Reaction of Aluminum with Bromine
When pieces cut from a sheet of aluminum foil are added to liquid bromine on a watch glass, a vigorous, exothermic reaction ensues. White aluminum bromide is the product.
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Keywords
aluminum, combination reaction, descriptive chemistry, enthalpy/heat, evidence of chemical reaction, exothermic process, halogens/halides/hydrohalic acids, reactivity - kinetic/thermodynamic stability, redox reaction, spontaneous process
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(QuickTime 3.0 Sorenson, duration 93 seconds, size 6.3 MB)
Pieces of aluminum are cut from a strip of foil. Liquid bromine is placed on a watch glass and the pieces of aluminum are added. As the bromine evaporates, brown fumes are given off. At first there is no reaction because of the protective oxide coating on the aluminum. An exothermic reaction between bromine and aluminum causes more brown fumes of bromine to be given off. White fumes are also given off. When a fan is turned on, we can better observe the residue, which consists of aluminum bromide, excess bromine and aluminum. The brown color is caused by the excess bromine.
 Aluminum is added to bromine. |
 There is no reaction at first. |
 An exothermic reaction generates brown fumes of bromine. |
 The residue. |
Additional still images for this movie
Discussion
The equation for the principal reaction is
2 Al(s ) + 3 Br2(l ) --> 2 AlBr3(s )
Some of the aluminum bromide is produced as fumes, causing the white smoke seen in the video. In addition, aluminum bromide reacts violently with water to produce HBr and aluminum hydroxide or oxide.
Demonstration Notes, Warnings, Safety Information, etc.
Exam and Quiz Questions
1. What observable evidence indicates that a chemical reaction is taking place?
2. Is the reaction shown exothermic or endothermic? Cite observations that justify your choice.
3. What kinds of experimental work would you need to do to determine that the empirical formula for the product of the reaction of aluminum with bromine is AlBr3?