Page 32 - Curriculum Visions Dynamic Book

Preparing nitrogen dioxide
This demonstration shows how nitrogen dioxide is produced and what happens if it is cooled.
The demonstration uses lead nitrate as a source of gases. Lead is not a
very reactive metal. As a result, its compounds are not very stable and they decompose easily. This is why lead nitrate is a good substance to use for a laboratory demonstration.
In this demonstration, lead nitrate is heated. Heating causes the lead nitrate to decompose to lead oxide. During this process, energy is released, which can be heard as the crystals of lead nitrate break up.
This breaking down process is called decrepitation. It releases both nitrogen oxides and oxygen, as shown by the gas collected at the end of
the apparatus.
In the final stage the
gases are dissolved in water, creating nitric acid. In the atmosphere nitrogen dioxide would dissolve in raindrops, helping give rise to a natural fertiliser, or, in greater concentrations, to acid rain.
 Lead nitrate, a white powder, is heated. It changes colour as it melts and decomposes to lead oxide. The bubbles and the brown fumes are oxygen gas and nitrogen oxides, which will be separated out in step 2.
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