Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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lead nitrate : Pb(NO3)2
sodium chlorite : NaClO2
Class:
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elem=Cl,Pb
precipitation
redox
Summary:
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Lead(II) ion and chlorite ion produce a pale yellow precipitate. This solid,
when dried, explodes when heated in a test tube, it deflagrates when heated in
an open flame.
Description:
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Dissolve some lead nitrate in water. Let the solution be quite dilute (e.g. 100
mg of lead nitrate in at least 5 ml of water).
Dissolve an excess amount of sodium chlorite in water. Also make this solution
quite dilute (e.g. 100 mg of sodium chlorite in 5 ml of water).
Mix the two liquids: When this is done, then a pale yellow precipitate is
formed. It looks a little like powdered sulphur.
Allow the precipitate to settle in a few hours. Carefully decant most of the
liquid and add 20 ml of distilled water and stir. This washes away most
impurities.
Allow the precipitate to settle again for several hours. After that period,
pipette away the colorless liquid above the precipitate and carefully pour the
remaining liquid with yellow precipitate on a piece of filter paper, which is
put on a pile of paper tissue.
Allow most of the water to be absorbed by the paper tissue and press the
precipitate dry in the folded filter paper between new pieces of paper tissue.
Next, allow it to dry for one day in a warm place.
The final result is a pale yellow solid, which has a glittery/shiny appearance.
It is quite hydrophobic, if it is added to water, it is not wetted at once and
it tends to float on the surface of the water.
Put a small amount on a metal spatula and hold this in a flame: The material
can be ignited very easily. It burns very fast, with a soft hissing/whoosh
sound and no residue remains. All is converted to white smoke. There hardly is
a visible flame. AVOID INHALATION OF THE WHITE SMOKE, IT CONTAINS LEAD AND
HENCE IS TOXIC.
Put a small amount in a dry test tube and then heat this test tube over a
flame: At a certain moment, when the glass becomes sufficiently hot, a POP
sound is produced. The small quantity of yellow material explodes and only some
white smoke remains in the test tube. DO NOT SCALE UP THIS EXPERIMENT. Only use
a tiny amount (e.g. a pile of yellow powder not larger than 3 mm x 3mm and not
higher than 3 mm).
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The yellow powder is Pb(ClO2)2. This compound is quite unstable and easily can
be provoked to decomposition. When it is somewhat confined, then it explodes on
heating.