gas and ion tests Flashcards
give test for hydrogen
lit splint forms squeaky pop
why does the hydrogen test work
hydrogen combusts and expands
what is the test for oxygen
glowing splint relights
why does the test for oxygen work
air on oxygen = 20%
O2 test= 100%
therefore reaction is 10x faster
what is the test for carbon dioxide
bubble through limewater
turns cloudy
why does the test for carbon dioxide work
white precipitate of CaCO3 forms
what happens when too much CO2 is added to limewater
turns colourless again as precipitate disappears
what is the test for chlorine
bleaches damp blue litmus paper
why does the test for chlorine work
Cl2 + H2O -> HCl + HClO
Cl 1+ takes e- from litmus paper making it lose its colour
what is the test for ammonia (NH3)
turns damp red litmus paper blue
why does the test for ammonia work
NH3 + H2O -> NH4 + OH-
OH- is alkali so turns red litmus paper blue
what is the test for ammonium (NH4)
- add NAOH
-warm
-test gas for ammonia by waving damp red litmus paper –> blue
Why does the test for ammonium work
NaOH causes ammonia and water to be formed
what is the test for carbonates
- add dilute acid (HNO3)
- bubble gas through limewater to test for CO2
why does the test for carbonates work
The acid forms carbon dioxide and water
what is the tests for sulphates
- first, test for + rule out carbonate using HNO3
- then add BaCl2
- white precipitate should form
why, when testing for sulphates, do you test for carbonates first
to avoid a false positive when BaCO3 forms
what are the halides
Cl-
Br-
I-
for halides test, why do you rule out CO£ and SO4
both Ag2CO3 and AgSO4 give white precipitates giving false positives
what are the results for the halides for the halides test
Cl - white
Br - cream
I - yellow
what is the test for halides
- test for, and rule out CO3 and SO4 using HNO3
- add AgNO3
-add NH3
what concs of NH3 will the results of the halides precipitates formed disappear in
Cl disappears if NH3is dilute
Br disappears if NH3 is concentrated
I never disappears
