Chapter 9 Multiple choice questions

This question is concerned with internal energy modes in the ideal diatomic gas. Which one of the following assertions is correct?

Translation energy modes are never affected by the presence of internal energy modes.

The Born-Oppenheimer approximation is used to decouple rotational modes from vibrational modes.

An energetic collision between two molecules can equilibrate the internal energy modes.

If all energy modes are assumed to be separable, we can write for the total energy of molecule j:

This question concerns the concept of weak coupling and the ways in which molecular energy modes can be factorised. Which one of the statements below is correct?

Molecular energy modes can reach thermal equilibrium and be treated as behaving independently if there is zero coupling between them.

Weak coupling allows each molecular energy mode to be treated as enjoying its own thermal equilibrium, independent of any of the other molecular modes.

If energy modes are separable, the molecular translational partition function can be broken into three parts, one for each independent direction in three dimensions:
q_trs = q_trs,xx q_trs,yx q_trs,z

Under the weak coupling assumption, the partition functions in each of three directions of motion, q_trs,xand q_trs,yand q_trs,z, can no longer be considered to be independent.

This question concerns the factorisation of internal energy modes and its effect on the canonical partition function Q. Which one of the statements below is correct?

The concept of separability allows us to factorise the overall molecular partition function into the following terms: q_tot = q·_rotq·_vibq_el

In contrast to the molecular partition function, the canonical partition function can not be written Q_tot = Q_trs^·Q_rot^·Q _vib^·Q_el

Internal energy states are intrinsically distinguishable

NlnQ_tot= Nlnq_trs × Nln(q_rotq_vibq_el)

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