Answer:
the entropy change for the surroundings when 1.68 moles of Fe2O3(s) react at standard conditions = 49.73 J/K.
Explanation:
3Fe2O3(s) + H2(g)-----------2Fe3O4(s) + H2O(g)
âS°rxn = n x sum of âS° products - n x sum of âS° reactants
âS°rxn = [2xâS°Fe3O4(s) + âS°H2O(g)] - [3xâS°Fe2O3(s) + âS°H2(g)]
âS°rxn = [(2x146.44)+(188.72)] - [(3x87.40)+(130.59)] J/K
âS°rxn = (481.6 - 392.79) J/K =88.81J/K.
For 3 moles of Fe2O3 react, âS° =88.81 J/K,
then for 1.68 moles Fe2O3 react, âS° = (1.68 mol x 88.81 J/K)/(3 mol) = 49.73 J/K the entropy change for the surroundings when 1.68 moles of Fe2O3(s) react at standard conditions.