chemical test for functional group

Question 1

What is the chemical test and observation for alkenes

Answer 1

• add drops of bromine water
• bromine water decolourised from orange to colourless if alkene is present

Question 2

What is the chemical test and observation for haloalkanes

Answer 2

• add silver nitrate and ethanol and warm to 50 degrees Celsius in a water bath
• precipitate should form : white = chloroalkane, cream = bromoalkane, yellow = iodoalkane

Question 3

What is the chemical test and observation for carbonyl

Answer 3

• add 2,4 DNP (dinitrophenylhydrazine)
• observe orange precipitate

Question 4

What is the chemical test and observation for aldehyde

Answer 4

• add Tollens’ reagent and warm
• silver mirror should be observed

Question 5

What is the chemical test and observation for primary and secondary alchohol, and aldehyde

Answer 5

• add acidified potassium dichromate(VI) and warm in a water bath
• observe colour change from orange to green

Question 6

What is the chemical test and observation for carboxylic acid

Answer 6

• add aqueous sodium carbonate
• observe effervescence (bubbling)

Question 7

What is the chemical test and observation for phenol

Answer 7

• phenols acidic so use pH indicator paper / react with bromine water
• observe bromine decolourising and a white precipitate forming