Chemical

Demonstrate the formation of coordinate covalent bonds using Lewis electron dot structures

(draw diagram)

Precipitation reactions cation

* Addition of Cl- precipitates Pb2+ — white * SO42- precipitate Ba2+ and Ca2+ to form white precipitate * To distinguish — add F- (NaF) OR flame test * If Colourless = Ca2+ * OH- ions * Precipitate Cu, Fe2 and Fe3 * To distinguish — blue = Cu, brown =Fe3+, green to brown = Fe2+ * Fe2+ and Fe3+ — adding SCN- * Fe2+ no reaction (to confirm, addition of MnO4- makes decoloursied) but Fe3+ blood red (to confirm at SCN- again)

Perform first hadn't investigation to carry out a range of tests, including fallen tests, to identity the following ions: phosphate, sulphate, carbonate, chloride,barium, calcium, lead, copper, iron

* Appropriate tests in flow charts above were used ot identify a range of cations and anions * Remember: flame tests cannot be used to identify anions as it doesn't release colour * When testing for the cations via flame test, all the cations are in a nitrate solution * When testing cations via precipitation: dropped onto a plastic sheet wiht coloured paper on the back, table below When testing for anions: * All the anions are in a solution with sodium ions. (look at notes for the table) Flame test -- spray bottle/PET set pu with a bunsen burner to test flame colour

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

* As there are a variety of occupations in chemistry there is a need for chemists to collaborate as they collect and analyse data which requires more than one specialty. For example in industry, the production of a certain product requires knowledge of an: * Industrial chemist — to design the industrial process for maximum yield and reaction rate * Analytical chemist — to analyse amount of substances used in the reaction and contaminants * Environmental chemist — to ensure and manage the release of waste * If issues do arise in the process of e.g. GLC, then the chemist collaborates with technicians operating the reaction vessel to resolve them efficiently — this occurs on hourly basis to ensure that enviornemtal factors e.g. temperature can be closely controlled * Can also allow for peer review and checking to improve the validity — allows for scientists with certain specialties to check and reduce any errors when undertaking an experiment Also, collaboration between different branches of chemistry improves the reliability fo the product or results obtained. Hence it is essential for chemists in different branches, and also other professions (e.g. chemical engineers), to collaborate as they collect and analyse data

Why does reaction rate increase with temperature

* At higher temperature, the increase in thermal energy is converted into an increase in the kinetic energy of gaseous molecules * This increases the number of successful collisions between particles, where the activation energy is overcome, hence increasing the rate of reaction, reaching equilibrium faster

Anions

* Cannot use flame test as produces no colour and when they are dissolved in solution, it is clear. Therefore precipitation CO3 2-, PO4 3-, SO4 2-, Cl- * Add HNO3 to remove the CO32-, forms bubbles * 2H+ + CO32- —> H2O + CO2(g) * To confirm —pass gas bubbles through lime water, and milky = * No bubbles and ppt (acidic solution) add BaNO3 * White ppt = SO42- * none = add AgNO3 white ppt = Cl- None = PO43-

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

* Incomplete combustion occurs when there is a limited supply of oxygen, forming CO2, water and also toxic pollutants such as CO and C. For example, the incomplete combustion of octane: Fuel + oxygen —> carbon dioxide + water + CO + C(s) C8H18(g) + 8O2(g) —> 6CO2(g) + 9H2O(l) + CO(g) + C(s) Incomplete: CO + H2O C + H2O C + CO + H2O * Combustion is a chemical reaction involving a fuel and an oxidant (usually oxygen) which products different products depending on the availability of oxygen * Complete combustion occurs when there is an excess supply of oxygen, forming carbon dioxide and water. For example, the complete combustion of octane * Very efficient therefore products more heat * Non toxic Fuel + oxygen —> CO2 + water C8H18(g) + 25/2 O2(g) —> 8CO2(g) + 9H2O(l) *Note: write the products as what they would be at room temperature NEED TO MONITOR * Combustion reactions need to be monitored to ensure there is a sufficient supply of oxygen to aovoid incomplete combustion * This prevents the release of toxic pollutants such sa CO and carbon soot which may cause respiratory diseases and maximises the efficiency of fuel burnt * Combustion reactions also need to be monitored to avoid the release of SO2 and NOx pollutants which contribute to acid rain, photochemical smog which reduces visibility and causes respiratory problems

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

* Prior to the invention of the Haber process, one of the world's sources of nitrogen fertilisers was natural salt petre deposits (NaNO3) from Chile * However the depleting natural sources of saltpetre (NaNO3) + guano depositsand growing world population increased the demand for fertilisers to grow food * During WWI, the Allied troops cut off Germany's supply of saltpetre in an attempt to starve them and prevent the manufacture of explosives * Fritz Haber was a German Chemist who synthesised ammonia from nitrogen and hydrogen using an iron catalyst, and Carl Bosch scaled the Haber process to an industrial level. * This, combined with the rise of the Ostwald process to convert ammonia into nitric acid and nitrates, provided Germany with an industrial source of nitrogen compounds which could be used to produce fertilisers and explosives * This allowed crops and food to be grown, avoiding a world famine and provided Germany with weapons which prolonged the war effort (they wanted nitrogen compounds)

How does the flame test work and what are the colours

* Some cations when placed in a flame will produce a distinct colour * To perform — a piece of platinum wire in a loop (inoculating loop) is cleaned with conc HCl and heated until red in flame (removes cations e.g. Na+ or K+ which can change the colour) * Its dipped into the sample and placed in the flame Pb2+ -- blue hiwte Ca2+ -- brick red Cu2+ -- emerald green Ba2+ -- apple green

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

* the monitoring of the vessel's temperature, pressreu, ratio of reactants, catalyst, contaminants and removal of ammonia is crucial to maintain ROR, yield, safety and efficiency SAFETY * Dangerous as it can affect the lungs (it is a caustic gas and thus can eat away at the lungs. Liquefied ammonia can lead to prostate like injuries and burn the skin)and it also has a pungent odour in concentrations larger in 0.6ppm * At high temperatures it can decompose to form H2 and NO, leading to explosiosn * Sately * Wear gloves, safety goggles and lab coat * All contact with ammonia should be done in a fume cupboard in a well ventilated ooms * Work places with ammonia must have gas masks and respiratory protection as part of OHS guidelines TEMPERATURE * Monitoring the temperature of the reaction vessel is required so it remains at its compromise temperature of 450 degrees * This is to ensure the optimal rate of reaction and yield (as discussed above). Also, extremely high temperatures will melt and destroy the iron catlyst PRESSURE * Monitoring the pressure of the reaction vessel is required so it remains at its compromise pressure of 200atm * This is to ensure a high rate of reaciton and yield as well as avoiding extremely high pressures which are expensive to maintain and may cause explosions (as explained before) RATIO OF REACTANTS The ratio fo H2 and N2 should be in a 3:1 ratio to avoid build up of reactant gases which may increase pressure and reduce the efficiency of reaction CATALYST * ensure that it is granulated so that enough surface area for highest rate of reaction CONTAMINANT (ensure not to poison catalyst with CO and SO4 compounds, ensure no oxygen as can react with H2 = explosion as exothermic, ensure nno inert gases) * The reaction mixture is monitored to ensure there are no contaminants such as OC or sulfur compounds which may po8isoin the Fe3O4 catalyst and prevent it from functioning * It is monitored to ensure there is no oxygen which may react with teh hydrogen's in an extremely exothermic reaction and cause an explosion * Monitored for inert gases. Whilst they do not change the partial pressure of the system, which means they have no effect of equilibrium, the addition of any gas including inert gasesintroduces inefficiencies in the reaction, reducing the rate of reaction. The yield of the substances will not be affected, however ti will take longer to reach maximum yield because any collusion that occurs between a reactant and tom and the inert gas wastes energy for the reaction REMOVAL

