Catalysts
Catalysts
Catalysts (pronounced: /ˈkat(ə)lɪst/) are substances that increase the rate of a chemical reaction by reducing the amount of energy needed to start the reaction, without being consumed in the process.
Etymology
The term "catalyst" originates from the Greek words "kata" meaning "down" and "lyein" meaning "to loosen". It was first used in the scientific context by Swedish chemist Jöns Jakob Berzelius in 1835 to describe substances that speed up chemical reactions.
Types of Catalysts
There are two main types of catalysts: homogeneous catalysts and heterogeneous catalysts. Homogeneous catalysts are in the same phase as the reactants, while heterogeneous catalysts are in a different phase.
Homogeneous Catalysts
Homogeneous catalysts are typically in the same phase as the reactants. They can be gases, liquids, or dissolved substances in solution. An example of a homogeneous catalyst is the use of sulfuric acid (H2SO4) in the esterification of carboxylic acids.
Heterogeneous Catalysts
Heterogeneous catalysts are in a different phase than the reactants. They are often solids that are in contact with gaseous or liquid reactants. An example of a heterogeneous catalyst is the use of platinum in the catalytic conversion of carbon monoxide in car exhausts.
Related Terms
- Enzymes: Biological catalysts that speed up chemical reactions in living organisms.
- Catalysis: The process of increasing the rate of a chemical reaction using a catalyst.
- Inhibitors: Substances that slow down or prevent chemical reactions.
- Promoters: Substances that increase the activity of catalysts.
- Poisons: Substances that decrease the activity of catalysts.
External links
- Medical encyclopedia article on Catalysts
- Wikipedia's article - Catalysts
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