FAQ - Chemistry of Materials

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  • Created by: Lalala
  • Created on: 06-04-13 02:02

1.

  • WHY DO ______ AND ______ SHOW E/Z ISOMERISM?
    • Restricted rotation about C double bond.
    • 2 different groups on each C of C double bond.
  • WHY ARE 2 STEREOISOMERS EXPECTED TO HAVE DIFFERENT ACTIVITIES IN THE BODY?
    • Have different shapes.
    • Only one forms E-S complex/form different E-S complexes.
  • WHAT PROPERTIES SHOULD A SOLVENT HAVE TO ACHIEVE EFFICIENT RECRYSTALLISATION?
    • Solvent should dissolve solute at higher temperatures.
    • Solvent should dissolve no solute/insoluble at lower temperatures.
  • WHY IS RATE OF REACTION MEASURED WHEN AMOUNTS OF REACTANTS USED UP ARE SMALL?
    • As reactants used up, concentration changes.
    • Using small volume - concentrations remain almost constant.
  • INFRARED SPECTROSCOPY QUESTION
    • Write no peak at _____ indicating no C double bond present, etc.
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2.

  • WHY CAN ____ BEHAVE AS A BASE?
    • Has LP of electrons.
    • Can accept H+ ions.
  • EXPLAIN TERM ENANTIOMER
    • Non superimposable.
    • Mirror image.
  • HOW ARE CROSS-LINKS FORMED?
    • Addition reaction.
    • C double bonds on side chains open up and form covalent bonds.
  • WHY DO MOLECULES WITH CROSSLINKS NOT DISSOLVE IN WATER?
    • Crosslinks prevent chains moving apart.
    • Without crosslinks, water forces polymer chains apart and will dissolve.
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3.

  • WHY IS IT EASIER TO RECYCLE SUPER-ABSORBENT POLYMERS FROM USED NAPPIES THAN FROM POLYMERS FROM MIXTURE OF USED PACKAGING?
    • Used packaging consists of many different polymers which need to be sorted/separated first.
    • Lots of other compounds in plastics used for packaging need to be removed.
  • WHY MAY VALUE FOR Ecell NOT BE TRUE VALUE?
    • Concentration of OH- ions in Ni/Cd battery greater than/not 1.00moldm3.
    • Ni/Cd battery not at standard conditions.
    • Measured voltage not done at standard conditions.
  • WHY IS IRON ENVIRONMENTALLY FRIENDLY TO DISPOSE OF?
    • Forms rust - non-polluting.
    • Put in landfill sites - don't need special methods of disposal.
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DESCRIBE HOW COLORIMETRY CAN BE USED TO FIND OUT C

1. Select complementary colour for filter.

2. Make up dye solutions of different known concentrations.

3. Measure absorbance of dye solutions of different known concentrations.

4. Plot calibration graph of absorbance readings V concentration.

5. Add polymer to dye solution and measure new absorbance.

6. Repeat measurements until no further change in absorbance over period of time.

7. Use calibration curve to find out how concentration of dye changes.

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