Analyse information to evaluate the reliability of the results of the above investigation and to propose solutions to problems encountered in the procedure

1. BaSO4 particles too small and would pass through the filter >Fine grade filter paper + sintered glass crucible to minimise prod size > Solution was digested and barium chloride was added in drops to increase BaSO4 size > Agar solution was used as a coagulant, causing the BaSO4 particles to clump together, increasing particle size 2. Loss of precipitate when transferring from beaker to funnel > The beaker was washed with distilled water to ensure all the precipitate is transferred 3. Excess chloride ions not removed from residue = larger mass of precipitate > The crucible was washed several times with distilled water until there was no more chloride ions left, indicated by adding AgNO3 to filtrate 4. Fertiliser was not completely dissolved = leading to a larger mass of precipitate > HCl help to further dissolve 5. Precipitae still contained water and was not completely dried = larger mass of preipciate > Longer period of drying was used until the preicpaite remained at a constant mass

Calcaution of sulphate in fertslier

1. Mass percentage of sulfate in BaSO4 2. Mass of sulfate in precipitate by multiplying precipitae wiht percentage 3. Percentage sulphate in fertilsier = mass SO42-/mass fertislier * 100

Describe the composition and layered structure of the atmosphere

78 percent N2 21 percent O2 0.93 argon NOx, SO2, H2O, CH4, O3, CO2 * these gases exist in PPM * the percentage of water vapour in atmosphre varies LAYERED STRUCTRUE * the atmosphere is divided on the basis of the changes in temperature and chemcial compositon not altitude * troposphere, stratosphere, mesophere, thermosphere (ionisophere part of it), exosphere 1. Troposphere 0-15km, temperature decrsaes as altitude increases, where whether is experineced 2. Stratosphere, 15-50, temperature increases as altitude increases, where planes fly and contians the ozone at 25km 3. Mesosphere 50-85, temperature decrease and increase altitude, meteorites burn up 4. Thermosphere, 85+, temperature incresaes as altitude incersaes, space shuttle orbit

What is a CCB

A coordinate covalent bond is a type of covalent bond where both electrons shared between 2 atoms comes from one atom

Compare the properties of the gaseous forms of oxygen and the oxygen free radical

A free radical is a highly reactive yet neutral atom or molecule with upaired electrons They only exist in the lower atomsphere for a brief amount of time before they react to become more stbale MOLECULAR SHAPE * O2 is linear whereas O is a monoatomic oxygen atom * lewis dot * reactivity of O2 less than O which is extremeely reactive

Describe the assess the effectiveness of methods used to purify and sanitise mass water supplies

A series of physical and chemical tests are done to purify and sanitise mass water supplies for drinking including: monitoring catchment, screening, aeration, flocculation, sedminentation, filtration, chlorination, fluoridation, addition of KMnO4 and controlling pH Purifying = removing suspended solids, odour and colour Sanitising = removing harmful organisms such as bacteria or viruses Note: fluoridation, addition of KMnO4 and controlling pH improves the quality of water for domestic use and is not part of the purificaiton or sanitisation for mass water supply MONITORING CATCHMENT * the catchment is the area of land where all the streams and rainfall drain into a ctiy's water storage dam * the first step in ensuring good water quality is to protect the catchment and keep it clean * involves preventing land clearing, agriculture or idstry in the ntire catchment area to ensure that water that flows into the dam is free of sediments and animal waste SCREENING (physical) * metal screens which act as sieves are used to remove large debris such as land matter in the raw water AERATION (physical) * The water is sprayed into air to increase the concentration of dissolved oxygen * This oxidises the iron and manganese salts which contribute to the yellow colour and odour of water. This forms insoluble solids which are later removed * Increasing DO improves taste of drinking water FLOCCULATION * Fine particles suspended in water have electric charges on their surface which repel each other preventing them from forming larger particles * These small particles are unable to settle down as sediment and are too small to be removed by conventional filtration, so flocculation is used to form larger particles which can be more easily removed * Slaked lime ( Ca(OH)2 ) is added to water to increase the pH and encourage the formation of precipitates * Floculation, also known as coagulation, involves adding an electrolyte such as iron (III) chloride, FeCl3, which reacts with water to form the flocculant (or coagulant) Fe(OH)3 FeCl3 + H2O —> Fe(OH)3 + 3HCl * The flocculant adsorbs fine, suspended particles and some bacteria, joining and forming larger particles called flocs SEDIMENTATION (physical) * involves sending the flocculated water to large settling tanks which allows the water to sediment * the sediment forms a sludge at the bottom which can be easily removed and used for agriculture fertilsier FILTRATION (physical) * process of passing the water from the settling tank through layers of fine sand, gravel and anthracite coal filter beds to remove any remaining suspended particles * anthracite coal rmeoves unpleasant odour and taste from the organic matter * however, some bacterias and viruses are not removed CHLORINATION (chemical) * process of bubbling chlorine gas (1-2ppm) into the water as a means of sanitising the water. It forms hypochlorite * these ions sanitise the water by killing most harmul bacteria and viruses * too much contributes to an unpleasant taste of drinking water ASSESSMENT * * These methods are effective to purify water as the process is fast and reliable. None of the method are effective on their own * Sand filtration removes high proportion of particulate matter after flocculation, but not extremely small particles. Fast enough to produce volume of treated water required by cities without the expense of using finer filters e.g. membrane filters * While chlorination is a cost effective way of removing most disease causing agents, it is not effective at killing viruses and protozons e.g Giadia. Excessive chlorine may leave unpleasant odour to water * A membrane filter more effective for fine suspended particles than sand filter, but costly and impractical for a town's water supply as it slows down the rate of water flow and purification. Due to high quality of Sydney's raw water, membrane filtration is currently considered too expensive for the relatively small improvements in water quality that it provides * Ozone sterilisation effective at removing harmful organisms that chlorination cannot destroy. However, this is too expensive

