Answer
131.1 kJ
Work Step by Step
We obtain the required reaction by reversing the first reaction and then adding half of the second reaction with it.
Therefore, $\Delta G^{\circ}_{rxn}=-[\Delta G^{\circ}_{rxn}(\text{first reaction})]+\frac{1}{2}[\Delta G^{\circ}_{rxn}(\text{second reaction})]$
$=-(-734.4\,kJ)+\frac{1}{2}(-1206.6\,kJ)=131.1\,kJ$
