Question

The gas phase reaction, 2A  B  C, is carried out in a PFR. The feed is equal molar in A and B and the entering temperature is 650K and the entering pressure is 21 atm. If the exit conversion is X, then the exit concentration of B (in mol/dm3 ) is:

Answer 1

Initial Pressure P0 = 21 atm

Initial temperature T0 = 650K

Initial concentration of A CA0 = P/RT

CA0 = 21 atm/(0.0821 L-atm/mol-K x 650 K)

CA0 = 0.39 mol/L = 0.4 mol/L

Feed is equimolar

CB0 = 0.4 mol/L

We can write the equation

A + 0.5 B = 0.5 C

Exit concentration CB = [CB0 - (b/a) CA0*X]/[1+_AX]

_A  = (0.4 - 0.8)/0.4 = - 1

CB = [0.4 - 0.5*0.4*X] / [1 - X]

CB = 0.4 (1 - 0.5X)/(1-X)