Lab Quiz 1
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London Dispersion Interactions
Attraction of transient induced dipoles in greasy hydrocarbon molecules
Dipolar Interactions
Directional attraction of polarized electron clouds in molecules with electronegative atoms
Hydrogen Bonding
Directional attraction of a hydrogen attached to one N or O (H-bond donor) with a lone pair of a different N or O (H-bond acceptor) within one molecule (intramolecular) or between two molecules (intermolecular)
List the 5 main steps of Recrystallization
• Dissolution • Filtration • Crystallization • Collecting the crystals • Drying the crystals
What are some properties of an ideal solvent for crystallization?
-solvent should not react w compound -volatile so crystals can be easily removed -have a boiling point lower than the melting point of the compound to be purified -impurities should be either fully soluble or fully insoluble at all temperatures -compound to be purified should be very soluble in hot solvent and insoluble in cold solvent
What is the formula for % recovery?
final mass/starting mass x 100%
What is Extraction?
A method used to separate compounds based on their relative solubilities in two different immiscible liquids
Why is Dichloromethane one of the most commonly used solvents?
-it is immiscible with water -it has a different density than water -it has good solubility characteristics -low reactivity w organic compounds -high volatility
What are the three classes of molecules that are water soluble?
• inorganic salts • very polar organic molecules that can hydrogen bond • salts of organic molecules that have a charge
Partition Coefficient (K)
Concentration in organic layer/concentration in water
What is an emulsion?
A suspension of small droplets of one liquid in another liquid
What is a conjugate base?
The deprotonated form of the acid
What is a conjugate acid?
The protonated form of the base
When is the product side of the equilibrium favored?
When the acid is stronger than the conjugate acid (reactants have a lower pKa value)
When is the reactant side of the equilibrium favored?
When the acid is weaker than the conjugate acid
Why is sodium sulfate used in caffeine extraction?
It is a drying agent that will absorb any water left behind from the extraction
What is the purpose of adding sodium carbonate to the brewed tea prior to extraction?
To act as a base to deprotinate the tannins, making them water soluble