What is the law of action of the mass action of the primitive reaction

The law of mass action was in the 50s of the 19th century, Norway.

Scientists Guldberg and Waage proposed it on the basis of summarizing a large number of experiments.

They proposed: the rate of chemical reactions.

and the effective mass of the reactant, where the effective mass is the concentration.

At that time, people reacted to primitives.

The relationship between the total response and the total response is not very clear.

In fact, the law of mass action only applies to primitive reactions.

The law of mass action - the rate of the reaction of the primitives is proportional to the concentration of each reactant, where the degree on each concentration term is the stoichiometric coefficient of the corresponding components in the reaction formula.

At constant temperature, in a simple (primitive) reaction, the rate of chemical reaction is proportional to the product of the concentration of each reactant. A simple reaction (primitive reaction) is a reaction in which the molecules, atoms, or ions of the reactants are converted into products in a direct step due to collisions. Such as:

no2＋co=no＋co2

At constant temperature, it is known from the experimental measurement that the positive reaction rate is proportional to the product of nitrogen dioxide and carbon monoxide concentrations, which can be expressed by the reaction rate equation v=k[NO2][CO], and k is the rate constant; When the concentration changes, the reaction rate changes, but the rate constant does not change, that is, the K value is not affected by the concentration, but changes with the temperature. In a primitive reaction, the product of the reaction rate and the power of the reactant concentration is proportional, and the concentration square is numerically the same as the reactant coefficient. As for primitive reactions:

ma＋nb=qc＋pd

The positive reaction rate equation is expressed as v=k[a]m[b]n, which is also known as the expression of the law of mass action. The law of mass action does not apply to non-primitive reactions, and special attention should be paid when applying the law, which was developed by the Norwegian chemist C, MGuldberg and P

Wag proposed it in 1863.

Primitive reaction refers to the reaction that is directly converted into a product in one step in the reaction, also known as a simple reaction.

The reaction is a bimolecular reaction, at a temperature higher than 225, carbon monoxide molecules and nitrogen dioxide molecules collide to convert carbon dioxide molecules and nitric oxide molecules into carbon dioxide molecules in one step, which is a primitive reaction.

From a microscopic point of view, reactant molecules generally go through a number of simple reaction steps before finally being converted into product molecules. Every simple reaction step is a primitive reaction.

Note: (1) At a given temperature, the value of k is related to the nature of the reaction. For a given chemical reaction, the value of k is related to factors such as reaction temperature, catalyst, etc., but not to the concentration of reactants. At the same temperature, it is generally believed that the greater the k value, the faster the reaction proceeds.

2) Only the order of the primitive reaction is equal to the sum of the number of stages of each reaction in the reaction equation.

3) The law of mass action only applies to primitive reactions.

Primitive reaction is a simple microscopic reaction step that describes the reaction mechanism, which refers to a reaction that is completed in one step without intermediate products.

At present, we can only continue to explore through experiments, and there is no universal good method. The meta-reaction through which a reaction takes place can only be speculated by some experimental phenomena, and sometimes, several experimental phenomena of a reaction can be explained by several possible mechanisms at the same time.

Therefore, the apparent reaction is a black box, and it is necessary to constantly design new experiments from new angles to open new observation windows, so as to propose a more realistic reaction mechanism. As science advances, the original mechanism may be overturned and new mechanisms accepted.

Judgment method

In fact, in judging whether there is an intermediate reaction, in the early days, it was generally through the epikinetic method, and after some epikinetic tests and verifications after assuming that the reaction was primitive, it was proved that there was no intermediate product, and it could be completed in one step. However, this method later proved to be unscientific, because many intermediates and intermediate reaction steps of multi-step reactions could not be controlled, or the rate was too fast and the life was too short.

At present, scientific methods include the simulation of quantum chemistry and molecular dynamics represented by femtosecond lasers. Through computer simulation of the reaction process can get a simulation process of the reaction, data is a good means, through the femtosecond laser to obtain the spectral changes of various substances in the reaction process, so as to infer the reaction process of what substance and what state of the substance reacts.

In this way, the process of the reaction can be determined, and the reaction process and reaction mechanism obtained in this way are the most scientific at present, and they are also the most scientific methods to verify the primitive reaction.

