Answer
(a) $47.5\,J/K\cdot mol$
(b) $-12.51\,J/K\cdot mol$
(c) $-242.8\,J/K\cdot mol$
Work Step by Step
Recall: $\Delta S^{\circ}_{rxn}=\Sigma nS^{\circ}(products)-\Sigma mS^{\circ}(reactants)$
(a) $\Delta S^{\circ}_{rxn}=[S^{\circ}(Cu)+S^{\circ}(H_{2}O(g))]-[S^{\circ}(H_{2})+S^{\circ}(CuO)]$
$=[(33.3\,J/K\cdot mol)+(188.7\,J/K\cdot mol)]-[(131\,J/K\cdot mol)+(43.5\,J/K\cdot mol)]=47.5\,J/K\cdot mol$
(b) $\Delta S^{\circ}_{rxn}=[S^{\circ}(Al_{2}O_{3})+3S^{\circ}(Zn)]-[2S^{\circ}(Al)+3S^{\circ}(ZnO)]$
$=[(50.99\,J/K\cdot mol)+3(41.6\,J/K\cdot mol)]-[2(28.3\,J/K\cdot mol)+3(43.9\,J/K\cdot mol)]$
$=-12.51\,J/K\cdot mol$
(c) $\Delta S^{\circ}_{rxn}=[S^{\circ}(CO_{2})+2S^{\circ}(H_{2}O(l))]-[S^{\circ}(CH_{4})+2S^{\circ}(O_{2})]$
$=[(213.6\,J/K\cdot mol)+2(69.9\,J/K\cdot mol)]-[(186.2\,J/K\cdot mol)+2(205.0\,J/K\cdot mol)]$
$=-242.8\,J/K\cdot mol$
