Anion Tests Flashcards
what type of ions are anions?
negative ions e.g. O2-
what is the test for halide ions?
Silver Nitrate Test
how do we complete a silver nitrate test?
- dissolve the sample in water
- add nitric acid
- add silver nitrate solution
if chloride, bromide, or iodide ions are presented, what will form?
a precipitate will form
what is the halide ion of AgCl?
Cl-
what is the halide ion of AgBr?
Br-
what is the halide ion of AgI?
I-
what is the precipitate colour of AgCl?
white
what is the precipitate colour of AgBr?
cream
what is the precipitate colour of AgI?
yellow
what is the equation for the formation of a halide precipitate?
Ag+(aq) + Cl-(aq) –> AgCl(s)
why is it important to add nitric acid to the experiment of the Silver Nitrate Test?
because Ag+ ions also form precipitates with other anions, so the nitric acid reacts with those anions, preventing false positives
how do we test for a sample of carbonate ions?
- add hydrochloric acid, look for effervescence
- if there is effervescence, bubble the gas through limewater
what would happen to the limewater if carbonate is present in gas?
the gas evolved turns the limewater cloudy
why is it important to confirm the gas evolved when testing for carbonates is CO2?
because acids also evolve a gas when they react with other things - check using the limewater test
how do you test for sulfate ions?
- add hydrochloric acid and look for effervescence
- if there’s no effervescence, add barium chloride solution
what happens if sulfate ions are present?
they will form a white precipitate with barium ions
why is it important to add hydrochloric acid in step one of testing for sulfates?
carbonate ions also form a white precipitate with barium ions - by only continuing to step two if there is no effervescence it prevents a false positive
