Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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ammonia : NH3
phenolphtalein : C (C6H4OH)2 C6H4 COO
hydrogen peroxide : H2O2
potassium ferrocyanide : K4 [Fe(CN)6] . 3H2O
Class:
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elem=Fe
redox
Summary:
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Ferrocyanide reacts with hydrogen peroxide, forming a fairly intensely
colored yellow compound (probably ferricyanide), but this reaction was
expected to make the liquid more alkaline, but this cannot be observed.
Description:
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Dissolve some potassium ferrocyanide in hydrogen peroxide (appr. 30% by
weight): The solid dissolves and the liquid becomes fairly intensively
colored yellow. A plain solution of potassium ferrocyanide is very pale.
Add a few drops of phenolphtalein indicator (dissolved in 70% ethanol):
No red/purple color, hence the liquid is not alkaline.
Add a few drops of ammonia (appr. 5% by weight): The liquid becomes red/pink.
From this experiment can be concluded that the reaction between H2O2 and
[Fe(CN)6]4- does not make the liquid more alkaline. The following was
expected: 2[Fe(CN)6]4- + H2O2 --> 2[Fe(CN)6]3- + 2OH-, but this apparently
does not happen. What is the real reaction?