Section E

Question 1

Equpartition

Answer 1

relates temperature of a system to its average energies

Question 2

Vibrational internal energy

Answer 2

at high tem

Question 3

Diatomic linear molecule

Answer 3

has 2 degrees of freedom

Question 4

a non-linear molecule

Answer 4

3 derees of freedom

Question 5

Vibrational modes

Answer 5

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

Question 6

slide 5 (vibrational mode) only happens at what?

Answer 6

HIGH TEMPERATURE

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

Question 7

AT high temp

Answer 7

T is substantially big compared to theta vib

Question 8

at low temp

Answer 8

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

Question 9

Electronic internal energy

Answer 9

• 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)

Question 10

translational entropy

Answer 10

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