Which of the following reactions has the smallest value of ΔS° at 25°C? A)C₆H₆(l)+ ⁹/₂O₂(g)→ 6CO(g)+ 3H₂O(g) B)C₆H₆(s)→ C₆H₆(l) C)C₆H₆(l)+ Br₂(l)→ C₆H₅Br(l)+ HBr(g) D)C₆H₆(s)→ C₆H₆(g) E)C₆H₆(l)+ ¹⁵/₂O₂(g)→ 6CO₂(g)+ 3H₂O(g)

Question

Quizplus · Accepted Answer

For a solid to liquid or liquid to gas phase change, there is an increase in entropy. Therefore, reactions involving a phase change tend to have a positive ΔS° value. In option B, the reaction shows a solid (s) changing to a liquid (l), which means that ΔS° is positive but likely to be smaller than others, making it the best choice for the smallest value of ΔS°. The other reactions either involve a gas phase change or have more complex molecules that can lead to larger ΔS° values.

Which of the Following Reactions Has the Smallest Value of ΔS°