Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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hydrochloric acid : HCl
potassium iodide : KI
stannous chloride : SnCl2
Class:
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elem=Sn,I
precipitation
Summary:
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Tin (II) compounds forms either a yellow or orange/red compound with
iodides. What compound is formed, depends on the concentration of the
reactants.
At very low pH such a compound is not formed anymore, and once formed,
it can be dissolved.
Description:
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Sequence 1:
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Add some tin chloride to distilled water: The solid quickly dissolves, the
liquid becomes turbid.
Add a solution of potassium iodide: Formation of a bright yellow precipitate.
Color resembles the color of sulphur, but it is slightly brighter.
Let stand for almost one day: On the bottom of the test tube some small red/
orange crystals can be observed, with the yellow precipitate on top of it.
Add some HCl (appr. 10% by weight): The precipitate dissolves, the liquid
becomes almost clear and colorless. A slight white turbidity remains.
Sequence 2:
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Add some tin chloride to distilled water: The solid quickly dissolves, the
liquid becomes turbid.
Add some HCl (appr. 10% by weight): The turbidity almost disappears, the
liquid becomes almost clear and colorless. A slight white turbidity remains.
Add a solution of potassium iodide: No visible reaction, no precipitate
appears.
Sequence 3:
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Prepare a very concentrated solution of potassium iodide and a very
concentrated solution of tin chloride. Add an excess amount of the solution
of tin chloride to the solution of potassium iodide: The liquid mixture
solidifies and a yellow crust is formed. This crust quickly changes color
from yellow to orange/red.
Add some HCl (10% by weight): The orange/red crust dissolves and the liquid
becomes colorless with a slight turbidity.