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What are Catalysts?
A catalyst is a substance that increases the rate of a chemical reaction and is not consumed by the reaction. They also do not undergo permanent chemical changes, meaning they are the same at the end as they were at the beginning.
Catalysts work by changing the way a reaction occurs. This is usually done by creating a new path for the reaction to follow or a new mechanism. Typically, the reactants sorb to the catalyst's surface. Sorption is the cohesion of an atom or molecule to a surface. So, it's a type of electrostatic interaction. Physisorption occurs when the reactant-catalyst interaction is caused by Van der Waal's forces. Chemisorption is when the reactants bond with the catalyst.
Once the reactants sorb to the catalyst the reaction proceeds. But, now it occurs on the catalyst's surface. When this happens, the activation energy is lowered. Remember, the activation energy is the amount of energy needed to start a chemical reaction. On the energy diagram, it's the difference between the reactants and the transition state. In catalysis, the interaction with the catalyst helps to stabilize the transition state. So, it requires less energy.
As a side note, we know that rate laws mathematically describe the reaction rate. We know to include the reactant concentration. Then we determine the reaction orders, experimentally. What part of the rate law is influenced by a catalyst? First, you need to know that the catalyst is not included in the equation. But, it is one of the factors that influence reaction rates. So, the addition of a catalyst will alter the rate constant.
Types of Catalysts
There are different types of catalysts:
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Heterogenous catalysts are in a different phase or state as the reactants. Most often these catalysts are in a solid state and are used with a liquid or gas.
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Homogeneous catalysts are in the same phase or state as the reactants. Organometallic catalysts are one type that is used frequently. These catalysts have transition metal and organic compound parts.
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Enzymes are catalysts found in living things. Enzymes are types of proteins that are involved in bodily processes.
Importance of Catalysts
Catalysts are important for bodily functions and processes that keep us alive. Life would not be sustainable without catalysts which greatly increase the reaction rate of reactions in living organisms.
They also are important in chemistry for the production of different materials. In the chemical industry catalysts are used to improve the actual yield of products. Remember, reactions never reach their theoretical yield. Sources of error and uncertainty reduce the yield. But, a catalyst helps to restore the actual yield closer to its theoretical maximum. It also helps lower the cost of materials, and speed up long reactions.
