What Are Catalysts and Inhibitors?
Catalysts and inhibitors are substances that change the speed of a chemical reaction without being consumed. Catalysts speed reactions up by lowering activation energy; inhibitors slow them down.
A catalyst speeds up a reaction by lowering activation energy and is regenerated unchanged. An inhibitor slows or blocks a reaction by raising activation energy or blocking active sites.
- •High activation energy
- •Slower reaction rate
- •Longer reaction time
- •Lower activation energy
- •Faster reaction rate
- •Shorter reaction time
Step-by-step worked examples
Hydrogen peroxide (H₂O₂) decomposes slowly, but adding MnO₂ causes rapid decomposition. MnO₂ is unchanged. What is MnO₂?
MnO₂ speeds up the decomposition without being consumed. MnO₂ is a catalyst.
An enzyme speeds up glucose breakdown 10⁶ times. Is it a catalyst?
The enzyme lowers activation energy and is regenerated. Yes, enzymes are biological catalysts.
Carbon monoxide binds to hemoglobin, preventing oxygen transport. Is CO an inhibitor?
CO blocks/inhibits the normal function of hemoglobin. Yes, CO acts as an inhibitor.
Flashcards
Quick quiz
Q1.What does a catalyst do?
Q2.Is a catalyst regenerated after the reaction?
Q3.What is an inhibitor?
Q4.Enzyme function depends on a catalyst-like mechanism. Why?
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Common mistakes
Catalysts are consumed in reactions. — Correct: Catalysts are regenerated and remain unchanged.
Catalysts change the equilibrium position. — Correct: Catalysts only speed reactions; equilibrium stays the same.
Only enzymes are catalysts. — Correct: Many inorganic substances (MnO₂, Pt) are catalysts.
Inhibitors always stop reactions. — Correct: Inhibitors slow or reduce reaction rate; they may not stop it completely.
FAQ
What is the difference between catalysts and inhibitors?
Catalysts speed up reactions by lowering activation energy; inhibitors slow reactions by raising activation energy or blocking pathways.
Are catalysts consumed in chemical reactions?
No. Catalysts are regenerated and chemically unchanged after the reaction.
How do catalysts lower activation energy?
They provide an alternative reaction pathway with a lower energy barrier.
Can an inhibitor be removed to restore reaction speed?
Yes — removing or neutralizing an inhibitor allows the reaction to proceed at normal speed.