= Solution
Under the stated vibrational-ground-state approximation and a nondegenerate electronic <ground state>, only translation and rotation contribute. Therefore
$$
S_m^{\circ}=R\left[\log\left(\frac{7.966\times10^{30}}{N_A}\right)+\frac52+log(265.4)+1\right]
=\boxed{211.84\ \mathrm{J\,mol^{-1}\,K^{-1}}}.
$$
A temperature-independent ground-state energy, including <zero-point energy>, contributes no <entropy>. This estimate deliberately omits thermal vibrational excitation; it need not equal a tabulated value that includes all modes.
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