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2022 O Level Chem P1 Q17 — Rate of Reaction / Catalysts Solution

Rate of Reaction / Catalysts 2022 O Level Pure Chemistry · Paper 1 · Q17

Question

These statements are about the activation energy of a chemical reaction. 1 Chemical reactions in gases and liquids take place when molecules collide with sufficient energy to overcome the activation energy. 2 If the activation energy for a reaction is high, many of the collisions have enough energy to be successful and the reaction is fast. 3 A catalyst reduces the activation energy for a reaction and therefore the overall enthalpy change of the reaction is lower. Which statements are correct?

A1 only
B1 and 2
C2 and 3
D3 only

Correct answer: A

Video Solution

Explanation

Answer: A. Evaluate each claim against the collision theory and the role of catalysts.

(1) Reactions occur when molecules collide with enough energy to overcome the activation energy. TRUE — this is the cornerstone of collision theory. ✓

(2) High activation energy means MANY collisions have enough energy. FALSE — high \(E_a\) means fewer collisions are energetic enough, so the reaction is slow, not fast. ✗

(3) A catalyst reduces the activation energy AND therefore lowers \(\Delta H\). FALSE — a catalyst lowers \(E_a\) by providing an alternative pathway, but the energy levels of reactants and products are unchanged. \(\Delta H\) is the same with or without a catalyst. ✗

Only statement 1 is correct — option A.

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