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Organic Chemistry LAB > Experiment#3: Recrystallization > Flashcards

Experiment#3: Recrystallization Flashcards

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1
Q

RECRYSTALLIZATION
Enumerate the 4 requirements a solvent must have.

A
  • Low BP, so oiling out doesn’t occur.
  • Volatile, so the solvent can be vaporized from the sample.
  • Chemically Inert - solvent must not decompose or oxidize the substance.
  • Unreactive with the solute.
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2
Q

The deposition of crystals from a solution.

A

Crystallization

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3
Q

Common method used to purify organic compounds that are solid at room temperature.

A

Crystallization

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4
Q

CRYSTALLIZATION
During crystallization, why is it that molecules have the tendency to be attached to a growing crystal composed with the same type of molecules?

A

Because they fit better in the molecule’s crystal lattice.

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5
Q

A fixed and rigid arrangement of atoms, molecules or ions.

A

Lattice Structure

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6
Q

LATTICE STRUCTURE
In each unit cell, there are 8 spheres at each end of a three-dimensional cube that represent an atom, ion, or molecule. What are these spheres called?

A

Lattice Point

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7
Q

LATTICE STRUCTURE
Repeating unit cells form the ______ ______ of a crystalline solid.

A

Lattice Structure

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8
Q

RECRYSTALLIZATION
What 2 factors does Recrystallization take advantage of being that it is a common method of purifying organic substances from the traces of foreign substances?

A

1) The difference in solubility at different temperatures and,
2) The tendency of a growing crystal to exclude anything that does not fit into its lattice.

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9
Q

The maximum amount of solute that dissolves in a given volume of solvent at a given temperature.

A

Solubility

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10
Q

RIGHT or WRONG | SOLUBILITY
NaCl - 100 mL water/35.9 g at 25 °C

Is this unit of solubility correct?

A

WRONG. The unit for solubility is grams of solute/mL of solvent meaning if we were to correct this, it would be:

NaCl - 35.9g/100 mL water at 25 °C

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11
Q

SOLUBILITY
The one to be dissolved.

A

Solute

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12
Q

SOLUBILITY
The one used to dissolve.

A

Solvent

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13
Q

SOLUBILITY
What is the unit for solubility?

A

grams of solute/mL of solvent

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14
Q

A solvent that shows the desired solubility behavior for the substance to be crystallized.

A

Recrystallizing Solvent

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15
Q

RECRYSTALLIZING SOLVENT
What are the 3 requirements in picking a solvent for the experiment?

A
  • INSOLUBLE at Room Temperature
  • SOLUBLE when Heated
  • INSOLUBLE/CRYSTALLIZES when Cooled
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16
Q

TRUE OR FALSE | RECRYSTALLIZATION
Unwanted impurities should be soluble at room temperature or insoluble during heating.

A

TRUE

17
Q

PROCESS OF RECRYSTALLIZATION
If there are colored impurities, what is added to the hot solution?

A

Activated Carbon

18
Q

PROCESS OF RECRYSTALLIZATION
If crystallization does not happen, what 3 things can be done in order to promote crystal growth?

A

1) Scratching the inside surface of the glass vessel
2) Adding in a ”seed” crystal of the compound
3) Dipping a glass rod in the solution, aerating it to dry off the solvent before returning the rod to the solution

19
Q

PROCESS OF RECRYSTALLIZATION
Enumerate the first 3 steps of Recrystallization.

A

1) Selection of Solvent
2) Dissolution of crystal in the solvent
3) Filtration of the hot mixture

20
Q

PROCESS OF RECRYSTALLIZATION
Enumerate the last 2 steps of Recrystallization.

A

4) Slow cooling to allow crystallization
5) Removal of soluble impurities

21
Q

PROCESS OF RECRYSTALLIZATION
Performed to separate insoluble impurities from the hot solution of the compound.

A

Hot Gravity Filtration

22
Q

PROCESS OF RECRYSTALLIZATION
Why is it a requirement for Hot Gravity Filtration to be done as rapidly as possible?

A

To avoid premature recrystallization on the funnel.

23
Q

PROCESS OF RECRYSTALLIZATION
Used to maximize the flow rate during the filtration because of its larger surface area.

A

Fluted Filter Paper

24
Q

PROCESS OF RECRYSTALLIZATION
Used to minimize clogging during filtration.

A

Short-stemmed Funnel

25
Q

PROCESS OF RECRYSTALLIZATION
This employs a vacuum to hasten the passage of filtrate through the filter paper.

A

Suction Filtration

26
Q

PROCESS OF RECRYSTALLIZATION
What is Suction Filtration also known as?

A

Vacuum Filtration

27
Q

PROCESS OF RECRYSTALLIZATION
The name of the porous funnel used in Suction Filtration.

A

Buchner Funnel

28
Q

PROCESS OF RECRYSTALLIZATION
The name of the flask used in Suction Filtration.

A

Suction Flask

29
Q

PROCESS OF RECRYSTALLIZATION
What are the 4 different solvents to choose from in the experiment?

A
  • Water
  • Ethanol
  • Benzene
  • Ethyl Acetate
30
Q

PROCESS OF RECRYSTALLIZATION
What compound do we use in the Recrystallization experiment?

A

Acetanilide

31
Q

PROCESS OF RECRYSTALLIZATION
Which of the 4 aforementioned solvents do we eventually end up using in the experiment?

A

Water, since the acetanilide - once dissolved - is insoluble in room temperature, soluble when heated, and insoluble/crystallizes when cooled.

32
Q

TRUE or FALSE | PROCESS OF RECRYSTALLIZATION
Adding activated carbon while the solution is boiling will cause it to boil over.

A

TRUE

33
Q

PROCESS OF RECRYSTALLIZATION
What do we call a substance after it has been filtered?

A

Filtrate

34
Q

PROCESS OF RECRYSTALLIZATION
In Suction Filtration, what a) ends up inside the suction flask and what b) ends up left behind on top of the Buchner funnel?

A

A) Filtrate (Solvent and Impurities)
B) Recovered Acetanilide

35
Q

PROCESS OF RECRYSTALLIZATION
If the initial mass of impure acetanilide is 3.506 g and the mass of the recrystallized acetanilide is 1.006 g, what is the percent recovery?

A

28.69%

[% Recovery = (mass of recrystallized solid/mass of crude sample)x100]
= (1.006/3.506)x100 = 28.69%

Organic Chemistry LAB (10 decks)

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