reactions graphically: Enthalpy change is represented by the symbol ∆H. (∆ is ‘the change in’ the ‘H’ is for enthalpy) The unit for enthalpy change is measured in Kilojoules per mole. For example if an alkane has a combustion enthalpy change of +296Kjmol-1 then the alkane takes in 296kJ of energy‚ from its surroundings‚ for every mole that is burnt. Enthalpy changes can easily be measured using equipment in a school laboratory. We can set up an experiment so that energy is transferred
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damage the brain’s dopaminergic system. Human studies show that exposure to beta-HCH is linked to Parkinson’s and Alzheimer’s disease. Beta-HCH was present in elevated levels in some patients as recently as 2009. It was manufactured by exhausting chlorination of benzene and for this reason was called erroneously beta-BHC. This synnonym still persists. In March 2005‚ the Italian
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Pollution is another form of environments change. Forty species of birds in the United States‚ including peregrine hawk‚ bald eagle‚ pelicans‚ and roseate terns‚ lay thin-shelled as a result of ingesting degradation products of and some other chlorination hydrocarbon insecticides that make their way into the food
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Discussion The reaction through which 4-mrthaoxyacetophenone is converted to 4-methoxybenzoic acid is a haloform reaction. This reaction involves two distinct stages that occur in the same environment. The first stage occurs through the based-catalyzed halogenation of the ketone that forms a trihalo ketone. First‚ the bleach is transformed into chlorine and hydroxide ions through the following reaction: Then‚ the hydroxyl is able to attack the rather acidic (pKa ~ 20) α-hydrogen of the ketone
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Revision checklist for IGCSE Chemistry 0620 A guide for Students Revision checklist for IGCSE Chemistry 0620 A guide for students How to use this guide The guide describes what you need to know about your IGSCE Chemistry examination. It will help you to plan your revision programme for the theory examinations and will explain what the examiners are looking for in the answers you write. It can also be used to help you to revise by using tick boxes in Section 3‚ ‘What you need to know’‚ to check
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beneficial amounts (F)‚ pollutants (N‚ Cl‚ P)‚ laxative properties (Mg‚ SO4) 2. Palatability/aesthetic acceptability e.g. temp.‚turbidity‚ colour‚ taste‚ odour 3. Economic usefulness e.g. soap consumption 4. Water treatment processes e.g. coagulation‚ chlorination etc. 5. Functional tests e.g. optimum alum dose of 89 10 WHO‚ USEPA‚ EU‚ AWWA Physical Chemical Biological of 89 11 of 89 12 of 89 13 of 89 14 of 89 15 of 89 16 of 89 17 of 89 18 5 µm
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Global epidemics Man-made and natural disasters can intensify the risk of epidemics considerably‚ as can conditions in crowded refugee camps. Explosive outbreaks with high case-fatality rates are often the result. For example‚ in the aftermath of the Rwanda crisis in 1994‚ outbreaks of cholera caused at least 48 000 cases and 23 800 deaths within one month in the refugee camps in Goma‚ the Congo. Although rarely so deadly‚ outbreaks continue to be of major public health concern‚ causing considerable
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1. A student neglected to add sodium carbonate when extracting the tea leaves with hot water. Yet a very high yield of caffeine was obtained. The crystals melted at 202-214°C. Explain. • The sodium carbonate is supposed to be added when extracting the tea leaves with hot water in order to help purify the caffeine. So since the student neglected to add sodium carbonate the caffeine won’t be pure but the student would still be able to recover a large amount of caffeine. The literature melting point
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An oil spill can be defined as an accidental or deliberate dumping of oil or petroleum products into the ocean and its coastal waters‚ bays‚ and harbors‚ or onto land‚ or into rivers or lakes (Holum 1977). Between one and ten million metric tons (one metric ton is 1000 kilograms) of oil are put into the oceans every year. The oil is released‚ most often‚ in small yet consistent doses from tankers‚ industry‚ or on shore waste disposal (Boesh‚ Hersher‚ et al. 1974). Tanker spills cost the United
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attached to the nitrogen atom and adding the word amine. In the IUPAC System‚ apply the following rules to name amines: 1. Pick out the longest continuous chain of carbon atoms. The parent name comes from the alkane of the same number of carbons. 2. Change the -e of the alkane to “amine.” 3. Locate and name any substituents‚ keeping in mind that the chain is numbered away from the amine group. Substituents‚ which are attached to the nitrogen atom instead of the carbon of the chain‚ are designated
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