Primitive reaction refers to the reaction that is directly converted into a liter product in one step in the reaction, also known as a simple reaction.

In most cases, the chemical reaction formula does not describe the process of the reaction. In reality, some reactions are done in one step, while most reactions take several steps to complete.

The kinetic law of the radical reaction conforms to the law of mass action, that is, the macroscopic rate of the chemical reaction of the radical reaction is proportional to the corresponding square product of the concentration value of the reactant; The order is the coefficient in front of each substance, and the positive value is taken.

Categories of primitive reactions:

The sum of the number of molecules of each reactant in the radical reaction equation is called the number of reactive molecules, and the primitive reaction can be divided into single-molecule reaction, bimolecular reaction and three-molecule reaction according to the number of reactive molecules, as follows:

1) Single-molecule reactions.

Equation: A product.

2) Bimolecular reactions.

Equation: A+B product or 2A product.

3) Three-molecule reactions.

Equation: A+B+C product or 2A+B product or A+2B product.

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Under certain conditions, the reversible reaction is in chemical equilibrium: d positive u inverse ≠ (Characteristics: (1) The composition of the system no longer changes with time.

2) Chemical equilibrium is a dynamic equilibrium. (3) The composition of equilibrium is not related to the way to equilibrium. H(g)+g)a2hi(g)[p(hi)p][p(h2)p][p(i2)p]k = - for reactions in solution:

SN * ( AQ ) + 2Fe * ( AQ ) - SN ( AQ ) + 2Fe?+(aq ) k .c( sn c ) [c ( fe c )] c ( sn * c ) [c ( fe c )] For general chemical reactions:

aa ( g ) + bb ( aq ) + c ( s ) a xx ( g ) + yy ( aq ) + z (1) k - l ip ( x ) p } r [ c ( y ) c ] y [ p ( a ) p *[e ( ce k is a function of temperature, independent of concentration, partial pressure.

How to express the law of mass action on the reversible primitive reaction + its inverse reaction.

Hello there! Haru cherry peel dear! Under certain conditions, the reversible reaction is in chemical equilibrium

d positive u inverse ≠ (Features: (1) The composition of the system no longer changes with time. 2) Chemical equilibrium is a dynamic equilibrium.

(3) The composition of equilibrium is not related to the way to equilibrium. H(g)+g)a2hi(g)[p(hi)p][p(h2)p][p(i2)p]k = - for reactions in solution: sn * (aq ) + 2fe * (aq ) sn (aq ) + 2fe?

aq ) k .C ( SN c )[ C ( Fe C )]C ( SN * C )[ C ( Fe C )] For general chemical reactions: Song or AA ( G ) + bb ( AQ ) + C ( S ) a xx ( G ) + YY ( AQ ) + Z (1) K - l IP ( X ) p } r [ C ( y ) c ] y [ p ( A ) p *[e ( ce k is a function of temperature, independent of concentration, partial pressure.

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According to the law of mass action, the velocity expressions for the positive reaction and the reverse reaction are as follows: v positive = k positive [h: Eggplant such as Honglu · [ n:

v inverse "k inverse nh312When the reversible reaction reaches equilibrium, v positive = v inverse, then there is k positive [h: two n:

1=k inverse [nh:

The reaction that can be done in one step is called a "primitive reaction".The individual primitive reactions contained in the total reaction and the set of sequences in which they occur are called the "reaction mechanism".

The number of chemical particles participating in each elemental chemical-physical reaction as reactants is called the number of reactive molecules, when its value is.

The first, second and third are called "unimolecular reactions", "bimolecular reactions" and "trimolecular reactions" respectively

Obviously, only primitive reactions obey the law of mass action. This law states that at a constant temperature, the rate of the reaction of the primitives is proportional to the product of the concentrations of all reactants, and the degree of concentration of each substance is equal to the stoichiometric number of the corresponding substance in the reaction formula.

Therefore, for the following three types of primitive reactions, the rate equations can be immediately written:

a Product r k[a] (8-102).

a b product r k[a][b] (8-103).

A b c product r k[a][b][c] (8-104).

Among the above-mentioned elemental reactions, bimolecular reactions are the most common; Single-molecule reactions are secondary; The number of trimolecular reactions is rare. So far, no primitive reaction with more than three molecules has been found.