Chem Urgent Help ?

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I have a lab dis monday .. plz someone help .. Lab Title is
(( Recrystallization of a Solid ))

Pre-Lab Questions....


Explain the purpose of the following in this experiment.

a) using hot filtration

b) not cooling (chilling) the hot filtered solution immediately

c) washing the crystals in the final step with ice cold water

d) using gravity filtratoin ( not vacuum filration) in the hot filtration step

e) using a stemless funnel in the hot filration step

-------------------------------------
in the experiment we have to determine the MP ( literature value 114 C ) ... and percent mass recovery of acetanilide in the orginal mixture ..

ANY clue how to approach to dese problems.. or is dere any kind of formula .. ot steps ..

Thnks for ur help in advance

REally appreciate ur help ..

thnks again

  • Chem Urgent Help ? -

    Not knowing what you are crystallizing or the procedure you are using, the following is the best I can do as far as guessing at the answers.
    a) using hot filtration
    You want as much of the solid as possible to go through with the filtrate. If it's the solute you are trying to separate from some solid material then it is the filtrate you don't want to lose. If it's the solute you are trying to get rid of then you don't want it crystallizing before you can separate it.

    b) not cooling (chilling) the hot filtered solution immediately
    I'm not sure what you are filtering an with what.

    c) washing the crystals in the final step with ice cold water
    You don't want the solid to dissolve during the washing procedure. Dissolution of the solid will cause the yield (percent recovery) to decrease.

    d) using gravity filtration ( not vacuum filtration) in the hot filtration step
    Vacuum filtration will cool the solution and you want to avoid that.

    e) using a stemless funnel in the hot filtration step
    Crystals may form in the stem of the funnel. If that happens the filtration step stops.

    -------------------------------------
    in the experiment we have to determine the MP ( literature value 114 C ) ... and percent mass recovery of acetanilide in the original mixture ..
    %recovery = (mass recovered/mass initially)*100 = ??
    By the way, your English and capitalization and the use of punctuation marks is very good; too made that "dis" and "dese" slipped into the question.

  • Chem Urgent Help ? -

    By the way...... too made (I meant too bad) that "dis" and "dese" slipped into the question.

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