Chapter 8: Multiple Reactions

Writing Net Rates of Formation

The reactions:

are elementary. Write the net rates of formation for A, B, C and D.

Hint 1: What is the net rate of formation of A?

$ (a) r_{A} = k_{1A}C_{A}{C_{B}}^2$

$ (b) r_{A} = -k_{1A}C_{A}{C_{B}}^2$

Hint 2: What is the net rate of formation of B?

$ (a) r_{B} = -k_{1A}C_{A}{C_{B}}^2-k_{2D}{C_{c}}^2{C_{B}}^{\frac{1}{2}}$

$ (b) r_{B} = -k_{1A}C_{A}{C_{B}}^2-6k_{2D}{C_{c}}^2{C_{B}}^{\frac{1}{2}}$

$ (c) r_{B} = -k_{1A}C_{A}{C_{B}}^2-\frac{1}{6}k_{2D}{C_{c}}^2{C_{B}}^{\frac{1}{2}}$

Hint 3: What is the net rate of formation of C?

$ (a) r_{C} = 2k_{1A}C_{A}{C_{B}}^2-\frac{2}{3}k_{2D}{C_{c}}^2{C_{B}}^{\frac{1}{2}} $

$ (b) r_{C} = 2k_{1A}C_{A}{C_{B}}^2-\frac{3}{2}k_{2D}{C_{c}}^2{C_{B}}^{\frac{1}{2}} $

$ (c) r_{C} = k_{1A}C_{A}{C_{B}}^2-\frac{2}{3}k_{2D}{C_{c}}^2{C_{B}}^{\frac{1}{2}} $

Hint 1

A.

Back to Problem

Hint 2

B.

Back to Problem

Hint 3

C.

Back to Problem

The reactions:

are elementary. Write the net rates of formation for A, B, C and D.

Solution

A.

B.

C.

D.

These net rates of reaction are now coupled with the appropriate mole balance of A, B, C, and D and solved using a numerical software package.

For example for a PFR:

etc.

Back to Chapter 8