alkyl groupo This means the polymer is unable to pack closely together,

reducing density, and the dispersion forces between the chains are weakened, reducing melting point and allows flexibility

High Density Polyethylene (HDPE)o This process uses lower pressure, only a few times

atmospheric pressure, and lower temperature, around 60°Co This type of polymerization requires the use of a Zeigler-

Natta catalyst, which are usually rare earth metal oxideso This polymer is relatively unbranched, allowing the chains

to pack closely together in an orderly fashiono There are larger crystalline regions which are rigido This reduces the space between molecules, and therefore

increases density, and the dispersion forces are stronger, making it more rigid and have a higher melting point

Identify vinyl chloride and styrene as commercially significant monomers by both their systematic and common names.

Vinyl Chloride o Systematic name: Chloroethene o Polymer: Polyvinylchloride (PVC)

Styreneo Systematic name: ethenylbenzene or phenyletheneo Polymer: Polystyrene

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

LDPEo Uses

Cling wrap, plastic bags, milk bottleso Properties

Flexible - chain branching prevents the molecules from lining up orderly which means the dispersion forces are spread out which means weaker intermolecular bonding. Therefore it is less rigid

Lower melting point – chain branching prevents the molecules from lining up in an orderly fashion

Chemically inert – After polymerisation, the molecule becomes saturated. Covalent bonds are strong, so chemically, it is very stable

HDPEo Uses

Kitchen utensils, wheelie bins, more rigid toyso Properties

Hard – virtually no chain branching meaning the molecules fit together in an orderly fashion. This makes HDPE crystalline and very strong

High melting points – when the molecules are packed together the strong dispersion forces hold it together hence more energy is required to break these bonds

PVCo Uses

Pipes, wire insulationo Properties

Hard – The C-Cl bonds are very electronegative, so the intermolecular forces are very strong. This makes PVC very hard

Plasticisers and inhibitors prevent UV from attacking the C-Cl bond. It can also soften it up to be used as wire insulation

Polystyreneo Uses

Tool handles, car battery cases, foam cupso Properties

Very hard – large phenyl side group means very strong intermolecular forces, makes it very rigid

Chemically stable – contains only C-C and C-H bonds which are very stable, making it resistant to chemicals and UV

Foam can be pumped into it to may polystyrene foam, used in cups

2. Some scientists research the extraction ofmaterials from biomass to reduce our dependence on fossil fuelsDiscuss the need for alternative sources of the compounds presently obtained from the petrochemical industry

Raw materials for making polymers come from crude oil, namely ethylene and propene

These are extracted from petroleum, or produced by the cracking of petroleum constituents, e.g. larger hydrocarbon chains

The majority of petroleum is used as petrol, and only a small percentage (5-10%) is used in the petrochemical industry

There is considerable concern that our oil reserves are going to run out, and diminishing resources will drive the price of petroleum up

Hence, there is a need to find a new source of raw materials and fuel

Some new sources of these raw materials include glucose and ethanol from agricultural crops.

These sugars are to be fermented to produce ethanol, and then this ethanol is dehydrated to form ethylene.

Explain what is meant by a condensation polymer A condensation polymer consists of two or more monomer units

which are linked together when their functional group reacts, emitting a small molecule in the process.

Describe the reaction involved when a condensation polymer is formed Condensation polymers are formed by the elimination of a small

molecule, often water, when two monomers are joined together n(HO-C6H10O4-OH) → H-(O-C6H10O4)n-OH + (n–1)H2O Nylon-6 is produced from the monomer unit 6-aminohexanoic

acid H2N-CH2-CH2-CH2-CH2-CH2-COOH The polymerisation equation is

o Ra-COOH + H2N-Rb → Ra-CO-NH-Rb + H2O Polyester – A polymer of ethylene glycol and terephthalic acid

Describe the structure of cellulose and identify it as a condensation polymer found as a major component of biomass

Monomer unit: Glucose During polymerisation, the linkage is a COC bond Each consecutive glucose unit is inverted Biomass is organic material derived from organic matter

including animals and plants They produce naturally occurring polymers known as

biopolymers Cellulose is the main constituent of plant cell walls, and it is the

most abundant polymer in the biosphere The strong hydrogen bonding and linear structure means that it

is rigid and very strongIdentify that cellulose contains the basic carbon-chain structures needed to build petrochemicals and discuss its potential as a raw material

Since glucose contains 6 Carbons chained together, it can be seen as a raw material for other petrochemicals with smaller carbon chains such as ethylene (2 carbons), propylene (3 carbons)

Then a chemical process can convert cellulose to a petrochemical Cellulose is broken down into glucose in two different ways

o Digestion by enzymeso Digestion by a strong acid (Moderately concentrated

sulphuric acid) o Both cases produce a solution of glucose

Cellulose → Glucose → Ethanol → Ethylene → Polymer Its potential to be used as a raw material is based on the fact

that it is renewable and contains the ethylene monomer within the molecule - it only needs to be separated

As the supply of petroleum decreases, alternative sources of petroleum products is required

Cellulose is readily available and is the main component of biomass which can be obtained from plants

Cellulose can also be obtained from waste products such as sawdust and woodchip, making which means that waste can be reused

However, food crops to make raw materials presents ethical problems as there are people starving in the world

3. Other sources, such as ethanol, are readily available from renewable resources such as plants

Describe the dehydration of ethanol to ethylene and identify the need for a catalyst in this process and the catalyst used

A H2O molecule is removed from ethanol to form ethylene A catalyst of concentrated H2SO4 is used The catalyst speeds up the reaction by sucking the H2O from the

glucoseo CH3CH2OH → CH2CH2 + H2O

Describe the addition of water to ethylene resulting in the production of ethanol and identify the need for a catalyst and the catalyst used

The addition of water to ethylene to produce ethanol is an addition reaction

The catalyst used is dilute H2SO4

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

Ethanol contains the –OH radical, and creates a permanent dipole, making the O slightly negative, H slightly positive

The intermolecular forces include dispersion forces, dipole-dipole interaction and hydrogen bonding due to the electronegative O

This means that ethanol is a polar molecule, and hence will dissolve other polar substances via dipole-dipole interactions and hydrogen bonds

The carbon chain means that it is also suitable for dissolving non-polar substances, allowing them to mix through the ethanol via dispersion forces

Because of this, it has many applications in industry, as a solvent to mix both polar and non polar substances, e.g. perfume