Describe how AAS work

ABSORPTION AND EMISSION SPECTRA * When an atom is irradiated with white light i.e. visible, then it absorbs specific frequencies of light known as absorption spectrum * This radiation excites electrons which exist as discrete energy levels, to higher energy levels * After a short time, the electron will jump back down to ground state, and release a photon * The emission fo specific frequencies of light is known as emission spectrum * For any one element the light is absorbed and light emitted are identical, discrete wavelengths. Each element has a unique absorption and emission spectrum AAS * Quantitative form of analysis that uses the absorption of light to measure the concentration of metal ions in solution * A spectrophotometer (or spectrometer) is a device that detects and measures a substance by its absorbance of certain wavelengths of light from the electromagnetic spectrum. * It uses emission and absorption spectra to deteirne the amount fo light absorbed by an element in a sample and hence its concentration NOTE: first you make a standard solution of the metal to be analsyed and diltued to obtain a series of standards with accurately known concentration. The standard solutions are aspirated into teh flame and the absorbance of each is determined, and this is plotted to give a calibration curve. Then you do the second solution of unknown concentration and repeat (the process down below) * First: an aqueous solutoin f a sample with known conc (standard soln) to be analysed is drawn through a capillary tube into a nebuliser (or atomiser) where it is aspirated into a fine mist or spray of liquid particles * The fine mist is mixed with a fuel and its oxidant in a flame which burns off the solvent and provides energy to convert ions and molecules into ground state atoms (atomisation) * A specific hollow cathode lamp, which emits light in the wavelenght fo emission/absorption spectrum of the element being analysed, is passed through th flame and absorbed by the atomised sample * The light passes through the flame in a prism or monochromator which splits the light into different wavelengths on the photomultipllier * By measuring the intensity fo particular wavelengths on the photomultiplier with teh aspirated sample and without the aspirated sample, the amount of light absorbed by the atomised sample (absorbance) can be determined OR the amount of light absorbed by the flame is measured, can be used to determine conc * This is proportional to the concentration fo atoms present via Beer Lambert Law Absorbance = log10Io/I = εlc * Io = intensity of light wiht no sample * I with sample * E is molar absorptivity * I is the path length * C is concentration of sampel * Can use calculation C= k x absorbance and find k, then use C1A1 = C2A2 to find final concentration * The absorbance of this sample is plotted over concentraiton to make a calibration curve * the process is repeated to find the absorbance of the solution iwth unknown conc, and then using the calibration curve from before the info is interpolated * Curve is absorbance over concentration (ppm) * To convert to ppm, multiply C by molar mass and by 1000 * At higher concentrations, interactions between the atoms being analysed affect teh absorption characteristics, resulting in a non linear relationship between absorbance and concencetration * Hnece best results when A is 0.1 to 0.8 which is achieved by diluting teh sample

Ad and dis of AAS, the uses and evaluate impact on tract elements

ADVANTAGE * Very sensitive and accurate method of quantitative analysis (up to ppt) * Relatively simple and fast (when element tested is known) * the metal ion doesn't have to be isolated from the mixture because a specific lamp is used which corresponds to the absorption spectrum of the metal ion being investigated * reliable as repetitions of measurements can be made DIS * Only works for metal cations * the type of metal ion needs to be known * Time consuming and inconvenient when testing for a large range f elemtns as AAS can only test for one element at a time * Expensive equipment USES * measuring the amount of heavy metals in the environment, measuring the concentrations of trace elemtns in soils and living organism TRACE * Trace elements are elemtns which are required by living organisms in vey small amounts (1 to 100ppm) for healthy functionign * Prior to invention fo AA, gravimetric analsy was used to determine the concentration of elements in a sample however this method of analyse was not accurate enough to detect small concentrations of trace elements in soils and living oragnisms * The invention of AAS allowed a sensitive technique to detect and measure small concnetartiosn fo trace elements in soils and liven orgasnims * It was discovered taht the presence of trace elemtns was related to teh good healthy of living organisms and a deficiency of trace elemtns related to bad health and disease * E.g. legume crops in arid parts of Victoria failed to grow until AAS was used to determinee molybdenum (Mo) deficiency * This deficiency was rectified and legume crops thrived * Hence AAS has a significant impact on our scientific understanding to detect the existence of trace elements and their effect on living organisms e.g. MO in legume crops

Present information from secondary sources to identify alternative chemicals used to replace CFCs and evaluate the effectiveness of their use as a replacement for CFCs

ALTERNATIVES 1. HCFCs (hydrochlorofluorocarbons) * these are moderately effective in minimising the ozone depletion thus serve only as a temporary solution * when released to the atmosphere, the high reactivity of the C-H bond means that it will be broken down easily by reactive radicals in the troposphere so only a small proportion reach the stratosphere to deplete the ozone layer * however, because a small amount still reach the stratosphere and there is still the presence of the chlorine atom, it can break down the ozone 2. HFCs (hydrofluorocarbons) * Very effective in minimising ozone depletion * Contain reactive C-H bond therefore can decompose in the troposphere * No C-Cl bond to form chlorine free radicals = no ozone depleting potential is * E.g. HFC-134a used in refrigeration and air conditioning * While HFC-134a is non flammable and has suitable properties, it is more expensive and less efficient than the CFCs it replaces, but this is a small price to pay for protecting stratospheric ozone EVALUATION Although HCFCs and HFCs are more expensive to produce than CFCs, HFCs are extremely effective as an alternative replacement for CFCs due to their low and 0 ozone depletion potential. Also, HFCs are not as efficient as the CFCs it replaces, thus more research is required to develop effective alternative chemicals to CFCs

Gather, process and present information to interpret secondary data from AAS measurement and evaluate the effectiveness of this in pollution control

Ad and dis Evaluation * Although AAS not useful for anions, range of pollutants, unknown pollutant or limited budget, teh ad of AAS e.g. can measure very low conc of elements such as heavy metals outweighs its disadvantges * Hence AAS is extremely effective in measuring low ocncnetariotns of heavy metal pollutants in air, water soil or food E.g. lead in water * PB is bioaccumulatvie, toxic heavy metal pollutant which causes neurological damage * Samples of drinking water were analysed to determine the concentration fo lead * A calibration curve was made with standard solution fo known Pb concentrations and absorbance measured using AAS * The absorbance of drinking water samples was then measured using AAS and compared to teh calibration curve to determine the concentration fo Pb and whether the water is toxic * Hence AAS is effectively used to monitor and manage heavy metal pollution e.g. Pb

Data, plan, select equipment and perform first hand investigation to measure the sulfate content of lawn fertiliser and explain the chemistry involved

