Functional group tests

Question 1

Aldehyde and ketone

Answer 1

2,4 - DNPH
Orange-yellow precipitate forms

Question 2

Alkene

Answer 2

Bromine water
Orange colour decolourises

OR

KMnO4
Purple colour decolourises

Question 3

Aldehyde

Answer 3

Tollen’s reagent —> silver mirror formed
Fehling’s solution —> blue solution to red precipitate

Question 4

Carboxylic acid

Answer 4

Sodium carbonate/sodium hydrogencarbonate
Effervescence, CO2 made

Question 5

Primary alcohol, secondary alcohol and aldehyde

Answer 5

Potassium dichromate and sulphuric acid
Orange to green colour change seen

Question 6

Chloroalkane

Answer 6

Add NaOH, heat, add nitric acid, add silver nitrate solution
White precipitate formed

Question 7

Bromoalkane

Answer 7

Add NaOH, heat, add nitric acid, add silver nitrate solution
Cream precipitate formed

Question 8

Iodoalkane

Answer 8

Add NaOH, heat, add nitric acid, add silver nitrate solution
Yellow precipitate formed

Question 9

Phenol

Answer 9

Neutral iron (III) chloride —> purple/violet solution
Bromine water —> white precipitate formed, antiseptic smell

Question 10

Amide

Answer 10

Heat with NaOH, test gas formed with damp red litmus paper
Red —> blue as NH3 is made

Question 11

2-ols, 2-ones, ethanol, ethanal

Answer 11

Add aqueous odium hydroxide and aqueous iodine solution, heat
Yellow crystalline solid of iodoform CHI3 formed

Question 12

Amine

Answer 12

Test with moist red litmus —> tuns blue

Or

Nitric (III) acid HNO2 —> Bubbles of nitrogen gas formed (effervescence)