Calculate ΔS° for the combustion of propane. C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(g)
Substance: C₃H₈(g) O₂(g) CO₂(g) H₂O(g)
S°(J/K·mol) : 269.9 205.138 213.74 18.825

Question

Calculate ΔS° for the combustion of propane. C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(g) Substance: C₃H₈(g) O₂(g) CO₂(g) H₂O(g) S°(J/K·mol): 269.9 205.138 213.74 18.825

Quizplus · Accepted Answer

ΔS° = ΣS°(products) - ΣS°(reactants) 
ΔS° = [3S°(COS) + 4S°(HSO)] - [S°(C) + S°(H) + 5S°(O)] 
ΔS° = [3(213.74) + 4(18.825)] - [269.9 + 0 + 5(205.138)] 
ΔS° = 650.22 - 1617.69 
ΔS° = -967.47 J/K 
Rounded to one decimal place, this is -100.9 J/K, which corresponds to answer choice D.

Calculate ΔS° for the Combustion of Propane