Aim: to measure the sulphate content in fertiliser Method 1. Measure 0.2g of lawn fertiliser (ammonium sulphate) in a beaker using an electronic balance 2. Dissolve the lawn fertiliser with 1-2mL of 0.1M HCl and 100mL of distilled water in 500mL beaker and stirring the solution to remove CO3 ions 3. Dilute the solution with another 200mL of distilled water 4. Add 10mL of BaCl2 in drops to form a white precipitate BaSO4 1. Ba2+ +SO42- —> BaSO4 5. Continue to add until no more precipitate then add further 10 drops 6. Heat the solution until almost boiling 80 degrees. Add 10mL of 0.1 percent agar solution while stirring to coagulate the barium sulphate precipitate, increasing the particle size of teh preicpate 1. Ensure to account for this weight 7. The solution filtered using fine grade filter paper in a sintered glass crucible, ensuring all the solution is transferred by washing it with distilled water 8. The crucible was washed several times with distilled water (to remove excess chloride ions) until no more precipitate forms when silver nitrate (AgNO3) is added to the filtrate 9. The precipitate dried adn weight

Solubility rules

All ammonium salts and group 1 soluble All acetates, nitrates and bicarbontes soluble All chlorides, bromides, iodides soluble except lead, silver, mercury All phosphates, carbonates, hydroxides, sulphides and oxides are insoluble except group 1 and ammonium All sulphates are soluble excpet lead, mercury, barium, silver and calcium partially

Identify and describe the industrial uses of ammonia

Ammonium sulphate fertilisers * nitrogen in the ammonia is needed for fertilisers to help plant growth Explosives * ammonia is used to make nitric acid via the Ostwald process which is then used to make TNT explosives for things such as mining * nitric acid can also be used for dyes and plastics Pharmeceuticals Cationic detergents Used in the rubber industry for vulcanisation and stabiliser

Compare the properties of oxygen allotropes O2 and O3 and account for them on the basis of molecular structure and bonding Also what is an allotrope

An allotrope is a different structural arrangement of same element with different physical and chemicial properties Allotropes of oxygen are O2 and O3 Structure * O3 is bent whereas O2 is linear * this is becasue O3 has a lone pair electron therefore creates triangular planar/bend shep Lewis dot Density * O2 is less dense than O3 becasue O2 only has 2 atoms per molecule whereas O3 has 3 i.e. O2 similar density to air whereas 03 is 1.5 Reactivity O2 has double bond = larger amount of energy to break O3 has double bond and a single CC bond = single bond CC need less energy to break than double covalent = lower amount fo energy = more reactive Solubility O2 is non polar = weak dispersion forces with water = lower O3 polar from resonance effect = can form DD and H bonds with H2O = higher MP/BP * O2 has lower MP that O3 * this is becasue O2 is non polar, therefore it only forms weak dispersion inter forces = less energy to overocme * O3 is polar due to the resonance effect therefore can form DD inter forces = more energy to break Smell O2 has none but O3 is acrid Colour * pale blue of O3 but O2 is colourless

Gather, process and present information on the features of the local town water supply in terms of catchment area, possible sources of contamination in this catchment, chemical tests available to determine levels and types of contaminants, physical and chemical processes used to purify water chemical additives in the water and the reasons for the presence of these additives

CATCHMENT AREA * the Warragamba dam is Sydney's main water storage dam, accounting for about 80 percent of Sydney's water with its catchment area of about 9000km^-2 SOURCES OF CONTAMINATION Agriculture -- agricultural run off contains high levels of phosphate and nitrate ions from leeching from fertilisers in soils and crops. Cattle graze along creeks and rivers. Therefore, the water may run through animal faeces which increases pathogens and BOD Land clearing and deforestation -- increases turbidity and TDS in the water flowing into the dam Sewage -- sewage treatment plants along some of the catchment rivers discharge treated sewage into the river. During floods sewage treatment plants cannot handle heavy input of storm water flows, so raw untreated sewage is allowed to flow into the water body. This leads to contamination of water with bacteria and excess ions Mining -- the rain water can leech out minerals (iron and manganese) from the natural soil and rock strata around catchment areas TESTING FOR CONTAMINANTS Common ions -- tested using electrical conductivity Heavy metal ions -- tested with sulfide test (qualitative analysis) and AAS/AES (quantitative) WATER PURIFICATION * water is passed through metal screens to remove large debris * this water is then flocculated with FeCl3 and stirred to encourage precipitation formation * water left in settling tanks to allow for sedimentation which is then removed (the sludge) and water is filtered through layers of sand and gravel * water is finally sanitised by chlorination CHEMICAL ADDITIVES * Chlorine (Cl2) added as disinfecting agent to sanitise water — Cl2(g) dissolved, forms hypochlorite ions which kill bacteria and some viruses * Cl2(g) + H2O(l) —> HOCl(aq) + HCl(aq) * Fluoride (F-) is added in the form of NaF to strengthen tooth enamel, decreasing the likelihood of tooth decay (but doesn't improve safety fo water) * pH readjustment with lime water Ca(OH)2 to prevent corrosion fo pipes

Identify the main pollutants found in the lower atmosphree and their sources

CO AND C SOOT * incompletely combustion of coal at power stations, bushfires and cars NOX * internal combustion of cars and power tations SO2 * the smelting of metals contianing sulfide * the extraction of sulfur via the frasch process ASBESTOS * insulation CFCS * refrigerant, prpellants and blowing agents HALONS * fire extinguisher OZONE * the chemical decomposition via UV radiation of the NOx in photochemical smog LEAD * From the sanding/knocking down of buildings wiht leaded paint * Lead smelters * Pottery glazes * Burning leaded petrol

What are the colours of the cations in solution

Ca -- colourles Pb -- colorless Fe2 -- pale green Fe3 -- yellow orange Cu -- blue green Ba -- colourless

Identify factors that affect the concentrations of a range of ions in solution in natural bodies of water such as rivers and oceans

