[en] Cross sections were calculated for a number of gaseous ion-molecule reactions, using the phase-space model. The calculated results of both the [H₂⁺ + He] and the [H₂⁺ + Ne] reactions were compared to published quantum dynamical calculations as well as to experimental work. Cross sections for the following reactions were calculated: the isotope exchange reaction [¹⁵N¹⁶O⁺ + ¹⁴N¹⁸O], the reactions [N₂⁺ + N₂], [O₂⁺ + O₂] and [CO⁺ + CO]. The [H₂⁺ + H₂] reaction, for which phase-space calculations have been published by several authors, was recalculated as a control. Gaps in polarizability data as well as vibrational frequencies were filled by calculations using an empirical model and ab initio method, respectively. (Author)