Answer: Enthalpy change ΔH.
- A Rate constant k
- B Reaction rate
- C Enthalpy change ΔH
- D Pre-exponential factor A
Correct answer: C. Enthalpy change ΔH
Explanation: A catalyst affects Ea, k, and rate. Thermodynamic quantities like ΔH are unchanged since start and end states are the same.
First-order decay curve: concentration halves every t½, and that half-life is constant - a defining test for first-order kinetics.
Concept context
Study the speed of reactions and what affects it: concentration, temperature, and catalysts. Covers rate law, order of reaction, the Arrhenius equation, and reaction mechanisms step by step.