Assuming the compounds form ideal solutions, what is the flow rate of C in the exiting stream?

Question

A feed stream of 50 mol/minof A and 50 mol/min of B at 500 K enter an adiabatic steady state reactor. The reaction is A + B ? C and occurs in the liquid phase. The stream leaving the reactor is at equilibrium. CP = 80 J/mol•K for compound C, and ?CP for the reaction is 0. At 298.15 K,?HR0 = -13 kJ/mol and ?GR0 = -20 kJ/mol.
A. 0.0009 mol/min
B. 32.63 mol/min
C. 46.35 mol/min
D. 47.45 mol/min
E. 53.65 mol/min

Answer 1

A. Incorrect. Take another look at your calculation of the equilibrium constant, paying particular attention to signs.
B. Incorrect. Your arithmetic is probably incorrect in the shortcut van ‘t Hoff equation. Try again.
C. Correct. This is the solution when the equilibrium expression and the energy balance are solved simultaneously. Note that ?CP being zero had two significances—it meant the shortcut van ‘t Hoff equation was valid and it meant that when CP,A + CP,B appears in the energy balance it can be set equal to CP,C.
D. Incorrect. This is the answer if the reactor is isothermal at 500 K, but the adiabatic exothermic reaction leads to a temperature rise which in turn affects K.
E. Incorrect. You may be calculating the total flow rate of the exiting stream rather than the flow rate of C in the exiting stream. The molar flow rate of C can’t exceed 50 mol/s.