A fresh feed stream contains 50.0 mol/s each of A and B and no other compounds. It is mixed with a recycle stream and enters a reactor. The reaction A + B ? C is carried out in the reactor at P= 0.1 MPa. The reaction reaches equilibrium and the reactor effluent is 40 mol% A, 40 mol% B and 20 mol% C. The reactor effluent is sent to a flash vessel, and the streams leaving the flash vessel are at VLE. The liquid leaving the flash is essentially pure C and is the product from the process. The vapor leaving the flash contains 49.0 mol% A, 49.0 mol% B and 2.0 mol% C, and this entire stream is recycled. The entire process operates at steady state. Which of the following is accurate, based on this process description?

Question

A. The molar flow rate of the product stream is 50 mol/s.
B. The equilibrium constant is 0.8, IF the mixture leaving the reactor is an ideal gas.
C. The equilibrium constant is 0.8, IF the mixture leaving the reactor is an ideal liquid solution and the Poynting correction factor is negligible.
D. All of the statements A through C are true, based upon the process description.
E. The process description does not contain enough information to determine whether statements A, B and C are true or not.

Answer 1

A. Correct.This is the only way to close the mole balance, since the product stream is the only stream leaving the process.
B. Incorrect. If this is an ideal gas mixture at P=P0, then K=yC/yAyB=0.2/(0.4)2=1.25, not 0.8.
C. Incorrect. If this is an ideal solution, then K=xC/xAxB=0.2/(0.4)2=1.25, not 0.8.
D. Incorrect. Only one is true.
E. Incorrect. If you write mole balances and model the equilibrium in the reactor, you will be able to confirm or rule out each of the three statements.