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O Level Chemistry – Rate of Reaction Mini Series Part 3

In the last blogpost, we have discussed on the 5 FACTORS that will determine and affect the Rate of Reactions.

Today we shall discuss on the last factor – Effect of Catalysts on Rate of Reaction

Definition:
A catalyst is a substance that speeds up a reaction and remains chemically unchanged at the end of the reaction.

A catalyst works by allowing the reaction to proceed by an alternative pathway that involves a lower activation energy.

Characteristics of a Catalyst:

1. Only a small amount is needed to speed up a chemical reaction

2. It lowers the activation energy of a reaction
3. It is not used up during the reaction. Same amount of catalyst is present at beginning & at the end of reaction

4. It is selective in action. One catalyst cannot act on or speed up all types of reactions. Different catalysts speed up different reactions

5. The physical appearance of catalyst may change at the end of reaction, but it?s chemical properties remain unchanged

6. A catalyst increases the speed, and NOT the yield of a chemical reaction, i.e. the same amount of products is formed whether a catalysts is used of not

7. Impurities can prevent catalysts from working, i.e. catalysts is poisoned or inactivated

In O Level Chemistry Exams, there has been a recent trends that more questions are associated with Catalysts and how it affects the Rate of Reaction.

Let’s check out an exam-based question to see how much you understand:

Question 1:
What statement about catalysis is NOT true?
A. They speed up chemical reactions.
B. They are used up in a chemical reactions
C. Different catalysts catalyse different reactions.
D. Many transition metals are good catalysts.

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