Description of experiment
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Needed compounds:
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nitric acid : HNO3
hydrochloric acid : HCl
copper : Cu
Class:
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elem=Cu,Cl,N
redox
Summary:
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When copper dissolves in aqua regia, then a colorless gas is produced.
Oxidation apparently proceeds in a different way, when compared with
dissolving copper in nitric acid.
Description:
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Prepare some aqua regia by mixing 3 parts of hydrochloric acid (appr. 30%
by weight) with 1 part of nitric acid (appr. 52% by weight) and add some
copper metal: The copper dissolves, but this proceeds very slowly. No gas
is evolved. The liquid turns yellow/green.
Heat the liquid: The copper now quickly dissolves and a lot of a colorless
gas is produced. The gas mixture above the liquid becomes very light brown.
The liquid itself becomes dark green. A strong smell of chlorine can be
observed.
Let liquid cool down: The liquid becomes intense grass green, there is a
strong smell of chlorine above the liquid.
Dilute strongly with water: The diluted liquid becomes light blue (color
of aqueous Cu2+ ions).