Test for anions

Question 1

What are the five anions?

Answer 1

Carbonate
Chloride
Iodide
Nitrate
Sulfate

Question 2

Describe observations for test of carbonate; add dilute acid and bubble gas evolved into limewater.

Answer 2

Effervescence observed.
Gas is colourless and odourless.
Moist blue litmus paper turns red.
White ppt. forms when gas is bubbled in limewater.
Gas is carbon dioxide.

Question 3

Describe test for Chloride.

Answer 3

1. Add dilute nitric acid
2. Add aqueous silver nitrate
   (White ppt. forms that is insoluble in dilute nitric acid)

Question 4

What colour ppt. does Iodide form?

Answer 4

Pale yellow ppt.

Question 5

Describe test for Nitrate.

Answer 5

Add aqueous sodium hydroxide followed by a piece of aluminium foil. Warm gently.

Question 6

Describe observations for Nitrate test.

Answer 6

Effervescence observed.
Colourless and pungent gas evolved.
Moist red litmus paper turns blue.
Gas is ammonia.

Question 7

Describe test for Sulfate.

Answer 7

Add dilute nitric acid followed by aqueous barium nitrate.
(White ppt. forms)

Question 8

Describe test for Iodide.

Answer 8

Add dilute nitric acid followed by aqueous silver nitrate

Question 9

What is the purpose of adding dilute nitric acid in the tests above?

Answer 9

The dilute nitric acid reacts with and removes ions that might give a confusing observation.