1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution Hello, Here is a homework problem that I have been working on. I am wondering if for the mass balance of substance A, do I include the terms in the reaction rate that involve species R and B? Also, wouldn't A and B start reacting in the pipe before they even go into the CSTR? (I guess put in 2 different pipes then!). Also, I wasn't sure if my mass balance for the PFR is right, I'm pretty sure it isn't. The trouble is I don't know how to put it in terms of volumes when given moles for the PFR, so I just did a volume flow rate (or rather just a velocity I suppose, in terms of z, a length).