Solution
= Solution
The substituted molecule has the larger <entropy>. Increased <mass> and <moment of inertia> reduce translational and rotational spacings and make more states thermally accessible. The largest contribution here is the loss of the twofold rotational indistinguishability of the oxygen ends, contributing $R\log2$. It is a <rotational symmetry number> correction for one isotope-defined species, not an <entropy of mixing> between different molecules.