Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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aluminum : Al
sodium chloride : NaCl
copper nitrate : Cu(NO3)2 . 3H2O
copper sulfate penta hydrate : CuSO4 . 5H2O
cupric chloride dihydrate : CuCl2 . 2H2O
Class:
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elem=Cu,Al,Cl
redox
Summary:
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Copper (II) chloride reacts violently with metallic aluminium. When copper
sulfate or nitrate is used, then this reaction does not occur. When sodium
chloride is used, this reaction also does not occur. Both cupric ions and
chloride ions are needed for quick reaction with aluminium, but if they are
present, then a very violent reaction occurs.
Description:
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Sequence 1:
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Dissolve some cupric chloride in a small amount of water and add a crumbled
small piece of aluminium foil: Within a few seconds a violent reaction starts,
with the production of a lot of gas. The liquid becomes dark brown and appears
to be almost clear.
Add a lot of water: The water becomes milky-white and a white precipitate is
formed, which quickly sinks to the bottom. This precipitate probably is
copper (I) chloride, possibly contaminated with aluminium hydroxide.
Sequence 2:
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Dissolve some cupric chloride in a small amount of water and add a crumbled
large piece of aluminium foil: Within a few seconds a violent reaction starts,
with the production of a lot of gas. The liquid becomes dark brown and fairly
large pieces of a brown solid are formed.
Add a lot of water: The water remains fairly clear and the large brown/red
pieces collect at the bottom. These large pieces are metallic copper. The
excess amount of aluminium reduces all copper to the metallic state.
Sequence 3:
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Put some crystals of copper nitrate on a piece of aluminium foil and add a
small amount of water: The copper nitrate dissolves in the water and no further
changes can be observed. Even a concentrated solution of copper nitrate does
not attack aluminium foil (at least not within several minutes).
Sequence 4:
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Put a piece of aluminium foil in a solution of copper sulfate: No visible
reaction, the foil is not affected.
Sequence 5:
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Prepare a concentrated solution of sodium chloride and add some aluminium
foil to this: No reaction.
Add a small amount of a solution of copper sulfate to the sodium chloride
and shake well: The piece of aluminium foil starts bubbling violently and a
lot of heat is produced. The foil dissolves quickly and many pieces of brown
copper are produced, floating around in the liquid. The liquid becomes
turbid grey.