Tuesday 12 April 2016

DEFINITION OF RATE OF REACTION

Definition of rate of reaction
The reaction rate is the rate at which a species loses its chemical identity per unit volume.
The rate of a reaction can be expressed as the rate of disappearance of a reactant or as the rate of appearance of a product.
Following is single phase reaction

Rate of reaction of component A
-rA = rate of disappearance of A, minus sign means disappearance
The rates of reaction of all components in above reaction are related by
The rate of change in a number of moles of any component i due to reaction is dNi/dt, then the rate of reaction in its various forms is defined as follows.
Based on unit volume of reacting fluid,


Based on unit mass of solid in fluid-solid systems


Based on unit interfacial surface in two-fluid systems or based on unit surface of solid in gas-solid systems


Based on unit volume of solid in gas-solid systems


Based on unit volume of reactor, if different from the rate based on unit volume of fluid




In homogeneous systems the volume of fluid in the reactor is often identical to the volume of reactor. In such a case V and Vr are identical.
so that