12/10/10 6:15 PM

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 Cracking

High temperature (800oC)

Uses steam – inert dilatant

Absence of air

Just above atmospheric pressure

Keeps the concentration of gases low enough so it can flow through the tubes

E.g. C3H8 → C2H4 + CH4

Catalytic cracking

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

Lower temperatures (500oC)

The catalysts commonly used for catalytic cracking are silicon and aluminium oxides, or powdered zeolite.

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 general

Initiation → Propagation → Termination

Initiation: an initiator, e.g. peroxide

Low Density Polyethylene (LDPE)

Uses temperatures, around 300°C, and at very high pressures, around 3000 atmospheres

This does not use a catalyst

An initiator such as oxygen, or an organic peroxide which contains a –O-O- bond is used

Both long and short chains are produced, and at some carbons, the hydrogen is replaced by the alkyl group

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)

This process uses lower pressure, only a few times atmospheric pressure, and lower temperature, around 60°C

This type of polymerization requires the use of a Zeigler-Natta catalyst, which are usually rare earth metal oxides

This polymer is relatively unbranched, allowing the chains to pack closely together in an orderly fashion

There are larger crystalline regions which are rigid

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

Systematic name: Chloroethene

Polymer: Polyvinylchloride (PVC)

Styrene

Systematic name: ethenylbenzene or phenylethene

Polymer: Polystyrene

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

LDPE

Uses

Cling wrap, plastic bags, milk bottles

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

HDPE

Uses

Kitchen utensils, wheelie bins, more rigid toys

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

PVC

Uses

Pipes, wire insulation

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

Polystyrene

Uses

Tool handles, car battery cases, foam cups

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 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

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

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 strong

Identify 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

Digestion by enzymes

Digestion by a strong acid (Moderately concentrated sulphuric acid)

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 glucose

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

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 ethanol

Process 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

C6H12O6(aq) → 2CH3CH2OH(aq) + 2CO2(g)

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

Advantages

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

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

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

Disadvantages

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

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

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.

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

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

Judgement

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

prefix is the length of the carbon chain

number is where the –OH group is located

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 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 copper

Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)

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?

Impurities in the electrodes will increase electrical resistance and thus the experimental voltage will be less than theoretical

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

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 Gain

Outline 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 cell

A galvanic cell consists of two half cells

Each half cell consists of a conductive metal in ionic solution known as the electrolyte

A salt bridge connects the two electrolytic solutions

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 cell

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) electrolyte

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

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

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

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 cell

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 iodide

Cost

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

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 pacemakers

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

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 materials

Distinguish 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

Emits an alpha particle (Helium nucleus) in the process

Beta decay is due to a unbalanced NP ratio

A beta particle is either an electron or positrion

About 1:1 for smaller nuclei and up to about 1.5:1 in larger ones

Too many neutrons = β- decay

Too many protons = β+ decay

[neutrinos not required in chemistry]

Gamma radiation is emitted from an unstable nucleus. Nuclear transmutation does not occur

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 decay

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

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

Cyclotrons

The target nuclei is bombarded with charged particles, often alpha-particles or protons at high speeds

This is achieved by accelerating the charged particles with very strong magnetic fields around a large radius

Identify 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

Used in diagnostic radiology to diagnose cancers and abnormal organ functionality

In industry: Strontium-90

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

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

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

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

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

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

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

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 Medicine

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

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

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

Benefits in Industry

Monitoring with radioisotopes is much more sensitive than conventional means, therefore quality control is much better

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

Problems

Radiation is dangerous and the ionising ability destroys the complex DNA within cells

Causes tissue and genetic damage

Can cause cancer and damage to DNA

Production of MaterialsDennis Mok

1. Indicators were identified with the observation that the colour of some flowers depends on soil composition

Classify 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

Litmus

pH range: 5-8

Red → Blue

Phenolphthalein

pH range: 8-10

Colourless → Pink

Methyl Orange

pH range: 3-4.5

Red → Yellow

Bromothymol Blue

pH range: 6-7.5

Yellow → Blue

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

Testing soil acidity

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 pool

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 Revolution

Identify oxides of non-metals which act as acids and describe the conditions under which they act as acids

Acidic Oxides

Reacts with water to form an acid

Reacts with bases to form salts

Reactions:

Acid + metal → Hydrogen + Salt

Acid + carbonate → Carbon Dioxide + Water + salt

Acid + metal oxide → Water + salt

Acid + metal hydroxide → Water + Salt

Examples

Carbon Dioxide + Water → Carbonic Acid

Carbon Dioxide + Sodium Hydroxide → Water + Sodium Carbonate

P2O5(s) + 3H2O(l) → 2H3PO4(aq)

Basic Oxides

Reacts with water to form an alkali

Reacts with acid to form water and salt

Reactions:

Reacts with amphoteric metals to produce H2

Dissolves amphoteric metal hydroxides

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 often formed by oxygen-rich non-metals

e.g. CO2, SO3, NO3

Basic Oxides are often formed by metals

e.g. Na, Mg, Fe, Cu

Neutral oxides are formed by oxygen-poor non-metals

E.g. CO, NO, N2O

Amphoteric oxides are formed by semi-metals

They have both acidic and basic properties

They can behave as a weak base or acid

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 disturbance

Identify factors which can affect the equilibrium in a reversible reaction

Temperature

Increase temperature = Favours endothermic reaction

Decrease temperature = Favours exothermic reaction

Partial pressures of gases

Partial pressure → concentration

Concentration of products/reagents

Changing the concentration of products/reagents will cause the system to act to minimise the change

E.g. Products added, system will shift to reduce products

Total pressure of volumes

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

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

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

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.

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 springs

Calculate 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

SO2(g) + H2O(l) H2SO3(aq)

SO3(g) + H2O(l) H2SO4(aq)

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

Effects

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 pH

Dissolves the waxy coating of some leaves

Erosion of marble structures

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

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 stomachs

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

Acids donate a proton (hydrogen atom)

E.g. HCl → H+ + Cl-

The H+ is actually a hydronium ion H3O+

Acids ionise in water to produce hydronium ions

H+ + H2O → H3O+

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

Acetic acid

Weak acid

CH3COOH CH3COO- + H+

Citric acid

Tri-protic

Weak acid

Stronger than acetic

C6H8O7 C6H5O7 + 3H+

Hydrochloric acid

Strong acid – ionises completely

HCl → H+ + Cl-

Sulfuric acid

Diprotic

Strong acid (1st ionisation)

Weaker 2nd ionisation

H2SO4 → HSO4- + H+

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 low

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

pH is a measurement of the concentration of H+ ions

Identify 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 ions

Compare 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

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 refined

Outline the historical development of ideas about acids including those of Lavoisier, Davy and Arrhenius

Lavoisier

Theorise that acids were substances which contained oxygen

The word oxygen was derived from Greek words meaning acid forming

This was disproved as many substances containing oxygen such as calcium oxide were, in fact, basic

Also, there were many substances such as hydrochloric acid which were acidic and did not contain oxygen

Davy

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

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

Arrhenius

Proposed that acids were substances which ionised in water to produce hydrogen ions

Suggested that a base was a substance which would produce hydroxide ions

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

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 salts

Oxygen-rich non-metal oxides

Neutral salts

Oxygen-poor non-metal oxides

Basic salts

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

Equipment

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

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 needed

Pipette

Used to accurately deliver a specified volume of solution

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

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

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

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 solution

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 moisture

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 indicator

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

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

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

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

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

Method

Fill burette with the solution of known concentration

This solution is called the titrant

Record the level of the solution in the burette

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 clearly

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 water

The end point is reached when there is a permanent colour change

The first titration is a rough titration to find out where the equivalence point is

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 systems

Some animals are very sensitive to pH range

Some enzymes work only in a narrow pH range

E.g. Human blood has a pH of about 7.4

Buffers maintain the pH within 7.35 – 7.45

Outside this range, the enzymes in the body start failing

The buffer system is a carbonic acid/hydrgogencarbonate system

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

If H+ is added then it will shift to the left, reducing its effect

Similarly is OH- is added then it will shift to the right, to reduce its concentration

Analyse 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

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

Safe to use in excess

Can neutralise both acids and base

Cheap and safe to handle

Sodium hydrogencarbonate is often used for this because it is

A stable solid which is easy to store

Amphoteric so it can neutralise both strong bases and acidic spills

Non-toxic and safe to handle in excess, since it is difficult to determine the exact amount of chemicals spilt

