Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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glucose : CH2OH (CHOH)4 CHO
ammonium thiocyanate : NH4SCN
glycerol : CH2OH CHOH CH2OH
ethanol : CH3CH2OH
sodium sulfite : Na2SO3
ascorbic acid : C6H8O6
hydrochloric acid : HCl
sulphuric acid : H2SO4
potassium dichromate : K2Cr2O7
Class:
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elem=Cr
coordination
redox
Summary:
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When chromium (III) is created from dichromate, its color depends on the
reductor used and on the acid which is used for supporting the redox
reaction.
Description:
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Two sets of experiments are performed. In one set of experiments potassium
dichromate is dissolved in 10% H2SO4 and several compounds are oxidized
by this liquid. In the other set of experiments potassium dichromate is
dissolved in 10% HCl and the same set of compounds are oxidized again.
In all experiments an excess amount of reductor is used. The color of the
resulting liquid is recorded below.
Sequence 1: Potassium dichromate in 10% H2SO4
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ascorbic acid : violet/grey, addition of Na2SO3 gives no change of color.
sodium sulfite : bluish green
ethanol : blue/violet/grey
glycerol : violet/grey
ammonium thiocyanate: intensely colored, deep purple
glucose : not oxidized, not even on heating at 60 C
Sequence 2: Potassium dichromate in 10% HCl
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ascorbic acid : grey
sodium sulfite : green / bluish green
ethanol : mossy green, with bluish shade
glycerol : grey to greyish green, depending on light source
ammonium thiocyanate: intensely colored, deep purple
glucose : not oxidized, not even on heating at 60 C