## Chemistry 9th Edition

a. $\Delta$S$^{\circ}$= -186 J/K x mol$rxn$ b.$\Delta$S$^{\circ}$= 187 J/K x mol$rxn$ c. $\Delta$S$^{\circ}$= 348 J/K x mol$rxn$
a. 2$H_{2}$S +S$O_{2}$ -> 3 $S_{rhombic}$ + 2 $H_{2}O$ $\Delta$ S$^{\circ}$= Sum of S$^{\circ}$ (Products) - Sum of S$^{\circ}$ (Reactants) $\Delta$ S$^{\circ}$= 3 S$^{\circ}$ (S) +2 S$^{\circ}$ ($H_{2}O$)- S$^{\circ}$ (S$O_{2}$)- 2 S$^{\circ}$ ($H_{2}S$) $\Delta$ S$^{\circ}$=3 S$^{\circ}$ (32) +2 S$^{\circ}$ (189)- S$^{\circ}$ (248)- 2 S$^{\circ}$ (206) $\Delta$S$^{\circ}$= -186 J/K x mol$rxn$ b. 2S$O_{3}$ -> 2S$O_{2}$ +$O_{2}$ $\Delta$ S$^{\circ}$= Sum of S$^{\circ}$ (Products) - Sum of S$^{\circ}$ (Reactants) $\Delta$ S$^{\circ}$= 2 S$^{\circ}$ (S$O_{2}$)- S$^{\circ}$ ($O_{2}$)- 2 S$^{\circ}$ (S$O_{3}$) $\Delta$ S$^{\circ}$= 2 S$^{\circ}$ (248)- S$^{\circ}$ (205)- 2 S$^{\circ}$ (257) $\Delta$S$^{\circ}$= 187 J/K x mol$rxn$ c. $Fe_{2}$$O_{3} + 3H_{2} -> 2 Fe + 3H_{2}O \Delta S^{\circ}= Sum of S^{\circ} (Products) - Sum of S^{\circ} (Reactants) \Delta S^{\circ}= 2 S^{\circ}(Fe) +3 S^{\circ} (H_{2}O)- 3 S^{\circ} (H_{2}) - S^{\circ} (Fe_{2}$$O_{3}$) $\Delta$ S$^{\circ}$= 2 S$^{\circ}$(108) +3 S$^{\circ}$ (189)- 3 S$^{\circ}$ (115) - S$^{\circ}$ (90) $\Delta$S$^{\circ}$= 348 J/K x mol$rxn$