ADVERTISEMENTS:
The below mentioned article provides a note on the theory of activity along with formulae.
The Theory of activity was developed by GN. Lewis in order to account for the behaviour of strong electrolytes. A very simple example to understand this theory would be that: “when a football player is surrounded closely on all sides by other players his capacity to run and execute the maneuvers of football is different from when no one is near him.
In general the activity of the player is conditioned by other players surrounding him.” The activity theory as applied to strong electrolytes considers these electrolytes to be 100 per cent ionized. Each ion possesses an activity or capacity to function. The position of equilibrium of any chemical reaction is known by its equilibrium constant which can be shown for a generalized reaction.
Hence, equilibrium constant can be defined in terms of the concentrations or reactants (A and B) and products (C and D) present at equilibrium:
To be very concise, the concentration terms should be the activities or effective concentrations in non-ideal solutions, of each species. In very accurate work the equilibrium constant may be approximated by measuring the concentration at equilibrium. Enzyme activity is affected by pH.
