Page 15 - Curriculum Visions Dynamic Book

Preparation of carbon dioxide gas
Carbon dioxide gas can be produced in numerous ways in the laboratory. For example, if dilute hydrochloric acid is
added to calcium carbonate, it begins to fizz. The reaction produces a solution of calcium chloride and releases carbon dioxide gas.
gelatinous: a term meaning made with water. Because a gelatinous precipitate is mostly water, it is of a similar density to water and will float or lie suspended in the liquid.
noncombustible: a substance that will not burn. reagent: a starting material for a reaction.
sublimation: the change of a substance from solid to gas, or vice versa, without going through a liquid phase.
EQUATION: Preparation of carbon dioxide gas
Dilute hydrochloric acid + calcium carbonate ➪ calcium chloride + carbon dioxide + water
2HCl(aq) + CaCO3(s)
 Some antacid tablets contain calcium carbonate, which acts on the dilute hydrochloric acid in the stomach. This demonstration shows that a reaction occurs in the stomach, releasing carbon dioxide gas. This explains why some antacid tablets cause people to “burp”.
➪ CaCl2(aq) + CO2(g) + H2O(l) Carbon dioxide as a fire extinguisher gas
Because carbon dioxide gas is noncombustible, it is ideal for use in extinguishing fires.
Fire extinguishers may contain two reagents (liquids that will react) to produce carbon dioxide quickly. The equation below shows the reaction of aluminium sulphate and sodium carbonate. These reagents were used as a source of carbon dioxide gas and a source of foam for many years until they were replaced by pressurised carbon dioxide cylinders.
In use, the two reagents are kept apart inside the extinguisher. When in use, a knob on the extinguisher is struck, breaking the seal between the liquids and causing them to react.
The reaction produces a gelatinous liquid
and carbon dioxide gas. This gas cannot easily escape through this sticky liquid, and instead forms bubbles inside it. The result is that a foam containing carbon dioxide immediately issues from the extinguisher nozzle. This has the effect of blanketing the fire with materials that will not burn. It also prevents oxygen from reaching the flames.
Also...
Many modern carbon dioxide extinguishers do not rely on a chemical reaction, but instead contain carbon dioxide gas under pressure in a strong cylinder.
EQUATION: Fire extinguishing
Aluminium sulphate (alum) + sodium carbonate + water ➪ aluminium hydroxide (gelatinous precipitate) + carbon dioxide (gas) + sodium sulphate (solution)
Al2(SO4)3(aq)+ 3Na2CO3(aq)+ 3H2O(l) ➪ 2Al(OH)3(s) + 3CO2(g) + 3Na2SO4(aq)
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