There is a chemical reaction, the lower the temperature, the faster the reaction rate?

Generally speaking, the higher the temperature, the faster the reaction, the lower the temperature, the slower the reaction, which is not only a familiar phenomenon for chemists, but also a common sense of people's life, the room temperature is high in summer, and the food is easy to rot and deteriorate, but the food in the refrigerator can be stored for a longer time. The oxidation reaction rate of steel at room temperature is extremely slow, which is greatly accelerated with the increase of temperature, and a large amount of iron oxide scale has been produced when it is red-hot. The reaction of hydrogen and oxidation to form water can not be detected for several years at room temperature, and if it is heated to 973K, it will be completed instantaneously at the rate of **.

For most reactions, the reaction rate increases significantly as the temperature increases, either exothermic or endothermic. Van't Hoff has found that for every 10 °C increase in temperature around room temperature, the rate of general chemical reactions increases by a factor of about 2 4. The effect of temperature on the reaction rate mainly affects the reaction rate constant or rate coefficient.

A definite reaction has different k values at different temperatures. In general, the reaction rate accelerates as the temperature increases and the k value increases, as shown in Table 2-9. The rate constants k values corresponding to different temperatures in the Hi generation and N2O5 decomposition reactions are listed in the table.

The empirical law is relatively rough, and the applicable temperature range is not large. In 1889, Arrhenius proposed the relationship between the rate constant and temperature based on the experimental results - Arrhenius formula. In order to find the intrinsic cause of chemical reactions, a theoretical explanation of the reaction rate, the collision theory, was established on the basis of the Arrhenius formula.

No. The higher the temperature, the higher the number of activated molecules, the more effective collisions, and the faster the chemical reaction.

The rate of chemical reaction is often not calculated by the difference between the forward and reverse reaction rates, but is studied based on the ratio of the change in concentration per unit time to the stoichiometry. The symbol is more difficult to hit, I will send ** to you.

In ordinary applications, the chemical reaction rate equation is generally obtained from the reaction rate equation. For non-primitive reactions, the rate equation must be determined experimentally.

Primitive reaction rate equation.

Secondly, the relationship between temperature and the rate of chemical reaction is not so simple, it is not linear.

The effect of temperature on the reaction rate is mainly manifested in the effect of temperature on the rate constant, and the degree of its influence can be calculated by the Arrhenius equation.

Arrhenius equation.

where k1k2 is the reaction rate constant at t1t2 and r is the molar gas constant. EA is the activation energy of the reaction, which is determined by the experiment (it will be given when doing the question).

The increase of temperature increases the activation energy of the reactants, so it is easy for chemical reactions to occur, but the reaction rate increases due to the increase of activation energy, whether it is a forward reaction or a reverse reaction. As for which reaction rate increases more, it depends on whether it is an endothermic reaction or an exothermic reaction.

In general, for every 10 degrees Celsius increase in temperature, the rate increases by 2 or 4 times. The rate of a chemical reaction is an indication of how fast a chemical reaction proceeds. It is usually expressed as the change in the concentration of reactants or products per unit time (reduction or value-added), and the reaction speed is related to the nature and concentration of the reactants, temperature, pressure, catalyst, etc.

I think you're completely confusing the kinetics and thermodynamics of chemical reactions. First of all, for a reversible reaction, both the forward reaction and the reverse reaction have their corresponding rates, and the temperature increases, both increase the reaction rate, that is to say, the rate of the positive reaction increases, and the rate of the reverse reaction also increases. But the problem of equilibrium movement can be taken into account, which is the thermodynamics of the reaction, and the rate of increase of the two is not consistent.

As the temperature increases, all reaction rates increase. But the magnitude varies.

1. For every 10 degrees Celsius increase in temperature, the rate increases by 2 4 times the original rate.

2. If a reaction is reversible, then the direction of the endothermic reaction is affected by temperature more than that of the exothermic reaction.

