average rate

instantaneous rate

Concept: a reaction in which reactant molecules are directly converted into products in one step

Number of reaction molecules: the number of (atoms, molecules, ions or free radicals) participating in the elementary reaction Non-elementary reactions do not have the number of reacting molecules

Classification: Single molecule reaction Number of reacting molecules = 1 Bimolecular reaction Number of reacting molecules = 2 Trimolecular reaction Number of reacting molecules = 3

Law of mass action aA bB=gC hH r= k[c(A)]a*[c(B)]b The law of mass action only applies to elementary reactions The rate equation measured experimentally is consistent with the rate equation written by the law of mass action, which does not mean that the reaction is an elementary reaction.

The slowest elementary reaction in the reaction mechanism controls the rate of the overall reaction. Steps to control the reaction rate

zero order reaction

first order reaction

Secondary reaction

Tertiary reaction

The size of k directly determines the reaction rate and the difficulty of the reaction.

k is a function of T. For the same reaction, if T is different, k will be different.

k is related to reactants, reaction media, catalysts, reaction vessels, etc.

Zero order mol/(L³*s)

Level 1 s⁻¹

Secondary mol⁻¹/(L*s⁻¹)

n level mol¹⁻ⁿ/(Lⁿ⁻¹*s⁻¹)

Prerequisite: The collision between reactant molecules is the reaction The higher the frequency of collisions between reactant molecules, the greater the reaction rate.

Effective collision: A collision that can produce a chemical reaction

Activating molecules: molecules capable of efficient collisions

Activation energy: The lowest energy that an activated molecule has

Boltzmann distribution f=e⁻Ea/RT f is the energy factor

r=ZfP=ZPe⁻Ea/RT P is the orientation factor Z is the total number of collisions

The reactant molecules must pass through an intermediate transition state to form an activated complex. Chemical equilibrium is quickly reached between the reactants and activated complexes.

The greater the activation energy of a reaction at a certain temperature, the higher the energy peak, and the reactants that can cross the energy peak The smaller the ratio of molecules, the slower the reaction rate