Chapter 6 - IM Forces and Lab Techniques Flashcards
Describe the relationship between strong intermolecular forces and boiling point, melting point, and vapor pressure
If a compound has strong IM forces = increased BP, increase MP, and decreased VP
If two compounds have the same weight, describe the relationship between branching, boiling point, and melting point.
more branching = decreased BP
more branching = increased MP
Purpose of the following lab technique - extraction
Describe the layers in the separation funnel.
Is the solvent that is added last non polar or polar? organic or aqueous?
Separate polar substances from non polar
The top layer is the non polar, organic layer - while the bottom is the aqueous polar layer.
The solvent is non polar, organic
in what type of scenario will the organic solvent be in the aqueous layer, instead of on top of the organic layer?
if the solvent is chlorinated; this is because it is dense in water
Describe how to extract COOH in an acid base extraction
extract COOH using aqueous NaOH or NaHCO3, separate, then add acid to the water layer to precipitate COOH and decrease the pH of water
Describe how to extract phenol in an acid base extraction
Extract phone by using aq NaOH, separate, then add HCl to precipitate and decrease pH of water
Describe how to extract an amine in acid base extraction
Add HCl first to protonate and make amine water soluble, then neutralize with base to precipitate amine
What is the purpose of simple and fractional distillation?
separate two or more volatile liquids; simple is for compounds that have BP’s that differ by about 25 degrees and fractional is to separate compounds with similar BP’s
What is the purpose of sublimation?
purification of volatile solids
heat the solid and collect on accompanying test tube
What is the purpose of recrystallization
purification of a solid
heat solid in hot solvent and collect solid as the solvent cools
Gas liquid chromatography will determine the relative _____ of each compound in a ____ mix by observing the ___ ___
abundance, liquid, boiling point
Thin layer chromatography will separate ____ ____ substances by _____
Because the plate is (polar/nonpolar) and the solvent is (polar/nonpolar), the most soluble substances will travel ____ and the least soluble substances will travel the ______.
non volatile, solubility/polarity
plate = polar
solvent = non polar
most soluble = travels least
least soluble = travels fastest/furthest distance
Polar substances will have a ____ Rf value, while a non polar will have a ____ Rf value
smaller, larger
Describe the purpose of column chromatography
What type of compound will dissolve the best in the eluent?
separate compounds by polarity
polar compounds - remember like dissolves like
Which of the following is sometimes used to purify volatile solids?
A. Thin-layer chromatography
B. Gas-liquid chromatography
C. Sublimation
D. Distillation
E. Fractional distillation
C
