PEAK Chemical Monitoring and Management

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    Roy Fu HSCCHEMISTRY –     MODULETHREE   Roy Fu Chemical Monitoring and Management The chemical industry The Haber process Monitoring ions Atmospheric chemistry Monitoring water quality  The chemical industry 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. (1.1.1) Gather, process and present information from secondary sources about the work of practising scientists identifying: - the variety of ------chemical =-----------occupations - a specific chemical ---occupation for a -------more detailed study (1.2.1) -   There are many different branches of chemistry including:    Analytical chemistry; the determination of what substances are in a sample and how much of each is present.    Physical chemistry; the study and measurement of physical aspects of compounds and reactions such as rates of reaction/kinetics and the structure and bonding in compounds.    Environmental chemistry; the study of how substances interact in the environment and the monitoring of pollutants in air, water and soil.    Polymer chemistry; the development of new polymers, working out how polymerisation occurs and how to make it more efficient and studying the properties of polymers.    Nuclear chemistry; the production and uses of radioisotopes for medicine and industry and the study of the fundamental nature of nuclear reactions. -   Luke (not his real name) is an analytical chemist at Qenos , an Australian chemical manufacturing company in Botany Bay. -   This company makes ethylene by the thermal cracking of ethane and then polymerises it to form polyethylene. It also sells some ethylene to other companies that make ethylene oxide, ethylene glycol, non-ionic surfactants and other plastics. -   Luke has many roles as an analytical chemist. He must:    Monitor the quality of ethylene and polyethylene products, particularly checking the nature and amount of any impurities present.    Monitor waste water and gaseous emissions to ensure environmental standards are met.    Collaborate with process engineers at the cracking furnace to adjust operating conditions for yield optimisation.    Ensure instruments are calibrated and are operating properly. -   Gas-Liquid chromatography   (GLC) is a chemical principle used by Luke in his analysis. This technique involves a gas mobile phase  being vaporised into a stream of “He   carrier gas” that flows over a liquid stationary phase  coated onto the GLC column.   -   The gaseous components will dissolve in the stationary phase and then evaporate  back out of it at differing rates. The solubility of the gas will depend on its polarity relative to the stationary liquid. -   More soluble components will have longer retention times through the column as they move through the column more slowly. -   A separation is achieved and a detector measures the amount of each component as it emerges from the GLC column. A graph or chromatogram is produced which can be analysed.    -   The height of the peak and the area under the peak/integral provides a measure for the relative proportions of each component. Identify the need for collaboration between chemists as they collect and analyse data. (1.1.2) -   Since chemistry is such a board discipline, chemists will specialise in particular branches of chemistry. However, many chemical problems in the real world require expertise from many branches of chemistry and science. -   Solving complex problems will require chemists with different specialities and thus it is essential that chemists collaborate and  communicate  with each other. -   For example, environmental chemists may collaborate with analytical chemists to monitor pollutant levels and if there are excessive levels, they may collaborate to deduce a possible source of the contamination such as an industrial plant. They may then collaborate with industrial chemists to reduce these excessive emissions. Describe an example of a chemical reaction such as combustion, where reactants form different products under different conditions and thus would need monitoring. (1.1.3) -   Combustion reactions produce different products under different conditions. -   In a plentiful supply of oxygen, complete combustion  occurs which produces carbon dioxide and water only.               -   If there is insufficient oxygen, incomplete combustion  will occur which produces any combination of water, carbon monoxide and soot.                    Carbon monoxide  is a toxic gas even at low ppm concentrations as it combines preferentially with haemoglobins  in the red blood cells 200 times better than oxygen. This reduces the efficiency of the red blood cells ability to carry oxygen, leading to suffocation.    Soot is carcinogenic  ; it may cause cancer. -   Because of the toxic nature of these 2 products, combustion reactions must be monitored to ensure that there is an ideal air : fuel ratio so that the production of these substances is avoided. -   Combustion can also release acidic oxides such as sulfur dioxide, unburnt hydrocarbons, particulates and lead. The emission of these substances must also be monitored for environmental and health reasons. -   Finally, since incomplete combustion releases less energy than complete combustion, it is necessary to monitor combustion reactions to ensure that the maximum energy output from the reaction is achieved.  The Haber process Identify and describe the industrial uses of ammonia. (2.1.1) -    Ammonia  is used to make:    Fertilisers in the form of ammonium nitrate or ammonium sulfate as a source of nitrogen for plants.    Nitric acid   from the Ostwald process which is used for explosives such as TNT, synthetic dyes, fibres and plastics.    Sodium carbonate  from the Solvay process   which is used to make glass.    Household cleaners and  detergents  Identify that ammonia can be synthesised from its component gases, nitrogen and hydrogen. (2.1.2) Describe that synthesis of ammonia occurs as a reversible reaction that will reach equilibrium. (2.1.3) Identify the reaction of hydrogen with nitrogen as exothermic. (2.1.4) Explain why the yield of product in the Haber process is reduced at higher temperatures using Le Chatelier’s principle. (2.1.6) -   Ammonia can be produced in an exothermic equilibrium reaction:              At ordinary temperatures and pressures, this equilibrium lies well to the left. -   When the temperature is increased  , Le Chatelier’s principle predicts that the equilibrium will shift left towards the heating absorbing endothermic reaction in an attempt to decrease the temperature. Thus, the yield of ammonia is reduced  . Explain why the rate of reaction is increased by higher temperatures. (2.1.5) -   The collision theory   predicts that the rate of a reaction depends on the frequency of successful collisions   between reactant particles. “Successful” collisions involve the reactants particles colliding with enough KE to overcome activation energy so that products can be formed. -   Higher temperatures results in an increase in the average KE of the reactant particles. This in turn leads to an increased reaction rate  as the frequency of collisions will increase and the proportion of reactant particles colliding with     will also increase.
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