Equilibrium constants and associated error bars for the reactions (a) (Eq. (2), K₂ = k₂∕k_-2) and (Eq. (4), K₄ = k₄∕k_-4); (b) (Eq. (3), K₃ = k₃∕k_-3) and (Eq. (5), K₅ = k₅∕k_-5) at temperatures up to 600 K. Points and solid thick lines are obtained from Eq. (14) using the QCT thermally averaged rates and their analytic forms in Eq. (13), respectively, while dashed thick lines represent theoretical estimates based on statistical mechanics (Eq. (15)). Also shown are the corresponding values predicted via capture theory (Roueff et al. 2015; Colzi et al. 2020) for reactions (2) and (3) and experimental data (exp) for ¹³ C⁺ +¹²CO⇌¹³CO + ¹²C⁺ (Eq. (1), K₁ = k₁∕k_-1) as taken from Liszt & Ziurys (2012). For clarity, the K values for the thermoneutral reactions (11) and (12) are also indicated. High-temperature limits are represented by gray solid lines.