Concentration of a range of ions in natural bodies of water such as rivers and oceans is affected by both natural and human acitivty NATURAL The pathway from rain to river/ocean * if the rain falls into bushland and runs into streams, it may pick up small amounts of ions e.g. phosphates and nitrates from the surface minerals and Ca2+ and Mg2+ from the surface. TDS will be below 50ppm * the rain travels through underground aquifers to the stream, it will pick up Ca2+, Mg2+, SO4 2-, Cl- and CO3 2- which are dissolved from the soils and rocks it flows through. TDS around 100-300ppm * if the rain percolates in underground aquifers or artesian basins and emerges to the surface centuries later, has high concentrations of the above ions as well as Fe3+, Mn2+, Cu2+ and Zn2+. The TDS will be above 1000ppm pH of rain: Acidic rain (pH < 5) is able to leech cations from soils and rocks easier e.g. Ca2+, Mg2+ and Fe3+ leading to increased concentration of ions HUMAN ACTIVITY Agriculture Fertiliser run off used in agriculture increases concentration of phosphates and nitrates in the water Effluent discharge * Discharge of sewage into bodies of water increases concentration of NO3- and PO4 3- as well as turbidity, TDS and pathogen levels * Industrial effluents can increase the concentrations of toxic heavy metal ions e.g. Pb2+, Hg2+, Cd2+, Cr2+, Cu2+ and Zn2+ * Storm water run off can increase the concentration of a variety of ions in water Leeching from rubbish dumps When water passes over rubbish dumps it may leach toxic heavy metals such as Pb2+, Hg2+, Cd2+, Cr2+, Cu2+ and Zn2+ Land clearing Land clearing increases the water flow from land to streams, increasing the sediment and dissolved ions e.g. K+, Na+, Ca2+, Cl-, Mg2+, Cl-, SO42- and CO32-

Describe the design and composition of microscopic membrane filters and explain how they purify contaminated water

DEFINITION -- microscopic membrane filters consist of a thin film made from a synthetic polymer (PTFE) which has small, uniform pores used to filter out colloidal particles, solutes and microorganisms from solution * the membrane can filter using gravity, vacuum or a pump to force the liquid through the membrane so clean water can be collected from the inside of the tube There are 2 types of membrane filters. 1. the simplest type consists of a sheet of porous polymer which is folded around a hollow core and is surrounded by a casing. The water is pushed across the membrane (not through it) so that is reduces blockages and filters out the particles larger than the pore size whereby the clean water exits out the hollow core 2. the second type is where the membranes are formed into hollow capillaries known as hollow fibre membrane filters. Many are bounded together to form a filtering unit with a very large surface area. Raw water runs along the outside of the capillary fibres and clean wter penetrates the pores to inside each capillary * microscopic membrane filters have microscopic pores and the appropriate sized filters can reduce the need for the water to be chemically treated * depending on the pore sizes, the filters can be classified as microfiltration, ultrafiltration, nanofiltration and reverse osmosis * MMF can remove small suspended particles but they can't remove ions e.g. heavy metal ions, nitrate or phosphate ions. Therefore, reverse osmosis is used which involves applyign pressure to a solution to push the water molecules through the membrane, leaving impurities behind * the filters can be cleaned by back flushing and then reused

What is the equation for Haber process, who came up with it, and where are the reactants obtained from

Fritz Haber developed the process in the early 20th century of the synthesis of ammonia from N2 and H2 but Carl Bosch made it on the industrial scale N2 + 3H2 <-> 2NH3 where H = -92kJ/mol OBtaning reactants Nitrogen from air as air is around 78 percent N2 Hydrogen from other processes e.g. steam reforming of natural gas whereby methane decomposed to CO and H2

Gather, process and present information on the range and chemistry of the tests used to identify heavy metal pollution fo water and monitor possible eutrophication of waterways

HEAVY METALS * heavy metals are transition metals in addition to lead and arsenic. Hg, Pb, Cd, Cr, As the most concern QUALTITATIVE (sulfide test) * H2O acidified and few drops of Na2S is added * If precipitate forms, then one of these ions is present: Pb, Ag, Hg, Cu, Cadmium or arsenic * If no precipitate forms with acid present, sample is made slightly alkaline. If this produces precipitate then * Chromium, Zn, Fe, Nickel, Cobalt, Manganese or aluminium is present How it works * The sulphide test is based on the equilibrium S2- + 2H3O+ <-> H2S + 2H2O * In acid solution, the equilbiurm lies to the right. Even though only small amount of S present, sufficient enough to precipitate very insoluble sulphides e.g. Pb2+, Cu2+ * (Eq'n with Pb2+ and S-_ * Alkaline conditions, equilibrium lies to the left. Large amount fo sulphide so precipitation cations that form less insoluble sulphides e.g. Zn2+ and Fe2+ * (Eq'n) Other tests * Can use flame test for Cu2+ and precipitation tests e.g. NaOH forms precipitate with mercury, cadmium, zinc, chromium, and aluminium ions QUANTITATIVE * Gravimetric and volumetric analysis but limited due to low concentrations involve din environmental water samples * AES — can analyse several metals in one measurement * Qualitatively identifying elements in a sample * AAS — can only analyse one metal at a time as each requires a separate lamp * Quantitatively identifying elements in a sample EUTROPHICATION * process in which a water body becomes enriched with nutrients e.g. phosphates, nitrates to such an extent that algal blooms become likely Effect of algal blooms * sunlight is blocked by excessive plant growth at the water surface therefore photosynthesis is disrupted * algal blooms interfere with diffusion of oxygen from the air into the water * when algae dies, their decomposition leads to severe oxygen depletion in the waterway that threatens survival * blue green algae (cyanobacteria) in algal blooms produce poisons that can kill livestock and cause serious illness in humans. water unsuitable for normal uses as clogged up with algae and has an unpleasant taste * the effect of eutrophication measured by assessing DO and BOD and observing for any unprecedented presence of algae * generally phosphate is the growth limit nutrient (present in the least amount) so it is the best one to check for eutrophication PHOSPHATE Qualitative — presence of phosphate ions indicated by pale yellow precipitate with ammonium molybdate Quantitative * Phosphate concentrations measured using sensitive colorimetric method which relies on the quantitative measurement of the absorption of light by coloured solution * A measured quantity of solution of ammonium molybdate is added, followed by a measured quantity of ascorbic acid (vitamin C). This produces an intense blue colour * By comparing the absorbance of this soliton with standard known solutions the concentration of phosphate can be calculated colorimetrically NITRATE Qualitative -- qualitatively identified using the brown ring method. This is when the water sample is added into a test tube with concentration H2SO4 and FeSO4. The brown ring at the junction indicates the presence of phosphate ions Quantitative -- quantitatively measured by also using colorimetry. A reductant is added to convert the nitrate ions into nitrite ions. The nitrite ions are then reacted with a coloured reagent to produce a pink purple dye that is measured colorimetrically against known standards

Analyse the information available that indicates changes in atmospheric ozone concentrations, describe the changes observed and how this information was obtained

