Description of experiment
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Needed compounds:
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nitric acid : HNO3
hydrogen peroxide : H2O2
hydrochloric acid : HCl
potassium bromide : KBr
Class:
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elem=Br,O,N
redox
Summary:
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Bromide is oxidized by hydrogen peroxide in acidic environments. Addition
of nitric acid strongly enhances the reaction.
Description:
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Add 1 volume of H2O2 (30% by weight) to 1 volume of hydrochloric acid (10%
by weight) and add solid KBr: The solid dissolves and the liquid becomes
yellow. After a few minutes it is orange and a faint brown color can be
observed above the liquid, due to gaseous bromine.
Add a little amount of HNO3 (appr. 50% by weight): The liquid turns dark
red/brown and thick red/brown vapors of Br2 are formed above the liquid.
No dark drops of Br2 can be observed.
Heat liquid to appr. 60 C: The liquid starts bubbling and very thick vapors
of Br2 are formed. The bromine in the liquid boils away as a red/brown gas.
Cool down under running tap with cold water: Thick drops of liquid bromine
are formed on the inside of the glass. These drops can be recognized as
dark brown drops, sticking on the glass.