This document discusses the properties and behavior of gases. It defines several key concepts: - Gases can be compressed or expanded depending on pressure and will exert an even pressure on their container. - The kinetic molecular theory of gases states that gas particles are in constant, random motion and collide elastically with each other and container walls. - Gas laws like Boyle's, Charles', and the combined gas law mathematically relate the pressure, volume, temperature and amount of a gas. - The ideal gas law combines these relationships into one equation that can be used to calculate gas properties under any conditions. - Avogadro's law states that equal volumes of gases under the same conditions contain

1. PROPERTIES OF GASES
1. Gases may be compressed
2. Gases expand when less pressure is applied.
3. Gases can be mixed
4. Gases exert a constant pressure on its
container walls.
5. Gases have low densities.

2. PROPERTIES OF GASES
1. Gases may be compressed
2. Gases expand when less
pressure is applied.
3. Gases can be mixed
4. Gases exert a constant
pressure on its container
walls.
5. Gases have low densities.
KINETIC MOLECULAR THEORY OF GASES
1. Gases always move in straight
lines and in constant motion
2. Gases are widely spaced
3. Gases collide with each other
and with their container walls
without loss of kinetic energy
4. Gases behave as individual
particles, attraction between
them is negligible
5. The actual volumes of gases are
insignificant compared to the
space they previously occupy

3. Origin of
Pressure

4. KINETIC MOLECULAR THEORY OF GASES
1. Gases always move in straight lines and in
constant motion
2. Gases are widely spaced
3. Gases collide with each other and with their
container walls without loss of kinetic energy
4. Gases behave as individual particles, attraction
between them is negligible
5. The actual volumes of gases are insignificant
compared to the space they previously occupy

5. PARAMETERS OF GASES
• Pressure- chaotic movement of gases make
pressure measurement important
– 1 atm. = 760 mmHg = 760 torr
•
• Temperature = gases expand when heated,
contract when cooled
K = 0C + 273
• Volume = mL, liter 1 liter = 1000 mL
• Quantity= grams and or moles

6. GAS LAWS
• Mathematical statements of the properties
and behaviour of gases

7. • Boyle’s Law= At constant temperature, the
volume of a gas is inversely proportional to its
pressure
•
• VP = K

8. • Charles’ Law= At constant pressure the
volume of a gas is directly proportional to its
absolute temperature
• V/T = K

9. • Gay Lussac’s Law = At constant volume the
pressure of a gas is directly proportional to its
absolute
• temperature
•
• P/T = K

10. Combined Gas Law
• For a given amount of the gas, any change in
the condition of one of the variables will also
cause a change in the other two variables in
accordance to Boyle’s Law and Charles’ law.
For this reason we can combine the 2 gas laws
into one mathematical equation called
combined gas law.
• VP/T = K

11. Ideal Gas Law
• PV = nRT
• Where P=pressure in atm.
• V= volume in liter
• T = absolute temperature
• n = moles of gas
R = 0.082 l-atm/mole 0K (universal gas constant)
•

12. •
• P V = K Boyle’s law
• P/T = K Charle’s law
• P/n = K
•
• Combining the 3 laws
• PV/nT = K
•
• PV = nKT
•
• PV = nRT
•

13. 1 mole = 22.4 liters
0 C = 273 K
1 atm.
molar gas volumeo o
standard conditions of
temperature and
pressure

14. Avogadro’s Law
• Equal volumes of gases under same
conditions of temperature and pressure
contain equal number of molecules
• Means Mole Ratio = Volume Ratio
•

15. Example :
CH4
+
2 O2 >>>>> CO2
+
2H2O
at STP
mole ratio
2 moles O2
1 mole CH4
volume ratio 1 mole CH4 x 22.4 liter
2 moles O2 x 22.4 liters
s
2
1
=

16. Graham’s law of Diffusion
• = The rate of diffusion of a gas is inversely
proportional to the square root of the
molecular mass of the gas
• MW increaseas rate decreases ( slow)
• MW decreases rate increases (fast)
•