Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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ferric chloride : FeCl3 . 6H2O
sodium hydroxide : NaOH
sodium citrate : COONa CH2 COH(COONa) CH2 COONa
nickel nitrate : Ni(NO3)2 . 6H2O
Class:
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elem=Ni,Fe
coordination
precipitation
Summary:
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Nickel (II) forms a complex with citrate. In a strongly alkaline environment
the nickel (II) does not precipitate. With just a small amount of ferric
ions present in the liquid, the complete liquid solidifies to a gelatin-
like constitution.
When the same experiment is done, without the nickel (II) present, no
solidification is observed.
Description:
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Sequence 1:
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Add a large excess amount of sodium citrate to a solution of nickel nitrate:
The solid dissolves and the color of the liquid turns into a more intense
green, with a shade of blue.
Add a fairly large amount of NaOH to the green/blue liquid: The solid
dissolves. The liquid remains clear and remains green. The color shifts from
bluish green to yellowish green.
Add a few drops of a solution of ferric chloride to the liquid: Where the
drops touch the liquid, it becomes brown and turbid for a while. When the
liquid is shaken, the brown precipitate dissolves again. The entire liquid
becomes brown/green and just a little turbid. After a few minutes of standing
the liquid has solidified. The test tube can be kept upside down and can be
shaken, without the liquid going from its place. The liquid is not viscous
syrup-like, it is like gelatin.
Add a large amount of water, which is added to the solidified liquid with
force: The solidified liquid breaks apart in little pieces, which do not
dissolve.
Sequence 2:
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Dissolve a fairly large amount of sodium citrate and sodium hydroxide in a
little amount of water and add a few drops of a solution of ferric chloride:
The liquid turns brown/red and turbid. Little flakes of a brown solid keep
floating around in the liquid. The liquid does not solidify.
Sequence 3:
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Add a large amount of sodium citrate to a solution of ferric chloride: The
yellow/brown color of the liquid changes to yellow/green, when the solid
dissolves. The liquid remains clear.
Add a little amount of NaOH and shake well: The color of the liquid changes
from yellow/green to rusty brown. The liquid becomes slightly turbid.
Add much more NaOH and shake: The liquid turns darker brown and more turbid.
It does not solidify.