Thermodynamics vs kinetics Which statement best describes a system that is not at equilibrium?

Introduction / Context:
Chemical systems are governed by thermodynamics (which states are favored) and kinetics (how fast states are reached). Many biological and chemical processes sit far from equilibrium. Understanding the distinction explains phenomena such as metastability of ATP, protein folding barriers, and how enzymes alter rates without changing equilibrium positions.

Given Data / Assumptions:

• Equilibrium corresponds to minimum Gibbs free energy under given conditions.
• Systems not at equilibrium have a spontaneous driving force toward equilibrium (negative ΔG for the forward direction).
• Kinetic barriers (activation energies) can slow or prevent rapid equilibration.

Concept / Approach:
Thermodynamic stability concerns relative free energies of states. Kinetic stability concerns reaction rates and activation barriers. A non-equilibrium state is thermodynamically unstable because a lower-free-energy state exists, but it can persist if the activation barrier is high (kinetic stability). Enzymes lower activation energy, accelerating approach to equilibrium without altering the equilibrium constant or ΔG°'.

Step-by-Step Solution:

Verification / Alternative check:
Consider diamond → graphite at STP. Graphite is thermodynamically favored, but diamond persists for geological times because the activation barrier is high. Similarly, ATP is thermodynamically poised to hydrolyze but is kinetically stable without catalysts, validating the distinction.

Why Other Options Are Wrong:

• Kinetically unstable but thermodynamically stable: contradicts the definition; if thermodynamically stable, the system is at or near equilibrium.
• Rushing very rapidly: rates can be slow; not necessarily rapid.
• Requires an enzyme: catalysts are not required to reach equilibrium; they only speed up attainment.
• Must have higher entropy: equilibrium depends on Gibbs free energy (ΔG = ΔH − TΔS), not entropy alone.

Common Pitfalls:
Equating spontaneity with speed. A reaction can be spontaneous (ΔG < 0) yet proceed imperceptibly slowly without a catalyst. Always separate thermodynamic favorability from kinetic accessibility.

Final Answer:
It is thermodynamically unstable, although it may be kinetically stable