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Name: G. P.
Status: educator
Age: 50s
Location: N/A
Country: N/A
Date: 4/21/2003


Question:
Aluminum chunks (pea size) in bromine in an Erlenmeyer flask were supposed to react and give off a "glow" and it did not work. I used bromine water instead of bromine. Could you give me a hint as to why it did not react?


Replies:
You already gave the hint: you "used bromine water instead of bromine." The great excess amount of water in bromine water inhibits the reaction of bromine with aluminum in several ways. First, it removes heat energy from the reaction so that the reaction cannot get underway. Also, the water hydrolyzes the aluminum bromide formed, making aluminum oxides and hydroxides. These compounds coat the aluminum, protecting it from further attack.

Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois


G.P.

The reaction only works if you use pure bromine. By the way, as you may suspect, the demonstration is very dangerous. Elemental bromine is nasty stuff -- corrosive, irritating fumes, causes ghastly burns if contacted. Also, the Al/Br reaction can be very violent. Do not under any circumstances use aluminum foil. That reaction occurs quickly, can run out of control, and lead to serious injury.

Regards,
ProfHoff 650



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