Reaction Mechanisms and Introduction to Equilibrium
This page introduces reaction mechanisms and transitions into the concept of chemical equilibrium. It explains how complex reactions can occur through multiple elementary steps.
Definition: A reaction mechanism is the sequence of events describing the actual process by which reactants are converted into products.
The molecularity of process in reaction mechanisms is discussed, explaining how it relates to the number of molecules involved in an elementary step.
Vocabulary: Molecularity refers to the number of molecules participating in an elementary reaction step, such as unimolecular or bimolecular processes.
The page then shifts focus to chemical equilibrium, explaining that many reactions are reversible and reach a state of balance rather than going to completion.
Highlight: Chemical equilibrium occurs when the forward and reverse reactions proceed at the same rate, resulting in constant concentrations of reactants and products.
The dynamic nature of equilibrium is emphasized, noting that reactions continue to occur even when the system appears macroscopically static.
The equilibrium constant Kc is introduced, along with its mathematical expression:
Kc = C^cD^d / A^aB^b
For the reaction: aA + bB ⇌ cC + dD
Example: For the reaction SnO₂s + 2COg ⇌ Sns + 2CO₂g, the equilibrium constant expression is Kc = CO2² / CO², excluding solid species.