chemical analysis 4.6 Flashcards
what is the test for hydrogen?
squeaky pop test:
complete a sample of gas in test tube
attempt to ignite the gas using a lit splint
squeaky pop sound
2H2(g) + O2(g) > 2H2O(g)
what’s the test for oxygen?
glowing splint test:
collect oxygen in test tube
place a glowing splint into the tube
splint relights
relights because pure O2 is more concentrated than O2 in normal air
what’s the test for water?
copper sulfate test:
add anhydrous copper sulfate (CuSO4)
colour change from white to blue (hydrated)
what’s the test for purity of water?
measuring BP:
meaning boiling point
closer to 100 degrees = more pure
what’s the test for carbon dioxide?
limewater test:
bubble a sample of gas through limewater
a white precipitate forms (turns cloudy)
limewater - saturated calcium hydroxide forms calcium carbonate
what’s the test for chlorine?
damp blue litmus paper test:
place damp blue litmus paper in a sample of gas
turns white (bleaches)
Cl2 is a good bleaching agent, removes colour
what’s the test for ammonia?
damp red litmus test:
place damp red litmus paper in a sample of gas
turns blue
alkaline
what are cations and name some?
positive ions
Li+, Na+, K+, Ca2+, Cu2+, Fe2+, Fe3+, NH4+
how do you conduct a flame test?
- dip a piece of nichrome/ platinum wire into hydrochloric acid, cleaning the wire
- dip wire into sample of solid or solution
- place tip of wire into non-luminous bunsen flame
if flame colour is red what type of metal cation is it?
Li+ lithium
if flame colour is yellow what type of metal cation is it?
Na+ sodium
if flame colour is lilac what type of metal cation is it?
K+ potassium
if flame colour is orange-red what type of metal cation is it?
Ca2+ calcium
if flame colour is blue-green what type of metal cation is it?
Cu2+ copper
how do you conduct a sodium hydroxide test? (NaOH)
- dissolve the sample in water
- add a few drops of NaOH(aq)
if the precipitate colour is blue in a NaOH test what is the metal cation?
Cu2+ copper
Cu(OH)2
if the precipitate colour is green in a NaOH test what is the metal cation?
Fe2+ iron
Fe(OH)2
if the precipitate colour is brown in a NaOH test what is the metal cation?
Fe3+ iron
Fe(OH)3
how do you conduct the ammonium test?
- dissolve the sample in water
- add some NaOH(aq) and warm it
- test the gas evolved with damp red litmus paper
if NH4+ is present the litmus paper will turn blue
what are anions and name some examples?
negative ions
Cl-, Br-, I-, CO3 2-, SO4 2-
how to conduct the test for halides/ silver nitrate test?
- dissolve sample in water
- add nitric acids (HNO3)
- add silver nitrate (AgNO3) solution
if a white precipitate forms when testing for halides/ silver nitrate test what type of halide ion?
Cl- chlorine
AgCl
if a cream precipitate forms when testing for halides/ silver nitrate test what type of halide ion?
Br- bromide
AgBr
if a yellow precipitate forms when testing for halides/ silver nitrate test what type of halide ion?
I- iodine
AgI
what is important to do when testing for halides/ silver nitrate test?
add nitric acid as silver ions form precipitates so nitric acid so stops false positives
how do you test for carbonate ions?
- add hydrochloric acid HCl and look for effervescence
- if there is effervescent bundle the gas through limewater
if carbonate ions were present the gas evolved would turn limewater cloudy
what is important to check/ do with the carbonate test?
check gas evolved is CO2 using limewater as acids also evolve a gas so preventing false positives
how do you conduct the test for sulfate ions?
- add hydrochloric acid look for effervescence
- if no effervescence add barium chloride solution
if sulfate is present they will form a white precipitate
what is important to do in a sulfate test?
adding HCl as carbonate ions can also form a white precipitate preventing a false positive
