For a first-order reaction, compare the volume required for CSTR vs PFR to achieve the same conversion.

For first-order reaction: -rA = k*CA = k*CA0*(1-X). CSTR: V_CSTR = FA0*X/(k*CA0*(1-X)) = v0*X/(k*(1-X)). PFR: V_PFR = FA0*integral(dX/(-rA)) = v0/k * ln(1/(1-X)). Ratio: V_CSTR/V_PFR = X*(1-X)/[(1-X)*ln(1/(1-X))] = X/[(1-X)*ln(1/(1-X))]. At 90% conversion: V_CSTR/V_PFR = 0.9/[(0.1)*2.3] = 3.9. CSTR requires 3.9 times larger volume. The difference increases with conversion.