Hydrogen Popping Noise
Name: Marisa B.
Date: Saturday, June 01, 2002
When sodium hydroxide reacts with aluminum metal and
water hydrogen gas is formed. when this gas is lit with a flame, it
eventually makes a popping noise. what is the reason for this noise?
If the hydrogen is collected and burned at a jet it will burn silently. If
mixed with the proper amount of air (oxygen) and then ignited, hydrogen can
explode with a pronounced report -- bang!
You refer to a "popping noise." Am I to assume you are setting the gas
ablaze as it bubbles from the reaction zone? If so, the sound you hear is
the explosion of hydrogen bubbling from the solution as it mixes with air.
If this is what is happening, I would advise you to be very careful. The
reaction of sodium hydroxide solution and aluminum can form aerosols that
entrain sodium hydroxide. This mist is very corrosive to eyes and skin. Wear
proper protection and have supervision during the experiment.
The reaction of H2 gas with atmospheric oxygen is explosively fast. What
you hear is a mini-shock wave. If the H2 is collected in a balloon, about
10-15 cm. in diameter, the "pop" becomes a very loud "bang".
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Update: June 2012