3.1.4 Qualitative Analysis

Question 1

Carbonate test

Answer 1

Add dilute nitric acid to compound that’s being tested
If bubbles are produced, it could be a carbonate
Bubble gas through lime water, if it turns cloudy, the compound was a carbonate as the gas was CO2

Question 2

Sulphate test

Answer 2

Add aqueous barium ions to solution of an unknown compound, if its a sulphate a white precipitate will form

Question 3

Halide test

Answer 3

Add aqueous silver nitrate to an aqueous solution of a halide
Silver chloride is white, silver bromide is cream, silver iodide is yellow
Add aqueous ammonia to test solubility of precipitate if the colours are hard to tell apart
Silver chloride is soluble in dilute NH3, silver bromide is soluble in conc NH3, silver iodide is insoluble in conc NH3

Question 4

What order should you carry out tests for anions in

Answer 4

Carbonate then sulphate then halide

Question 5

Ammonium ion test

Answer 5

Add aqueous sodium hydroxide to solution of ammonium ion
Ammonia gas produced, warm mixture to release gas
Use damp red litmus paper to test gas, should turn blue