involved in physical and chemical processes; write expressions for equilibrium constants; establish a relationship between K p and K c ; explain various factors that affect the equilibrium state of a reaction; classify substances as acids or bases according to Arrhenius, Bronsted-Lowry and Lewis concepts; classify acids and bases as weak or strong in terms of their ionization constants; explain the dependence of degree of ionization on concentration of the electrolyte and that of the common ion; describe pH scale for representing hydrogen ion concentration; explain ionisation of water and its duel role as acid and base; describe ionic product ( K w ) and p K w for water; appreciate use of buffer solutions; calculate solubility product constant. this dynamic equilibrium stage that there is no change in the concentrations of various species in the reaction mixture. Based on the extent to which the reactions proceed to reach the state of chemical equilibrium, these may be classified in three groups. (i) The reactions that proceed nearly to completion and only negligible concentrations of the reactants are left.
In some cases, it may not be even possible to detect these experimentally. (ii) The reactions in which only small amounts of products are formed and most of the reactants remain unchanged at equilibrium stage. (iii) The reactions in which the concentrations of the reactants and products are comparable, when the system is in equilibrium. The extent of a reaction in equilibrium varies with the experimental conditions such as concentrations of reactants, temperature, etc.
Optimisation of the operational conditions is very important in industry and laboratory so that equilibrium is favorable in the direction of the desired product. Some important aspects of equilibrium involving physical and chemical processes are dealt in this unit along with the equilibrium involving ions in aqueous solutions which is called as ionic equilibrium . . E Q U I L I B R I U M I N P H Y S I C A L PROCESSES The characteristics of system at equilibrium are better understood if we examine some physical processes.
The most familiar examples