Answer to Example 3.3

In this example, two CSTR's in series were examined. In order to determine which variable, C_A1 or C_A2, reacted faster to a step input in the inlet concentration of A, one simply had to refer to Figure 3.7.

As we would expect the output of the first CSTR when responding to a step input is a first order response. In contrast, the second reactor does not experience a step input, but rather the output of the first reactor. The resulting output of the second CSTR is a more gradual second order curve, as demonstrated by the figure.

The input to the second tank is the output from the first tank, C_A1.   Clearly, the first tank has to respond before the second.