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

Alkanols

Contain the -OH (hydroxyl) group

Soluble in water due to hydrogen bonding

However this decreases as the length of the carbon chain increases

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

Alkanoic acids

Contain the –COOH (carboxyl) group

Soluble in water due to hydrogen bonding

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

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

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

This gives them a higher MP/BP than alkanols

Identify 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:

Alkanol + Alkanoic acid Ester + water

Concentrate sulfuric acid catalyst

All products and reactants are liquid

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 right

Explain 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 cosmetics

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

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

Processed foods

If the ester which is responsible for the flavour can be isolated, it can often be manufactured

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

The Acidic Environment12/10/10 6:15 PM

1. Much of the work of chemists involves monitoring reactants and products of reactions and managing reaction conditions

Outline 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 Principles

Solubility in gas-liquid chromatography

This is used to separate mixtures to their components so they can be measured

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:

An industrial chemist to maximise yield and reaction rates and reduce costs

An analytical chemist to monitor these reaction rates, as well as the quality of the product

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:

Fuel + Excess Oxygen → Water + Carbon Dioxide

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 occupations

Analytical chemistry – measures concentrations

Industrial chemistry – maximise efficientcy

Environmental chemistry – monitors pollution

Physical chemistry – the physical properties

Electrochemistry – making electricity with chemicals

Organic chemistry – petroleum products

Inorganic chemistry – Minerals and stuff

A specific chemical occupation for a more detailed study

Analytical chemistry involves the quantitative analysis of chemical reactions

These include reaction rates, conditions and concentrations

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

2. Chemical processes in industry require monitoring and management to maximise production

Identify 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 hydrogen

Describe that the synthesis of ammonia occurs as a reversible reaction that will reach equilibrium

Identify 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 disturbance

Increasing 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

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 catalyst

Analyse 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

Temperature

The temperature must be monitored so that it remains between the optimum temperatures of 400-550 ˚C

Since the reaction is exothermic, energy will be released and thus the temperature will increase

It must be monitored so that production rates are maintained at a high level

Also, the catalyst will decompose if the temperature is too high

Pressure

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

If the pressure drops, reaction rate and yield decreases

If the pressure increases, then the equipment could get damaged and explode

Other conditions

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

Recycling unreacted gases so that it is not wasted

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:

The Haber process was invented at the beginning of the 20th C, and it was during a crucial time in world history

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

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

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

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

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

Evaluation:

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

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

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 composition

Deduce 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 test

White precipitate with HCl = Pb2+

Reacts with I- to form yellow precipitate

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 test

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

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-]

CO32-

Solution has a pH of about 8-11

Effervescence when reacts with acid

HNO3 used because the NO3- ion is soluble

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 precipitate

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

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

Chemical Monitoring and Management12/10/10 6:15 PM

1. Industrial chemistry processes have enabled scientists to develop replacements for natural products

Discuss 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 Product

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

There are two types of natural resources: Inexhaustible and Exhaustible

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

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

Need For Replacements

Humans exploit their surroundings for resources

Due to the population boom following the Industrial Revolution about 250 years ago the demand for natural resources has exponentially increased with the population.

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

Hence replacements are needed

Type of replacements

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

E.g. drug synthesis

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]

Define natural resource

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

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

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

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

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

Briefly describe the Haber Process

The Haber Process solved the problem in the early 20th century, but the process is very costly due to high pressures and temperatures

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 reactions

Explain the effect of changing the following factors on identified equilibrium reactions

Pressure

Only affects gases

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

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

Partial pressure can be likened to concentration

Increasing pressure will favour the reaction to less moles

Volume

Concentration

Temperature

Increased temperature favours the endothermic reaction

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 temperature

3. Sulfuric acid is one of the most important industrial chemicals

Outline 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 Process

Superheated water is pumped into underground sulfur deposits at about 165°C, which melts the sulfur which has a melting point of 119°C

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

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

Environmental concerns

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 electrolysis

Explain the difference between galvanic cells and electrolytic cells
in terms of energy requirements

Galvanic cells produce electricity, electrolytic cells require energy

Outline the steps in the industrial production of sodium hydroxide and describe the reaction in terms of net ionic and full formulae equations

Blah blah

Distinguish 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 process

blah blah blah

6. The Solvay process has been in use since the 1860s

Identify the raw materials used in the Solvay process and name the products

Raw materials

Brine (concentrated NaCl solution)

Ammonia (reused)

Calcium Carbonate

Products

Calcium Chloride

Sodium Carbonate

Ammonia