4.2.3 Organic Synthesis Practical Skills

Question 1

Describe how a Quickfit
apparatus is connected

Answer 1

Grease the joints using some petroleum
jelly on the inside of the joints before
connecting the pieces together.

Question 2

In a distillation setup, why is it
necessary to have a
continuous water flow around
the condenser?

Answer 2

So that the water remains cool in order
for the mixture to be distilled

Question 3

Describe a method that can be
used to separate immiscible
liquids

Answer 3

● Pour the mixture into a separating funnel and some distilled
water
● Add the stopper and invert the flask to mix the mixture
● Equalise the pressure by opening the stopper as required
● Continue shaking until there is no ‘whistle’ sound
● To collect the water in the lower layer, open the stopper and
place a beaker under the spout
● Use another beaker to collect the desired organic layer
● Shake the liquid with some drying agent

Question 4

Name two drying agents

Answer 4

Magnesium sulphate
Calcium chloride

Question 5

How to use drying agents

Answer 5

● Add a selected drying agent to the organic product
● If the drying agent forms clumps add some more until they
are moving freely
● Use gravity filtration to collect the dry product.
● Filtrate is the product

Question 6

What does re-distillation
mean?

Answer 6

When a liquid is purified by using
multiple distillations

Question 7

How can unsaturated
hydrocarbon be tested? What
are the observations?

Answer 7

Use bromine water
Add few drops of bromine water to the sample and
mix well
Positive test - bromine water turns colourless

Question 8

How can unsaturated
hydrocarbon be tested? What
are the observations?

Answer 8

Use bromine water
Add few drops of bromine water to the sample and
mix well
Positive test - bromine water turns colourless

Question 9

What are the reagents used to
test haloalkanes and what are
the observations?

Answer 9

Reagents - silver nitrate, ethanol and water
Observations - chloro- : white precipitate
Bromo- : cream precipitate iodo- : yellow precipitate

Question 10

What are the 3 reagents that
can be used to test carbonyls?

Answer 10

Acidified potassium dichromate
Fehling’s solution
Tollens’ reagent

Question 11

What are the 3 reagents that
can be used to test carbonyls?

Answer 11

Acidified potassium dichromate
Fehling’s solution
Tollens’ reagent

Question 12

What are the observations
when acidified potassium
dichromate reacts with
ketones and aldehydes?

Answer 12

Ketones - no change
Aldehyde - turns from orange to green
colour

Question 13

What are the observations
when Fehling’s solution is
reacted with ketones and
aldehydes?

Answer 13

Ketones - no change
Aldehyde - dark red precipitate

Question 14

What are the observations
when Tollens’ reagent is
reacted with ketones and
aldehydes?

Answer 14

Ketones - no silver mirror
Aldehydes - silver mirror

Question 15

What are the reagents that
can be used to test carboxylic
acid? What are the
corresponding observations?

Answer 15

Universal indicator - pH of weak acid
Reactive metal - hydrogen effervescence
Metal carbonate - carbon dioxide
effervescence