# Section E Flashcards

## The internal energy, U

1

Q

Equpartition

A

relates temperature of a system to its average energies

2

Q

Vibrational internal energy

A

at high tem

3

Q

Diatomic linear molecule

A

has 2 degrees of freedom

4

Q

a non-linear molecule

A

3 derees of freedom

5

Q

Vibrational modes

A

contributes two increments of 1/2 kT to the internal energy, U.

- 1/2 from Kinetic and 1/2 from Potential
- = 1 = U= kT per vibrational mode
- U = RT per mole per molecule

6

Q

slide 5 (vibrational mode) only happens at what?

A

HIGH TEMPERATURE

- most vibrational modes of most moleucles at room temp, even the first excited state almost has no occupancy

7

Q

AT high temp

A

T is substantially big compared to theta vib

8

Q

at low temp

A

the exponential term gets very big (almost all the population is in the ground state)

9

Q

Electronic internal energy

A

- usually the lowest lying electronic states have a relative energy greater thena kT
- but if there are unusually low lying states with energy similar to kT, then they will be thermally populated
- we would have to calculate the populations and internal energy explicitly from the measured energies of the state. (generally not a simple formula for this)

10

Q

translational entropy

A

- for non-linear molecules, 1, 2 or 3 rotational degrees of freedom
- linear molecules have 2 rotational degrees of freedom