Chemistry - Tests for Anions

Question 1

Test for carbonates
(CO3)2-

Answer 1

Add acid.
If carbon dioxide is produced, limewater will go milky

Question 2

Test for halides

Answer 2

Acidify with dilute nitric acid.
Then add aqueous silver nitrate.
If:
Cl- ; white precipitate
Br- ; cream precipitate
I- ; yellow precipitate

Question 3

Test for nitrates
(NO3)-

Answer 3

Add sodium hydroxide + aluminium foil and warm gently.
Ammonia produced if nitrates are present.

(Check for ammonia using damp red litmus paper)

Question 4

Test for sulfates
(SO4)2-

Answer 4

Acidify.
Then add aqueous barium nitrate.
Insoluble white precipitate will form if sulfates are present.

Question 5

Test for sulfites
(SO3)2-

Answer 5

Add some acidified aqueous potassium manganate (VII). Colour goes from purple to colourless.

Add dilute hydrochloric acid and heat gently.
Sulfur dioxide produced which can be tested using acidified aqueous potassium manganate (VII).

Purple -> colourless