Hah, it's getting into the horns.

In fact, this kind of controlled experiment can be compared as long as it can be compared.

For example, whether it is the use of hot glass rods or hot water baths mentioned in the question, as long as the two experiments have different results, the purpose of the experiment is achieved. For example, in this question, you can record the time it takes to collect a bottle of oxygen, (or observe the speed at which bubbles are generated), and the hot side must have a fast reaction and a short time. As long as this result occurs, the experiment is considered a success.

Of course, you are thinking about the further rigor of the experiment, but this question does not require such a high degree of rigor, so the original question is okay, but it is not the best experimental method.

Most of them are due to increased temperatures and increased rates of chemical reactions. A small part is due to the increase in temperature and the decrease in reaction rate.

The temperature rises, proceeding in the direction of endothermy; The temperature is lowered and proceeded in the direction of heat release.

This is uncertain, the temperature is like a catalyst, divided into positive and negative, sometimes the higher the temperature, the faster the reaction rate (such as potassium permanganate pyrolysis), and sometimes the opposite (such as nitrogen dioxide polymerization into nitrogen tetroxide requires low temperature), and some reactions require specific temperatures (such as industrial sulfuric acid, vanadium pentoxide is used as a catalyst, so that sulfur dioxide and oxygen reaction need 500 constant temperature heating).

Huh, got it? Another classic saying: there is no absolute, only relative.

As the temperature increases, the reaction rate increases.

The main reason why increasing the temperature can accelerate the rate of chemical reaction is that the temperature is increased, and the reactant molecules gain energy, so that some of the original molecules with lower energy become activated molecules, which increases the percentage of activated molecules, so that the number of effective collisions increases, so the reaction rate increases, and the secondary reason: due to the increase in temperature, the molecular movement rate accelerates, and the reaction will be accelerated accordingly when the number of reactant molecule collisions increases per unit time.

1. Chemical reaction rate

The rate of chemical reaction chain hunger refers to the speed of the chemical reaction. It is usually expressed as the change value (reduction value or added value) of the concentration of reactants or products per unit time, and the reaction speed is related to the nature and concentration of the reactants, temperature, pressure, catalyst, etc., and if the reaction is carried out in solution, it is also related to the properties and amount of solvents. Among them, the pressure relationship is small (except for gas reaction), and the influence of catalyst is greater.

The reaction rate can be controlled by controlling the reaction conditions to achieve certain purposes.

2. Factors influencing the rate of chemical reactions.

1. Internal causes: the properties of the reactants themselves.

2. External factors: temperature, concentration, pressure, catalyst, light, laser, reactant particle size, contact area between reactants and reactant state. In addition, X-rays, radiation, the contact area between the surface area of the solid substance and the reactants, and the concentration of the reactants will also affect the reaction rate of the reactor.

The higher the temperature, the faster the rate of chemical reactions

When the concentration is constant, the energy of the reactant molecules increases when the temperature is raised, so that some of the molecules with lower energy become activated molecules, thereby increasing the number of activated molecules in the reactant molecules, increasing the number of effective collisions, and thus making the chemical reaction rate as smooth as faster.

As the temperature increases, all reaction rates increase. But the magnitude varies.

1. For every 10 degrees Celsius increase in temperature, the rate increases by 2 4 times the original rate.

2. If a reaction is reversible, then the chain direction of its endothermic reaction section is affected by temperature more than that of the exothermic reaction direction.

Factors influencing the rate of chemical reactions:

Main factor: the nature of the reactant itself.

External factors: temperature, ignition, concentration, pressure, catalyst, light, laser, reactant particle size, contact area between reactants and reactant state.

A chemical reaction is the process by which a molecule breaks down into atoms and the atoms rearrange and combine to form new molecules. In the reaction, it is often accompanied by luminescence, heating, discoloration, precipitate, etc., and the basis for judging whether a reaction is a chemical reaction is whether the reaction generates new molecules.

