Description of experiment
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Needed compounds:
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formic acid : HCOOH
bromine : Br2
aluminum : Al
Class:
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elem=C,Al,Br
redox
Summary:
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Bromine does not react with formic acid, or it reacts very slowly. When
aluminium is added, then this quickly shows a violent reaction and all of the
aluminium dissolves, leaving a clear orange/red and someawhat viscous liquid.
On dilution with water, a clear yellow liquid is obtained.
Description:
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Add a few big drops of bromine to approximately 1 ml of 85% formic acid: The
bromine partially dissolves, but most of it sinks to the bottom and remains
undissolved at the bottom. The solution gets a dark red color and the gas mix
above the solution becomes pale brown.
Let the liquid stand for 1 hour in bright sunshine: After this hour not much
has changed. Still there is a blob of liquid bromine under a deep red and clear
liquid.
Add a small piece of household aluminium foil: This reacts with the liquid at
once, giving a colorless gas. Initially there is bubbling, nice and fairly
fast, but not violent. After a minute or so, the reaction suddenly becomes much
more violent. A lot of heat is produced and bromine vapor is driven out of the
test tube. A lot of white fume/smoke is produced as well. After the reaction,
approximately 1/3 of all liquid has gone. The remaining liquid is bright
orange, clear and somewhat viscous. All of the a
Add a few ml of water: The liquid mixes with the water and the resulting liquid
is almost clear (slight opalescense) and yellow.
Remark: Apparently, bromine does not oxidize formic acid nor does it replace
the hydrogen atom on the C atom. The sunlight did not help getting a faster
reaction.