chemical analysis Flashcards
what is the chemical test for hydrogen?
-collect a sample of gas in a test tube
-attempt to ignite the gas using a lit split
-squeaky pop sound
what chemical reaction is taking place during the hydrogen test?
the combustion of H2 to form H20
what is the pop sound caused by/
the hot gas rushing out of the test tube
what is the test for oxygen?
-collect a sample of gas in a test tube
-place a glowing splint into the tube
-the splint relights
what is the reaction taking place when testing for oxygen?
the combustion of the wood in the splint
why does the glowing splint relight?
pure 02 is more concentrated than the 02 in normal air- the wood in the splint combusts faster
what is the chemical test for the presence of H20?
-add water to anhydrous copper sulfate
changes from anhydrous white to hydrated blue
what is the test for the purity of H20?
measure its boiling point and compare it to 100 degrees celsius-if it is closer to 100 degrees celsius, it is more pure
what is the chemical test for carbon dioxide?
-bubble a sample of gas through limewater-turns cloudy
what is limewater?
saturated calcium hydroxide solution
what is the test for chlorine?
-place damp blue litmus paper in a sample of gas- it turns white (bleaches it)
what does the chlorine do in the experiment?
dissolves into the dampness (H20) and removes the colour from blue litmus
what is the test for ammonia?
-place damp red litmus paper in a sample of gas
-it turns blue
why does the ammonia conduct this reaction?
-the NH3 reacts with the dampness (H20) to form 0H- ions
-the NH3 acts as a base by accepting H+ ions from the H20
-the OH- ions are whats left after H20 has lost H+ and they are alkaline so the red litmus paper turns blue
are cations positive or negative?
positive
many metal cations cause what to change colour?
a non-luminous (blue) bunsen flame
how to conduct a flame test?
-dip a piece of nichrome into hydrochloric acid
-dip the wire into a sample of solid or solution
-place the tip of the wire into a non-luminous bunsen flame
lithium turns a blue flame what colour?
red
sodium turns a blue flame what colour?
yellow
potassium turns a blue flame what colour?
lilac
what colour does calcium turn a blue flame?
orange-red
what colour does copper turn a blue flame?
blue-green
what do you use sodium hydroxide to test for?
copper, iron (II) and iron (III)
what do we use to test for copper, iron 2+ and iron 3+
sodium hydroxide
if copper, iron (II) or iron (III) is present, what will form?
a metal hydroxide precipitate
how to conduct the NaOH test?
-dissolve the sample in water
-add a few drops of NaOH
if the precipitate for NaOH turns blue, what metal cation is it?
Cu2+
if the precipitate for NaOH turns green, what metal cation is it?
Fe2+
if the precipitate for NaOH turns brown, what metal cation is it?
Fe3+
how do we test for ammonium?
using sodium hydroxide
how to conduct an ammonium test?
-dissolve the sample in water
-add some NaOH and warm it
test the gas with red litmus paper (the ammonium test)
if NH4+ ions are present in the original sample, what colour will the litmus paper turn?
blue
what do we use to test for halides?
the silver nitrate test
what are the halide ions?
Cl-, Br- and I-
how to conduct the halides test?
-dissolve the sample in water
-add nitric acid (HNO3)
-add silver nitrate solution (AgNO3)
what happens in the halides test if Cl-, Br- or I- ions are present?
a precipitate forms with the Ag+ ions from the AgNO3
if a white precipitate is formed in the halides test what halide ion was it?
Cl-
if a cream precipitate is formed in the halides test what halide ion was it?
Br-
if a yellow precipitate forms in the halides test, what halide was it?
I-
what is the test for carbonates?
the gas turns the limewater cloudy
how do you conduct an experiment to test for carbonates?
-add hydrochloric acid and look for effervescence
-if effervescence is present, bubble the gas through limewater
-if CO32- were present, the gas evolved turns the limewater cloudy
what is the test for sulfates?
white precipitate will form
how do you conduct an experiment for sulfates?
-add hydrochloric acid and look for effervescence
-if there is no effervescence, add barium chloride solution
-if SO42- ions are present, they will form a white precipitate with the Ba2+ ions from the BaCl2
