Qualitative tests

Question 1

How to test for halides?

Answer 1

Add AgNO3 and HNO3 in solution. F- no precipitate, Cl- white precipitate, Br- cream, I- yellow.

Question 2

What can be done further to distinguish between the halide precipitates?

Answer 2

Add dilute NH3. Cl- precipitate dissolves, Br- partially, and I- does not.
Add concentrated NH3. Cl- and Br- dissolve, I- does not.

Question 3

How to test for the ammonium ion?

Answer 3

Add NaOH and heat (turn NH3 to gas). Hold damp litmus paper at mouth of test tube. Positive = red to blue colour change.

Question 4

How to test for the carbonate ion?

Answer 4

Add dilute HCl. If gas produced, bubble through limewater. Positive = limewater turns cloudy.

Question 5

How to test for the sulfate ion?

Answer 5

Add barium chloride (BaCl) and HCl. Positive: white precipitate.

Question 6

4 tests for organic functional groups?

Answer 6

Decolourise bromine water?
Acidified potassium dichromate
Brady’s reagent (2,4-DNP)
Tollen’s reagent