Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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phosphorus red : P
magnesium : Mg
Class:
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elem=Mg,P
redox
Summary:
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Powdered magnesium and powdered red phosphorus react violently, when heated
sufficiently. The reaction product contains considerable amounts of magnesium
phosphide.
Description:
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In a test tube put approximately equal amounts of powdered magnesium metal and
powdered red P. Mix the two chemicals throroughly. Don't use large amounts, use
a small spatula full of each of the chemicals (appr. 50 mg).
Heat the test tube with the mix of the two chemicals: At first, no reaction
occurs. Only after quite some time of heating, the reaction starts. But once
the reaction starts, it goes very violently. A loud hissing noise is produced,
with production of a lot of orange light. After the reaction, inside the test
tube, phosphorus had condensed on the glass.
A grey mass remains, with remaining evaporated/recondensed red phosphorus mixed
with it. Add some water to this (after it has cooled down): A gas is produced
vigorously. Let the evolution of gas continue for some time.
Light the gas by keeping the flame of a cigarette lighter at the open end of
the test tube: The gas burns with a greyish flame, and a lot of white smoke is
produced.
Remark:
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The reaction first produces Mg3P2, and when water is added, PH3 is produced,
together with Mg(OH)2. The PH3 burns with a smoking greyish flame, when
ignited.
Careful: PH3 is very toxic. Also, the reaction between Mg and P is very
violent, and in one of the experiments, the test tube cracked, due to the
sudden very strong production of heat.