Collision Theory Explains Rate Increase

Steps:

• Reaction rate depends on collision frequency between reactant particles.
• Increasing propanone concentration raises its particle number in the same volume.
• More propanone particles lead to more frequent collisions with iodine particles.
• Higher collision frequency directly increases the initial reaction rate.

Why D is correct:

• Collision theory states reaction rate is proportional to collision frequency, which scales with reactant concentration per the rate law (rate = k [CH₃COCH₃]^m [I₂]^n, m > 0).

Why the others are wrong:

• A: Successful collision proportion depends on activation energy and orientation, unchanged by concentration.
• B: Particle energy distribution is governed by temperature, not concentration.
• C: Identical to D but listed separately; no distinction justifies difference.

Final answer: D