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Qualitative Analysis
What is it? The process of separating and identifying ions in an aqueous solution.
Why is it done? • to test the purity of products, such as drinking water• in crime detection laboratories• in medical testing, blood and urine analysis
There are many different techniques in qualitative analysis, we will use three. 1
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1) Solution Colour
Some ions produce a distinct colour in solution.
Limitationsmost solutions are colourlesssome ions produce the same coloursex. copper and nickel ions both produce blue/green solutions
2) Selective Precipitation A solution known to precipitate a certain ion is added. If a precipitate results, the ion is present, if there is no precipitate, the ion is not present.Ex. You have a solution that might contain Mg2+ and/or Ca2+ What solution could you add to find out if Mg2+ is present?
Limitationssome ions will never precipitate (ex. NO3 always soluble)some ions precipitate more than one ion
Use your Solubility Table!!!
Mg2+ Ca2+
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3) Flame TestMany ions give off a distinct colour when placed in a Bunsen burner flame.
Limitations intensity varies widely impurities can affect results not all ions show a distinctive colour
Try the Flame Test Activity!!!
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8. Explain how fireworks are made.
http://www.youtube.com/watch?v=nPHegSulI_M
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