topic 8 - chemical analysis Flashcards
whats a pure substance
only contains one compound or element (not mixed with anything else)
how do you test for a pure substance with melting and boiling points
test its melting and boiling point and because pure substances have specific melting and boiling points, the closer it is to these, the more pure it is
what are formulations
useful mixtures with a precise purpose made following a formula (recipe/method)
examples of formulations
- paints
- medicines
- cleaning poruducts
- fertilisers
mobile and stationary phase - chromatography
mobile - where molecules can move -> liquid/gas
stationary - molecules cant move -> solid/thick liquid
what does a pure substance look like in chromotography
just one dot anywhere on the paper
what are the phases in PAPER chromatography
- stationary - chromatography paper/filter paper
- mobile - solvent eg water/ethonol
what spends more time in the mobile phase
molecules with a higher solubility which are less attracted to the paper
formula for the Rf value
distance travelled by substance / distance travelled by solvent
test for 4 common gasses: CHLORINE, OXYGEN, CO2, HYROGEN
- chlorine - bleaches damp litmus paper white
- oxygen - relight a glowing splint in a test tube
- CO2 - bubbling it through limewater - goes cloudy
- hydrogen - lit splint in test tube - squeaky pop
name the 3 tests for ANIONS
- carbonates
- sulfates
- halides
what is the test for carbonates (ANIONS 1)
add DILUTE ACID to test tube and connect to test tube of LIMEWATER - if positive - CO2 released making limewater cloudy
what is the test for sulfates (ANIONS 2)
add drops of DILUTE HCL to sample with BARIUM CHLORIDE solution - if posiitve - white [precipitate forms
what is the test for halides (ANIONS 3) and anogram
add drops of dilute nitric acid and silver nitrate:
- chloride - WHITE - silver chloride
- bromide - CREAM - silver bromide
- iodide - YELLOW - silver iodide
whats the test for CATIONS 1
the flame test
results of the flame test for CATIONS identifying metal ions
lithium - red
sodium - yellow
potassium - lilac
calcium - orange
copper - green
Lola
Rides
Stalions
Yawning
Penelope
Licks
Corolines
Ovaries
Copper
Green
how do you carry out the test for CATIONS that gives you a precipitate (other than the flame test)
add few drops of SODIUM HYDROXIDE to mystery solution
results of sodium hydroxide test with metal ions for CATIONS
calcium - white
copper (II) - blue
iron (II) - green
iron (III) - brown
aluminium - white then colourless
magnesium - white
Coroline
Wets
Charlies
Bread
In
Greece
Inigo
Buts
Away
Wailing
‘My
Wife’
why is flame spectroscopy better than the flame test
- very sensitive - detects tiny amounts of light
- very fast - tests are automated
- very accurate
explain flame emission spectroscopy
- a sample is placed in flame and as it heats the electrons become excited and transfer energy as light
- this light passes through a spectroscope which detects different wavelengths which produce a line spectrum
- this creates different patterns so we can identify what ions are in the solution
- and the intensity of the line can tell us the concentration of that ion in the solutions
when would you need to use flame emission spectroscopy
- if 2 metals have similar colours
- sample may contain multiple metals so colours could get mixed up
what does it mean in chormatography if your dot has reached the furthest
its the most soluable
