Question

If the temperature increases, what happens to the molecular collision frequency?

(a) Increases

(b) Decreases

(c) No change

(d) First increases then decreases

This question was posed to me in an interview.

I would like to ask this question from Introduction to Nonequilibrium Systems in section Properties of High Temperature Gases of Aerodynamics

Answer 1

Correct choice is (b) Decreases

Explanation: The molecular collision frequency (Z) is given by the relation:

Z ∝ \(\frac {p}{\sqrt {T}}\)

Therefore, molecular collision frequency is inversely proportional to the square root of temperature which means that as the temperature increases, collision frequency decreases.