Answer
$-217.6\,kJ/mol$
Work Step by Step
We find:
$\Delta n_{g}=0-1=-1$
$P\Delta V^{\circ}_{rxn}=\Delta n_{g}RT$
$=(-1)(8.3145\,Jmol^{-1}K^{-1})(298\,K)$
$=-2.4777\,kJ/mol$
$\Delta U^{\circ}_{rxn}=\Delta H^{\circ}_{rxn}-P\Delta V^{\circ}_{rxn}$
$=-220.1\,kJ/mol-(-2.4777\,kJ/mol)$
$=-217.6\,kJ/mol$
