Collision Theory and Reaction Rates

Steps:

• Recall collision theory: reaction rate depends on frequency of effective collisions between particles.
• For sodium thiosulfate and HCl: increasing concentration raises particle number, boosting collision frequency.
• For N2 and H2: increasing pressure compresses gases, raising particle density and collision frequency.
• Neither change affects activation energy, which remains constant.

Why A is correct:

• Collision theory states rate proportional to collision frequency; both changes increase collisions without altering activation energy.

Why the others are wrong:

• B: Pressure increases collision frequency, not activation energy.
• C: Concentration increases collisions, not activation energy.
• D: Neither factor decreases activation energy.

Final answer: A