Page 22 - Curriculum Visions Dynamic Book

Hydrochloric acid
Hydrochloric acid is the gas hydrogen
chloride (HCl) in water. Hydrochloric acid
is a strong, mineral acid, found close to the site of erupting volcanoes. It is also one of
the main acids that break down the food in our stomachs (in a concentration of 0.25%).
Most hydrochloric acid is produced as
a byproduct when chlorine is reacted with organic compounds as part of the process of making plastics. It is vital for the manufacture of a common plastic, vinyl, or PVC. It is also used in steelworks for cleaning steel, and in extracting metals from their ores.
A mixture of three parts hydrochloric acid and one part nitric acid is called aqua regia (royal water) and was traditionally used to dissolve gold (which was known as the “king of metals” by alchemists).
Because hydrochloric acid is readily available as a gas, it can be reacted with a basic gas, such as ammonia, to show that, in the gaseous state, an acid plus a base produces a salt. The demonstration is shown here.
 Two colourless gases, one in each cylinder, are brought together. The upper one is ammonia, the lower one hydrogen chloride gas.
Hydrogen chloride gas
Gas jars are placed on top of one another with a blocking glass plate in between. The glass plate is removed to allow the gases to mix and react.
Ammonia gas
Chlorine
EQUATION: Reaction of hydrochloric acid gas and ammonia
Hydrogen chloride + ammonia ➪ ammonium chloride HCl(g) + NH3(g) ➪ NH4Cl(s)
Hydrogen Nitrogen
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