It also has applications in medicine, allowing substances which are insoluble in water to be taken as liquid

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

Ethanol undergoes complete combustion quite readily, and the reaction is very exothermic

o CH3CH2OH + 3O2 → 2CO2 + 3H2O ∆Hc=1367kJ/mol Currently it is being used to “extend” petrol up to 10% It is a renewable resource because it can be made from biomass

which can be regrown to replenish the consumed ethanolProcess information from secondary sources to summarise the processes involved in the industrial production of ethanol from sugar cane

A suitable fruit or grain containing simple sugars such as glucose, sucrose and fructose, or molasses are used as a raw material in producing ethanol

Solids are filtered out and the sugar solution is fermented It is fermented by yeast or other similar enzymes A higher concentration is produced by fractional distillation

Describe the conditions under which the fermentation of sugars is promoted

Anaerobic conditions at about 37oC Yeast is the enzyme which is used Glucose mixture

Summarise the chemistry of the fermentation process Enzymes ferment yeast into ethanol in anaerobic conditions

o C6H12O6(aq) → 2CH3CH2OH(aq) + 2CO2(g) o Yeast should be written on top of the arrow

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

The molar heat of combustion is the amount of energy released when one mole of substance undergoes complete combustion with oxygen at standard temperature and pressure

The products will only be water and carbon dioxide ∆Hc=-∆H

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

Advantageso Renewable: Ethanol can be produced by fermenting

biomass, which comes from plants which are renewable since more plants can be grown to replace used ones

o Burns more completely/cleanly: The oxygen in the ethanol molecule ensures that less oxygen is required to allow the complete combustion of a fuel. As a result, CO and C as by-products are reduced, which is beneficial to the environment as well as the engine

o 10% ethanol can be added to extend petrol with no modification to engines. This makes petrol supplies last longer.

Disadvantageso Lower heat of combustion: Ethanol produces less energy

per mole than octane, meaning cars can travel further on octane than the same amount of ethanol. Thus, ethanol may be more expensive

o Engines may get damaged from the water dissolved in ethanol: This is why engines need to be modified for fuels containing >10% ethanol. It is difficult to remove all the water during the distillation of ethanol, and hence the water will corrode engines

o Large areas of land needed: Large areas of land are required to grow crops for ethanol, so large areas will need to be cleared for this. This may require the clearing of forests and other natural areas.

o Technical difficulties: Ethanol is carbon theoretically carbon neutral, however, fossil fuels are required to power the process, hence it is somewhat redundant to use fossil fuels to make ethanol as a fuel

o Ethical problems: growing crops to make ethanol rather than food when there are starving people in the world may seem unethical

Judgemento Even though there are significant disadvantages, these can

be overcome technically, and it maybe inevitable that we will need to use renewable resources such as ethanol.

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

1: Methanol 2: Ethanol 3-8: [prefix]an-[number]-ol

o prefix is the length of the carbon chaino number is where the –OH group is located

4. Oxidation-reduction reactions are increasingly important as a source of energyExplain the displacement of metals from solution in terms of transfer of electrons

A metal displacement reaction is one which a metal converts another metal ion to its neutral atom by transferring one or more electrons

The metal ion gains electrons and is reduced The metal which displaces the other metal is oxidised

Identify the relationship between displacement of metal ions in solution by other metals to the relative reactivity of metals

A list of metals arranged in decreasing ease of oxidation is called the activity series

A metal of a more active metal placed in a solution of a less active metal ion will displace it from solution

E.g. Zinc is more active than coppero Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)o Zn is oxidised (more active) while Cu is reduced

K > Na > Mg > Al > Zn > Cr > Fe > Ni > Sn > Pb > H > Cu > Ag > Hg > Pt > Au

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

Why isn’t the voltage produced equal to the theoretical voltage?o Impurities in the electrodes will increase electrical

resistance and thus the experimental voltage will be less than theoretical

o If the salt bridge is not soaked sufficiently, the flow of ions is impeded so the voltage is reduced

When drawing a salt bridge make sure it is double lined

o Electrical resistance in wires means the not all of the electricity is measured

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

When a species gains electrons it is reduced, the oxidation number is decreased

When a species loses electrons it is oxidised, the oxidation number is increased

OILRIG: Oxidation is Loss, Reduction is GainOutline the construction of galvanic cells and trace the direction of electron flow

Oxidation and reduction reactions can be used to generate electricity if the reactions are physically separated

A wire connected to an external circuit can be used to facilitate the flow of electrons, and thus produces electricity (moving electrons)

This is known as a galvanic cello A galvanic cell consists of two half cellso Each half cell consists of a conductive metal in ionic

solution known as the electrolyteo A salt bridge connects the two electrolytic solutionso The purpose of the salt bridge is to allow the migration

of ions to occur, preventing a build up of electrical charge Electrons flow from the anode to the cathode

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

Anode: The electrode where oxidation occurs Cathode: The electrode where reduction occurs Electrode: The conductors of a cell which is connected to the

external circuit Electrolyte: The solution of ions which conducts electricity

Gather and present information on the structure and chemistry of a dry cell or lead-acid cell and evaluate it in comparison to one of the following: button cell, fuel cell, vanadium redox cell, lithium cell liquid junction photovoltaic cell (Gratzel cell) in terms of chemistry, cost and practicality, impact on society, environmental impact

Lead acid cello Chemistry:

Anode: Pb(s) + SO42-(aq) → PbSO4(s) + 2e- Pb is oxidised (0 → +II) Made of lead

Cathode: PbO2(s) + 4H+(aq) + SO42–(aq) + 2e– → PbSO4(s) + 2H2O(l)

Pb is reduced (+IV → +II) Made of lead dioxide

Concentrated H2SO4 (~5M) electrolyteo Cost

Lead acid batteries are expensive however, this is counteracted by the fact that they can be recharged many times. Hence the overall cost is lower than many alternative sources

o Practicality Heavy: not very practical for appliances However, this is not a problem in its most common

application, in car batteries since it isn’t moved around that much

Contains concentrated sulfuric acid and lead: dangerous to handle

o Impact on society Used in cars: Huge impact on society because it

allows cars to be started much more easily and reliably

Therefore allows people to move around and travel long distances

o Environmental impact The concentrated sulfuric acid is very corrosive and

must be disposed of safely Lead is a heavy metal and must be disposed of safely

as well However, some car batteries still end up in land fills

and the toxic heavy metals seep into the environment

Lithium cello Chemistry

Anode: Li(s) → Li+(aq) + e-

Lithium is oxidised Anode is made of lithium

Cathode: I2 + 2e- → 2I- Involves either silver chromate or iodine Anode is made of carbon (graphite)

