Qualitative Analysis Flashcards
(16 cards)
What is qualitative analysis?
Measurements based on observations rather than using values
What are common observations in qualitative analysis?
-Bubbles
-Precipitate
-Gas identification
How do test for a carbonate in an unknown solution?
- Add dilute nitric acid into the solution
- Bubble the gas through limewater
- If a carbonate is present, a white calcium hydroxide precipitate will form
How do you test for sulphates?
- Add aqueous barium ions into the unknown solution
- If sulphate ions are present, a precipitate of Barium Sulphate will form+
How do you test for halide ions?
- Add aqueous silver nitrate to a solution with a halide
- A precipitate (of different colours dependant on the halide present) will form
What’s the colour of Silver Chloride precipitate?
White
What’s the colour of Silver Bromide precipitate?
Cream
What’s the colour of Silver iodide precipitate?
Yellow
What further tests can you do to be sure of the halide in a solution?
Add dilute aqueous ammonia and if a solution doesn’t dissolve, add concentrated aqueous ammonia
What happens to AgCl once you add dilute aqueous ammonia?
Precipitate dissolves
What happens to AgBr once you add concentrated aqueous ammonia?
Precipitate dissolves
What happens to AgI once you add either concentration of aqueous ammonia?
Nothing happens
What is the sequence of tests you should carry out?
- Carbonate test
- Sulphate test
- Halide test
Why do you do carbonate tests before sulphate tests?
Because aqueous barium ions can form precipitates with CO3 ions (BaCO3)
Why do you use HNO3 (nitric acid) in carbonate tests and not another acid?
-HCl contains chloride ions that will show up in chloride tests
-H2SO4 has sulphate ions which will show up in sulphate tests
How do you test for ammonium ions?
Add aqueous hydroxide ions to an aqueous solution containing ammonium. Ammonia gas will be produced and can be seen on damp litmus paper turning blue
