Answer
$173.01\,JK^{-1}mol^{-1}$
Work Step by Step
$\Delta S^{\circ}_{rxn}=\Sigma n_{p}S^{\circ}(products)-\Sigma n_{r}S^{\circ}(reactants)$
$=[2S^{\circ}(CO,g)+S^{\circ}(O_{2},g)]-[2S^{\circ}(CO_{2},g)]$
$=[2(197.674\,JK^{-1}mol^{-1})+(205.138\,JK^{-1}mol^{-1})]-[2(213.74\,JK^{-1}mol^{-1})]$
$=173.01\,JK^{-1}mol^{-1}$
$\Delta S^{\circ}_{rxn}$ is positive because of the increase in entropy.
