Qualitative tests Flashcards
How do you test for carbonate ions
- add HCI
- collect gas produced (should be CO2)
- pass gas through limewater
What are the observations for a positive test of carbonate ions
fizzing, limewater turns cloudy
How do you test for sulphate ions
add barium nitrate(Ba(NO3)2) or barium chloride (BaCl2)
What are the observations for a positive test of sulphate ions
white precipitate of barium sulphate formed
What do you use to test for halide ions
acidified AgNO3
How do you test for bromide ions
Add AgNO3(aq)
What is the result for the Cl- test
white precipitate
What are the observations for a positive test of bromide ions
Cream precipitate
How can you test for a halide ion
-dissolve the sample in water
-add AgNO3
-record the colour change
-if its difficult to distinguish the colour add aqueous ammonia
What is the result for the Br- test
cream precipitate
what is the result for the I- test
yellow precipitate
When testing for sulphate carbonate and halide ions what order should you test in and why
-carbonate
-sulphate
-halide
because barium ions form insoluble precipitate BaCO3 and silver ions form insoluble precipitate of Ag2SO4
How can you test for ammonium ions
Add Na(OH) to the sample to warm it up and test the gas produced with red litmus paper
What are the observations for a positive test of ammonium ions
red litmus paper turns blue and ammonia has a pungent smell
Why do you use HNO3 to test for halides and not HCI
to remove carbonate ions, adding HCI will add Cl- ions giving it a false positive
