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**1. Homework Statement**

This is for one of my engineering classes. I missed class due to sickness, and can't figure out how to even begin this problem. No numbers are present, so I'm confused. Here is the problem:

Problem 1 (7 points). A conservative (non-reactive) pesticide is injected into the input flow of a CFSTR on continuous basis, beginning at time t = 0 and resulting in a constant input concentration of pesticide = Cin.

(a) Determine C, the reactor output concentration of this pesticide, as a function of time, and

(b) plot the pesticide output response curve (i.e., reactor output (C/Cin) versus the hydraulic residence time. Use C/Cin scale from 0 to 1 and HRT scale from 0 to 10.

(C) What is the ratio of C/Cin for 1 HRT?

(d) How many HRTs are required to reach 95% of input concentration at the reactor output?

(e) How many HRTs are required to reach 99% of input concentration at the reactor output?

---I think it is actually CSTR(continuous Flow/Stiring). The problem is also about mass balance, if that helps.

I understand that these reactors have inflow and outflow(equal I think). They are considered instantaneous and perfect in mixing.

**2. Homework Equations**

I understand that these reactors have inflow and outflow(equal I think). They are considered instantaneous and perfect in mixing.

**3. The Attempt at a Solution**

I'm not sure if this is even relevant, but in an example problem we showed that C = constant = dC/dt = 0.

Thank you for the help.

Brad