Beginner Topic 450 of 1102 Kinetics & Equilibrium
Catalyst
A substance that speeds up a reaction by providing a lower-energy path without being consumed.
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In-depth explanation of Catalyst
A catalyst is a substance that speeds up a chemical reaction by providing an alternative mechanism with a lower activation energy, and it is regenerated unchanged at the end of the reaction. Because it does not appear in the overall stoichiometric equation, a catalyst can act repeatedly on many molecules. A catalyst speeds up the forward and reverse reactions equally, so it does not change the equilibrium position, the equilibrium constant or the overall free energy change. Catalysts are central to industrial chemistry, pollution control and biology, where enzymes act as highly specific catalysts.
Going deeper: Catalyst
Key ideas: A catalyst raises k by lowering Ea; a drop of 10 kJ per mol at 300 K speeds a reaction by about exp(10000/(8.314 x 300)) = 55 times. It appears in the rate law but not in the net equation, and it can be homogeneous, heterogeneous or enzymatic. Turnover number and turnover frequency measure how many molecules one site converts per unit time.
Common mistakes and connections: Students claim a catalyst increases yield, makes a non-spontaneous reaction spontaneous or is not involved in the reaction. It participates but is regenerated, and it cannot change delta G or K. Another error is saying that it lowers the energy of reactants. A catalyst also can lower the barrier of the reverse reaction by the same amount, linking to microscopic reversibility.
Visualization of Catalyst
The catalyst opens a path with a lower barrier; reactants and products sit at the same energies, so the equilibrium is unchanged and only the speed increases. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Manganese dioxide catalyses the decomposition of hydrogen peroxide into water and oxygen without being used up.
Frequently asked questions about Catalyst
What is Catalyst?
A substance that speeds up a reaction by providing a lower-energy path without being consumed.
Is Catalyst a beginner, intermediate or advanced topic?
Catalyst is a beginner topic in Kinetics & Equilibrium. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Catalyst?
Study these earlier topics in Kinetics & Equilibrium first: Temperature Effect on Rate, Effect of Concentration on Rate, Effect of Surface Area.
What comes after Catalyst?
The next topics in Kinetics & Equilibrium are Homogeneous Catalysis and Heterogeneous Catalysis.
Can I practise Catalyst with quizzes?
Yes. The interactive lesson includes a self-check question on Catalyst, and the Kinetics & Equilibrium quiz draws on every topic in this area.
Where Catalyst fits in Kinetics & Equilibrium
Catalyst is topic 31 of 91 in Kinetics & Equilibrium.