Exam 2

Question 1

Types of extraction

Answer 1

Solid/liquid, Liquid/liquid, acid/base

Question 2

Solid/Liquid extraction

Answer 2

removal of a substance from a solid mixture using a suitable solvent

Question 3

liquid/liquid extraction

Answer 3

transfer of a solute from one liquid phase to another

Question 4

Suitable solvent criteria

Answer 4

• should readily dissolve substance to be extracted
• should not react chemically with substance to be extracted
• should not react with or be miscible with other solvent
• low BP (easily removed)

Question 5

Acid/Base Extraction

Answer 5

one of the compounds in mixture is altered chemically to change solubility characteristics. from there, liquid/liquid extraction

Question 6

Partition coefficient (k)

Answer 6

used to evaluate the effectiveness of an extraction by calculating the amount of solute in each layer (EX on page 105 txt bk)

Question 7

Distillation definition

Answer 7

heating a liquid until it boils, capturing and cooling the resultant hot vapors, collecting the condensed vapors.

Question 8

What do boiling chips do

Answer 8

lessen the bubbles in a liquid while it boils (never boil without them)

Question 9

smiple distillation

Answer 9

• liquid is less than 10% contaminated
• liquid has non volatile component (or solid)
• BP are at leas 70c apart
• condensed 1 time

Question 10

Fractional distillation

Answer 10

• BPs are closer
• condensed and revaporized many times

Question 11

What piece is used in fractional distillation but not in simple distillation

Answer 11

fractional distillation column

Question 12

Gas chromatography

Answer 12

analytical technique used to separate and analyze a variety of mixtures based on the components BP

Question 13

Retention time

Answer 13

time it takes a solute to travel through the column

Question 14

What affect does polarity of the compound have on RT

Answer 14

polar compounds will move slower especially if the packing of the column is polar (incr RT)

Question 15

Stationary phase (GC)

Answer 15

Consists of a large MW, High BP, liquids coated on diatomaceous earth (Polyethylene glycol, etc.)

Question 16

Type of columns used in GC

Answer 16

Capillary columns

Question 17

Mobile phase

Answer 17

a carrier gas (Helium, nitrogen, argon, etc.) flows through the column carrying the sample.

Question 18

Length of column affects RT

Answer 18

the longer the column, the longer it will take compounds to elute (better separation) (higher RT)

Question 19

column temp affects RT

Answer 19

Raising column temp speeds up passing of compounds through the column (Decr RT)

Question 20

Flow rate of carrier gas affects RT

Answer 20

Increase the carrier gas flow will increase the speed of the compounds move (Decreases RT)

Question 21

column packing polarity affects RT

Answer 21

All compunds move slower through polar columns but polar compounds show larger effect (INCR RT)

Question 22

volatility of compound affects RT

Answer 22

Low BP compounts (volatile) travel faster than HIgh BP (Decr RT)

Question 23

role of acetic acid in oxidation of cyclohexanol

Answer 23

Catalyst

Question 24

Why would someone do a multi-step extraction

Answer 24

multiple steps allow for more product to be recovered

Question 25

What does drying an organic agent mean?

Answer 25

it means the excess water is reacted out using something like NaCl

Question 26

why do we do the shake/vent sequence

Answer 26

pressure builds up inside the funnel, so it needs to be vented

Question 27

Caffeine Solubility in DCM vs Water

Answer 27

Caffeine is more soluble in DCM than in water

Question 28

Can simple distillation separate azeotropes?

Answer 28

No, because the vapors formed contain almost the same proportions of liquids as the liquid itself

Question 29

What does the packing in the fractional distillation column do?

Answer 29

the material allows rising vapors to contact descending condensate. The more vapor liquid contact, the better the separation

Question 30

What happens if you distill to dryness

Answer 30

could cause apparatus to explode

Question 31

How to choose the size of the round bottom flask

Answer 31

the round bottom flask should be filled no less than 1/3 and more more than 2/3

Question 32

What carrier gas was used in the lab

Answer 32

Helium

Question 33

Peak area of a GC

Answer 33

the peak shows how much of a component is present in a mixture

Question 34

what accounts for the ratio of 2-methyl-2-butene and 2-methyl-1-butene

Answer 34

saytzeff's rule tells us that the more substituted DB will be the dominating product

Question 35

Why is the temp range in the oxidation rxn important

Answer 35

If it gets too low- RX will be incomplete if it gets too high- Rc will produce unwanted products

Question 36

role of sodium bisulfate in oxidation

Answer 36

it neutralizes the excess hypochlorite

Question 37

role of sodium hydroxide in OX

Answer 37

it neutralizes regenerated acetic acid

Question 38

Why was the salting out step done in the oxidation

Answer 38

to minimize the solubility of cyclohexanone in water

Question 39

Why was the mixture distilled in oxidation?

Answer 39

separate cyclohexanone from most of the water

Question 40

how was cyclohexanone isolated?

Answer 40

multistep extraction

Question 41

Why was ether used as the wash?

Answer 41

ether has a low BP and is insoluble in water (it was boiled out)