10/22/2012

1

Announcements

• Lon-Capa Homework #7 due this Wed. • Lon-Capa Homework #8 (available Wed.)

– On Chemical Kinetics (Due next week)

• Will post a revised lecture schedule later today – Make sure you refer the new one from now

• From our course policy “As a rule, you are responsible for all the material covered in lecture, lecture notes, reading assignments in the textbook, and for material covered by your TAs in your quiz sections.

10/22/2012 1

Review from last lecture

• Molecular speed and effusion

10/19/2012 2

10/22/2012

2

Example

An unknown gas effuses 2.3 times faster than N2O4 at the same temperature. What is the identity of the unknown gas?

A) CN2

B) NH3

C) N2O

D) O3

3

rate of effusion of gas1rate of effusion of gas2

= 𝑀2

𝑀1

Example (# 4.71 Atkins and Jones)

What is the molecular formula of a compound of empirical formula CH that diffuses 1.24 times more slowly than krypton at the same temperature and pressure?

10/19/2012 4

10/22/2012

3

Kinetic Molecular Theory

1. A gas consists of a collection of molecules in continuous random motion.

2. Gas molecules are infinitesimally small points.

3. The molecules move in straight lines until they collide.

4. The molecules do not influence on another except during collisions .

5

Kinetic-Molecular Theory and Temperature

6

• Root mean square speed

𝑣𝑟𝑚𝑠 =3𝑅𝑇

𝑀

10/22/2012

4

Maxwell Distribution

10/22/2012 7