Chemical kinetics — assessing correct statements Which of the following statements about reaction kinetics and equilibrium is correct under standard definitions?

Introduction / Context:
Basic kinetic and equilibrium concepts predict how reactions respond to temperature and energy inputs, and what “equilibrium” really means at the molecular level.

Given Data / Assumptions:

• Arrhenius behavior: k = A exp(−Ea/RT).
• Equilibrium is a dynamic balance of forward and reverse rates.
• Activation energy defines the energetic threshold for reaction.

Concept / Approach:
(a) follows directly from Arrhenius law: larger Ea yields larger fractional change in k for a given temperature change. (b) is incorrect because equilibrium is dynamic (forward and reverse rates equal but nonzero). (c) is misleading; light supplies energy to access excited states but is not a catalyst in the classical sense (a catalyst is regenerated and lowers Ea). (d) is incorrect; molecules must meet or exceed Ea to react.

Step-by-Step Solution:
Apply Arrhenius to compare sensitivity: higher Ea → stronger temperature dependence → (a) is true.Recall the definition of equilibrium: dynamic, not static → (b) false.Clarify photochemistry: light initiates reactions but is not a catalyst → (c) false as phrased.Activation criterion: energy must be ≥ Ea → (d) false.

Verification / Alternative check:
Plot ln k versus 1/T; steeper slope (−Ea/R) for higher Ea confirms greater sensitivity.

Why Other Options Are Wrong:

• (b) Misstates equilibrium; it is dynamic.
• (c) Mislabels the role of light; it provides energy, it is not a catalytic species.
• (d) Contradicts the energetic requirement for reaction.

Common Pitfalls:

• Equating “no net change” with “no molecular activity.”

Final Answer:
Reactions with high activation energies are very temperature sensitive.