Intermediate Topic 451 of 1102 Kinetics & Equilibrium
Homogeneous Catalysis
The catalyst and reactants are in the same phase.
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In-depth explanation of Homogeneous Catalysis
In homogeneous catalysis the catalyst and the reactants are in the same phase, usually dissolved together in one liquid or mixed as gases. The catalyst often forms a reactive intermediate with one of the reactants, opening a pathway with a lower activation energy than the uncatalysed reaction. Acid and base catalysis in solution are common examples, where a proton transfers to or from the substrate and then back. Free radical species such as chlorine atoms can also act as homogeneous catalysts in gas phase reactions, as in the depletion of stratospheric ozone.
Going deeper: Homogeneous Catalysis
Key ideas: The mechanism usually has two or more steps: catalyst combines with a reactant to give an intermediate, which then reacts further and releases the catalyst. Rate often is proportional to catalyst concentration. Acid catalysis can be specific, depending on [H+], or general, depending on all acids present. Gas phase examples include NO in ozone chemistry and Cl atoms in the Cl cycle.
Common mistakes and connections: Students confuse a catalyst with an intermediate or forget that the catalyst appears in the rate law. Another error is to claim homogeneous catalysts are easy to recover; in practice separating a dissolved catalyst is difficult, which is its main disadvantage versus solid catalysts. Related topics are enzyme catalysis and ozone depletion chain cycles.
Visualization of Homogeneous Catalysis
A catalyst in the same phase forms an intermediate, splitting one tall barrier into two lower ones, as H+ does when it protonates a carbonyl in esterification. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Hydrogen ions catalyse the esterification of carboxylic acids with alcohols by protonating the carbonyl oxygen.
Frequently asked questions about Homogeneous Catalysis
What is Homogeneous Catalysis?
The catalyst and reactants are in the same phase.
Is Homogeneous Catalysis a beginner, intermediate or advanced topic?
Homogeneous Catalysis is a intermediate topic in Kinetics & Equilibrium. It builds on the vocabulary of beginner topics in this area.
What should I learn before Homogeneous Catalysis?
Study these earlier topics in Kinetics & Equilibrium first: Effect of Concentration on Rate, Effect of Surface Area, Catalyst.
What comes after Homogeneous Catalysis?
The next topics in Kinetics & Equilibrium are Heterogeneous Catalysis and Enzyme Catalysis.
Can I practise Homogeneous Catalysis with quizzes?
Yes. The interactive lesson includes a self-check question on Homogeneous Catalysis, and the Kinetics & Equilibrium quiz draws on every topic in this area.
Where Homogeneous Catalysis fits in Kinetics & Equilibrium
Homogeneous Catalysis is topic 32 of 91 in Kinetics & Equilibrium.