Effect of catalysis on the rate of chemical reaction

The catalyst only speeds up the reaction and does not increase the degree of the reaction.

The speed of the reaction is accelerated because the catalyst and the reactant form an intermediate, which reduces the activation energy, so the energy required for the reaction is reduced, and the reaction rate is accelerated.

Faster reaction rate The equilibrium constant does not affect.

Catalysts make chemical reactions faster or slower, or chemical reactions occur at lower temperatures. Catalysts are also known as catalysts in industry. The composition, chemical properties and mass of the catalyst itself do not change before and after the reaction; Its relationship with the reaction system is like that of a lock and a key, with a high degree of selectivity (or specificity).

For example, manganese dioxide plays a catalytic role in the thermal decomposition of potassium chlorate, accelerating the rate of chemical reactions, but it does not necessarily have a catalytic effect on other chemical reactions. Some chemical reactions are not the only catalyst, such as magnesium oxide, iron oxide and copper oxide, which can also be catalyzed in the thermal decomposition of potassium chlorate.

The definition in the junior high school book is: a substance that can change the chemical reaction rate of other substances in a chemical reaction, but its mass and chemical properties have not changed before and after the reaction is called a catalyst, also known as a catalyst. The role that a catalyst plays in a chemical reaction is called catalysis.

There is also a saying that the catalyst reacts with one of the reactants, and then the products of the two continue to carry out new chemical reactions under the original conditions, and the reaction conditions of the products of the catalyst reaction are changed compared with the reaction conditions of the original reactants. The substances that were originally formed by the chemical reaction of the catalyst will be regenerated into the original catalyst in a further reaction, i.e., the mass and chemical properties mentioned above have not changed before and after the reaction.

1.Catalyst: It can change the reaction rate, the mass before and after the reaction does not change, the chemical properties do not change, and the physical properties can be changed (such as the original solid, after the reaction becomes a powder).

2.Catalysts accelerate the reaction rate by reducing the activation energy. Activation energy refers to the minimum amount of energy required to enable a reaction to occur, which is the condition that determines how fast or slow the reaction is.

3.The catalyst must have been able to add to the reaction. If it turns out to be A+B C, after adding catalyst D, it becomes A+D E, E+B C+D, and the two formulas are added together, and the total reaction can be seen

a+d+e+b e+c+d, get a+b cHere, d is the catalyst and e is the intermediate. Because the A+D E,E+B C+D reaction is easier than A+B C, that is, the activation energy is low, so the reaction rate is accelerated.

So the catalyst changes the flow of the chemical reaction.

<>1. The effect is that the amount of catalyst in a certain range will affect the size of the reaction rate, and it can be used within a certain range, and there is no effect if it is used too much; Affects the rate of reaction, not necessarily larger, but also smaller.

2. Catalyst: It can change the chemical reaction rate of reactants in chemical reactions.

It raises or decreases without changing the chemical equilibrium, and its own quality and chemical properties.

Substances that do not change before and after a chemical reaction are called catalysts, and solid catalysts are also called catalysts.

According to statistics, more than 90% of industrial processes use catalysts, such as chemical, petrochemical, biochemical, environmental protection, etc.

The higher the catalyst concentration, the faster the chemical reaction rate, and for some chemical reactions, the use of catalysts can speed up the chemical reaction rate

Rate. The reason is that the catalyst reduces the energy required for the reaction, making some ordinary molecules become activated molecules.

When other conditions remain unchanged, increasing the concentration of reactants can increase the chemical reaction rate, and the larger the concentration, the greater the chemical reaction rate. Minish.

The concentration of reactants can reduce the rate of chemical reactions, and the smaller the concentration, the smaller the rate of chemical reactions. The reason is the change in the concentration of the substance.

The number of activated molecules per unit volume changes, and the probability of effective collision of molecules changes.

For chemical reactions with gas participation, when other conditions are constant, increase the pressure, increase the chemical reaction rate, and the pressure will be larger.

The greater the rate of learning; Reduce the pressure, reduce the chemical reaction rate, the lower the pressure, the smaller the chemical reaction rate. The reason is gaseous.

The change in mass concentration usually varies with the change in pressure.

Increasing the temperature can accelerate the chemical reaction rate, and the higher the temperature, the greater the chemical reaction rate. Lowering the temperature can reduce the chemical reaction.

rate, the lower the temperature, the smaller the rate of chemical reaction. The reason is that increasing the temperature causes some ordinary molecules to absorb energy and become activated molecules;

Lowering the temperature causes some activated molecules to release energy and become ordinary molecules.

The effect is that the amount of catalyst used in a certain range will affect the size of the reaction rate, and it can be used within a certain range, and if it is used too much, it will not.

Effect; Affects the rate of reaction, not necessarily larger, but also smaller.

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Analysis: A substance that can significantly change the reaction rate and its chemical properties and quantity remain basically unchanged before and after the reaction. There are positive catalysts (i.e., accelerating the reaction rate) and negative catalysts (i.e., reducing the reaction rate), which are generally referred to as positive catalysts.

Catalytic principle Whether a chemical reaction can be carried out depends on the change of free energy, but only according to the change of free energy can not judge whether the reaction can be completed, because the completion of the chemical reaction also depends on the energy barrier of the reaction, that is, if the reaction energy barrier is very high, a certain amount of energy must be provided for it, and the energy barrier must be crossed to complete the reaction. This energy barrier is called activation energy. The role of the catalyst is to reduce the activation energy, so that the chemical reaction can occur in a relatively non-harsh environment.

The catalyst changes the reaction rate because it changes the reaction pathway, which reduces the activation energy of the reaction.

For example, the chemical reaction between hydrogen and oxygen:

Standard electrode potential for dissolved oxygen in water.

g=-nf =-2 96500 1 229=-237kj, where f is Faraday's constant 96500c

n is the number of electrons involved in the reaction, which is equal to 2 in this formula

Because δg 0 and it is very large, the reaction should be able to proceed very quickly and automatically, but the reaction is never possible at room temperature, and it must be ignited by a spark and so on, and the energy generated by the reaction can continue the reaction. A palladium-coated resin acts as a catalyst for hydrogen and oxygen to be combined to form water at room temperature. According to this principle, an appropriate amount of hydrogen is injected into the dissolved oxygen-containing water, and after sufficient contact with the catalyst, water is formed to produce water, so as to achieve the purpose of oxygen removal.

The effect of the catalyst on the reaction rate is (denier).

a.The number of activated molecules was increased.

b.The percentage of activated bent molecules was increased.

c.Changed the reaction pathway.

d.The activation energy of the reaction is increased.

Correct answer: c