What are Catalysts?
A catalyst is a substance that speeds up a chemical reaction without being consumed in the process. Catalysts lower the activation energy, allowing reactions to proceed faster at the same temperature.
A catalyst accelerates a reaction by lowering the activation energy (Ea), enabling more molecules to react per unit time. It emerges unchanged from the reaction.
Step-by-step worked examples
Why does a catalyst not get consumed even though it participates in the reaction?
A catalyst lowers activation energy by bonding to reactants, forming an intermediate complex This intermediate reacts with other reactants The catalyst is regenerated after the reaction — not consumed
At 25°C, an uncatalyzed reaction takes 2 hours. With a catalyst, it takes 5 minutes. How much faster?
Time ratio = 2 hours / 5 minutes = 120 min / 5 min = 24× The catalyst made the reaction 24 times faster Note: same temperature, same final equilibrium position
A car's catalytic converter uses platinum. Why is platinum not 'used up'?
Platinum is a catalyst — it speeds up the breakdown of harmful gases After each reaction cycle, platinum returns to its original form One platinum atom can catalyze billions of reaction cycles
Flashcards
Quick quiz
Q1.What does a catalyst lower?
Q2.Is a catalyst consumed in the reaction?
Q3.A reaction without catalyst takes 10 hours; with catalyst, 1 hour. The ratio is:
Q4.Does a catalyst change the equilibrium position?
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Common mistakes
Catalysts are consumed in the reaction. — Correct: Catalysts are regenerated and emerge unchanged.
Catalysts change the equilibrium position. — Correct: They speed up reaching equilibrium without changing the final ratio of products to reactants.
All catalysts work by the same mechanism. — Correct: Catalysts use different mechanisms: surface catalysis, enzyme catalysis, acid-base catalysis, etc.
Temperature and catalysts have the same effect. — Correct: Both increase reaction rate, but catalysts don't change temperature and are reusable.
FAQ
How do catalysts work?
By providing an alternative reaction pathway with a lower activation energy, allowing more reactant molecules to have enough energy to react per unit time.
Why don't catalysts get consumed?
Catalysts form a temporary intermediate complex with reactants, which then decomposes, regenerating the catalyst unchanged.
Can a catalyst change which product is formed?
No, catalysts speed up all reaction pathways equally — they do not alter the products or equilibrium.
What is an enzyme?
An enzyme is a biological catalyst (usually a protein) that speeds up metabolic reactions without being consumed.