Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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hydrochloric acid : HCl
ammonia : NH3
copper sulfate penta hydrate : CuSO4 . 5H2O
hydrogen peroxide : H2O2
copper tetrammine sulfate mono hydrate : [Cu(NH3)4] SO4 . H2O
Class:
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elem=Cu,O
redox
Summary:
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Decomposition of hydrogen peroxide is catalyzed by cuprammine complex.
Description:
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Experiment 1:
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Add some solid cuprammine sulfate to H2O2 (appr. 10% by weight): A violent
reaction occurs, with the evolution of a gas (oxygen). The liquid becomes
turbid and brown. A fairly large amount of heat is produced. When the vigorous
evolution of gas ceases, then the brown turbidity remains. After some time
the brown compound sinks to the bottom of the test tube.
Add some HCl (30% by weight) to the liquid with the precipitate: The HCl
mixes with the liquid and dissolves the precipitate. The final liquid is
clear and pale blue.
Experiment 2:
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Add some solid copper sulfate to H2O2 (appr. 25% by weight): The copper
sulfate dissolves and the liquid becomes pale blue. A very slow evolution
of a gas can be observed.
Add an excess amount of ammonia (appr. 15% by weight): Before the ammonia is
actually added to the H2O2, the vapour of the ammonia causes some light blue
drops of the H2O2-CuSO4 solution to turn brown. As soon as the ammonia is
added to the H2O2-CuSO4 solution a very vigorous reaction starts, with the
production of a lot of gas (oxygen) and heat. After the reaction, the liquid
is deep blue (color of cuprammine complex).
Experiment 3:
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Add some solid copper sulfate to H2O2 (appr. 5% by weight): The copper
sulfate dissolves and the liquid becomes pale blue. A very slow evolution
of a gas can be observed.
Add one drop of ammonia (15%): The liquid becomes brown and turbid. A fairly
vigorous evolution of gas is started.
Add an excess amount of HCl (30% by weight): The liquid becomes almost color-
less and clear.