Description of experiment
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Needed compounds:
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sodium hydroxide : NaOH
p-aminophenol HCl : NH2 C6H4 OH . HCl
potassium nitrite : KNO2
Class:
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elem=C,N
redox
Summary:
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Nitrite reacts with p-aminophenol violently in alkaline environments.
Description:
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Add some solid KNO2 to a solution of p-aminophenol HCl in dilute HCl (appr.
3% by weight): A faint brown color is observed above the liquid (formation
of nitrous vapors, NO/NO2). The liquid turns brown/purple, not particularly
intensely coloured.
Add a few pieces of solid NaOH: Strong evolution of a colorless gas, liquid
starts foaming and becomes hot. The liquid turns black quickly. Even after
a 10 times dilution, the liquid still is black.
Remark:
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It is expected that the colorless gas is nitrogen (from amino group and
nitrite).