Past exam of the chemistry A course of the University of Cambridge / 2025 / Paper 2 / A8 / b / i / Solution

The quantities $f_A$ and $f_B$ are molecular partition functions per unit volume for the two reactants, with their internal rotational, vibrational and electronic factors included. Thus their translational factors are $(2\pi m_{j}kT/h^2{)}^{3/2}$, rather than those factors multiplied by $V$. Their energy zeros must match the separately displayed barrier convention.