Answer
$-1154\,kJ/mol$
Work Step by Step
We find:
$\Delta n_{g}=4-(4+5)=-5$
$P\Delta V^{\circ}_{rxn}=\Delta n_{g}RT$
$=(-5)(8.3145\,Jmol^{-1}K^{-1})(298\,K)$
$=-12.3886\,kJ/mol$
$\Delta U^{\circ}_{rxn}=\Delta H^{\circ}_{rxn}-P\Delta V^{\circ}_{rxn}$
$=-1166\,kJ/mol-(-12.3886\,kJ/mol)$
$=-1154\,kJ/mol$
