C8 - Chemical Analysis Flashcards
what is a pure substance
a single element or compound not mixed with any other substance
what can be used to distinguish pure substances from mixtures
melting and boiling point data
what is a formulation
a mixture that has been designed as a useful product
how are formulations made
mixing the components in carefully measured quantities to ensure the product has the required properties
give examples of formulations
fuels
cleaning agents
paints
medicines
alloys
fertilisers
food
formula to calculate rF value
distance moved by substance/ distance moved by solvent
what may affect the rF value
the solvent
what is the test for hydrogen
using a burning splint held at the open end of a test tube of gas. hydrogen makes a pop sound and burns
how can a chromotogram be used to identify substances by comparing them with known substances
the number of spots they produce and the colour
how far the spots have moved up the paper or have the same Rf value
oxygen test
using a glowing splint inserted into a test tube of the gas. the splint relights in oxygen
carbon dioxide test
using an aqueous solution calcium hydroxide. carbon dioxide when shakened or bubbled through will turn the limewater milky
chlorine test
if damp litmus paper is put onto chlorine gas it is bleached
what can flame tests be used to identify
some metal ions
what colour do lithium compounds turn in the flame test
crimson flame
what colour do sodium compounds turn in the flame test
yellow flame
what colour do potassium compounds turn in the flame test
lilac flame
what colour do calcium compounds turn in the flame test
an orange-red flame
what colour do copper compounds turn in the flame test
green flame
what can be done if a sample contains a mixture of ions
some flame colours can be masked
what can sodium hydroxide solution be used to identify
some metal ions
which ions form white precipitates when added to sodium hydroxide
aluminium (but then redissolves in excess NaOH to form a colourless solution), calcium and magnesium ions
what ions form coloured precipitates when added to sodium hydroxide
copper ii, iron ii, iron iii
what colour does copper ii form when added to sodium hydroxide
blue precipitate
what colour do iron ii ions form when added to sodium hydroxide
green precipitate
what colour do iron iii ions form when added to sodium hydroxide
brown precipitate
balanced equation to represent calcium reacting with insoluble hydroxide
Ca2+ + 2OH- ——> Ca(OH)2
balanced equation to represent copper ii reacting with insoluble hydroxides
Cu2+ + 2OH- —-> 20
balanced equation to represent iron ii reacting with insoluble hydroxides
Fe2+ + 2OH- —> Fe(OH)2
balanced equation to represent iron iii reacting with insoluble hydroxides
Fe3+ + 3OH- ——> Fe(OH)3
balanced equation to represent alumminium reacting with insoluble hydroxides
Al3+ + 3OH- —> Al(OH)3
balanced equation to represent magnesium reacting with insoluble hydroxides
Mg2+ + 2OH- —> Mg(OH)2
what do carbonates to react with to form carbon dioxide gas
dilute acids
what can CO2 be identified with
limewater
what do halide ions produce and when
precipitates with silver nitrate when there is dilute nitirc acid
what colour precipitate is silver chloride
white
what colour precipitate is silver bromide
cream
what colour is silver iodide
yellow
what do sulfate ions produce
white precipitate with barium chloride solution in the presence of hydrochloric acid
what can be detected using instrumental methods
elements and compounds
benefits of instrumental methods
accurate
sensitive
rapid
can be used to identify ions in mixtures
how does flame emission spectroscopy work
the sample is put into a flame and the light given out is passed through a spectroscope. the output is a line spectrum that can be analysed to identify the metal ions in the solution and measure their concentrations
