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Comprehensive and Detailed Chemistry notes

Extracts from this document...

Introduction

1. MUCH OF THE WORK OF CHEMISTS INVOLVES MONITORING THE 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 * identify the need for collaboration between chemists as they collect and analyse data Chemists usually work in teams. The needs for collaboration are: - The sharing of expertise. Not all chemists work in the same field. - There is a wider knowledge available - Incraeses validity and acuuracy of data and results - Time is saved since data is gathered and analysed in teamwork * describe an example of a chemical reaction such as combustion, where reactants form different products under different conditions and thus would need monitoring Once a reaction takes place, it is important to monitor the reaction. This is because if conditions in the reaction chamber are altered, harmful products may be produced and reaction wouldn't go to completion. Eg: Incomplete combustion - Incomplete combustion of octane: C8H18(l) + 9O2(g) � 3CO2(g) + 3CO(g) + 2C(s) + 9H2O(g) - CO is a poisonous gas which combines strongly with haemoglobin preventing transport of oxygen - Carbon is a pollutant and forms soot - Incomplete combustion occurs in poorly started engines. Eg: Complete combustion - Complete combustion of octane: C8H18(l) + 12.5O2(g) � 8CO2(g) + 9H2O(g) - In order for complete combustion to occur there must be sufficient oxygen available for the octane to burn completely. - The products of complete combustion are CO2 and H2O. 2. CHEMICAL PROCESSES IN INDUSTRY REQUIRE MONITORING AND MANAGEMENT TO MAXIMISE PRODUCTION * identify and describe the industrial uses of ammonia Ammonia is the feedstock for a variety of industrial chemicals. The making of fertilisers accounts for 80% of the world wide use of ammonia. ...read more.

Middle

of oxidation half cell and travel to the cathode (+) of the reduction half cell through a conducting wire -- A voltmeter is not required. Only used to meausre electric potential between the 2 cells -- An electrolyte is required for ions to move through internal circuit -- Cations move towards reduction half cell and anions move towards oxidation half cell * define the terms anode, cathode, electrode and electrolyte to describe galvanic cells Electrodes are the 2 metallic conducting terminals of a galvanic cell Anode is the electrode at which oxidation takes place. It is negative. Cathode is the electrode at which reduction takes place. It is positive. Electrolyte is a substance that releases ions in solution and carries an electric current 5. NUCLEAR CHEMISTRY PROVIDES A RANGE OF MATERIALS * distinguish between stable and radioactive isotopes and describe the conditions under which a nucleus is unstable -- Isotopes exist when there is a different number of neutrons than protons -- Radioisotopes are unstable isotopes that emit radiation -- In stable light elements, the number of neutrons is generally the same as number of protons -- In heavier elements, more neutrons are required to keep nucleus stable -- Unstable nuclei decay to achieve stability. -- This process releases small particles/rays called radiation There are three types of radiation: ALPHA EMISSION: o Alpha particles are helium nuclei ( 4He2 ). o Alpha emission tends to occur in nuclei with atomic number greater than 83 o They are ejected from heavy nuclei to remove surplus of protons and neutrons E.g: 23090Th � 22688Ra + 42He o Alpha perticles are fast but do not travel far in air BETA EMISSION: o Beta particles re electrons ( 0e-1 ) that are released from nucleus when a neutron decays into a proton and electron o Beta decay occurs when n : p ratio is too high due to surplus of neutrons E.g: 13153I � 13154Xe + 0-1e o Some unstable nuclei have a surplus of protons( n : p ratio is too low) ...read more.

Conclusion

identify esterification as the reaction between an acid and an alkanol and describe, using equations, examples of esterification -- Esters are organic compounds with the general formula RCOOR' where R and R' are carbon chains -- Esters are sweet-smelling, volatile organic compounds -- Esters are formed as a result of a condensation reaction between an alkanol and an alkanoic acid. This process is called esterification ALKANOIC ACID + ALKANOL ESTER + WATER RCOOH + R'OH RCOOR' + H2O describe the purpose of using acid in esterification for catalysis -- A small quantity of an acid is needed in esterification to spped up the reaction to reach equilibrium faster -- Most commonly used catalyst is concentrated sulfuric acid. -- Sulfuric acid acts as a dehydrating agent thus removing the water produced in the esterification process in order to maximise yield of ester explain the need for refluxing during esterification -- Esterification takes place in a reflux apparatus -- Heating is required as it allows increase in rate of reaction giving more kinetic energy resulting in successful collisions. -- Also, as esterification is endothermic, heating the flask encourages forward reaction favouring production of the ester -- The ester, alkanol and alkanoic acid are highly volatile and could evaporate away in open heating. -- A reflux apparatus is a condenser placed vertically onto boiling flask in order to cool any vapours which results in dripping of vapours back into the flask outline some examples of the occurrence, production and uses of esters -- Esters occur naturally in the form of flavouring agents and scents -- Aninal fats and oils are natural esters -- Many natural esters are used in wood garnish and coatings. This is due to high volatility -- Esters with high molecular weights are used in latex paints due to low volatility -- Esters are aslo used in body care products. Phenylmethyl acetate is an ester with jasmine fragrance and is used in cosmetics -- Esters can also be used as emulsifying agents. These prevent separation of oils and water in layers in foods. COPYRIGHT (c) WAZZA BARD 2008 ...read more.

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