ChemistryCode 9701
Chemical equilibria: reversible reactions, dynamic equilibrium
What this topic asks you to be able to do
- understand the definition of a reversible reaction
- understand dynamic equilibrium as the condition in which the forward and reverse reactions proceed at identical rates while the concentrations of reactants and products stay steady
- understand why a closed system is necessary for dynamic equilibrium to be set up
- define Le Chatelier's principle as follows: after a change is imposed on a system at dynamic equilibrium, the equilibrium position shifts in the direction that minimises that change
- use Le Chatelier’s principle to infer, qualitatively and from suitable information, the consequences of altering temperature, concentration or pressure, or of the presence of a catalyst, for a system at equilibrium
- deduce expressions giving equilibrium constants using concentrations, Kc
- use mole fraction and partial pressure correctly as terms
- deduce the expressions for equilibrium constants that use partial pressures, Kp (applying the link between Kp and Kc is not necessary)
- use the expressions for Kc and Kp in calculations (these calculations will not involve solving quadratic equations)
- determine the quantities present once equilibrium is reached, from appropriate data
- state whether altering temperature, concentration or pressure, or introducing a catalyst, changes the numerical value of the equilibrium constant of a reaction
- describe and explain the conditions chosen for the Haber process and the Contact process, which show why an understanding of dynamic equilibrium and the use of Le Chatelier’s principle matter to the chemical industry