What is the difference between catalyst and reactant

Catalysts are substances that increase the reaction rate of a chemical reaction without being consumed in the process. A catalyst, therefore, does not appear in the overall stoichiometry of the reaction it catalyzes, but it must appear in at least one of the elementary reactions in the mechanism for the catalyzed reaction.

Nevertheless, because of its lower E a , the reaction rate of a catalyzed reaction is faster than the reaction rate of the uncatalyzed reaction at the same temperature. Because a catalyst decreases the height of the energy barrier, its presence increases the reaction rates of both the forward and the reverse reactions by the same amount. In this section, we will examine the three major classes of catalysts: heterogeneous catalysts, homogeneous catalysts, and enzymes.

In heterogeneous catalysis , the catalyst is in a different phase from the reactants. At least one of the reactants interacts with the solid surface in a physical process called adsorption in such a way that a chemical bond in the reactant becomes weak and then breaks.

An example of heterogeneous catalysis is the interaction of hydrogen gas with the surface of a metal, such as Ni, Pd, or Pt. Because the adsorbed atoms can move around on the surface, two hydrogen atoms can collide and form a molecule of hydrogen gas that can then leave the surface in the reverse process, called desorption.

Adsorbed H atoms on a metal surface are substantially more reactive than a hydrogen molecule. Hydrogenation is used in the food industry to convert vegetable oils, which consist of long chains of alkenes, to more commercially valuable solid derivatives that contain alkyl chains. Hydrogenation of some of the double bonds in polyunsaturated vegetable oils, for example, produces margarine, a product with a melting point, texture, and other physical properties similar to those of butter. Although the mechanisms of these reactions are considerably more complex than the simple hydrogenation reaction described here, they all involve adsorption of the reactants onto a solid catalytic surface, chemical reaction of the adsorbed species sometimes via a number of intermediate species , and finally desorption of the products from the surface.

In homogeneous catalysis , the catalyst is in the same phase as the reactant s. The number of collisions between reactants and catalyst is at a maximum because the catalyst is uniformly dispersed throughout the reaction mixture. As an added barrier to their widespread commercial use, many homogeneous catalysts can be used only at relatively low temperatures, and even then they tend to decompose slowly in solution.

Despite these problems, a number of commercially viable processes have been developed in recent years. High-density polyethylene and polypropylene are produced by homogeneous catalysis.

Some people also use the two terms reagent and reactant interchangeably even though there is a slight difference between them. Catalyst is a substance that can increase the reaction rate of a particular chemical reaction, while reagent is a substance or mixture for use in chemical analysis or other reactions.

Overview and Key Difference 2. What is a Catalyst 3. What is a Reagent 4. Catalyst is a substance that can increase the reaction rate of a particular chemical reaction. The most specific property of a catalyst is that the chemical reaction does not consume the catalysts during the progression of the reaction. However, this substance directly participates in the reaction. Therefore, this substance recycles, and we can separate it from the reaction mixture in order to use it in another reaction.

Moreover, we need only a small amount of the catalyst for the catalysis of a chemical reaction. Generally, chemical reactions occur faster when there is a catalyst. However, unlike with heterogeneous catalysis, the homogeneous catalyst is often irrecoverable after the reaction has run to completion.

Homogeneous catalysts are used in variety of industrial applications, as they allow for an increase in reaction rate without an increase in temperature. In this case the model has been set so the activation energy is high. Try running the reaction with and without a catalyst to see the effect catalysts have on chemical reactions.

Run the model to observe what happens without a catalyst. Pause the model. Add a few 3 — 4 catalyst atoms to the container by clicking the button.

Run the model again, and observe how the catalyst affects the reaction. Enzymes are proteins that accelerate biochemical transformations by lowering the activation energy of reactions. Synthetic catalysts are used to accelerate a variety of industrial processes and are crucial to the chemical manufacturing industry. However, catalysts are also found in nature in the form of enzymes.

Enzymes are proteins that are able to lower the activation energy for various biochemical reactions. They do this by binding the reactant s , known as the substrate s , to an active site within the enzyme. At the active site, the substrate s can form an activated complex at lower energy. Once the reaction completes, the product s leaves the active site, so the enzyme is free to catalyze more reactions. Enzyme catalysis : An enzyme catalyzes a biochemical reaction by binding a substrate at the active site.

After the reaction has proceeded, the products are released and the enzyme can catalyze further reactions. One model of enzyme mechanism is called the induced fit model. This model proposes that the binding of the reactant, or substrate, to the enzyme active site results in a conformational change to the enzyme. This change stabilizes the transition state complex, and thus lowers the activation energy.

Privacy Policy. Skip to main content. Chemical Kinetics. Search for:. Catalysis Heterogeneous Catalysis Heterogeneous catalysis is a type of catalysis in which the catalyst occupies a different phase than the reaction mixture.