Electrolyte: Lithium iodideo Cost

They are expensive compared to other batteries, however sometimes there is no substitute possible

o Practicality Long lasting and have a high voltage (3V compared

to 1.5V in alkaline batteries) They are used in mobile phones, computers, cameras

and pacemakerso Social Impact

Allows long lasting, high voltage and reliable supply of electricity to be portable

Use in pacemakers which have saved lives Small size allows them to be used in smaller and

more portable equipment such as mobile phones. This has greatly improved our ability to communicate

o Environmental impact Although not a hazard, un-recycled lithium ion

batteries contribute significantly to waste due to the large volume of the batteries which is being used

5. Nuclear chemistry provides a range of materialsDistinguish between stable and radioactive isotopes and describe the conditions under which a nucleus is stable

A stable isotope does not undergo radioactive decay An unstable isotope undergoes radioactive decay in the form of

alpha, beta or gamma radiation Alpha decay commonly occurs in large atoms (Z>83) since the

electrostatic repulsion by the protons becomes too large for the strong nuclear force to hold it together

o Emits an alpha particle (Helium nucleus) in the process Beta decay is due to a unbalanced NP ratio

o A beta particle is either an electron or positriono About 1:1 for smaller nuclei and up to about 1.5:1 in larger

oneso Too many neutrons = β- decay

n01 → H1

1 + e−10 + v0

0

o Too many protons = β+ decay

H11 → n0

1 + e10 + v0

0

[neutrinos not required in chemistry] Gamma radiation is emitted from an unstable nucleus. Nuclear

transmutation does not occuro E.g. 99mTc → 99Tc + γ

Describe how transuranic elements are produced Transmutation occurs when an atom changes atomic number,

such as in alpha or beta decay Transuranic elements can be produced by bombarding heavy

atoms with neutrons to induce beta decayo E.g. 238U + 1n → 239U → 239Np + -1e → 239Pu + -1e

They can also be produced by bombarding large nuclei or previously made transuranic elements with smaller nuclei

Describe how commercial radioisotopes are produced Commercial radioisotopes are made in nuclear reactors called

breeder reactors and cyclotrons Breeder reactors

o The target nuclei is placed into the core of the reactor and is bombarded with neutrons to produce the desired radioisotope

Cyclotronso The target nuclei is bombarded with charged particles,

often alpha-particles or protons at high speedso This is achieved by accelerating the charged particles with

very strong magnetic fields around a large radiusIdentify instruments and processes that can be used to detect radiation

Geiger-Muller counter Scintillation counter Photographic film Cloud Chambers/Bubble Chambers

Identify one use of a named isotope In medicine: Technetium-99m

o Used in diagnostic radiology to diagnose cancers and abnormal organ functionality

In industry: Strontium-90o Used in thickness gauges

Describe the way in which the named industrial and medical radioisotopes are used and explain their use in terms of their properties

Technetium-99m is injected into the blood in a serum and its distribution in the blood as it circulates can be detected by gamma cameras

o It can detect blood clots, tumours and other abnormalities as these regions often have excessive blood flow, and hence more of the radioisotope will accumulate in that region

o This is an advantage over x-rays, which can only detect structural damage easily

o Properties Short half-life (6 hours): Patient and doctors are only

exposed to radiation for short amounts of time Also the radiation would be more intense for a

shorter period, making it easier to detect Attaches itself to blood cells so it can monitor the

circulation of blood Biocompatible: even though radioactivity has nothing

to do with chemical properties, radioisotopes behave in the same way as their stable counterparts, hence it must be non-toxic

Gamma emission: Alpha and beta radiation are much more ionising, and hence dangerous in the body (especially alpha)

Strontium-90 is used in thickness gauges to detect the thickness in production of materials, such as sheets of metal

o Thickness can be calculated/extrapolated from the amount of radiation it detects. As thickness increases, more is absorbed and vice versa.

o It is connected to the machine via a feedback loop, and if the thickness deviates, the controller adjusts the machine accordingly to maintain the desired thickness

o Advantage is that this is very sensitive, allowing a high quality product to be manufactured

o Properties Long half-life (28 years): Does not need to be

replaced often meaning that workers do not need to expose themselves to radiation

Low energy emissions means that the material does not become radioactive, and the workers remain safe

Beta radiation: Alpha radiation will be blocked entirely, while gamma rays would pass right through the material. Beta particles are only partially blocked, meaning it can be used to detect the thickness

Analyse benefits and problems associated with the use of radioactive isotopes in identified industries and medicine

Benefits in Medicineo More sophisticated diagnosis can provide more details

about a patient than conventional x-rays E.g. 3D images can be taken by using gamma cameras from all different angles and can aid diagnosis

o Able to generate images of the organ over time (few minutes to a few hours), rather than just taking a static image. Multiple x-rays overtime will overdose the patient with radiation

o Non-invasive method to diagnose cancers and other problems with internal organs. This is not possible otherwise

Benefits in Industryo Monitoring with radioisotopes is much more sensitive than

conventional means, therefore quality control is much better

o Examining for internal structural faults is not possible without the use of radioisotopes

Problems o Radiation is dangerous and the ionising ability destroys the

complex DNA within cells

o Causes tissue and genetic damageo Can cause cancer and damage to DNA

The Acidic Environment 12/10/10 6:15 PM

1. Indicators were identified with the observation that the colour of some flowers depends on soil compositionClassify common substances as acidic, basic or neutral

Vinegar, lemon juice, etc. are acidic Caustic soda, ammonia, etc. are basic Water, oil, etc. are neutral

Identify that indicators such as litmus, phenolphthalein, methyl orange and bromothymol blue can be used to determine the acidic or basic nature of a material over a range, and that the range is identified by change in indicator colour

Litmuso pH range: 5-8 o Red → Blue

Phenolphthaleino pH range: 8-10o Colourless → Pink

Methyl Orangeo pH range: 3-4.5o Red → Yellow

Bromothymol Blueo pH range: 6-7.5o Yellow → Blue

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

Testing soil acidityo Barium sulfate is poured on top of the soil sample and

allows it to soak up some of the water. The indicator can be used on the white barium sulfate and the colour can be determined

