Collision Theory and Reaction Rates

Steps:

• Increasing sodium thiosulfate concentration raises particle number, boosting collisions with HCl particles.
• Higher pressure on N2 and H2 gases compresses particles, increasing collision frequency.
• Collision theory states rate depends on effective collision frequency, not activation energy changes here.
• Option A matches: more collisions with acid for first; higher collision frequency for second.

Why A is correct:

• Collision theory defines rate increase from greater reactant particle collisions, as in concentration (more particles) and pressure (denser particles).

Why the others are wrong:

• B: Activation energy unchanged by concentration or pressure; only collisions increase.
• C: Activation energy not decreased by pressure; collisions drive gas rate.
• D: No evidence concentration or pressure lowers activation energy.

Final answer: A