Flame Tests - AS Chemistry

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also has an explanation of what determines the colour.

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  • Created on: 28-02-11 17:37
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Flame Tests:
Method of Procedure
- For the wire to heat the ions, we used nichrom (nickelchromium). This is because it
is a very unreactive metal with a high melting point.
- We used a cobalt blue strip for Potassium to eliminate the yellow colour given off by
sodium.
- We kept the nichrom loops with a specific ion so there was no need for cleaning the
loops.
- We first moistened the wired loop in hydrochloric acid before dipping it into a small
amount of solid powder of the ions we were testing.
- We then placed the end of the wire into the hottest part of the Bunsen, just above
the cone.
- We then observed the colour shown and recorded the information.
- If the colour was weak, we simply moistened the wire with more acid.
- We then repeated this procedure for all the ions. We recorded the results in a table
below:
Cat Ion Symbol Flame Colour
Sodium Na+ Persistent Yellow
+
Barium Ba² Apple Green
Potassium K+ Purple or Lilac
+
Calcium Ca² Brick Red
Copper Cu²+ Green, Blue Centre
+
Lead Pb² Ice Blue
Strontium Sr²+ Scarlet Red
+
Lithium Li Crimson Red
Explanation:
Flame colours are produced from the movement of the electrons in the metal ions present in
the compounds. When you heat it, the electrons gain energy and can jump into any of the
empty orbital's at higher levels, depending on how much energy a particular electron
happens to absorb from the flame. Because the electrons are now at a higher and more
Tommy Broadley DUE IN: 5th October 2010

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An
electron which had jumped from the 2p level to an orbital in the 7 level, for example, might
jump back to the 2p level in one go. That would release a certain amount of energy which
would be seen as light of a particular colour. However, it might jump back in two or more
stages for example, first to the 5 level and then back to the 2 level.…read more

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