Testing acidity of swimming poolo Using in indicator

2. While we usually think of the air around us as neutral, the atmosphere naturally contains acidic oxides of carbon, nitrogen and sulfur. The concentrations of the se acidic oxides have been increasing since the Industrial RevolutionIdentify oxides of non-metals which act as acids and describe the conditions under which they act as acids

Acidic Oxideso Reacts with water to form an acido Reacts with bases to form salts o Reactions:

Acid + metal → Hydrogen + Salt Acid + carbonate → Carbon Dioxide + Water + salt Acid + metal oxide → Water + salt Acid + metal hydroxide → Water + Salt

o Examples Carbon Dioxide + Water → Carbonic Acid Carbon Dioxide + Sodium Hydroxide → Water +

Sodium Carbonate P2O5(s) + 3H2O(l) → 2H3PO4(aq)

Basic Oxideso Reacts with water to form an alkalio Reacts with acid to form water and salto Reactions:

Reacts with amphoteric metals to produce H2

Dissolves amphoteric metal hydroxidesAnalyse 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 often formed by oxygen-rich non-metalso e.g. CO2, SO3, NO3

Basic Oxides are often formed by metalso e.g. Na, Mg, Fe, Cu

Neutral oxides are formed by oxygen-poor non-metalso E.g. CO, NO, N2O

Amphoteric oxides are formed by semi-metalso They have both acidic and basic propertieso They can behave as a weak base or acido E.g. BeO, SnO, PbO, Al2O3, Cr2O3

The acidity or alkalinity depend on the electronegativity of the atom bound to the oxygen

Define Le Chatelier’s Principle When a system at equilibrium is disturbed, the system adjusts

itself to minimise the disturbanceIdentify factors which can affect the equilibrium in a reversible reaction

Temperatureo Increase temperature = Favours endothermic reactiono Decrease temperature = Favours exothermic reaction

Partial pressures of gaseso Partial pressure → concentration

Concentration of products/reagentso Changing the concentration of products/reagents will cause

the system to act to minimise the changeo E.g. Products added, system will shift to reduce products

Total pressure of volumeso Increasing pressure = Decreasing volume

Describe the solubility of carbon dioxide in water under various conditions as an equilibrium process and explain in terms of Le Chatelier’s principle

CO2(g) CO2(aq) ∆H<0 [1] CO2(aq) + H2O(l) H2CO3(aq) ∆H<0 [2] H2CO3(aq) H+(aq) + HCO3-(aq) [3] HCO3-(aq) H+(aq) + CO3-(aq) [4] Pressure

o Increasing the pressure will be likened to increasing the concentration of CO2(g), and hence will shift [1] to the right, increasing solubility

o Increasing temperature will favour the endothermic reaction in [1], shifting the equilibrium to the left and decrease solubility

o Increasing acidity, will cause [3] and [4] to shift to the left, since, [H+] is increased. This will in turn shift [2] to the left as [H2CO3] increases and will shift [1] to the left as [CO2(aq)] increases. Therefore solubility decreases.

o Adding a base will cause the opposite to happen (increase solubility of CO2)

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

Do this later (technology is weak since it only since 1950s) About 2/3 of the SO2 in the atmosphere comes from volcanos and

geothermal hot springsCalculate volumes of gases of some substances in reactions and calculate the masses of substances given gaseous volumes in reactions involving gases at 0oC and 100kPa or 25oC and 100kPa

v=nV m=nM

Explain the formation and effects of acid rain Concentration of CO2 in the atmosphere is about 360ppm, and

some of it dissolves in water forming carbonic acid. Hence rain water is naturally slightly acidic

Acid rain is defined as a rain with a [H+] higher than 10-5mol/L Since the industrial revolution, oxides of nitrogen and sulfur have

been released into the atmosphere Formation

o SO2(g) + H2O(l) H2SO3(aq)o SO3(g) + H2O(l) H2SO4(aq)o 2NO2(g) + 2H2O(l) HNO3(aq) + HNO2(aq)

Effectso Increased acidity of bodies of water e.g. lakes

Increased acidity can easily kill fish eggs which are sensitive to changes in pH

Some fish are sensitive to pHo Dissolves the waxy coating of some leaves o Erosion of marble structures

Marble are carbonates, which is a base so it is neutralised by acid rain

o Dissolves heavy metals into waterways Toxic heavy metals such as lead bio accumulates and

biomagnifies 3. Acids occur in many foods, drinks and even our own stomachsDefine acids as proton donors and describe the ionisation of acids in water

Acids donate a proton (hydrogen atom)o E.g. HCl → H+ + Cl-

o The H+ is actually a hydronium ion H3O+ Acids ionise in water to produce hydronium ions

o H+ + H2O → H3O+

Identify acids including acetic (ethanoic), citric (2-hydroxypropane-1,2,3-tricarboxilic acid), hydrochloric and sulfuric acid

Acetic acido Weak acido CH3COOH CH3COO- + H+

Citric acido Tri-protico Weak acido Stronger than acetico C6H8O7 C6H5O7 + 3H+

Hydrochloric acid o Strong acid – ionises completelyo HCl → H+ + Cl-

Sulfuric acido Diprotico Strong acid (1st ionisation) o Weaker 2nd ionisationo H2SO4 → HSO4- + H+

o HSO4- SO42- + H+

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

Strong acid – ionises completely Weak acid – does not ionise completely Concentrated acid – When the concentration of acid molecules,

whether ionised or not, in solution is high Dilute acid – When the concentration of acid molecules in

solution is lowDescribe the use of the pH scale in comparing acids and bases

pH is a measurement of the concentration of H+ ionsIdentify pH as –log10[H+] and explain that a change in pH of 1 means a ten-fold change in [H+]

pH = –log10[H+] since it's a log scale to base 10, a pH change of 1 means 10

times more or less hydrogen ionsCompare the relative strengths of equal concentrations of citric, acetic and hydrochloric acids and explain in terms of the degree of ionisation of their molecules

Acetic acid: CH3COOH CH3COO- + H+

Citric acid: C6H8O7 C6H5O7 + 3H+

Hydrochloric acid: HCl → H+ + Cl- Citric acid is triprotic and weak Acetic is monoprotic and weak Hydrochloric is monoprotic and strong Hydrochloric > Citric > Acetic Why does hydrochloric acid ionise completely?

