Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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stannous chloride : SnCl2
sodium sulfite : Na2SO3
hydrochloric acid : HCl
potassium tetrachloroplatinate (II) : K2PtCl4
Class:
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elem=Pt,Sn
coordination
Summary:
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Platinum (II) gives a highly coloured compound with tin (II), it is not
reduced to metallic platinum.
Description:
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Sequence 1:
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Add a drop of a solution of K2PtCl4 (appr. 35 g/l) to a solution of SnCl2 and
Na2SO3 in dilute HCl (appr. 10 % by weight): The liquid becomes fairly
intense yellow/brown, much darker than one would expect on the basis of the
amount of K2PtCl4. No metallic platinum is formed, not the sulfite, nor the
stannous chloride is capable of reducing platinum to its metallic state.
Sequence 2:
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Prepare a solution of stannous chloride in dilute HCl (appr. 7% by weight)
and add a single drop of a solution of K2PtCl4 (appr. 35 g/l): The liquid
becomes orange/red and remains clear. The color is really bright, it is a
beautiful brilliant orange/red.
Keep the orange/red liquid in contact with air: After two days, the liquid
still is beautiful orange/red. After almost three days, it appears to be a
little less brilliant. A few hours later it suddenly is colorless.
Add a few crystals of SnCl2 to the colorless liquid: The liquid becomes nice
orange/red again.
Hypothesis:
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The tin(II) compound is slowly oxidized by oxygen from the air and when all
tin(II) is oxidized, then the platinum-tin complex does not exist any longer.
When some new SnCl2 is added, then the orange/red complex is formed again,
until the tin(II) is oxidized to tin(IV) again.