Chemical Changes: Clues from Catalysts?

📌 CONCEPT: A catalyst lowers the activation energy of a reaction without altering the overall energy change, thereby increasing the rate of the reaction.

📐 RULE / FORMULA: The catalyst affects the activation energy (Ea) of the reaction, but not the overall energy change (ΔH).

💡 WORKED EXAMPLE: Consider a reaction where a catalyst (C) is added to a reaction mixture:

Reaction: A → B

Without catalyst: E → A → B

With catalyst: E → A → C → B

The catalyst lowers the activation energy (Ea) by providing an alternative pathway with a lower energy barrier, thus increasing the rate of the reaction.

⚠️ COMMON MISTAKE: Students often confuse the effect of a catalyst on the activation energy with the overall energy change of the reaction, leading to incorrect conclusions about the reaction's spontaneity and exothermicity.