Describe the difference between a strong and a weak acid in terms of an equilibrium between the intact molecule and its ions

In a weak acid, not all the acid molecules ionize compelely, but rather they reaction is an equilibrium

o HA H+ + A-

As H+ ions are formed (Le Chatelier’s principle), the reverse reaction also begins, and eventually the system will reach equilibrium

Because of this, not all the acid molecules get ionised This needs more detail

4. Because of the prevalence and importance of acids, they have been used and studied for hundreds of years. Over the time, the definitions of acid and base have been refinedOutline the historical development of ideas about acids including those of Lavoisier, Davy and Arrhenius

Lavoisiero Theorise that acids were substances which contained

oxygen The word oxygen was derived from Greek words

meaning acid formingo This was disproved as many substances containing oxygen

such as calcium oxide were, in fact, basico Also, there were many substances such as hydrochloric

acid which were acidic and did not contain oxygen Davy

o Suggested that acids contained replaceable hydrogen That is, the hydrogen could be replaced by metals

E.g. when HCl reacts with Zn, the H in HCl would be replaced with Zn, forming ZnCl2

o He stated bases where substances which reacted with acids to form salts and water

Arrheniuso Proposed that acids were substances which ionised in

water to produce hydrogen ionso Suggested that a base was a substance which would

produce hydroxide ionso Limitations:

Metallic oxides were basic e.g. CaCO2, as they neutralised acids, but do not contain hydroxide ions hence did not fit the Arrhenius definition

Does not take into the account the role of the solvent. E.g. HCl is a strong acid when the solvent is water, but a weak acid when the solvent is ethanol

Some substances such as ammonia, NH3, acted as a base even though it contained no hydroxide, and reacts with acid to from salt and water

Outline the Brönsted-Lowry theory of acids and bases An acid is a proton donor A base is a proton acceptor

Distinguish the relationship between and acid and its conjugate base and a base and its conjugate acid

A strong acid has a weak conjugate base A strong base has a weak conjugate acid They always occur in pairs

o E.g. HCl + OH- → H2O + Cl- The two pairs are: HCl (acid) & Cl- (conjugate base) OH- (base) & H2O (conjugate acid)

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

Acidic saltso Oxygen-rich non-metal oxides

Neutral saltso Oxygen-poor non-metal oxides

Basic saltso Metallic oxides

Identify neutralisation as a proton transfer reaction which is exothermic

Neutralisation is the transfer of a proton from an acid to a base Energy is released in the process, hence it is exothermic

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

An acid-base titration determines the pH of an unknown by calculating how much of it is required to react with a known volume and known concentration

Equipmento It is important that the equipment is of accurate and

analytical grade to ensure accurate measurements. This is because the colour change over the equivalence point happens over less than a drop

o Volumetric flask The volume stated is when the solution reaches the

mark etched onto the side of the flask It is used to prepare standard solutions where the

concentration is accurately neededo Pipette

Used to accurately deliver a specified volume of solution

o Burette Used to accurately deliver a variable volume of

solution Accurate to ±0.05 mL The difference in volume of initial vs final is the

amount used in the titration Rinsing

o Burettes and pipettes are to be rinsed with distilled water initially, and then twice with the solution to be used

o The thin film of water will dilute the solution inside if it is only rinsed with water

o Conical and volumetric flasks are just to be rinsed with distilled water as the number of moles of solution is known. Adding water doesn't change this

Standard solutiono Primary standards

A primary standard must have the following properties

Obtainable in a pure form with a known chemical formula

Is not hydroscopic Relatively high molar mass to reduce weighing

errors Examples include sodium carbonate (NaCO3) and

hydrated oxalic acid (H2C2O4.2H2O) Before sodium carbonate is weighed it is heated in an

oven to remove any moistureo Secondary standards

Sometimes we may need to use some substances which are not suitable for primary standards such as H2SO4 or NaOH since they are hydroscopic

Before these can be used, their concentration must be found by titrating it against a primary standard

The resulting solution is known as a standard solution, which should be used rather quickly to avoid changes in concentration due to volatility or absorption of water

Choice of indicatoro An appropriate indicator which changes colour at the

equivalence point needs to be chosen. If not, then the results will not be accurate, as the colour change will be either before or after all the reactants have reacted

o Strong acid – weak base: Methyl red, since the equivalence point is at pH <7

o Strong acid – strong base: Bromothymol blue, since the equivalence point is at pH = 7

o Weak acid – strong base: Phenolphthalein, since the equivalence point is at pH >7

o Weak acid – weak base: generally not performed since rather than a sudden change in colour, it changes over several drops

Methodo Fill burette with the solution of known concentration

This solution is called the titrant

Record the level of the solution in the buretteo Place sample to be analysed in a flask under the burette

Add indicator to this sample Place flask on a white tile or paper to see the colour

change more clearlyo Run the solution into the flask, until it starts to change

colour When this happens, then slowly add drops of the

titrant Wash off any titrant off the side with a bottle of

distilled watero The end point is reached when there is a permanent colour

changeo The first titration is a rough titration to find out where the

equivalence point iso Repeat until there are at least three results within ±0.1mL

Qualitatively describe the effects of buffers with reference to a specific example in a natural system

A buffer is a solution containing a weak acid and large amounts of its conjugate base which is able to maintain a relatively constant pH despite adding significant amounts of strong acids or base to it

Buffers are very important in natural systemso Some animals are very sensitive to pH rangeo Some enzymes work only in a narrow pH range

E.g. Human blood has a pH of about 7.4 o Buffers maintain the pH within 7.35 – 7.45o Outside this range, the enzymes in the body start failing o The buffer system is a carbonic acid/hydrgogencarbonate

system H2CO3(aq) HCO3-(aq) + H+(aq)

o If H+ is added then it will shift to the left, reducing its effect o Similarly is OH- is added then it will shift to the right, to

reduce its concentrationAnalyse information from secondary sources to assess the use of neutralisation reactions as a safety measure of to minimise damage in accidents or chemical spills

When acids or bases are spilt, they must be neutralised quickly to reduce damage

Substances used to neutralise spills should have the following properties

o Weak acid/base – heat generated from neutralisation with strong acids/bases would be too great since it reacts too fast

o Safe to use in excesso Can neutralise both acids and baseo Cheap and safe to handle

