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Name: Marisa B.
Status: student
Age: 16
Location: N/A
Country: N/A
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.

ProfHoff 432

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".

Vince Calder

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