Answer
Can be harnessed to do useful work.
Work Step by Step
$\Delta_{r}G^{\circ}=\Sigma n_{p}\Delta_{f}G^{\circ}(products)-\Sigma n_{r}\Delta _{f}G^{\circ}(reactants)$
$=[12\Delta_{f}G^{\circ}(CO_{2},g)+6\Delta_{f}G^{\circ}(H_{2}O,g)]-[2\Delta_{f}G^{\circ}(C_{6}H_{6},l)+15\Delta_{f}G^{\circ}(O_{2},g)]$
$=[12(-394.359\,kJ/mol)+6(-228.572\,kJ/mol)]-[2(124.5\,kJ/mol)+15(0)]$
$=-6352.7\,kJ/mol$
As $\Delta _{r}G^{\circ}$ is negative, the reaction is capable of being harnessed to do useful work.
Up to 6352.7 kJ/mol of useful work can be done.
