chemical analysis 4.6
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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