C12 - Testing substances Flashcards
test for hydrogen = positive
lighted splint pops
test for o2 = positive
a glowing splint relights
test fro co2
turns limewater milky
test for chlorine
damp blue litmus paper turns white (bleaches)
flame tests process
-nichrome wire loop dipped into concentrated HCL to clean it
-dipped into HCL + metal compound
-hold loop in blue bunsen burner flame
-colour = identifies metal ion
flame tests
identifies metal ion by colour of flame
mixture of metal ions in flame test
colours can be masked
Li+ flame colour
crimson
Na+ flame colour
yellow
K+ flame colour
lilac
flame colour of Ca2+
orange - red
Cu2+ flame colour
green
Mg2+ flame colour
no colour
metal cation test is with
sodium hydroxide
metal cation test with sodium hydroxide test
identifies metal positive ions in unknown compound
metal cation test with sodium hydroxide for aluminium, calcium, magnesium
white precipitate
metal cation test with sodium hydroxide - aluminium
precipitate will dissolve
metal cation test with sodium hydroxide test - mg and ca
precipitate will not dissolve
-then can be distinguished with a flame test
copper II ions colour precipitate
blue
iron II ions colour precipitate
green
iron III ions colour precipitate
brown
testing for carbonate
fizzing + co2 produced
-when dilute acid is dded
group 1 carbonates
soluble whereas most aren’t
Halide test
add dilute nitric acid and silver nitrate solution
-if a precipitate forms = present
halide test - why add nitric acid
-to dissolve compound and remove carbonate ions
-prevents a precipitate forming with silver ions + carbonate and interfere with the test
halide colour precipitate
I = yellow
Cl = white
Br = cream
sulfate test
-add dilute HCL and barium chloride solution
sulfate test - why add HCL
removes carbonate ions to precipitatae doesn’t form with barium ions
sulfate test present
-white precipitate
-this is insoluble barium sulfate
modern instrumental pros
-highly accurate
-sensitive
-quicker
-allow small samples to be analysed
cons of modern instruments
-expensive
-special training
-only interpreted by comparing to known substances
flame emission spectroscopy
-analyse samples for metal ions
flame emission spectroscopy process
-sample is heated in a flame
-energy provided excites electrons in metal ions
-allows them o jump to higher energy levels
-when they fall back to lower levels = energy is released as light
spectrometer
wavelengths of light produced can be analysed by passing through this
spectrometer - metal ions
-each type absorbs/emits its own line spectrum
line spectrum
own characteristic pattern of radiation
-identifies metal ions by comparing to a database on a computer
spectrometer on concentration
-measures intensity of light with a specific wavelength of a particular metal ion
-machine is calibrated sing known concentrations to give a value
spectrometer pros
-provide accurate ways to monitor water for metal ions
spectrometer used in
steel industry
-controls trace metals present = quality
