A single reactant can isomerize to form either product X or product Y by separate…
CHEMISTRY · Single correct · AP · Chemistry · Thermodynamics and Electrochemistry · Thermodynamics and Electrochemistry
Problem
A single reactant can isomerize to form either product X or product Y by separate one-step pathways.
• Pathway to X: ΔG° = –5 kJ mol⁻¹, Eₐ = 30 kJ mol⁻¹
• Pathway to Y: ΔG° = –10 kJ mol⁻¹, Eₐ = 90 kJ mol⁻¹
A freshly prepared sample of the reactant is held at 298 K for 5 minutes. Which of the following best predicts the composition of the mixture after this time?
(a) Equal amounts of X and Y, because both pathways have negative ΔG∘ values.
(b) Mostly X, because its lower activation energy leads to a faster rate even though Y is more thermodynamically stable.
(c) Mostly Y, because its more negative ΔG∘ makes its pathway the only spontaneous one.
(d) Mostly X at first, but it will all convert to Y within 5min because Y is lower in free energy.