Dip nichrome wire into HCl acid and then into unknown substances.Then place on the peak of the blue flame on the bunsen burner:
METAL FLAME COLOUR
Calcium Brick Red
Barium Apple Green
Many metal hydroxides form a precipitate with NaOH
Add a few drops of NaOH into mixture and then you can tell what the metal is by the coloured precipitate:
Calcium white precipitate ammonium compound+NaOH gives off
Aluminium white precipitate which redissolves a stinky aroma and turns
Magnesium white precipitate red litmus blue.
Copper blue precipitate
Iron II green precipitate
Iron III brown/red precipitate
Testing for carbonates
You can test if there is CO2 in the mixture by bubling it through limewater- if the limewater goes cloudy then CO2 is present
Acid+carbonate = CO2 + H20 + salt
Or you can decompse the mixture to see for colour change
copper carbonate= copper oxide + CO2
green to black colour
zinc carbonate=CO2 + zinc oxide
white to yellow to white colour
Testing for sulfates and halides and nitrates
Add HCl and thenbarium chloride. If a precipitate of barium sulfate comes out then the former compound was a sulfate
To test for chloride, iodide or bromide, addHNO3 and thensilver nitrate solution, these are the results
Chloride White precipitate
Bromide Cream precipitate
Iodide Yellow precipitate
Mix mystery compound with aluminium compound
Add a few drops of NaOH , if it was a nitrate before hand it will reduce to ammonia
Tests for organic compounds
Organic compounds burn when heated
When there is plenty of air available burning a Hydroncarbon produces CO2 and H2O. If amount of air is reduced then then carbon monoxide and carbon could also be produced.
THE GREATER THE PROPORTION OF CARBON= THE MORE YELLWO AND SMOKY A FLAME IS
Compounds with double carbon bonds decolourise bromine water
If organic compound is unsaturated it will decolourise bromine water
If it is saturates the brominw ater will stay brown.
Machines are useful for medical purposes, police forensic work, environmental analysis, checking whether an athlete has taken a banned substamce, analysis of products in industry
Advantages of using machines
- can be operated by technicians. Lab methods need trained chemists to do everything.
- More accurate than lab method and can detect the tiniest amounts
- Much faster than lab methods and tests can be automated
- Its very epenisve to buy , run and maintain the machines
Atomic absorption spectroscopy identifies metals
The patterns of lights absorbed by the metals in the sample area analysed , each metal present in the produces a different pattern
Its much faster and more reliable than the human eye
Used in the steel industry to check the composition of metals - only takes a couple of minute compared to lab method.
1) Infrared Spectrometry -identifies which frequencies of infrared radiation are absorbed - the pattern of absorbion is different for each compound .
2) UV Spectroscopy- similar to above but with UV rays
3) Nuclear magnetic spectroscopy -used for organic compounds - helps find the structure of the molecule .
4) Gas-liquid chromotography- similar principles to paper chromotography, used to identify liquids and gases
5)Mass spectroscopy- for elements and compounds - tells you the mass of each particle.