Lab Quiz 1

Question 1

London Dispersion Interactions

Answer 1

Attraction of transient induced dipoles in greasy hydrocarbon molecules

Question 2

Dipolar Interactions

Answer 2

Directional attraction of polarized electron clouds in molecules with electronegative atoms

Question 3

Hydrogen Bonding

Answer 3

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)

Question 4

List the 5 main steps of Recrystallization

Answer 4

1. Dissolution
2. Filtration
3. Crystallization
4. Collecting the crystals
5. Drying the crystals

Question 5

What are some properties of an ideal solvent for crystallization?

Answer 5

-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

Question 6

What is the formula for % recovery?

Answer 6

final mass/starting mass x 100%

Question 7

What is Extraction?

Answer 7

A method used to separate compounds based on their relative solubilities in two different immiscible liquids

Question 8

Why is Dichloromethane one of the most commonly used solvents?

Answer 8

-it is immiscible with water
-it has a different density than water
-it has good solubility characteristics
-low reactivity w organic compounds
-high volatility

Question 9

What are the three classes of molecules that are water soluble?

Answer 9

1. inorganic salts
2. very polar organic molecules that can hydrogen bond
3. salts of organic molecules that have a charge

Question 10

Partition Coefficient (K)

Answer 10

Concentration in organic layer/concentration in water

Question 11

What is an emulsion?

Answer 11

A suspension of small droplets of one liquid in another liquid

Question 12

What is a conjugate base?

Answer 12

The deprotonated form of the acid

Question 13

What is a conjugate acid?

Answer 13

The protonated form of the base

Question 14

When is the product side of the equilibrium favored?

Answer 14

When the acid is stronger than the conjugate acid (reactants have a lower pKa value)

Question 15

When is the reactant side of the equilibrium favored?

Answer 15

When the acid is weaker than the conjugate acid

Question 16

Why is sodium sulfate used in caffeine extraction?

Answer 16

It is a drying agent that will absorb any water left behind from the extraction

Question 17

What is the purpose of adding sodium carbonate to the brewed tea prior to extraction?

Answer 17

To act as a base to deprotinate the tannins, making them water soluble