A gas evolution reaction is a chemical process that produces a gas, such as oxygen or carbon dioxide.
A gas evolution reaction is a chemical process that produces a gas, such as oxygen or carbon dioxide. In the following examples, an acid reacts with a carbonate, producing salt, carbon dioxide, and water, respectively.
Nitric acid reacts with sodium carbonate to form sodium nitrate, carbon dioxide, and water:
Sulfuric acid reacts with calcium carbonate to form calcium sulfate, carbon dioxide, and water:
Hydrochloric acid reacts with calcium carbonate to form calcium chloride, carbon dioxide, and water:
The following setup demonstrates this type of reaction:
Reaction of acids with carbonates: In this reaction setup, lime water is poured into one of the test tubes and sealed with a stopper. A small amount of hydrochloric acid is carefully poured into the remaining test tube. A small amount of sodium carbonate is added to the acid, and the tube is sealed with a rubber stopper. The two tubes are connected. As a result of the acid-carbonate reaction, carbon dioxide is produced and the lime water turns milky.
The test tube on the right contains limewater (a solution of calcium hydroxide, Ca(OH)2). On the left, a solution of hydrochloric acid has been added to a solution of sodium carbonate to generate CO2(g)CO2(g). The test tubes are sealed with rubber stoppers and connected with a delivery tube. As the reaction proceeds, the limewater on the right turns from clear to milky; this is due to the CO2(g)CO2(g) reacting with the aqueous calcium hydroxide to form calcium carbonate, which is only slightly soluble in water.