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CHM 111 > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

Types of extraction

A

Solid/liquid, Liquid/liquid, acid/base

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2
Q

Solid/Liquid extraction

A

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

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3
Q

liquid/liquid extraction

A

transfer of a solute from one liquid phase to another

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4
Q

Suitable solvent criteria

A
  • 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)
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5
Q

Acid/Base Extraction

A

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

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6
Q

Partition coefficient (k)

A

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

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7
Q

Distillation definition

A

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

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8
Q

What do boiling chips do

A

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

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9
Q

smiple distillation

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

Fractional distillation

A
  • BPs are closer
  • condensed and revaporized many times
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11
Q

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

A

fractional distillation column

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12
Q

Gas chromatography

A

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

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13
Q

Retention time

A

time it takes a solute to travel through the column

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14
Q

What affect does polarity of the compound have on RT

A

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

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15
Q

Stationary phase (GC)

A

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

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16
Q

Type of columns used in GC

A

Capillary columns

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17
Q

Mobile phase

A

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

18
Q

Length of column affects RT

A

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

19
Q

column temp affects RT

A

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

20
Q

Flow rate of carrier gas affects RT

A

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

21
Q

column packing polarity affects RT

A

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

22
Q

volatility of compound affects RT

A

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

23
Q

role of acetic acid in oxidation of cyclohexanol

A

Catalyst

24
Q

Why would someone do a multi-step extraction

A

multiple steps allow for more product to be recovered

25
Q

What does drying an organic agent mean?

A

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

26
Q

why do we do the shake/vent sequence

A

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

27
Q

Caffeine Solubility in DCM vs Water

A

Caffeine is more soluble in DCM than in water

28
Q

Can simple distillation separate azeotropes?

A

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

29
Q

What does the packing in the fractional distillation column do?

A

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

30
Q

What happens if you distill to dryness

A

could cause apparatus to explode

31
Q

How to choose the size of the round bottom flask

A

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

32
Q

What carrier gas was used in the lab

A

Helium

33
Q

Peak area of a GC

A

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

34
Q

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

A

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

35
Q

Why is the temp range in the oxidation rxn important

A

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

36
Q

role of sodium bisulfate in oxidation

A

it neutralizes the excess hypochlorite

37
Q

role of sodium hydroxide in OX

A

it neutralizes regenerated acetic acid

38
Q

Why was the salting out step done in the oxidation

A

to minimize the solubility of cyclohexanone in water

39
Q

Why was the mixture distilled in oxidation?

A

separate cyclohexanone from most of the water

40
Q

how was cyclohexanone isolated?

A

multistep extraction

41
Q

Why was ether used as the wash?

A

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

CHM 111 (1 decks)

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