Chemical Equilibrium

About this course

It is an experimental fact that most of the process including chemical reactions, whencarried out in a closed vessel, do not go to completion. They proceed to some extent leaving considerable amounts of reactants & products. When such stage is reached in a reaction, it is said that the reaction has attained the state of equilibrium. Equilibriumrepresents the state of a process in which the properties like temperature, pressure, concentration etc. of the system do not show any change with passage of time. In all processes which attain equilibrium, two opposing processes are involved. Equilibrium is attained when the rates of the two opposing processes become equal.If the opposing processes involve only physical changes, the equilibrium is called Physical Equilibrium. If the opposing processes are chemical reactions, the equilibrium is called Chemical Equilibrium.If you add more and more salt in water taken in a container of a glass and stirredwith a glass rod, after dissolving of some amount. You will find out no furthersalt is going to the solution and it settles down at the bottom. The solution is nowsaid to be saturated and in a state of equilibrium. At this stage, many molecule ofsalt from the undissolved salt go into the solution (dissolution) and same amountof dissolved salt are deposited back (Precipitation).Thus, at equilibrium rate of dissolution is equal to rate of precipitation.