chem 1,2,3,5

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  • Created by: Simbaaax
  • Created on: 13-06-17 02:20
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  • 1,2,3,5
    • mod 1
      • lab exps= controlled, variables kept constant, meaningful results
        • independent variable = YOU CHANGE, e.g. temp
          • PIPETTE= narrow, accurate vol, calibrated= less error
          • BURETTE= use to take initial and final readings
          • VOLUMETRIC FLASK= accurate, specific amount of liquid, accurate dilutions or standard solutions
          • GASES measured with gas syringe
        • dependent variable = YOU MEASURE
      • planning exps; aims, variables, equipment, risk assessment, detailed method, evidence from tests
        • techniques
          • reflux= volatile/ flammable/ low B.P, heated in flask w/ vertical liebig condenser, heating usually electric= avoid naked flames
          • distillation= gentle heating, substances evaporate in order of increasing B.P. Some products may react further e.g. aldehydes,
          • VOLATLE liquids purified via REDISTILLATION= heat impure product, when liquid you want boils, place flask at open end of condenser. Use thermometer to tell u when its boiling. When thermometer changes ,move flask bc diff liquid now
          • seperation- remove water soluble impurities; impure product at top (organic), aqueous layer always on bottom. Organic layer= less dense= floats.
            • water soluble impurities dissolved in aqueous layer
              • organic layer has trace amounts of impurities; add anhydrous salt e.g. MgSO4, binds to water. filter mixture to remove drying agent.
            • DISCARD aqueous layer
      • dm3 to m3, divide the dm by 1000
        • percentage error= uncertainty/ reading x100
    • enthalpy change of solution= dissolving 1 mol of solute
    • enthalpy change of hydration= dissolving of 1 mol of gaseous ions in water
    • A + D = B + C
      • A= LE// B+C= hyd// D= sol

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