Sodium hydrogencarbonate is often used for this because it iso A stable solid which is easy to storeo Amphoteric so it can neutralise both strong bases and

acidic spillso Non-toxic and safe to handle in excess, since it is difficult

to determine the exact amount of chemicals spilto Cheap and readily available

5. Esterification is a naturally occurring process which can be performed in the laboratory Describe the differences between the alkanols and alkanoic acid functional groups in carbon compounds

Alkanolso Contain the -OH (hydroxyl) groupo Soluble in water due to hydrogen bonding

However this decreases as the length of the carbon chain increases

o Much higher MP/BP than alkane with similar molecular weight due to strong intermolecular forces (Hydrogen bonds and dipole-dipole interaction)

Alkanoic acidso Contain the –COOH (carboxyl) group o Soluble in water due to hydrogen bonding

Likewise, this decreases as the length of the carbon chain increases

o Even higher MP/BP than alkanols due to the more hydrogen bonding in the C=O and O-H groups within the molecule (Alkanols don't have the C=O group)

Identify the IUPAC nomenclature for describing the esters produced by reactions of straight-chained alkanoic acids from C1 to C8 and straight-chained primary alkanols from C1 to C8

Alkanols: [prefix]an-x-ol Alkanoic acid: [prefix]anoic acid

Explain the difference in melting point and boiling point caused by straight-chained alkanoic acid and straight-chained primary alkanol structures

In both cases, the –OH group in the molecule is able to form hydrogen bonds, hence the intermolecular forces are strong, giving them a high MP/BP

However in alkanoic acids, there is an additional C=O group where further hydrogen bonding occurs

o Hence the intermolecular forces are stronger, so more energy is require to separate them

o This gives them a higher MP/BP than alkanolsIdentify esterification as the reaction between an acid and an alkanol and describe, using equations, examples of esterification

Esterification is the reaction between an alkanoic acid and an alkanol, producing an ester and water

The general equation is:o Alkanol + Alkanoic acid Ester + water

Concentrate sulfuric acid catalyst All products and reactants are liquid

o The ester is named alkyl alkanoate The alkyl comes from the alkanol The alknanoate comes from the alkanoic acid

Describe the purpose of using acid in esterification for catalysts A catalyst speeds up the rate of reaction

Concentrated sulfuric acid is a dehydrating agent and will eliminate the water molecules as they are formed

This will shift the equilibrium to the rightExplain the need for refluxing during esterification

Esterification is carried out at temperatures close to the boiling points of the reagents

The reagents are also volatile and may be lost into the atmosphere

Hence a condenser is required to condense the vapours so they drip back into the reaction mixture

This is known as refluxing This allows the reaction to take place at a higher temperature

(and hence higher reaction rate) without losing too much of the reagents

Outline some examples of the occurrence, production and uses of esters Apple – methyl butanoate Production of esters

Process information from secondary sources to identify and describe the uses of esters as flavours and perfumes in processed foods and cosmetics

Perfumes and cosmeticso Some esters are used as a solvent e.g. ethyl acetate is

used as a common industrial solvent, which can also be used as nail polish remover

o Perfumes use esters as a solvent to dissolve both polar and non polar substances

Processed foodso If the ester which is responsible for the flavour can be

isolated, it can often be manufacturedo These artificial flavours are often cheaper than the real

flavour and provided that they only use the active ester, therefore have little adverse health affects

Chemical Monitoring and Management 12/10/10 6:15 PM

1. Much of the work of chemists involves monitoring reactants and products of reactions and managing reaction conditionsOutline the role of a chemist employed in a named industry or enterprise, identifying the branch of chemistry undertaken by the chemist and explaining a chemical principle that the chemist uses

Luke the chemist works in the polymer industry which makes polyethylene

It is industrial, analytical and petroleum chemistry Role: He is responsible for overlooking the overall production and

quality of the polyethylene produced by measuring the quality of the polyethylene, testing for impurities

He also monitors the condition such as the temperature and pressure of the reaction vessel

Chemical Principleso Solubility in gas-liquid chromatography o This is used to separate mixtures to their components so

they can be measuredo The different solubility affect how the chemicals separate

Identify the need for collaboration between chemists as they collect and analyse data

Chemistry is a very diverse field and in areas such as industry, many specialists are needed

For example, in an industrial plant may employ:o An industrial chemist to maximise yield and reaction rates

and reduce costso An analytical chemist to monitor these reaction rates, as

well as the quality of the producto An environmental chemist to assess the waste products

and environmental impacts of the process Hence, collaboration between the chemists are required for the

functioning of the plant. Describe an example of a chemical reaction such as combustion where reactants form different products under different conditions and thus would need monitoring

Combustion is reaction of a substance with oxygen Often it is a carbon compound containing only hydrogen, carbon

and oxygen such as alcohols and hydrocarbons When they react in excess oxygen the reaction is as follows:

o Fuel + Excess Oxygen → Water + Carbon Dioxideo E.g. C8H18 (g) + 25/2 O2 (g) → 9H2O (g) + 8CO2 (g)

However, if there is insufficient oxygen, the fuel will still burn, but will yield products that are harmful to the humans or the environment

This is called incomplete combustion and the products could include carbon dioxide, carbon monoxide, hydrocarbons and carbon (soot) and water

Note, not all the products need to be present (but water is always there)

Also, the energy yield from incomplete combustion is much less than the energy released from complete combustion and hence it is more economical

For both safety and economical reasons, combustion reactions should be monitored

E.g. in a Bunsen burner, complete combustion occurs when there is a light blue flame. It is much hotter than the yellow flame.

