Avogadro’s Law
Chemistry 10
Fourth Quarter
OBJECTIVES
At the end of the
session, the students
are able to illustrate
how gases behave
according to
Avogadro’s Law
“At the same
temperature and
pressure, equal volumes
of different gases
contains the same
number of molecules.”
AMEDEO
AVOGADRO
AVOGADRO’S LAW
At constant temperature and pressure
𝑉∝ 𝑛
where n represents the number of moles
AVOGADRO’S LAW
For two samples of gas at the same pressure and temperature,
the equation for Avogadro’s law can be written as:
𝑉1 𝑉2
=
𝑛1 𝑛2
AVOGADRO’S LAW
Chemists have selected standard condition, to be used for easy
comparison between gas samples:
T = 0°C = 273 K
P = 1.00 atm or 760 mmHg
V = 22.4 L
Sample Problem:
Burning of rubber tires produces SO2, a pollutant in air.
What is the volume of SO2 when 3.00 mol of it are
produced assuming that temperature and pressure are
constant?
Sample Problem:
Burning of rubber tires produces SO2, a pollutant in air.
What is the volume of SO2 when 3.00 mol of it are
produced assuming that temperature and pressure
are constant?
Sample Problem:
Burning of rubber tires produces SO2, a pollutant in air. What
is the volume of SO2 when 3.00 mol of it are produced
assuming that temperature and pressure are constant?
Given:
Use the standard conditions as the initial conditions:
V1 = 22.4 L
n1 = 1.00 mol
Required: V2 = ?
Equation:
𝑉1
𝑛1
=
𝑉2
𝑛2
n2 = 3.00 mol
Solution:
22.4 𝐿
𝑉2
=
1.00 𝑚𝑜𝑙 3.00 𝑚𝑜𝑙
22.4 𝐿 (3.00 𝑚𝑜𝑙) = 1.00 𝑚𝑜𝑙 𝑉2
22.4 𝐿 (3.00 𝑚𝑜𝑙)
= 𝑉2
1.00 𝑚𝑜𝑙
67.2 𝐿 = 𝑉2
Answer: The volume of SO2 when 3.00 mL of it are produced
is 67.2 L.
ACTIVITY
A 6.0 L sample at 25°C and 2.00 atm of pressure contains 0.5
mole of a gas. If an additional 0.25 mole of gas at the same
pressure and temperature are added, what is the final total
volume of the gas?
ACTIVITY
1. 5.00 L of a gas is known to contain 0.965 mol. If the
amount of gas is increased to 1.80 mol, what will be its
final volume (at an unchanged temperature and
pressure)?
2. A flexible container at an initial volume of 5.120 L
contains 8.500 mol of gas. More gas is then added to
the container until it reaches a final volume of 18.10 L.
Assuming the pressure and temperature of the gas
remain constant, calculate the number of moles of gas
added to the container
ACTIVITY
If 0.00810 mol neon gas at a particular temperature and
pressure occupies a volume of 214 mL, what volume would
0.00684 mol neon gas occupy under the same conditions?
ACTIVITY
A flexible container at an initial volume of 6.13 L contains 7.51
mol of gas. More gas is then added to the container until it
reaches a final volume of 13.5 L. Assuming the pressure and
temperature of the gas remain constant, calculate the number of
moles of gas added to the container.