However K c and K p can be functions of pressure and the non-idealty of the system i.e. activity coefficiency. Activity coefficients correct for deviations from ideal solutions and ideal gases, and are necessary under non-ideal solutions. A CSTR always assumed to be perfectly mixed. A sample of the reactive mixture taken anywhere from inside the reactor will be the same as that at the exit. A at the exit are the same as they are inside the reactor. .
Stoichiometry only depends on the reaction chemistry and inert gases or liquids present.
The equations for concentration, in terms of conversion, will change once a phase change begins to occur. Consequently, the expression for the rate law as a function of conversion might have different expressions for different conversion ranges. See example 3-10, p 108. It depends upon the steepness of the function you want to integrate. The greater the steepness, the larger the number of points you have to use.