Page 16 - Curriculum Visions Dynamic Book

Making oxygen chemically
Pure oxygen has a large number of uses in the modern world. It is used, for example, in medicine, but also on a much larger scale for making fuels burn more effectively, such as in an iron-making blast furnace or in an oxyacetylene welding and cutting lance.
On a large industrial scale, atmospheric air is cooled. At -183°C oxygen liquefies; it can then be stored in tanks and transported easily.
Hydrogen peroxide solution in dropper funnel is released gradually into the flask.
Oxygen passes from the flask and along this tube.
Laboratory preparation
In the school laboratory oxygen is made by reacting two chemicals together or by causing an oxygen-rich compound to decompose.
It is common to use the apparatus shown on this page for small samples. Here an oxygen-rich compound, hydrogen peroxide in solution in water is dripped
on to manganese oxide. The manganese oxide causes the hydrogen peroxide
to decompose and release oxygen and water. The oxygen is collected in a gas
jar over water using a support called a beehive shelf.
An alternative procedure involves heating a compound (for example potassium chlorate) which liberates oxygen as it is heated (i.e. as it decomposes).
Gas jar for collecting the oxygen initially filled with water.
The hydrogen peroxide decomposes without heat when in the presence of manganese oxide, which acts as a catalyst.
Gas jar submerged in water, standing on a beehive shelf.
Bubbles of oxygen being released. Oxygen can be collected over water because it is not very soluble.
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