Use of Separating Funnel

Question 1

why would separating funnel be used?

Answer 1

purify product of organic reaction that is currently mixed with other things in solution
separate two immiscible liquids/solns

Question 2

what does immiscible mean?

Answer 2

don’t mix, don’t dissolve in each other, form two layers

Question 3

describe the shape and parts of separating funnel

Answer 3

glass ball shape at top which goes into cone, for putting liquids into
tap at bottom for letting liquids out

Question 4

method

Answer 4

1. set up separating funnel securely in clamp stand and make sure tap is closed.
2. pour soln into sep funnel using glass funnel
3. add h2o or organic solvent (this depends on which reaction has been carried out) to sep funnel
4. securely add stopper to top of funnel
5. remove funnel carefully from clamp and shake for couple of seconds
6. holding stopper firmly in position, turn funnel upside down and open tap to release any pressure in flask
7. close tap, shake gently and release pressure again- 3x in total at least
8. place back on clamp stand and leave layers to separate for couple of mins
9. place clean con flask under flask and carefully remove bottom layer only
10. swap flask for new one and collect bottom layer
11. may have to repeat whole process to ensure product is completely purified
12. dry product using drying agent (insoluble in product) to remove water, add enough to flask so that it stops clumping
13. filter off solution
14. evaporate solvent off -> pure dry sample

Question 5

why do we do the whole releasing pressure thing?

Answer 5

make sure the glass doesn’t shatter/break

Question 6

when do you shut the tap off and get new flask

Answer 6

if product is in top layer, get rid of all bottom layer and bit of top layer
if product is in bottom layer, get rid of nearly all bottom layer into flask

Question 7

important points

Answer 7

make sure tap closed so you don’t get it all over bench
release pressure regularly when shaking so doesn’t shatter
remove layers very slowly so dont mess up and have to repeat
don’t throw away any layers until sure it’s defo impurity

Question 8

how to tell when thermal decomposition reaction is complete

Answer 8

heat to constant mass

Question 9

why is vacuum filtration good

Answer 9

saves time/quick

Question 10

how to find pH without contaminating it

Answer 10

take out sample and use indicator paper

pH probe