Video Transcript
What will happen when ammonia gas
passes by a glass rod wet with HCl? (A) White clouds of ammonia
carrying HCl are formed. (B) White clouds of ammonium
chloride are formed. (C) White clouds of hydrogen gas
are formed. (D) White clouds of water vapor are
formed.
We are asked what happens when
ammonia gas passes by a glass rod wet with HCl. HCl is the chemical formula for the
acid hydrochloric acid. It is also the chemical formula for
the substance hydrogen chloride, which is a gas. Before we can answer this question,
we need to know what happens when a glass rod is dipped into a concentrated
hydrochloric acid solution and then removed from that solution.
After the glass rod is removed from
the acid solution, the hydrochloric acid on the rod releases hydrogen chloride
gas. Hydrogen chloride gas is
colorless. Now if we pass ammonia gas, which
is also colorless, past the glass rod, something happens. We will notice white fumes or
clouds forming. The white clouds which form are
actually tiny solid particles of white ammonium chloride.
This is how they form. Ammonia gas and hydrogen chloride
gas undergo a chemical reaction with each other. These substances combine to form
one new substance, ammonium chloride, which is white. We call this a direct combination
reaction. A direct combination reaction is a
type of reaction where one product is formed from two or more reactants.
Finally, what will happen when
ammonia gas passes by a glass rod wet with HCl? The answer is (B); white clouds of
ammonium chloride are formed.
