= Solution
As a first estimate, neglect the small <mass> change and changes in geometry and vibrational populations. Removing an <electron> creates an unpaired spin, giving at least the spin-only electronic <entropy> increase
$$
\boxed{\Delta S_{m,\rm spin}\simeq R\log2=5.76\ \mathrm{J\,mol^{-1}\,K^{-1}}}.
$$
For a more specific estimate, the actual cation ground term is $X\,{}^2\Pi_g$, rather than an orbitally nondegenerate doublet. Ignoring <spin-orbit coupling>, its two orbital components and two spin components give electronic degeneracy four and
$$
\boxed{\Delta S_{m,\rm el}\simeq R\log4=11.53\ \mathrm{J\,mol^{-1}\,K^{-1}}}.
$$
The ground-state assignment is confirmed by state-resolved photoionization measurements.<Photoionization of CO2: Experimental Procedure by the National Institute of Standards and Technology>[Measurements restricted to channels leaving the cation in its X 2Πg ground electronic state]{ref} Spin-orbit splitting and changed vibrational/rotational constants refine this estimate; the question's supplied <partition functions> alone do not determine those corrections. The $R\log2$ answer is a spin-only estimate, while $R\log4$ additionally retains the orbital degeneracy.
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