In the reaction, it is often accompanied by luminescence, heating, discoloration, and the formation of precipitates. The basis for determining whether a reaction is chemical is whether the reaction produces a new substance. According to the theory of chemical bonds, it can be judged whether a chemical reaction is based on whether there is the breaking of old bonds and the formation of new bonds in a change process.

This is an important theorem in the chemical kinetics of inorganic chemistry - Le Chatelier's principle's principle）。

This principle can be expressed as follows: "When a factor of the equilibrium state is changed, the equilibrium state will be shifted in a direction that counteracts the effect of the original change of the factor." In other words, if a system in equilibrium is placed in an environment of increased pressure, the system will be as small as possible and re-equilibrium.

Because of this, the pressure does not increase as much as it should. For example, if the system is placed in an environment where the temperature increases normally, the system will undergo some kind of change and absorb an additional amount of heat.

If you change one of the conditions that affect the equilibrium (e.g., concentration, pressure, temperature, etc.), the equilibrium moves in a direction that can attenuate the change.

1.Concentration: Increasing the concentration of a reactant means that the reaction proceeds in the direction of decreasing the concentration of this reactant, that is, the reaction proceeds in the positive direction.

Decreasing the concentration of a product leads to an increase in the concentration of the product, i.e., the reaction proceeds in a positive direction. Vice versa.

2.Pressure: Increasing the pressure of a gaseous reactant means that the reaction proceeds in the direction of decreasing the pressure of the reactant, that is, the reaction proceeds in the positive direction.

Decreasing the pressure of a gaseous product results in the direction of increasing the pressure of the product, i.e., the reaction proceeds in a positive direction. Vice versa.

3.Temperature: If the reaction temperature increases, the reaction proceeds in the direction of reducing heat, that is, the exothermic reaction is carried out in the opposite direction, and the endothermic reaction is carried out in the forward direction; When the temperature is lowered, the reaction proceeds in the direction of heat generation, that is, the exothermic reaction proceeds in the forward direction and the endothermic reaction proceeds in the reverse direction.

4.Catalyst: only changes the speed at which the reaction is carried out, and does not affect the change of equilibrium, that is, the degree of influence on the forward and reverse reactions is the same.

As the temperature increases, the number of molecules activated by the reaction increases, the effective collision increases, and the reaction rate accelerates. The same for all reactions.

In addition, the rate of chemical reaction is not the same as chemical equilibrium. For endothermic reactions, the chemical equilibrium shifts positively as the temperature increases; For exothermic reactions, the elevated temperature equilibrium moves in the opposite direction.

The rate of chemical reaction has nothing to do with endothermic and exothermic discharge, as long as the temperature is raised, the rate increases.

According to the Arrhenius formula k=ae (-ea rt), in the same reaction, the fraction of the activated molecules in the total number of molecules is different depending on the temperature. When the temperature t is higher, the greater the e (-ea rt), the more collisions of the activated molecules, so the reaction velocity constant k is larger.

No, like some reactions require the use of catalysts (enzymatic reactions are common).High temperatures tend to destroy the activity of catalysts and do not have the effect of accelerating the rate of chemical reactions.

In addition to temperature, the reaction speed is more important to the concentration. Temperature affects the reaction rate constant, but the rate is the product of the rate constant and concentration, and even the concentration has a quadratic and tertiary relationship. Therefore, the concentration of the serving is heavier.

For a closed gas, the temperature increases, the gas volume expands, so the concentration becomes smaller, which will inevitably lead to a decrease in the reaction rate, one rise and one drop, and the amount of drop is more important, so the reaction rate decreases.

It should be noted that when other conditions remain unchanged, the rate of chemical reaction at increased temperature must increase.

Some reactions have different conditions and may decrease at a rate of temperature increase;

For pure solid, electrochemical reactions, heating does not change the reaction speed.