An activated molecule is one that has the minimumenergyStatefulmolecule。In case of chemical reaction between molecules, they must first contact (or collide) with each other, but not every collision can cause reaction. Only the molecules with higher energy collide with each other can cause reaction.These energies can occur when they exceed a certain valuechemical reactionA molecule of is an activated molecule.The concentration of activated molecules is determined byreaction rate Is an important factor.The higher the concentration of activated molecules, the faster the reaction rate.[1]
Energy higher than a certaincritical value(Low energy) molecules are called activated molecules.Molecules with energies lower than this value are called inactive molecules or ordinary molecules.In the process of motion and collision, the energy exchange between molecules constantly occurs, which makes the energy of each molecule change rapidly.Therefore, even the same kind of molecules have very different energies.This energy difference divides the molecule into active and inactive molecules.[2]
Active and inactive molecules are not static.Some activated molecules will lose energy due to molecular collision and become inactive molecules;Non activated molecules may get energy in collision and become activated molecules.However, at a certain temperature, the number of activated molecules (or the percentage of activated molecules) is unchanged.
The higher energy of activated molecules than ordinary molecules comes from the collision kinetic energy of molecules.Different molecules in the same system require different energies when they are activated, so when one molecule is activated, another molecule may not be activated.
reaction mechanism
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At the same temperature,moleculeOfenergyNot exactly the same. Some molecules have energies higher than the average energy of the molecules, which are called activated molecules.Can occurEffective collisionIt must be activatedmolecule, but activation molecules may not occurEffective collision。Not a reactantmoleculeAny direct action between can react, only thoseenergyThe reaction can take place only when the direct interaction between molecules is quite high.The activation of a reaction at a certain temperaturemoleculeThe number is determined by the activation energy Ea of the reaction.according toBoltzmann energy distribution lawIt can be seen that the energy is greater than EamoleculeThe fraction in the total number of molecules can be estimated by e-Ea/RT.activationmoleculeThe number (or concentration) is determinedChemical reaction rateImportant factors.For a given chemical reaction, when the temperature (T) rises, the value of e-Ea/RT increases, and activation occursmoleculeThe reaction rate increases with the increase of the proportion.usecatalyzerIt can reduce the reaction activation energy, so that the reactant with average energymoleculeAs long as it absorbs less energy, it can become activatedmolecule, conducive to increaseChemical reaction rate。
moleculeThere must be enoughenergyTo become an active molecule and react.Increase activationmoleculeThe methods are:
1. Increase the concentration because it is activated at a certain temperaturemoleculeThe percentage in the total number of molecules is fixed;
The concentration of activated molecules (that is, the fraction of the number of activated molecules in the total number of molecules) plays a decisive role in the reaction speed. The higher the concentration of activated molecules, the greater the reaction speed.It is also related to the concentration of reactants, temperature, catalyst and other factors.Generally, the higher the concentration of reactants and temperature, the greater the concentration of activated molecules.catalyzerBy changing the reactionactivation energyAnd affect the concentration of activated molecules.[3]
Percentage of activated molecules
Total number of molecules
Number of activated molecules
Concentration increase
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Pressure increase
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The number of activated molecules per unit volume increases
Temperature rise
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Energy increase
Adding catalyst
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Change the reaction process and reduce the activation energy