Incomplete combustion can be observed with the yellow flame, and deposits of soot, a product of incomplete combustion, can form at the base of glassware

Gather, process and present information from secondary sources about the work of practicing scientists identifying:

The variety of chemical occupationso Analytical chemistry – measures concentrationso Industrial chemistry – maximise efficientcyo Environmental chemistry – monitors pollution o Physical chemistry – the physical propertieso Electrochemistry – making electricity with chemicalso Organic chemistry – petroleum productso Inorganic chemistry – Minerals and stuff

A specific chemical occupation for a more detailed studyo Analytical chemistry involves the quantitative analysis of

chemical reactions o These include reaction rates, conditions and concentrations

o Some techniques they use include volumetric analysis, gravimetric analysis, AAS and mass spectroscopy

2. Chemical processes in industry require monitoring and management to maximise productionIdentify and describe the industrial uses of ammonia

Over 80% of ammonia is used in fertiliser It can be directly injected into the soil as liquid or used as a raw

material to make other nitrogen based fertilisers It is used to make nitric acid It is also used to make explosives such as TNT and nitroglycerine

which are nitrogen based Identify that ammonia can be synthesised from its component gases, nitrogen and hydrogenDescribe that the synthesis of ammonia occurs as a reversible reaction that will reach equilibriumIdentify the reaction of hydrogen with nitrogen as exothermic

Ammonia can be synthesised from its elements in the Haber process

N2(g) + 3H2(g) 2NH3(g) ∆H = -92 kJ/mol This reaction has a negative ∆H, so it releases energy into its

surroundings, making it exothermic This is an equilibrium reaction that does not go to completion,

hence the reaction must be monitored for maximum production Sources of hydrogen: reaction of steam with methane Sources of nitrogen: Fractional distillation of the atmosphere

Explain why the rate of reaction is increased by higher temperatures An increase in temperature gives the molecules more kinetic

energy, resulting in more energetic and frequent collisions More frequent collisions lead to faster reactions because of the

increased chance of a successful collision In an equilibrium reaction, the equilibrium will be reached faster

since both forward and backward reaction rates are increased Explain why the yield of product in the Haber process is reduced at higher temperatures using Le Châtelier’s principle

According to Le Chatelier’s principle, a system in equilibrium, when disturbed, will react in a way to minimise the disturbanceIncreasing temperature favours the endothermic reaction, hence in the Haber Process, it will shift the equilibrium to the left, reducing yield

Explain that the use of a catalyst will lower the reaction temperature required and identify the catalyst(s) used in the Haber process

A catalyst is used to provide an alternative reaction path with a lower activation energy and hence will lower the temperature required for a successful reaction

The catalyst used in the Haber process is an iron oxide It allows the reaction to take place at a higher rate, but lower

temperature, which means higher yield even at lower temperatures

Explain why the Haber process is based on a delicate balancing act involving reaction energy, reaction rate and equilibrium

The manufacture of ammonia in the Haber process involves the following reaction

o N2(g) + 3H2(g) 2NH3(g) ∆H = -92 kJ/mol An increased temperature will increase reaction rates, but

according to Le Chatelier’s principle, the yield will be decreased However, decreasing temperature to maximise yield will

decrease the energy of the molecules As a result, the reaction rate so much it becomes uneconomical Hence an compromised between yield and reaction rate must be

reached A catalyst is used to speed up the reaction at a lower reaction

rate, hence allowing a higher yield as well as reaction rate At a lower temperature, yield is increased because the

equilibrium is shifted to the right If the temperature is too high, it will also decompose the iron

oxide catalystAnalyse the impact of increased pressure on the system involved in the Haber process

Increased pressure will cause the equilibrium to the side with less moles of gas

In this case, it will favour the forward reaction, going from 4 moles to 2 moles

However, higher pressures are expensive to maintain, requiring very expensive equipment which can deal with these high pressures

Explain why monitoring of the reaction vessel used in the Haber process is crucial and discuss the monitoring required

The Haber process is an industrial process, hence it must be monitored to maintain optimum conditions for maximum production and least possible waste

A compromise between favourable reaction conditions and economic factors must be reached to optimise yield

Temperatureo The temperature must be monitored so that it remains

between the optimum temperatures of 400-550 ˚Co Since the reaction is exothermic, energy will be released

and thus the temperature will increaseo It must be monitored so that production rates are

maintained at a high levelo Also, the catalyst will decompose if the temperature is too

high Pressure

o The optimum pressure of 250-350 atmospheres needs to be maintained for economical and safety reasons

o If the pressure drops, reaction rate and yield decreaseso If the pressure increases, then the equipment could get

damaged and explode Other conditions

o Making sure that the reactants are fed into the reaction vessel in the correct ratio, i.e. the ratio of N2 to H2 is 1:3

o Recycling unreacted gases so that it is not wastedo Ammonia is constantly removed as a liquid

This will shift the equilibrium to favour the production of more ammonia

Gather and process information from secondary sources to describe the conditions under which Haber developed the industrial synthesis of ammonia and evaluate its significance at that time in world history

Historical context:o The Haber process was invented at the beginning of the

20th C, and it was during a crucial time in world history

o Following the industrial revolution, the world population was growing exponentially and hence the demand for fertilisers to feed its population was increasing

o Traditional sources of nitrogen for the fertilisers was Chilean saltpetre and Peruvian guano deposits from South America, however these were soon depleted

o Hence there was a high demand for an alternative source of nitrogen

o Furthermore, during WWI, the Allies had blockaded the German ships from accessing Chilean saltpetre, preventing the Germans from a source of nitrogen for explosives and fertiliser

o Bosch had later industrialised the Haber process and mass produced ammonia for the German war effort

Evaluation:o It is predicted that the Germans would have lost the war by

1916 if the Haber process did not get industrialised, as they would have run out of fertiliser to feed its people

o Hence it is arguable that the Haber process may have changed the course of history if Germany had won the war

o Today, its significance is still prevalent, as the Haber process produces ammonia to feed about a third of the world population

3. Manufactured products, including food, drugs and household chemicals are analysed to determine or ensure their chemical compositionDeduce the ions present in a sample from the results of tests

Cations [Pb2+, Ba2+, Ca2+, Fe2+, Fe3+, Cu2+] If we know that only one ion is in the sample then we perform the

HCl, H2SO4, NaOH testo White precipitate with HCl = Pb2+

Reacts with I- to form yellow precipitateo Precipitate with H2SO4 = Ba2+ or Ca2+

Ba2+ will not precipitate with F- ions apple green flame test

Ca2+

Will precipitate with F- ions forming a white precipitate

Brick red flame testo Precipitate with NaOH = Fe2+, Fe3+ or Cu2+

Fe2+

Green precipitate with OH- but may decompose into Fe3+ and turn brown

Decolourises acidified potassium permanganate solution

5Fe2+(aq) + MnO4–(aq) + 8H+(aq) → 5Fe3+(aq) + Mn2+(aq) + 4H2O(l)

