A Levels Chemistry (9701)•9701/12/M/J/18

Explanation
Temperature Effects on Gas Kinetics and Equilibrium
Steps:
- Temperature increase raises average kinetic energy of gas molecules per kinetic molecular theory.
- Higher kinetic energy boosts molecular speeds, increasing collision frequency.
- Collision theory links reaction rate to collision number and energy fraction exceeding activation energy (Ea).
- Both collision frequency and successful fraction rise with temperature, increasing successful collisions for forward and reverse reactions.
Why C is correct:
- Collision theory formula (rate = Z × e^(-Ea/RT)) shows both Z (collision frequency) and the exponential term increase with T, always yielding more successful collisions per unit time.
Why the others are wrong:
- A: Equilibrium position depends on ΔH; endothermic reactions favor more product, exothermic favor less (Le Châtelier's principle).
- B: Average speed increases with T (v_avg ∝ √T), but in a reacting mixture, composition shifts may alter effective average, not guaranteeing uniform increase across all particles.
Final answer: C
Topic: Equilibria
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