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Curious Maria

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what is the advantage of carrying out distillation processes under reduced pressures??

And ALSO
can someone tell me the criteria used in selecting primary standards? i.e. NaHCO3, Na2CO3, KIO3, (COOH)2 and its salt as primary standard

  • Curious Maria...STILL HELP! -

    yeh it is (provided that ur not being sarcastic here)

    i'm wondering if by at reduced pressure, it would be somewhat easier to collect the distillates because the temp. is also reduced thus it would be easier to ascertain them as the temp aren't changing too rapidly...

  • Curious Maria -

    The whole idea behind distillation at reduced pressure is that the boiling point is lowered, usually significantly. Therefore, something that boils at 250 C at 1 atmosphere (and is an organic material) PROBABLY will decompose (and there goes that compound it took you 2 weeks to prepare), BUT if the pressure is reduced it may boil at say 75 degrees C and it doesn't break apart at the lower temperature.
    The second question, regarding primary standards:
    For a primary standard, we want something that is relatively inexpensive, stable, has a known composition, reacts stoichiometrically with whatever we are trying to standardize, as well as reacting within a certain pH range (if acid/base) or redox potential (if a redox titration). I hope I have interpreted your question correctly.

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