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Avogadro’s lawAvogadro’s law
Avogadro’s lawAvogadro’s law
Joseph Louis Gay-Lussac of France studied the
volume relationship of reacting gases.
In 1809, he published his results. He summarized
in a statement known as GAY-LUSSAC’S LAW OF
COMBINING VOLUMES OF GASES: When measured
at the same temperature and pressure, the ratios
of the volumes of reacting gases are the small
whole numbers.
Avogadro’s lawAvogadro’s law
H2 + Cl2 2 HCl
1 volume 1 volume 2 volumes
1 molecule 1 molecule 2 molecules
1 mol 1 mol 2 mol
Avogadro’s lawAvogadro’s law
AVOGADRO’S LAW states that equal volumes of
different gases at the same temperature and
pressure contain the same number of molecules.
If the amount of gas in a container is increased, the
volume is increased.
If the amount of gas in a container is decreased,
the volume is decreased.
Avogadro’s lawAvogadro’s law
As you increase the
amount of gas (i.e.
through inhalation) the
volume of the balloon
increases likewise.
Avogadro’s lawAvogadro’s law
This law was a real breakthrough in understanding the
nature of gases.
1. It offered a rational explanation of Gay-Lussac’s law
of combining volumes of gases and indicated the
diatomic nature of elemental gases, such as hydrogen,
chlorine and oxygen.
Avogadro’s lawAvogadro’s law
2. It provided a method for determining the
molecular weights of gases of known molecular
weight.
3. It afforded a firm foundation for the development
of the kinetic molecular theory.
Avogadro’s lawAvogadro’s law
The mathematical form of Avogadro’s law is:
V ; V1 = V2
n n1 n2
Sample problem 1
A sample of gas with a volume of 9.20 L is known to contain 1.225 mol.
If the amount of gas is increased to 2.85 mol, what new volume will
result if the pressure and temperature remain constant?
Avogadro’s lawAvogadro’s law
Solution
Given: V1 = 9.20 L V2 = ?
n1 = 1.225 mol n2 = 2.85 mol
Solution:
V2 = n2V1 = (2.85 mol) (9.20 L) = 21.4 L
n1 (1.225 mol)
Avogadro’s lawAvogadro’s law
Sample exercises
1. If 0.25 mol of argon gas occupies a volume of 7.62
mL at a particular temperature and pressure, what
volume would 0.43 mol of argon have under the
same conditions?
Avogadro’s lawAvogadro’s law
Sample exercises
2. At a certain temperature and pressure, a balloon with
10.0 g of oxygen has a volume of 7.00 L. What is
the volume after 5.00 g of oxygen is added to the
balloon?
The EndThe End
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