Quantative Analysis

Question 1

Carbonate ion

Answer 1

CO3 2-

Question 2

Sulphate ions

Answer 2

SO4 2-

Question 3

Ammonium ions

Answer 3

NH4 +

Question 4

Why is nitric acid added before all tests

Answer 4

Gets rid of any ions that may give a false positive result eg hydroxide ions

Question 5

Test for carbonate ions
Ionic equation

Answer 5

Add Nitric acid
Bubble any gas formed through limewater
If Carbonate ions present limewater goes cloudy

CO3 2- (aq) + 2H+ (aq) ——> H2O + CO2

Question 6

Sulphate ion test
Ionic equation

Answer 6

Barium nitrate ( sometimes barium chloride)
White ppt of barium sulfate will form

Ba 2+ (aq) + SO4 2- (aq) ——> BaSO4 (s)

Question 7

Test for ammonium ions
Ionic equation

Answer 7

Add Dilute sodium hydroxide and warm, test any gas with damp red litmus paper

No ppt formed, red litmus paper turns blue

NH4 + (aq) + OH - (aq) ——> NH3 (aq) + H2O
On heating NH3 (aq) —-> NH3 (g)

Question 8

What is the correct sequence of tests when the unknown substance is a mixture

Answer 8

Carbonate, sulfate, halide
If testing for halides filter off white ppt before testing for halide ions

Question 9

Test for chlorine

Answer 9

Bleached damp red litmus paper and blue litmus paper turns red then is bleached