INTRODUCTION Stratospheric ozone is measured using ground based instruments, instruments on satellites and instruments on weather balloons. Measured in Dobson units GROUND BASED * UV spectrophotometers are used as ground based instruments * they are pointed directly upwards to the atmosphere * they measure the light intensity of wavelengths that ozone absorbs and then they measure the wavelengths on either side in which ozone doesn't absorb * by comparing the 2 light intensities, the total ozone concentration per unit area at that location is determined SATELLITE BASED * TOMS are placed on satellites (total ozone mapping spectrophotometers) and measure the ozone concentrations similar to the UV spectrophotometers * as the satellite orbits the earth, gives a measure of the ozone concentration as a funciton of altitude and geographical position WEATHER BALLOON BASED * also uses UV spectrophotometers which are placed on high altitude weather balloons which rise up to the stratosphere * They are pointed downwards and measure the intensity of light which ozone absorbs and at a wavelength on ether side at which ozone does not absorb * A comparioisn of these 2 intensities give a measure of the total ozone concentration per unit area in that location CHANGES OBSERVED * Stratospheric ozone concentrations have been measured since 1957 using the above technolgoies * TOMS have revealed a huge depletion in the ozone layer over the Antarctic due to the use of CFCs and halons * This is because of the polar region's favourable conditions for ozone destroying reaciotns * This is because cold temperatures form PSCs (polar stratospheric clouds) * Reactions occur on the surface of the PSCs, causing an increase in the chlorine radical, causing more ozone depletion to occur by the chemical reactions (cite them) * Since 1957 there has been a decline in the ozone concentration over Antarctica (30 percent by 1985) despite ban of CFCs and halons * This is becasue it takes time for these ozone depleting substances to be removed from the stratosphere * Recently concentration of the ozone layer over Antarctica has risen though

Describe ozone as a molecule able to act both as an upper atmosphere UV radiation shield and a lower atmosphere pollutant

In the upper atmosphere (stratosphere) * UV radiation is damaging to organisms therefore the ozone layer acts as a protective, radiation shield * high concentrations of ozone (up to 10ppm) * UV B and UV C causing damage such as melanoma, eye cataracts, sunburns. UV A is beneficial as it facilitates vitamin D absorption and photosynthesis How it is formed 1. O2 absorbs UV radiation from the sun and dissociates into 2 oxygen radicals O2 --UV Radiation--> 2O• (ΔH > 0) 2. The radicals and an oxygen react to form ozone. A third molecule is needed ot absorb the heat energy in the reaction (usually nitrogen). Since M absorbs the heat energy, this casues the temperature of the stratosphere to increase as altitude increases. O2 + O• + M --> O3 + M* (ΔH<0) 3. The ozone can absorb the UV radiation: O3 --UV--> O2 + O• (ΔH>0) O• + O3 --> 2O2 (ΔH<0) The net result is the continuous formation and decomposition cycle of ozone, where solar energy is converted into heat Therefore much of the sun's UV is absorbed by the ozone and fails to reach the surface of the earth LOWER ATMOSPHERE * ozone is a toxic air pollutant causing environmental and health issues in LA Health issues * ozone is a strong oxidant that reacts with sensitive mucous membranes when breathed in Effects -- irritation of the eyes, respiratory issues, headache and premature fatigue Photochemical fog -- air pollutant when sunlight relights with vehicle exhaust gases to form ozone and other harmful substances Ozone forms in troposphere when high amounts of sunlight and NO2 NO2 --sunlight--> NO + O• O• + O2 --> O3

Gather, process and present information to describe and explain evidence for the need to monitor levels of specific ions in substances used in society

Lead * causes neurological damages in children, behavioural disorders and hearing loss * disruptoin of enzyme systems causing damage to liver, kdiney and the reproductive system * anaemia * fatigue, headaches Pb may contaminate the environment from the following sources * Leaded petrol — Pb used to be added to prevent knocking in engines. When combusted, this lead would be released into amotsphre * Mining adn refining fo lead — mining and smelting of lad containing ores reeases Pb into the atmosphere as well as effluent discharge in water * Industries — industries which used lead acid batteries or soldering release lead through effluent discharge * Pottery glazing and stained glass window making — releases atmosphreic lead * Old paints — paints used to us lead based pigments which is released through emotion into water or particulates during sanding, demolition fo houses Lead from environment can enter body via: inhalation, drinking or eating contaminated food or drink. Hence necessary to monitor levels in environment via AAS because the concentration is low, to prevent this detrimental effects form occurring

What are the factors of good water quality?

Low salinity Low turbidity High percentage of dissolved oxygen for pleasant taste Is odourless, colourless, clear, neutral of pH 7 Low biological oxygen demand No pathogens Contains no toxic chemicals Low concentrations of phosphates and nitrates

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

NAME: Luke Smith INDUSTRY/ENTERPRISE: industrial chemist and analytical chemist in the industry responsible for cracking ethane to form ethene, then polymerising it to form polyethene. Located in qenos, australia BRANCH OF CHEMISTRY: industrial and analytical AN INDUSTRIAL CHEMIST MONITORS AND MANAGES INDUSTRIAL PROCESSES TO ENSURE * Reaction conditions of the production process to maximise reaction rate and yield * Products are free from toxic contaminants * monitors: catalyst e.g. may be poisoned from CO2, polymerisation * Quality control of products (polyethylene and ethene) * Releases of wastes into the environemnt do not exceed allowable amounts * Working environment is safe * Train shift workers to carry out chemical tests and checks reliability fo these results * Solves on site problems, calibrate instruments, perform analysis to ensure results are reliable. * Collaborate with other chemists in other occupations such as: physical chemists, analytical chemists and process engineers, to solve problems at catalytic furnaces and to improve the overall industry efficiency of the cracking process Industrial chemists are employed in many industrial processes e.g. * petrochemical industry * inorganic synthesis industry e.g. Haber * Mineral * Research and development CHEMICAL PRINCIPLE * Luke Smith uses the chemical principle of solubility in gas liquid chromatography and adsorption in gas-solid chromatography in order to separate and quantitatively measure and determine the substances in the gaseous mixture * the gaseous mixture is injected into an inert gaseous stream e.g. helium to form a gaseous mobile phase * this gaseous mobile phase flows into a column containing a liquid stationary phase e.g. polyethene glycol * the gaseous mobile phase will dissolve into the liquid stationary phase at different extents depending on the solubility and polarity (if it is non polar, then it interacts less therefore dissolves faster) * these components will pass through the column at different speeds (greater solubility will travel slower) and hence will be separated * a detector at the end of the column detects and quantitatively measures each substance Solid stationary phase • solid stationary phase • as the mixture travels through the stationary phase, different components adsorb (sticks to the solid) to the surface of the solid at different amounts • this results in difference in speed between different components (ie. more adsorption = slower) • the different components are separated out and analysed * Luke uses gas liquid chromatography to ensure that the ratio of nitrogen to hydrogen remains at 1:3 to maximise efficiency * he also ensures that there are no toxic contaminants within the reaction vessel which could poison the Fe3O4 catalyst e.g. CO which bonds with the catalyst preventing the H2 and N2 from bonding * he also checks the temperature, the rate of reaction, partial pressure and concentration, loosely monitoring them in order to maximise the yield * at the end of the day he must produce a report of what happened, which includes the amount of reactants used, the amount of products produced and any issues that occurred

