1. AP Chemistry Tutorials–01 Chp-05: Kinetic Theory
Srinivasan G. Srivilliputhur
December 03, 2015

2. Today’s Overview 1 2 Problems 81 – 93 in the Textbook AP MCQs
This is another option for an overview slide.

4. Kinetic Molecular Theory (KMT)
Terminology: Here, the term “molecule” refers to the individual chemical species in the gas, although some gases are composed of atomic species (e.g. the noble gases)
KMT:
Is a simple microscopic model
Accurately explains the gas laws
Five Postulates of KMT
The various gas laws can be derived from the KMT postulates, which have led to the belief that KMT accurately represent the properties of gas molecules.

5. Kinetic Molecular Theory (KMT)
Five Postulates of KMT
Gases are made of molecules that move continuously, travelling in straight lines and changing direction only when they collide with other molecules or with container walls.
The gas molecules are negligibly small compared to the distances between them (i.e. their volume is negligible compared to container volume).
The pressure exerted by a gas results from their collisions with the container walls.
Gas molecules exert no attractive or repulsive forces on each other or the container walls; therefore, their collisions are elastic (i.e. no loss of energy).
The average kinetic energy of the gas molecules is proportional to the Kelvin temperature of the gas.

7. T increases, P increases
Amonton’s Law from KMT
T increases, P increases
WHY? Increased force + more frequent molecular collisions

8. V decreases, P increases
Boyle’s Law from KMT
V decreases, P increases
WHY? Reduced wall area + more frequent wall collisions

9. Amount Increases, P constant
Avogadro Law from KMT
Amount Increases, P constant
WHY? Volume increases to yield a constant number of collisions per unit wall area (because P is constant)

10. Molecular Velocities & Kinetic Energy
Microsoft Engineering Excellence
Molecular Velocities & Kinetic Energy
Observations
Very few molecules move at either very low or very high speeds
The number of molecules with intermediate speeds increases rapidly up to a maximum, which is the most probable speed (vp), then drops off rapidly
Note that the most probable speed, νp, is a little less than 400 m/s, while the root mean square speed, urms, is ~500 m/s.
The molecular speed distribution for O2(g) at 300K
Microsoft Confidential

11. Molecular Velocities & Kinetic Energy
Microsoft Engineering Excellence
Molecular Velocities & Kinetic Energy
Observations
The molecular speed distribution for N2(g) shifts to the:
right and flattens as the temperature increases
left and heightens as the temperature decreases
Microsoft Confidential

12. Molecular Velocities & Kinetic Energy
Microsoft Engineering Excellence
Molecular Velocities & Kinetic Energy
Observations
The molecular speed distribution for N2(g) shifts to the:
right and flattens as the temperature increases
left and heightens as the temperature decreases
Microsoft Confidential

13. Microsoft Engineering Excellence
(Q-1) 2015 AP Chemistry
The three gases are in identical rigid containers under the conditions given in the table below.
Microsoft Confidential

14. Microsoft Engineering Excellence
(Q-2) 2015 AP Chemistry
The three gases are in identical rigid containers under the conditions given in the table below.
Microsoft Confidential

15. Microsoft Engineering Excellence
(Q-3) 2015 AP Chemistry
The three gases are in identical rigid containers under the conditions given in the table below.
Microsoft Confidential