Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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hydrochloric acid : HCl
praseodymium chloride : PrCl3
Class:
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elem=Cl,Pr
coordination
Summary:
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Praseodymium chloride dissolves in water very well and very easily, but it
hydrolyses. A solution of this is turbid. When the solution is slightly
acidified, then a very pale green and clear solution is obtained.
Praseodymium chloride only dissolves slowly in concentrated hydrochloric acid.
The solution also has another color than a plain slightly acidified solution.
The solution in concentrated hydrochloric acid is yellow and its color is much
more intense than the pale green color of aqueous praseodymium ions.
Description:
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Sequence 1:
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Add some solid PrCl3 to some distilled water: The solid dissolves almost at
once and a turbid pale green (almost milky white) liquid is obtained.
Add a single drop of dilute hydrochloric acid: The liquid becomes very pale
green, almost colorless, and the liquid becomes clear.
Sequence 2:
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Add some solid PrCl3 to some concentrated HCl (30% by weight): The solid only
dissolves very slowly. The liquid obtained in this way, however, is totally
clear and it is fairly intense yellow. The color of the solution is much more
intense than the color of a solution of the same concentrated in slightly
acidified water. Apparently, a yellow complex with high concentration of
chloride is formed.