Answer
-137 kJ
Work Step by Step
$\Delta H^{o}_{rxn}=\Sigma n_{p}\Delta H_{f}^{o}(products)-\Sigma n_{r}\Delta H_{f}^{o}(reactants)$
$=[2(\Delta H^{o}_{f,\,HNO_{3}(aq)})+1(\Delta H^{o}_{f,\,NO(g)})]-[3(\Delta H^{o}_{f,\,NO_{2}(g)})+1(\Delta H^{o}_{f,\,H_{2}O(l)})]$
$=[2(-207\,kJ)+1(91.3\,kJ)]-[3(33.2\,kJ)+1(-285.8\,kJ)]$
$=-137\,kJ$
