What is the essence of a catalytic reaction? What are the changes in the physical properties of cata

The chemical reaction that takes place under the action of a catalyst is called a catalytic reaction. In a chemical reaction, some of the original chemical bonds of the reactive molecules must be dissociated and new chemical bonds formed, which requires a certain amount of activation energy. In some systems where chemical reactions are difficult to occur, the addition of a third substance (catalyst) that helps to rearrange the chemical bonds of the reaction molecules can reduce the activation energy of the reaction, thereby accelerating the chemical reaction and controlling the selectivity and stereoregularity of the product.

It is characterized by the fact that a catalyst can only selectively accelerate a specific reaction, potentially directing a chemical reaction in one of several thermodynamically possible directions. A homogeneous catalytic reaction in which the catalyst and reactants are in the same phase is called homogeneous

catalytic

reaction), which is in different phases, is called heterogeneous catalytic reaction (or heterogeneous catalytic reaction).

catalytic

reaction)。A reaction in which an enzyme participates in a biocatalyst is called an enzyme-catalyzed reaction (enzymic).

cataly

ticreaction)。Most industrial reactions are catalytic. Metabolism, nutrient and energy conversion in living organisms are enzyme-catalyzed reaction processes. See Catalysis.

The essence of catalytic reactions is to reduce the activation energy of the reaction, thereby making the reaction easier.

In fact, the catalyst participates in the reaction, but after the reaction, the catalyst returns to its pre-reaction state. Therefore, during the reaction, the physical properties of the catalyst may change (such as crystals becoming powders, etc.), so it is said that "the mass and chemical properties of the catalyst remain unchanged before and after the chemical reaction".

The so-called catalyst is one change and three constants: one change: reaction rate.

Three constants: quality, yield, chemical properties.

Physical properties are subject to change. For example, some catalysts are solid before the reaction, and although there is no chemical change in the reaction, they become liquids due to the exothermic chemical reaction. Some catalysts are involved in chemical reactions.

Hence the structure of the crystal, the density. The hardness will change.

Some of them also change shapes.

o( o I'm sorry.,I haven't done the question for a long time.,If it's not right to the landlord, please bear with me.,Thank you downstairs.,I really don't have a clear definition of physical properties.,I'll check it.,(*.]

Hee-hee......Even on the first floor.

Before and after the catalyst reaction, one change and three unchanged: one change:

Reaction rate. Three constants: quality, yield, chemical properties.

In fact, the essence of the catalyst is to change the reaction pathway! Here's an example:

a+b===c+d

If a catalyst is added to the above reaction, then the actual reaction is that the A+ catalyst generates a new substance, and this new substance reacts with B to form a new substance and generate a catalyst at the same time, so the quality, output, and chemical properties of the catalyst before and after the reaction have not changed, that is, how much catalyst is generated by the reaction force.

I hope it helps.

Because the catalyst has a chemical reaction during the reaction, but the catalyst is generated at the end of the reaction, the catalyst does not participate in the chemical reaction for the whole reaction. His physical properties do not change before, after or during the reaction.

The physical and chemical properties of the catalyst change during the reaction, but before and after the reaction, the physical and chemical properties of the catalyst are the same.

Physical? Color, smell? Melting boiling point? Hardness, glossiness? Ductility, conductivity?

I'm very responsible to tell you, it's all the same.

On the first floor, please clarify the definition of physical properties.

During the reaction, there may be physical changes, such as the solid becoming liquid and small particles crystallizing into large particles.

But the physical properties do not change.

There is a possibility that will change.

A catalyst is defined as a substance that can "significantly" change the rate of the reaction in the presence of a "small amount" without any change in mass or chemical properties after the reaction.

It is very likely that the physical properties will change.

For example, I have done experiments on the synthesis of paraben esters catalyzed by nano-solid superacids, and the color and morphology of the catalyst change after the reaction, and it needs to be re-calcined before it can return to its original appearance.

The catalyst participates in the reaction, and the catalyst must participate in the reaction before the reaction rate can be changed, but in the end, the mass and chemical properties of the catalyst have not changed, and the physical properties must have changed. The catalyst participates in the reaction, changes the pathway of the reaction, and reduces the energy required for the reaction (that is, the activation energy), so that the reaction rate can be changed.

In a chemical reaction, a substance that can change the chemical reaction rate of reactants (increase or decrease) without changing the chemical equilibrium, and its own quality and chemical properties have not changed before and after the chemical reaction is called a catalyst (solid catalyst is also called a catalyst). According to statistics, more than 90% of industrial processes use catalysts, such as chemical, petrochemical, biochemical, environmental protection, etc.

There are many types of catalysts, which can be divided into liquid catalysts and solid catalysts according to their states; According to the phase state of the reaction system, it can be divided into homogeneous catalysts and heterogeneous catalysts, and homogeneous catalysts include acids, alkalis, soluble transition metal compounds and peroxide catalysts. Catalysts play an extremely important role in the modern chemical industry, for example, iron catalysts are used in the production of ammonia, vanadium catalysts are used in the production of sulfuric acid, and different catalysts are used in the polymerization of ethylene and the production of rubber from butadiene.

Generally speaking, a catalyst refers to a substance that participates in the intermediate process of a chemical reaction and can selectively change the rate of the chemical reaction, while its quantity and chemical properties remain basically unchanged before and after the reaction. The effect of the catalyst to accelerate the chemical reaction and make the reaction reach chemical equilibrium as soon as possible is called catalysis, but it does not change the balance of the reaction.

There are two types of catalysts:

One is a chain reaction with the reactants, but finally it changes back to the original substance, such as:

2h2o2=(mno2)=2h2o+o2

This can be done in two steps. 2h2o2+mno2=2h2o+mno32mno3=2mno2+o2

2kCl = (H2CO3) = 2kCl + O2 can be divided into three steps: 2kClO + H2CO3 = K2CO3 + 2HClo2HCo = 2HCl + O2

2HCl+K2CO3=2kCl+H2O+CO2 The other is only used as a catalyst, such as:

2co+2no2=(pt/pd)=2co2+n2<>

The most important thing in the reaction is the catalyst, how to describe it? Catalyst refers to a substance that can change the chemical reaction rate of reactants in a chemical reaction without changing the chemical equilibrium, and its own mass and chemical properties do not change before and after the chemical reaction.

In industrial production, catalysts play a very important role. How to improve the efficiency of catalysts to promote the development of industrial production is an important topic that scientists have been exploring and researching.

At present, most of the catalytic reactions involved in industrial production belong to heterogeneous catalysis. Heterogeneous catalytic reactions, on the other hand, usually occur on the surface of the catalyst. In order to improve the efficiency of catalysts, scientists have come up with a way to "break up" these catalysts, so that these dispersed catalyst particles can touch as many substances involved in the reaction as possible.

Therefore, scientists disperse some catalyst materials such as metals into tiny particles at the nanoscale, which are called nanoparticles.

In a reaction, a catalyst can accelerate the progress of the reaction without changing the chemical properties of the final product of the reaction.

The addition of catalysts can either speed up the reaction rate or slow down the reaction rate.