= Solution
The <Arrhenius equation> is
$$
\boxed{k(T)=A\exp\left(-\frac{E_a}{RT}\right)}.
$$
The exponential gives the strongly temperature-dependent energetic factor. For a simple bimolecular collision picture, $A$ collects the encounter frequency per reactant <concentration> and the fraction of encounters with a suitable orientation and other dynamical requirements. Thus a collision is not automatically a successful reaction even when its energy is sufficient.
$A$ has the same units as $k$, which depend on the <rate law>; it is not always a frequency in $\mathrm{s^{-1}}$. More generally it is an effective prefactor containing statistical and dynamical contributions rather than a literal universal collision count. Treating it as <temperature> independent is the approximation requested here.
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