Description of experiment
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Needed compounds:
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calcium carbide : CaC2
hydrochloric acid : HCl
bleach : NaClO
Class:
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elem=Cl,C
redox
Summary:
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Chlorine reacts with acetylene gas (C2H2), without the need to ignite it.
Description:
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Fill a glass bottle (100 ml) with appr. 25 ml bleach (4% active chlorine) and
add the same volume of concentrated HCl (appr. 30% by weight): The liquid
starts bubbling and fizzling. Wait a while and then loosely cap the bottom
with the fizzling liquid. While the liquid is doing so, put the capped bottle
upside down, under water. The liquid is driven out of the bottle and fairly
pure chlorine gas is obtained in this way, trapped in a 100 ml bottle.
Take a little piece of calcium carbide (technical quality, so called 'carbid')
and put this in a syringe of appr. 50 ml. Suck in a little amount of water
and put thumb on the tip of the syringe. Appr. 50 ml of ethyne (acetylene)
is produced this way. After this, some water is sucked in and pressed out
again in order to clean the syringe.
Keep the bottle with chlorine gas upside down in a tray of water and bubble
acetylene gas from the syringe in the chlorine (carefully!): As soon as a
bubble of acetylene reaches the water-surface inside the chlorine bottle,
a bright orange flash and a deep soft sound is produced. The gas reacts with
chlorine forming a lot of black soot, which is trapped inside the bottle.
A few tens of bubbles could be 'burned' in the chlorine gas.