Fe3+

Brown precipitate with OH-

Forms a blood red mixture with SCN-

Fe3+(aq) + SCN–(aq) Fe(SCN)2+(aq) Cu2+

Forms a blue precipitate with OH-

Reacts with ammonia to form the deep blue complex ion, Cu(NH3)42+

Blue-green flame test When multiple ions are present, then the tests must be

performed in a specific order: HCl→H2SO4→NaOH so that the tests do not upset the results for a following test

o E.g. if Pb2+ and Ba2+ are both present, then adding H2SO4 will precipitate both cations, then they become indistinguishable

The solubility of certain compounds, in particular PbCl2 and CaSO4

means that if the concentration of the substances are too low, then no precipitate will be formed even if it is present

Anions [CO32-, SO42-, Cl-, PO43-]o CO32-

Solution has a pH of about 8-11 Effervescence when reacts with acid

HNO3 used because the NO3- ion is solubleo SO42-

When added to a solution of acidified Ba2+, there will be a thick white precipitate of BaSO4

Can be confirmed with Pb2+ which will also precipitateo Cl-

Acidify to remove carbonates then add Ag Forms AgCl which is a white precipitate This darkens in the presence of UV light AgCl also dissolves in ammonia

o PO43-

Make the solution alkaline to produce more PO43- ions It shifts the following equilibrium to the right

using Le Chatelier’s principle, as the base will remove the hydronium ions

HPO42- + H2O H3O+ + PO43-

Then add Ba2+ to precipitate Acidify then add ammonium molybdate

Forms a blue complex ion

12/10/10 6:15 PM

1. Industrial chemistry processes have enabled scientists to develop replacements for natural productsDiscuss the issues associated with shrinking world resources with regard to one identified natural product that is not a fossil fuel, identifying the replacement materials used and/or current research in place to find a replacement for the named material.

Define Natural Producto A natural product is a product produced directly from

something found in nature with little or no modification. E.g. metal ores and guano fertiliser

o There are two types of natural resources: Inexhaustible and Exhaustible

o Inexhaustible natural resources are unlimited and are not likely to be exhausted by human activities. E.g. solar energy, wind

o Exhaustible resources are limited and can be depleted by human activities e.g. forests, animals, fossil fuels

Need For Replacementso Humans exploit their surroundings for resourceso Due to the population boom following the Industrial

Revolution about 250 years ago the demand for natural resources has exponentially increased with the population.

o We cannot generate more of a natural resource to satisfy this demand, since natural regeneration is slower than consumption

o Hence replacements are needed Type of replacements

o Synthetise the same material: find another way to obtain the same product

E.g. drug synthesis o Replace natural product with an alternative material which,

although chemically different, have the same desired physical properties

E.g. Synthesis of ammonia to replace guano Almost every material → plastics

Ammonia [Basically this is how answer to the question] o Define natural resource

o Rapid population growth following the Industrial Revolution meant that natural fertilisers such as animal dung was not sufficient to fertilise crops to feed the population

o Alternative sources of nitrogen such as guano deposits on many islands on the Pacific Coast were completely depleted before the end of the 19th Century

o Nitrogen sources were used to make fertilisers so that nitrogen would be presented in a form which would be usable by plants. Hence without an alternative source, there would not be enough fertiliser to grow food for a growing population

o Due to the Allie’s embargo on the trade of saltpetre from Chile, the Germans had to find a new way of producing a nitrogen based fertiliser

o The Bosch-Haber Process solved this problem by securing food supply by production of ammonia which would be used in fertilisers

o Briefly describe the Haber Processo The Haber Process solved the problem in the early 20th

century, but the process is very costly due to high pressures and temperatures

o Future options include genetic engineering Some algae and bacteria can absorb atmospheric

nitrogen and convert it into organic nitrogen via intermediate ammonium ions. The bacteria could be engineered to absorb nitrogen and release it into the soil as ammonia

Some micro-organisms have a gene known as the NIF-gene and create the enzyme nitrogenase which is able to fix atmospheric nitrogen to synthesis ammonia. This gene could be inserted directly into plants, allowing it to use the nitrogen in the air

2. Many industrial reactions involves manipulation of equilibrium reactionsExplain the effect of changing the following factors on identified equilibrium reactions

Pressureo Only affects gases

o Partial pressure is the pressure exerted on the vessel if only that gas is present

o Equilibrium is only affected when the partial pressure of the gas is changed

o Partial pressure can be likened to concentrationo Increasing pressure will favour the reaction to less moles

Volume Concentration Temperature

o Increased temperature favours the endothermic reactiono Decreased temperature favours the exothermic reaction

Identify that temperature is the only factor that changes the value of the equilibrium constant (K) for a given equation

The equilibrium constant is constant for a given temperature3. Sulfuric acid is one of the most important industrial chemicalsOutline three uses of sulphuric acid in industry

Source of sulphate in the production of superphosphate fertilisers and ammonium sulfate

It is often used as a strong acid to clean the oxide layer off iron before galvanising or electroplating

Manufacture of detergents, to make alkylbenzene sulfonates Used as a catalyst (such as manufacture of esters) Dehydrating agent (such as dehydration of ethanol

Describe the processes used to extract sulfur from mineral deposits, identifying the properties of sulfur which allow its extraction and analysing potential environmental issues that may be associated with its extraction

Frasch Processo Superheated water is pumped into underground sulfur

deposits at about 165°C, which melts the sulfur which has a melting point of 119°C

o Hot compressed air is pumped into the deposit to force it to the surface out the third pipe

o This sulfur and water emulsion can be separated easily since sulfur insoluble in water

Environmental concernso Forms cavities in the ground which may cause landslides

These need to be “backfilled”, which is very difficult to do

Sulfur is easily oxidised to sulfur dioxide and reduced to hydrogen sulphide which are both pollutants

4. The industrial production of sodium hydroxide requires the use of electrolysisExplain the difference between galvanic cells and electrolytic cellsin terms of energy requirements

Galvanic cells produce electricity, electrolytic cells require energyOutline the steps in the industrial production of sodium hydroxide and describe the reaction in terms of net ionic and full formulae equations

Blah blahDistinguish between the three electrolysis methods used to extract sodium hydroxide by describing each process and analyse the technical and environmental difficulties involved in each process

Mercury process Diaphragm process Membrane

5. Saponification is an important organic industrial processblah blah blah6. The Solvay process has been in use since the 1860sIdentify the raw materials used in the Solvay process and name the products

Raw materialso Brine (concentrated NaCl solution)o Ammonia (reused)o Calcium Carbonate

Productso Calcium Chlorideo Sodium Carbonateo Ammonia