Present information from secondary sources to write the equations to show the ractions involving CFCs and ozone to demonstrate the removal fo ozone front he atmosphere Discuss the problems associated with the use of CFCs and assess the effectiveness of steps taken to alleviate these problems

PROBLEMS WITH CFCS * CFCs used as refrigerants. Propellants and blowing agents released directly into the troposphere. Since they are inert and insoluble, cannot be decomposed by UV and cannot be washed out by rain respectively * Therefore they remain in troposphere for a long time until slowly diffuse into stratosphere where they destroy the ozone layer 1. CFCs undergo photodissociation to form chlorine radicals CCl3F --UV--> CCl2F + Cl• 2. Cl• + O3 --> ClO• + O2 3. The ClO• radical further reacts with oxygen radican which prevents the formation of ozone and regenerates a chlorine free raidcal and oxygen gas ClO• + O• -- O2 + Cl• This causes a chain reaction where the regenerated chlorine radical attacks another ozone molecule and the reactions repeat again Therefore only a small amount of CFC in the atmosphere can cause significant ozone destruction The depletion of ozone in the stratosphere (the thinning of the ozone layer) increases the amount of short wavelength UV into the lower atmosphere, causing problems such as: * sunburn * cancer in the tissue of living organisms * stunted plant growth * cracking of plastics Note: * halons produce bromine free radicals which are far more reactive than chlorine free radical = higher ozone depleting potential * C-F bond does NOT break under UV light * theoretically one CFC could destroy the whole ozone layer; however, it reacts with atmospheric methane which produces a methyl radical that has not ozone depleting potential CH4 + Cl• --> CH3• + HCl THE ANTARCTIC SPRING OZONE HOLE * the periodic depletion of the ozone layer in the Antarctic can be explained in terms of PSCs which act as catalytic surface. Formed in cold air fo polar vortex in the winter * in this vortex, produces molecular chlorine: ClONO2(g) + HCl(g) --> HNO3(s) + Cl2(g) * whilst the formation of chlorine gas is not a problem during winter, when the sun rises during spring: Cl2 --UV--> 2Cl• * this produces another source of chlorine radicals which increases the rate of ozone depletion in Antarctic and contributes to ozone hole (where the ozone layer is thinning) * in the summer, the polar vortex breaks up and the finite amount of Cl2 formed during winter is used up, and the rate of the ozone destruction returns to normal levels STEPS TAKEN TO ALLEVIATE THE PROBLEM The only way to stop ozone destruction is to stop releasing CFCs of any form: 1. the Montreal Protocol * this is an international agreement established in 1987 to phase out and ban the production and use of ozone depleting chemicals. CFCs banned by 1996, halons by 1994 and HCFCs by the early 21st century * also financial assistance for any developing countries to help phase out the use of these harmful ozone depleting chemcials * In Australia, all ozone depleting chemicals (CFCs, HCFCs, halons and tetrachloromethane) are all phased out 2. Alternative replacements for CFCs (another card) 3. Dealing with increased UV radiation * CFCs already in the stratosphere cannot be removed so measures are needed to reduce effects (High UV B and C i.e. short wavelength radiation) * Includes sunscreens with high sun protection (SPF 30+) and UV stabilisers in polymers to reduce breakdown in UV radiation EVALUATION * the Montreal Protocol, alternatives for CFCs and dealing with increased UV radiation has helped alleviate the problems of the ozone depleting layer

Identify between mixture and single ions

Single -- series of tests in separate smaples MIxture -- series of tests in a specific order. After identifying the action, excess anions added for complete precipitaiton and then filtered using a centrifuge -- this aoivds one cation interfering with the test of anotehr

Describe water quality tests for different components

TURBIDITY * this is a measure of the cloudiness or the amount of suspended solids in the water * high amounts unwanted because it decreases light penetration and gives an unpleasant taste and appearance * decreased light penetration means that plants can't photosynthesise, reducing the dissolved oxygen and negatively affecting aquatic life * therefore high water quality has low levels of turbidity How to measure * using a turbidity tube. This is a long, hollow cylindrical tube with a cross at the bottom. Fill it up with water sample until the cross is no longer visible. The reading on the side i.e. the height of the water is the measure of the turbidity in NTU HARDNESS * hardness is a measure of the concentration of divalent metal ions in the soluiton * you don't want high levels of Ca2+ and Mg2+ because this will precipitate with soap and decrease its cleaning action * ususally measured as a concentration of CaCO3 in ppm (mg/L) * high levels will create low quality water because hard water leads to limescale deposits on kettles and pipes How it is measured * titration with EDTA and eriochrome black t indicator. The Mg2+ or Ca2+ will react in a 1:1 ratio Ca2+ + EDTA4- —> CaEDTA2- n(Ca2+) = n(EDTA 4-) * AAS can measure the concentration of the cations (Mg2+ and Ca2+) TOTAL DISSOLVED SOLIDS (TDS) * the mass of solids dissolved in a unit volume of water (mg/L or ppm) * usually ionic compounds and smaller amounts of organic molecules * high quality water has low levels as it affects salinity and hardness How it is measured 1. Evaporation * any suspended, insoluble solids are filtered out otherwise they will be included in the mass of total dissolved solids * mass and volume of the sample is measured * sample is heated until the water evaporates (ensure no spitting otherwise there is a loss in mass) * * Mass of solid salt residue is then measured * Concentration can be determined: mass of solid (mg)/volume of sample (L) * Method inaccurate for low concentrations and usually used for high concentrations 2. Electrical conductivity * dissolved solids i.e. ions act as charged carreirs therefore the concentration can be determined via electrical conductivity * Dissolved solids i.e.g ions act as charged carriers therefore concentration can be determined via electrical conductivity * Conductivity meter is calibrated using standard solutions of KCl and calibration curve is constructed * 1V is applied across a unit cube of water to measure conductivity of solution and then compared to the calibration curve to determine TDS * Accurate for low concentrations DISSOLVED OXYGEN (DO) * measure of the concentration of molecular oxygen gas dissolved in a water sample * although O2 has low solubiliyt, it is necessary for aquatic lief (around 9ppm at SLC) for respiration * high water quality has sufficient concentration of O2 (>5ppm) How it is measured: 1. Winkler method titration * in an alkaline solution the dissolved oxygen oxidise the manganese ions into Mn (IV) * in an acidic solution the manganese (IV) ions will oxidise the iodide ions into iodide gas * the iodine is then titrated with Na2S2O3 using starch as an indicator 2. Oxygen electrode sensor * this method involves an electrolytic reaction where the rate of the electrolysis of oxygen is proportional to its concentration * a membrane which is permeable to oxygen but not water will allow the oxygen to pass through and be reduced at teh cathode * the chloride ions will be oxidised at the anode, resuting in a current to flow which can be measured and the concentration of the oxygen in determined CONCENTRATION OF COMMON IONS * * Common cations: Na+, Mg2+ and Ca2+ * Common anions: Cl-, PO4 3-, NO3 - * Mg and Ca ions contribute to water hardness * Excess levels of phosphates and nitrates contribute to eutrophication and algal blooms * High quality water = low concentrations of these ions * Na+ and Cl- = salinity of water which affects quality of life * Total concentaiotn of all ions make up total dissolved solids (TDS, below) How it is measured * Cations measured with AAS * Chloride ions measured using gravimetrical analysis or volumetric analysis with AgNO3 * Method for phosphates and nitrates explained later BIOCHEMICAL OXYGEN DEMAND (BOD) * Aerobic bacteria thrive in water samples by using dissolved oxygen (DO) to decompose organic matter into CO2, H2O, nitrates, sulphates and phosphates * Biochemical oxygen demand (BOD) is a measure of the concentration fo oxygen requried for the complete breakdown of organic matter by aerobic bacteria * Thus a high level of BOD indicates a large number of oxygen-consuming bacteria, leading to a drop in DO which negatively affects aquatic life To measure * Water samples expected to have low BOD i.e. unpolluted water: 2 samples of equal volume is taken and the DO of the first is measured and the second stored in an incubator 20 degrees cells in the dark. After 5 days teh DO level of the second sample is measured and the difference between DO is the BOD in * 5 days is standard as it is sufficient for oxygen to decompose organic matter * A constant temperature 20 degrees is used as different temps result in different DO * Incubated in the dark to avoid photosynthetic algae from producing oxygen * BOD = DO initial - DO after 5 days * For water samples expected to have a high BOD e.g. raw sewage, the same method as teh above is used expect water sampel is regularly aerated to ensure there is sufficient oxygen. The amount of oxygen used is measured before and after aeration ACIDIDTY * Measure of pH * High quality water is neutral as acidified or alkaline water samples affect aquatic life * pH meter * Calibrated using standard solutions * pH of water sample is measured

