Gas Chromatography (GC) Definition: Gas chromatography is a physical method of separation in which the components to be separated are distributed between two phases‚ one being a stationary bed of large surface area‚ and the other a gas that percolates through the stationary bed. When the stationary phase is a solid‚ the separation process is more precisely called gas-solid chromatography. Introduction: Gas Chromatography is a technique widely used to separate complex mixtures of substances. Compounds
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In the 18th and 19th centuries scientists wrestled with identifying and describing the nature of the “stuff” that produced change. One concept that became popular for a while was that of “caloric” (what we now call heat). “Caloric was originally conceived of as a quantity that would flow from a hotter object to a cooler one that would warm up as a result. It answered the need for a way for the cause of warming to get from here to there. Not only did caloric serve as a cause for warming‚ it
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Chemistry Ozone Depletion Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of about 4% per decade in the total volume of ozone in Earth’s stratosphere (the ozone layer)‚ and a much larger springtime decrease in stratospheric ozone over Earth’s polar regions. The latter phenomenon is referred to as theozone hole. In addition to these well-known stratospheric phenomena‚ there are also springtime polartropospheric ozone depletion events. The
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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Ordinary Level 5070/31 CHEMISTRY Paper 3 Practical Test October/November 2010 CONFIDENTIAL INSTRUCTIONS *4711088250* Great care should be taken to ensure that any confidential information given does not reach the candidates either directly or indirectly. The Supervisor’s attention is drawn to the form on page 7 which must be completed and returned with the scripts. If you have any problems
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Topic 6 Microscopic World II Unit 23 Shapes of molecules Unit 24 Bond polarity and intermolecular forces Key C o ncepts Microscopic World II Shapes of molecules • Covalent molecules with non-octet structures • Shapes of molecules • The VSEPR theory • Molecular crystals of buckminsterfullerene (C60) • Carbon nanotubes Bond polarity and intermolecular forces • Electronegativity and bond polarity • Van der Waals’ forces • Factors affecting the strength
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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Ordinary Level CHEMISTRY Paper 1 Multiple Choice May/June 2005 1 hour Additional Materials: Multiple Choice Answer Sheet Soft clean eraser Soft pencil (type B or HB is recommended) 5070/01 w w w e tr .X m eP e ap .c rs om READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples‚ paper clips‚ highlighters‚ glue or correction fluid. Write your name‚ Centre number and candidate number on the answer
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Chapter 1: Intermolecular Forces: Liquids‚ Solids‚ and Phase Changes Chem 11: General Chemistry 2 Topics 1.1 An Overview of Physical States and Phase Changes 1.2 Quantitative Aspects of Phase Changes 1.3 Types of Intermolecular Forces 1.4 Properties of the Liquid State 1.5 Uniqueness of Water 1.6 The Solid State: Structure‚ Properties and Bonding A hot spring on a snowy day The Kinetic Molecular View of the Three States The characteristic properties of gases‚ liquids
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Appendix APPENDIX 1 Chemical tests for functional groups Homologous series/ Typical compound Functional group(s) Alkanes CH3CH3 ethane C – C and C–H Alkenes CH2 = CH2 ethene C=C Chemical tests/Observations Add liquid bromine in ultraviolet light (or sunlight): White fumes of HBr liberated; decolourisation of bromine occurs slowly (a) Add Br2 in CCl4 at room temperature: Decolourisation of bromine occurs immediately CH2 = CH2 + Br2 → CH2BrCH2Br (b) Add acidified
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12U Equilibrium Unit Test Multiple Choice K/U Identify the letter of the choice that best completes the statement or answers the question. ____ 1. When solid lead(II) phosphate is in equilibrium with its ions‚ the ratio of lead(II) ions to phosphate ions is which of the following? a. 1:1 d. 2:3 b. 1:2 e. 3:2 c. 2:1 ____ 2. In a saturated solution of silver phosphate‚ the concentration of silver ion is 4.5 10-4 mol/L. The Ksp of silver phosphate would be which of the following
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Explain the effects of the Purges? Introduction The Great Purge was a campaign of political repression in the Soviet Union orchestrated by Joseph Stalin from 1934 to 1939. It involved a large-scale purge of the Communist Party and government officials‚ repression of peasants and the Red Army leadership‚ and widespread police surveillance‚ suspicion of "saboteurs"‚ imprisonment‚ and arbitrary executions. 1st Para Scientists‚ Doctors and Engineers‚ were heavily targeted‚ imprisoned and killed.
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