Review of Liquid-Liquid and Solid-Liquid Extraction

Question 1

what do distillation, l-l and s-l have in common?

Answer 1

all separatory processes to isolate desired component from compound or mixture

Question 2

2 reasons why safety trap is used in suction filtration?

Answer 2

1. prevent loss of filtrate down drain

2. prevent tap water diluting filtrate

Question 3

why is it important that the filtrate of suction filtration not go down the drain?

Answer 3

harmful to the environment

Question 4

what should be used as a transfer aide if transferring reside from funnel to beaker and the desired product is in the FILTRATE?

Answer 4

solvent

Question 5

why is solvent used as a transfer aide if the desired product is in the filtrate?

Answer 5

if filtrate (containing product) was used, the product could be lost.
Solvent washes more filtrate into receptacle and solvent will likely be evaporated off

Question 6

what should be used as a transfer aide if transferring residue from funnel to beaker and the desired product is in the SOLID?

Answer 6

filtrate

Question 7

why is filtrate used as a transfer aide if the desired product is the solid?

Answer 7

filtrate is already saturated with the solid, preventing it from dissolving and being lost.

Question 8

once the solid has been removed from filtrate, with what is it contaminated?

Answer 8

trace amounts of water-soluble impurities

Question 9

is it a concern if a desired solid is contaminated with water-soluble impurities? Why?

Answer 9

yes, b/c it will affect the purity of the solid and make the mass artificially high

Question 10

what can be done to improve the purity of solids?

Answer 10

remove impurities by rinsing with small amounts of cold solvent (small and cold to prevent solid dissolving)

Question 11

what chemical can develop slowly overt ime in ethers?

Answer 11

peroxides form when exposed to light/air

Question 12

why is the formation of peroxides in ethers a concern?

Answer 12

add to pre-existing danger (flammability) as they are highly explosive

Question 13

peroxides and ethers can form___. What are the dangers of this?

Answer 13

ethylenimine. Acutely toxic, carcinogenic, irritant to skin, eyes, mucus membranes

Question 14

what is used to treat ethylenimine in ethers?

Answer 14

5% ferrous sulfate

Question 15

l-l extraction requires that a desired component be miscible in

Answer 15

only one of the liquids used

Question 16

in s-l extraction, a solid is removed from a liquid based on

Answer 16

its insolubility with that liquid

Question 17

what apparatus is used for l-l extraction?

Answer 17

separatory funnel

Question 18

what apparatus is used for s-l extraction?

Answer 18

Buchner funnel gravity filtration

Question 19

why does caffeine move from the aqueous to the organic phase?

Answer 19

it is 8x more soluble in the organic phase, so it migrates there to dissolve better

Question 20

does adding drying agent increase yield?

Answer 20

increases purity, but decreases yield b/c removing water weight

Question 21

is the organic layer always on top in l-l separation?

Answer 21

no, it depends on which pahse is less dense

Question 22

give four reasons why distillation is used rather than boiling off the solvent

Answer 22

1. safety concerns with flammability of solvent
2. toxic vapour
3. save time, money, energy by recovering the solvent
4. also impacts environment by reducing need for packaging and transportation

Question 23

is it better to perform one large volume extraction, or several small ones?

Answer 23

several small ones, as it allows more to be extracted and less in the opposing phase