chem 1,2,3,5
- 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
- independent variable = YOU CHANGE, e.g. temp
- 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
- water soluble impurities dissolved in aqueous layer
- techniques
- dm3 to m3, divide the dm by 1000
- percentage error= uncertainty/ reading x100
- lab exps= controlled, variables kept constant, meaningful results
- 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
- mod 1
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