Role of catalysts in chemical reactions: Select the correct statement about how a catalyst functions.

Introduction / Context:
Catalysts are central to modern chemical industry, from petroleum refining to green synthesis. Understanding the real function of a catalyst avoids common misconceptions in kinetics and reactor design.

Given Data / Assumptions:

• A catalyst provides an alternative reaction pathway.
• Overall stoichiometry and equilibrium constant at a given temperature are unchanged by a catalyst.
• The catalyst emerges chemically unchanged after a cycle, although it may deactivate physically or chemically over time.

Concept / Approach:
Activation energy controls the rate according to Arrhenius behavior. A catalyst lowers the energy barrier for the rate determining step by stabilizing the transition state through adsorption, complexation, or surface mediation, thereby increasing rate without altering equilibrium composition at fixed temperature.

Step-by-Step Solution:
State the rate law sensitivity: k = A * exp(−Ea / RT).Lower Ea increases k at the same T.Catalyst participates in intermediate steps but is regenerated, so net consumption is zero.

Verification / Alternative check:
Equilibrium constant depends only on thermodynamics (ΔG°). Since catalyst does not change ΔG°, it does not change K. Faster approach to equilibrium confirms catalytic action.

Why Other Options Are Wrong:
A catalyst does not necessarily initiate an otherwise impossible reaction; it accelerates feasible ones. It is not consumed permanently and can be recovered chemically unchanged, allowing reuse until deactivation occurs.

Common Pitfalls:
Confusing catalytic participation in intermediates with consumption; overlooking deactivation and regeneration which are operational, not definitional, issues.

Final Answer:
A catalyst lowers the activation energy of reacting molecules.