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The steady state approximation, [1] occasionally called the stationary-state approximation or Bodenstein's quasi-steady state approximation, involves setting the rate of change of a reaction intermediate in a reaction mechanism equal to zero so that the kinetic equations can be simplified by setting the rate of formation of the intermediate equal to the rate of its destruction.
Steady state is also used as an approximation in systems with on-going transient signals, such as audio systems, to allow simplified analysis of first order performance. Sinusoidal Steady State Analysis is a method for analyzing alternating current circuits using the same techniques as for solving DC circuits.
The rate equation for the rate of formation of product P may be obtained by using the steady-state approximation, in which the concentration of intermediate A* is assumed constant because its rates of production and consumption are (almost) equal. [8] This assumption simplifies the calculation of the rate equation.
Reaction intermediates are often confused with the transition state. The transition state is a fleeting, high-energy configuration that exists only at the peak of the energy barrier during a reaction, while a reaction intermediate is a relatively stable species that exists for a measurable time between steps in a reaction. Unlike the transition ...
The steady-state approximation holds that the concentration of the catalyst-substrate complex is not changing over time; the total concentration of this complex remains low as it is whisked away almost immediately after formation. A steady-state rate law contains all of the rate constants and species required to go from starting material to ...
The QSS is defined as the steady state under the condition that the concentrations of other species do not change. The limiting step or bottleneck is a relatively small part of the reaction network, in the simplest cases it is a single reaction, which rate is a good approximation to the reaction rate of the whole network.
Under the steady-state approximation, the concentration of the active growing chains remains constant, i.e. the rates of initiation and of termination are equal. The concentration of active chain can be derived and expressed in terms of the other known species in the system.
In his kinetic studies, [5] he used the quasi-steady state approximation to derive the rate equation of the reaction. When an overall reaction is subdivided into elementary steps, Bodenstein's quasi-steady state approximation neglects the variations in the concentrations of reaction intermediates by assuming that these will remain quasi ...