Answers to Worksheet, Separation Techniques
1. B
11. C
2. C
12. C
3. B
4. C
5. D
6. B
7. D
8. C
9. B
10. B
Section B Q1
a) chromatography
b) Fractional distillation (separating miscible liq with
different bp)
c) Chromatography
d) Distillation (getting solvent from a mixture)
e) Use of a separating funnel (separating immiscible liquids)
f) Crystallisation
Section B Q2
a)
Water out
Water in
ii) To ensure smooth boiling of the liquid.
Section B Q2
b)
Ethanol starts to
distil
100/C
78 /C
Water starts to
distil
End of distillation
of ethanol
c) The top of the receiver should not be stoppered/corked.
Section B Q2 (d)
The boiling pts of ethanol and water are 78C and 100 C
respectively. In the experimental set up the
vapour from the boiling mixture of ethanol and water in the flask
contains a
higher percentage of lower bp ethanol. As the vapour moves up
the fractionating column, it repeatedly
condenses and boils inside the column. Each time the mixture
boils, the % of the lower bp ethanol
increases. By the time the vapour reaches the top of the
fractionating column, it has become almost pure
ethanol.
Section B Q2 (d) (cont’d)
This vapour then passes into the condenser where it is
cooled and condenses into
liquid ethanol. The thermometer shows a constant temperature
of
78C when the ethanol is being distilled. The water, which has a
higher bp, remains in the flask until almost all the ethanol has
distilled.
In this experiment,
complete/total separation is not effected. The distillate contains a
very large % of ethanol and a little water.
Section B Q4
a) Fruit juice X contains sucrose.
It does not contain maltose
It contains a sugar that is not sucrose, maltose or
glucose.
b) Label the 3 sugars as (1), (2) and (3) such that sugar
(1) is closest to the starting line and (3) the furthest.
Rf of sugar (1) = 0.7/4.3 = 0.16
Rf of sugar (2) = 2.4/4.3 = 0.56
Rf of sugar (3) = 3.7/4.3 = 0.86
c) Sucrose (closest match to 0.16), glucose and fructose