Answer
(a) $606.4\,JK^{-1}mol^{-1}$
(b) $24.8\,JK^{-1}mol^{-1}$
(c) $-324.2\,JK^{-1}mol^{-1}$
(d) $-120.8\,JK^{-1}mol^{-1}$
Work Step by Step
Recall: $\Delta S^{\circ}_{rxn}=\Sigma n_{p}S^{\circ}(products)-\Sigma n_{r}S^{\circ}(reactants)$
(a) $\Delta S^{\circ}_{rxn}=[S^{\circ}(N_{2},g)+4S^{\circ}(H_{2}O,g)]-[2S^{\circ}(H_{2}O_{2},l)+S^{\circ}(N_{2}H_{4},l)]$
$=[(191.6\,JK^{-1}mol^{-1})+4(188.8\,JK^{-1}mol^{-1})]-[2(109.6\,JK^{-1}mol^{-1})+(121.2\,JK^{-1}mol^{-1})]$
$=606.4\,JK^{-1}mol^{-1}$
(b) $\Delta S^{\circ}_{rxn}=[2S^{\circ}(NO,g)]-[S^{\circ}(N_{2},g)+S^{\circ}(O_{2},g)]$
$=[2(210.8\,JK^{-1}mol^{-1})]-[(191.6\,JK^{-1}mol^{-1})+(205.2\,JK^{-1}mol^{-1})]$
$=24.8\,JK^{-1}mol^{-1}$
(c) $\Delta S^{\circ}_{rxn}=[2S^{\circ}(CH_{3}OH,l)]-[2S^{\circ}(CH_{4},g)+S^{\circ}(O_{2},g)]$
$=[2(126.8\,JK^{-1}mol^{-1})]-[2(186.3\,JK^{-1}mol^{-1})+(205.2\,JK^{-1}mol^{-1})]$
$=-324.2\,JK^{-1}mol^{-1}$
(d) $\Delta S^{\circ}_{rxn}=[S^{\circ}(C_{2}H_{6},g)]-[S^{\circ}(C_{2}H_{4},g)+S^{\circ}(H_{2},g)]$
$=(229.2\,JK^{-1}mol^{-1})-[(219.3\,JK^{-1}mol^{-1})+(130.7\,JK^{-1}mol^{-1})]$
$=-120.8\,JK^{-1}mol^{-1}$
