Required Practical 6

Question 1

How can we identify the ALKENE functional group?

Answer 1

REAGENT: Bromine water.
RESULT: Orange colour decolourises.

Question 2

What two methods can we use to identify ALDEHYDES?

If we used these methods to test for KETONES, what would we observe?

Answer 2

METHOD 1

REAGENT: Fehling’s solution.
RESULT FOR ALDEHYDES: Blue solution to red precipitate.
RESULT FOR KETONES: No change.

METHOD 2

REAGENT: Tollens’ reagent.
RESULT FOR ALDEHYDES: Silver mirror formed.
RESULT FOR KETONES: No change.

Question 3

How can we identify the CARBOXYLIC ACID functional group?

Answer 3

REAGENT: Sodium carbonate.
RESULT: Effervescence of CO₂ evolved.

Question 4

How can we identify PRIMARY and SECONDARY ALCOHOLS?

Answer 4

REAGENT: Sodium/potassium dichromate & sulfuric acid (i.e. acidified sodium/potassium dichromate).
RESULT: Orange to green colour change.

Question 5

How can we identify a CHLOROALKANE?

Answer 5

REAGENT: Warm silver nitrate.
RESULT: Formation of white precipitate of AgCl.

Question 6

How can we identify a BROMOALKANE?

Answer 6

REAGENT: Warm silver nitrate.
RESULT: Formation of cream precipitate of AgBr.

Question 7

How can we identify an IODOALKANE?

Answer 7

REAGENT: Warm silver nitrate.
RESULT: Formation of yellow precipitate of AgI.