Reactor sizing (CSTR & PFR) worksheet with answers

Free printable Reactor sizing (CSTR & PFR) worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

New worksheetPractise online with hints

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________   Date: ____________

1.Easy
τ = ?k = 0.4 min⁻¹X = 90%

A first-order liquid-phase reaction with k = 0.4 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 90% conversion?

k = 0.4 min⁻¹X = 90%
τ = min
2.Easy
V = 250 L, k = 0.12 min⁻¹Q = 40 L/minCA0​ = 1 mol/LCA​ = ?

A liquid-phase first-order reaction A → B (k = 0.12 min⁻¹) runs in a 250 L continuous stirred-tank reactor (CSTR). The feed enters at 40 L/min with CA0 = 1 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 250 LQ = 40 L/mink = 0.12 min⁻¹CA0 = 1 mol/L
CA = mol/L
3.Medium
QX = 80%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 80% conversion. How many times larger must a CSTR be than a PFR for the same feed rate, rate constant and conversion? Find the ratio VCSTR/VPFR.

X = 80%first order, same k and Q
VCSTR/VPFR =
4.Medium
Q = 25 L/minX = 70%V = ?, k = 0.05 min⁻¹

A first-order liquid-phase reaction A → B with k = 0.05 min⁻¹ is carried out in a plug-flow reactor (PFR) fed at 25 L/min. The density is constant and the reactor is at steady state. Find the reactor volume V in litres for 70% conversion of A.

Q = 25 L/mink = 0.05 min⁻¹X = 70%
V = L
5.Hard
V = 500 LQ = 40 L/minX = ?

A first-order liquid-phase reaction (k = 0.3 min⁻¹) runs in a 500 L CSTR fed at 40 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 500 LQ = 40 L/mink = 0.3 min⁻¹
X = %
6.Hard
V = 500 LQ = 50 L/minX = ?

A first-order liquid-phase reaction (k = 0.15 min⁻¹) runs in a 500 L CSTR fed at 50 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 500 LQ = 50 L/mink = 0.15 min⁻¹
X = %

Answer key

  1. 1. τ = 22.5 min
  2. 2. CA = 0.5714 mol/L
  3. 3. VCSTR/VPFR = 2.485
  4. 4. V = 602 L
  5. 5. X = 78.95 %
  6. 6. X = 60 %

Full step-by-step solutions: practise this topic on examproblems.com.