Question
1.Consider the following solvent pairs when mixed: which are
immiscible/miscible? If the solvents are immiscible, which solvent
would be in the top layer?
a.hexane and water
immiscible- hexane on top bc less dense
b.methylene chloride and water
immiscible – water on top bc less dense
c.ethanol and water
miscible
d.ether and waterslightly
miscible, ether on top
Solvent with the lower density will be on the top layer
2. Phenols don’t exhibit the same pKa values as other
alcohols; they are generally more acidic. Using the knowledge that
hydrogen acidity is directly related to the stability of the anion
formed (the conjugate base), explain why phenol is much more acidic
than cyclohexanol.
Acidity is a measure of ionization. An acid will dissociate
to proton (H+) and the conjugate base (or anion). The more stable
the anion is, the stronger the acid. In your example, phenol
dissociates to phenoxide anion. This anion is resonance stabilized
-ie- the negative charge is spread out from the oxygen to 3 of the
ring carbons. In cyclohexanol anion, the charge is not resonance
stabilized and the minus charge is firmly placed on the one oxygen
atom.3. The pKa of 2,4-dinitrophenol is 3.96. Could you separate it
from benzoic acid using the extraction procedures in this
experiment?
1.Sodium bicarbonate (WB):deprotonate Carboxylic acid (COOH)
2.HCl:Acid neutralize, deprotonate COO-
3.Brine:dehydrates (remove dissolved water)
4.Mg2SO4(s) Anhydrous magnesium sulfate: remove dissolved
water, add solid until it no longer clumps together
Post-Lab:
1) Compare results to other teams in your lab. Do you all
agree on the composition of themixture? If your group disagrees,
how could you figure out who is right?
2) Did you recover all of the dissolved solids?
3) Write chemical equations for the acid-base reactions that
occur during extraction and neutralization of these compounds
4)What is the difference between “extracting” and
“washing”Extraction is the process of removing a compound you want
from a mixture using a solvent. The solvent and mixture must be
immiscible. Washing is different in that you are removing unwanted
from a mixture using a solvent. CHAPTER 6:Notes:?Steam distillation
– oils isolated from their plant sources. Have high BP so use
suspended in water. Water vaporizes its extracts the essential oils
and carries them overinto the collection flask. Separate water.
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