Kinetic equations for open systems

in the system examined, we can neglect spatial differences in the reactant concentrations, a continuous stirred tank reactor (CSTR) model for a reactor can be used. A set of equations is constructed accounting for the process of the totality of reactions under examination at a constant volume. It is then supplemented by a new factor which accounts for the substance exchange with the ambient medium. As usual, concentration equations are used that are analogues to those for substance quantities since the reaction system volume is assumed to be unchanged 

When considering catalytic reaction, the gas-phase processes occurring without a catalyst are often neglected. Equation (118) then takes the form 

It is often suggested (without sufficient grounds) that vin = vouV whereas both volume and pressure remain unchanged during the reaction. Strictly speaking, any catalytic reaction proceeds with changeable volume since 

We will make an attempt to determine vout from the equation of state assuming the pressure to remain unchanged 

As usual, the input concentrations are normalized in the following natural way 

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