CHEMICAL TESTS Flashcards
Test for HYDROGEN
METHOD: collect gas into boiling tube and place a lit splint inside
POSITIVE RESULT: there´s a squeaky pop if H+ is present
Test for OXYGEN
METHOD: collect gas into boiling tube and insert glowing splint
POSITIVE RESULT: splint relights if oxygen is present
Test for CO2
METHOD: boil gas through limewater and observe the colour change
POSITIE RESULT: limewater turns milky/cloudy if CO2 is present
Test for AMMONIA
METHOD: put damp red litmus paper or universal indicator paper into test solution
POSITIVE RESULT: Red litmus paper turns blue if ammonia is present.
- Universal indicator paper turns purple if ammonia is present.
Test for CHLORINE
METHOD: put damp litmus paper/ starch-iodide paper into test solution.
POSITIVE RESULT: Damp litmus paper bleached white if chlorine is present.
- Starch-iodine paper turns blue if chlorine is present.
How do you carry out a flame test?
- Dip platinum or nichrome wire into concentrated hydrochloric acid + then in salt you want to test
- Wire + salt held on top of bunsen burner + colour is observed
What flame colour does K+ produce?
Lilac
What flame colour does Ca2+ produce?
Orange-red
What flame colour does Li+ produce?
Red
What flame colour does Na+ produce?
Yellow
What flame colour does Cu2+ produce?
Blue-green
What precipitate colour does Copper turn?
When sodium hydroxide is added, turns BLUE
What precipitate colour does Iron II turn?
When sodium hydroxide is added, turns GREEN
What precipitate colour does Iron III turn?
When sodium hydroxide is added, turns BROWN
Test for anions CL-, Br- and I-
METHOD: add nitric acid followed by silver nitrate solution
POSITIVE RESULTS:
- Cl- turns white if chloride ions are present
- Br- turns cream if bromide ions are present
- I- ions turn yllow if iodide ions are present
Test for SO4(2-)
METHOD:
Add dilute hydochloric acid to remove carbonate ions + add barium chloride solution
POSITIVE RESULTS: white precipitate formed (barium sulfate)
Test for CO3(2-)
METHOD: Add dilute hydrochloric acid + bubble gas produced through limewater
POSITIVE RESULT: carbon dioxide formed if carbonate ions are present. (CO2 makes limewater milky)
Test for WATER
METHOD: add liquid to anhydrous copper (ii) sulfate
POSITIVE RESULT: anhydrous copper (ii) sulfate turns blue is water is present
Test for WATER PURITY
METHOD: measure freezing, melting or boiling point
POSITIVE RESULT: pure water freezes at 0C and boils at 100C
If water is impure, it will boil at higher temp + freeze at lower temp.
