Question

Which one of the following reactions would you expect to have highest ΔS°?
Answer
A. C2H2(g) + 5/2O2(g) → 2CO2(g) + H2O(g)
B. C2H4(g) + 3O2(g) → 2CO2(g) + 2H2O(g)
C. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)
D. C2H6(g) + 7/2O2(g) → 2CO2(g) + 3H2O(g)

Answer 1

Increase in dS in gases can be estimated from the number of mols difference between products and reactants.
A. mols on left = 3.5....right..3. decrease in S
B. left mols = 4; ....right...4 no change in S.
C. left 3...right 3 no change in S
D. left 4.5.....right 5 higher number of mols on right. higher dS for reaction.