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This project illustrates the use of pressure and chemical reaction to demonstrate how a controllable gas generator can be set up. For illustration, we will construct a carbon dioxide (CO2) generator.
WARNING: This project involves the use of strong acids, great care must be taken when handling them. Usual laboratory precaution must be observed at all times.
Carbon dioxide can be produced by the chemical reaction between dilute hydrochloric acid (HCl) and calcium carbonate (CaCO3). A rich source of the carbonate exists as marbles which are readily available in nature. In laboratory, this is usually stored in the form of marble chips. In this
project, we will use large pieces of marble slabs which are readily available for building constructions. Large pieces are essential as we shall see later. The schematic diagram of the generator set-up is shown below:
The body of the generator consists of a large glass jar. At the bottom of the jar put some glass beads (or glass marbles - NOT to confuse with the calcium carbonate marble!) to a depth of about 10 cm. On top of the glass marbles bed place some large pieces of CaCO3 slabs. It is essential that the slabs should be on top and not bury in the
glass marbles. Close the jar with an air-tight cap, seal if necessary.
To a plastic funnel connect the end to a plastic tubling. Ensure the joint is properly sealed with no leakage. Make a hole on top of the jar cap and place the funnel as shown in the diagram above. Notice that the length of the plastic tubing must be such that the other end is about 0.5 to 1 cm from the bottom of the jar. Similarly, place a bended long glass tubing supported on the plastic tubing (see diagram above). Once again, ensure that the bottom end
is as close as possible to, but not touching, the bottom of the jar. The glass tubing will be used to remove spent HCl.
Finally, place a shorter tubing with a tap on top of the jar cap. It is served as a gas outlet, controlled by the tap. Ensure all joints with the jar cap are air-tight and properly sealed. Congratulation! You have just constructed a simple gas generator!
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