Answer
(a) $173.4\,kJ/mol$
(b) $8.6\,kJ/mol$
(c) $-2470.4\,kJ/mol$
Work Step by Step
Recall: $\Delta G^{\circ}_{rxn}=\Sigma n\Delta G^{\circ}_{f}(products)-\Sigma m\Delta G_{f}^{\circ}(reactants)$
(a) $\Delta G^{\circ}_{rxn}=[2\Delta G_{f}^{\circ}(NO)]-[\Delta G_{f}^{\circ}(O_{2})+\Delta G_{f}^{\circ}(N_{2})]$
$=[(2)(86.7\,kJ/mol)]-[(0)+(0)]=173.4\,kJ/mol$
(b) $\Delta G^{\circ}_{rxn}=[\Delta G_{f}^{\circ}(H_{2}O(g))]-[\Delta G_{f}^{\circ}(H_{2}O(l))]$
$=(-228.6\,kJ/mol)-(-237.2\,kJ/mol)=8.6\,kJ/mol$
(c) $\Delta G^{\circ}_{rxn}=[4\Delta G_{f}^{\circ}(CO_{2})+2\Delta G_{f}^{\circ}(H_{2}O(l))]-[2\Delta G_{f}^{\circ}(C_{2}H_{2})+5\Delta G_{f}^{\circ}(O_{2})]$
$=[(4)(-394.4\,kJ/mol)+(2)(-237.2\,kJ/mol)]-[(2)(209.2\,kJ/mol)+(5)(0\,kJ/mol)]$
$=-2470.4\,kJ/mol$
