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How do we identify and analyse substances?
Flame tests identify metal ions. Produce distinctive colours in flame tests.
Limewater test CO2 cloudy/milky
Heating Copper+zinc carbonate decompose and distinctive colour change.
Sodium hydroxide Aluminium, calcium and magnesium white precipitates.
Copper (II), Iron (II)+(III) coloured precipitates
Dilute nitric acid Silver chloride is white, Silver bromide is cream, Silver iodide is yellow.
Dilute hydrochloric acid Sulfate ion, white precipitate.
Ammonia Ammonium ions react with sodium hydroxide solution to form ammonia.
- Gas turns damp litmus paper blue.
- Nitrate ions are reduced by aluminium powder in the presence of sodium hydroxide to
. form ammonia.
Organic compounds burn or char when heated in air.
Empirical formula can be found from the masses of the products formed
when a known mass of the compound is burned
Unsaturated containing double carbon carbon bonds decolourise bromine
Instrumental methods eg computing.
Accurate, sensitive and rapid.
Useful when very small sample.
Identifying elements=atomic absorption spectroscopy.
Identifying compounds=infrared spectroscopy, ultrared spectroscopy,
nuclear magnetic resonance spectroscopy, gas-liquid chromatography.
Mass spectrometry can be adopted for both.