What must be reconcilced in industrial production of ammonia? Describe the conditions

The Haber process involves a compromise of reaction conditions: temperature, pressure, concentration and a catalyst to optimise the reaction energy, reaction rate and equilirbium * In any industrial process you want to optimise the rate and yield with the lowest cost (and thus you always want to fix the rate-yield conflict i.e. want to obtain the highest yield with the highest rate of reaction) * I.e. The hayer process involves a delicate balance between yield nad rate of production of Ammonia (always quote this) * To fix yield: involves the shifting of the equilibrium ONLY (changing pressure is usually the last option because it is the most expensive) * To fix rate: catalyst and temperature N2(g) + 3H2(g) <-Fe3O4 catalyst -> 2NH3(g) ΔH = -92kJ/mol Temperature A lower temperature will result in a decreased rate of reaction and higher yield (by LCP, explain LCP etc) * A low temperature would decrease the rate of reaction because the number of collisions between molecules would be reduced. This means the activation energy would not be reached and the overall reaction would take a longer time * Hence a compromise temperature of 450 degrees is required to balance reaction rate and yield (anything between 400-500) Pressrue * Higher pressures produce greater yield: By LCP, an increase in pressure will cause the equilibrium to shift to the side with the fewer gaseous molecules. Since the RHS as 2 and the LHS has 4, the RHS of the reaction is favoured i.e. the forward reaction will be favoured * higher pressures, the increased concentration of reactants results in a greater number of successful collisions and hence reaction rate * Compromise pressure of 200 atm is used to increase reaction rate, yield but not too high because of cost and risk of explosion (i.e. thus there is a delicate balance between yield, pressure of the system and the rate of reaciton of Ammonia production) Catalyst Use magnetite (Fe3O4) ( * This catalyst provides an alternative pathway ot lower the activation energy and thus reaction temperature and increase the rate of reaciton * Note: it must be written at the top of the equilibrium arrow Producing the catalyst * Heterogenous surface iron catalyst * Produced by reduced magnetite (Fe3O4) * This reducing involves exposing it to very high temrpatuers in the presence of H2 gas, which removes most of the oxygen and leaves behind a highly porous iron substance with a large suraface area * This porous materials then impregnated with Ca and Al2O3 to help maintain the structure o the catalyst over increasing its lifetime Process of catalysis * Increases the SA where the reaciton takes place * Large SA = facilitates absorption of molecules , to spatially coordinate collisions instead of relying on the random collision of N2 and H2 in the air. Magnetite provides surface for reaction 1. H2 and N2 approach surface of the iron 2. When they interact with the surface they are able to dissociate into their atoms much easier than in free air, thus producing N2 —> 2N and H2 —> 2H 3. The bonding between N and H then begin to form until we have ammonia 4. Ammonia molecules leaves the surface Concentration In the Haber process, ammonia is constantly removed from the reaction mixture through condensation/liquified * Ammonia has a higher BP than N2 and H2 so after it is cooled, it will condense out ot eh vessel whereas the N2 and H2 will remain in their gaseous state and are recycled to minimise wastage of reactants The equilibrium shifts to oppose the change by increasing the concentration fo ammonia (LCP). This is the forward reaction making it go almost in completion, hence the yield of ammonia increases * The preferred ratio of the N and H is 1:3 (derived from the stoichiometric ratios). This is when the complete reaction will occur. Since this is difficult to maintain, the continual recycling of unreacted chemicals will occur * If it is not in 1:3 then the equilibrium will shift to the reactants side (left) by LCP. This will produce excess reactants = inefficient Haber process = lower yeild

* 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 * Gather, process and present information from secondary sources about the work of practicing scientists, identifying * The variety fo chemical occupations * A specific chemical occupation for a more detailed study

There are a variety of occupations where chemists are employed and rely on certain skills such as: * analysis fo various chemical substances * collaboration with peers within their own fields as well as other sicencs * probelm solving and theoretical understanding of chemistry ANALYTICAL CHEMIST * analysis of various substances to understand their compositions and effects PHYSICAL * Investigation and study of the chemical processes in order to make them more efficient e.g. polymer and industrial chemists INDUSTRIAL Design and monitor industrial chemical processes e.g. petrochemcial industry NUCLEAR * to figure out how to produce radioisotopes and create new radioisotopes ENVIRONMENTAL * Determine how substances interact with sth environment/ecosystem * Determine the concentration of substances in nature (particularly air pollutants) BIOLOGICAL * Using chemistry to understand the biological processes that occur within the body and sustain life in some way e.g. microbiologists and geneticists THEORETICAL * Academic side of chemistry used to study the develpomtn of new methods and materials e.g. theoretical organic chemist