Identifying Anions(Complete)

Question 1

What is an anion?

Answer 1

An ion with a negative charge and is attracted to the opposite charge of the anode- positive.

Question 2

What charge are anions attracted to?

Answer 2

Attracted to the opposite charge of the anode-positive.

Question 3

What anions do you need to know the tests for?

Answer 3

Chloride- Cl-
Sulphate- SO4
Sulphite- SO3
Nitrates- NO3
Carbonates- CO3
Hydrogen carbonates- HCO3
Phosphates- PO4

Question 4

Describe the test for chloride ions.

Include the proof.

Answer 4

Add silver nitrate (AgNO3) solution.
A white precipitate of AgCl is formed.
Ag+ + Cl- = AgCl

Proof:
Add ammonia solution to the precipitate.
It redissolves,

Question 5

Describe the test for nitrate ions.

Include the proof.

Answer 5

Dissolve in deionised water.
Add iron II sulphate solution- FeSO4.
Tilt the test tube at an angle.
Add concentrated sulphuric acid down the side of the test-tube.
A brown ring will form on the interface.
This is called the brown ring test.

Question 6

What is the test for nitrate ions called?

Answer 6

The brown ring test.

Question 7

Describe the test for sulphate ions.

Include the proof.

Answer 7

Dissolve in deionised water.
Add barium chloride solution- BaCl2.
A white precipitate of barium sulphate solution is formed.
Ba2+ + SO4 2- = BaSO4

Proof:
Add dilute hydrochloric acid to precipitate.
It does not redissolve.

Question 8

Describe the test for sulphite ions.

Include the proof.

Answer 8

Dissolve in deionised water.
Add barium chloride solution- BaCl2.
A white precipitate of barium sulphite is formed.
Ba2+ + SO3 = BaSO3.

Proof:
Add dilute hydrochloric acid.
The precipitate redissolves.
BaSO3 + 2HCL = BaCl2 + SO2 + H2O

Question 9

Describe the test for carbonate ions.

Include the proof.

Answer 9

Add hydrochloric acid solution.
CO2 is produced.
CaCO3 + 2HCL = CaCl2 + CO2 + H2O
If soluble the salt is potassium or sodium.

Proof:
Dissolve in water.
Add magnesium sulphate MgSO4 solution.
A white precipitate of MgCO3 is formed.
Mg2+ + CO3 2- = MgCO3.

Question 10

Describe the test for hydrogen carbonate ions.

Include the proof.

Answer 10

Add hydrochloric acid solution.
CO2 is produced.
Ca(HCO3)2 + 2HCL = CaCl2 + 2CO2 + 2H2O

Proof:
Dissolve fresh sample in water.
Add magnesium sulphate solution- MgSO4.
No precipitate forms.

Question 11

Describe the test for phosphate ions.

Include the proof.

Answer 11

Add concentrated nitric acid to some ammonium molybdate solution.
Add the mixture to the phosphate.
Heat gently using a water bath.
A yellow precipitate will form indicating the presence of a phosphate ion.