Chemical analysis
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what is a pure substance?
a substance made up of just one element or compound
How can you tell if something is pure?
measure the boiling/ melting point and see if its the same as the pure substance the closer your value is to the boiling/ melting point the more pure
what is a formulation?
substances that are designed for a specific use and are mixed in specific proportions
what are some uses of formulations?
pigments in paints medicines fertilizers tablets alloys fuels
what does chromotopgraphy seperate?
used to separate different solutes
what are the two phases of a paper chromatography?
stationary phase- when molecules can not move, this can be a liuid or gas, this is the paper mobile phase- when molecules can move, this can be a solid or really thick liquid, this is solvent
what will happen with a chromatography with a pure substance?
only one dot will appear
how do you calculate the retention factor (rf)?
distance travelled by substance B/ distance travelled by solvent A
what are the gases you need to know how to test for?
chlorine hydrogen carbon dioxide oxygen
chlorine test
chlorine bleaches damp blue litmus paper white
carbon dioxide test
pass gas through limewater should go from colourless cloudy
oxygen test
plunge glowing splint into a test tube and it should relight if oxygen is present
hydrogen test
plunge a lit split into test tube and you should hear a squeaky pop
how do you test for carbonates?
add an acid (HCl) theres fizzing and then the CO 2 should be bubbled through limewater which should go from colourless to cloudy
how do you test for sulfates?
add hydrochloric acid and then barium chloride solution if sulfate ions are present then a white precipate should form
how do you test for chloride, bromide and iodide ions and what is produced for each one?
add dilute nitric acid and silver nitrate solution chloride= white precipitate of silver chloride bromide= cream precipitate of silver bromide iodide= yellow precipitate of silver iodide
what are the colour of the flames for each flame test? there are 5
lithium = crimson flame sodium= yellow flame potassium= lilac flame calcium= orange/red flame copper= green flame
what do you need to remember before doing the flame tests?
dip the wire loop into some HCl and hold it in a flame until the flame burns without any colour
what is the drawback of the flame tests?
can identify ions when theres a single type of ions however when theres more than one they can hide others
how can you test for copper?
add sodium hydroxide and it should form a blue precipitate this is the copper hydroxide
how can you test for Iron (ll)?
add sodium hydroxide and a green precipitate forms
what are the 6 cations we need to know how to test for?
calcium copper iron (ll) iron (lll) aluminium magnesium
what colour precipitate is formed when sodium hydroxide is added not in excess?
calcium= white copper= blue iron (ll)= green iron (lll)= brown magnesium= white aluminium= white at first
what happens when you add excess sodium hydroxide to magnesium?
it appears white at first but then the precipitate redissolves to form a colourless solution