Answer
$-386.138\,J\,K^{-1}mol^{-1}$
Work Step by Step
$\Delta S^{\circ}_{rxn}=\Sigma n_{p}S^{\circ}(products)-\Sigma n_{r}S^{\circ}(reactants)$
$=[2S^{\circ}(CH_{3}COOH(l))]-[2S^{\circ}(CH_{3}CHO(g))+S^{\circ}(O_{2}(g))]$
$=[2(159.8 \,J\,K^{-1}mol^{-1})]-[2(250.3\,J\,K^{-1}mol^{-1})+205.138\,J\,K^{-1}mol^{-1}]$
$=-386.138\,J\,K^{-1}mol^{-1}$
