AVOGADROS LAW AND IDEAL GAS LAW

1. Avogadro’s Law, Amedeo Avogadro
(1776–1856)
• Volume directly proportional to the number of
gas molecules
Constant P and T
More gas molecules = larger volume
• Count number of gas molecules by moles.
• Equal volumes of gases contain equal numbers of
molecules.

2. Avogadro’s Law
The volume of a gas sample increases linearly with the number of moles of gas in the
sample.
When the amount of gas in a
sample increases at constant
temperature and pressure, its
volume increases in direct
proportion because
the greater number
of gas particles fill more space.

3. Avogadro’s Principle
• Equal volumes of gases contain equal numbers of moles
 at constant temp & pressure
 true for any ideal gas
V
n
V1
n1
=
V2
n2

4. Sample Problem:
What will be the final volume of a
5.0L He gas which contains
0.965mole at 30°C and 1 atm, if the
amount of this gas is increased to
1.80 moles provided that
temperature and pressure remains
unchanged?

5. Answer the following:
1. A 7.25L sample of nitrogen gas is
determined to contain 0.75 moles of
nitrogen. How many moles of
nitrogen gas would there be in a
20 L sample provided the
temperature and pressure remains
the same?

6. Answer the following:
2. What will be the final volume
of an 8.0 L Helium gas which
contains 0.95 mole at 350°C if the
amount of gas is increased to
1.75 moles?

7. Ideal Gas Law
• The relationships that we have discussed so
far can be combined into a single law that
encompasses all of them.

8. Ideal Gas Law
 By combining the gas laws we can write a general
equation.
 R is called the gas constant.
 The value of R depends on the units of P and V.
We will use and convert P to atm and V
to liters.
 The other gas laws are found in the ideal gas law if two
variables are kept constant.
 The ideal gas law allows us to find one of the variables if
we know the other three.

9. Ideal Gas Law
• UNIVERSAL GAS CONSTANT
• R=0.0821 Latm/molK
PV = nRT

10. Ideal Gas Law

11. Sample Problem:
• What is the volume of a container
that can hold 0.50 mole of gas at
25°C and 1.25 atm?

12. Answer the following:
1. Calculate the pressure exerted
by a 0.25 mole sulfur
hexaflouride in a steel vessel
having a capacity of 1250 Ml at
70°C.

13. Answer the following:
2. Fermentation of glucose
produce gas in the form of carbon
dioxide, how many moles of
carbon dioxide is produced if
0.78L of carbon dioxide at 20.1°C
and 1 atm was collected during
the process?