The Velocity Coefficient of a Homogeneous Bimolecular Gas Reaction

Abstract

THE theory of kinetic activation has been shown by Hinshelwood to lead to a simple explanation of homogeneous bimolecular reactions (“Kinetics of Chemical Change in Gaseous Systems”, Oxf. Univ. Press). According to this view, two molecules react on collision when their joint kinetic energy at impact exceeds a certain limiting value E, termed the critical increment for the reaction. The number of binary impacts of this kind per second in a gas can be calculated by means of the kinetic theory as v2²πσūn²e-E/RT where σ is the molecular diameter, ū the root mean square velocity, and n the number of particles per cubic centimetre. By comparing this expression with the actual number of molecules reacting, we can calculate the value of the critical increment E. Thus, if k is the velocity coefficient of a bimolecular reaction measured in gram molecules per minute per litre, we have 2v2πσ²ūn²e-E/RT = k. c₂. %frac6.06.10²³10³.60; where C is the concentration of the reacting substance in gram molecules per litre.