Chemical Reaction Engineering (CRE) is the field that studies the rates and mechanisms of

chemical reactions and the design of the reactors in which they take place.

Lecture 7

Lecture 7 – Tuesday 1/29/2013

2

Block 1: Mole Balances

Block 2: Rate Laws

Block 3: Stoichiometry

Block 4: Combine

California Professional Engineers Exam

In the past, the exam has not been curved,

75% or better to pass

Problem 4-12

3

General Guidelines for the California

Professional Engineering Exam

Some hints:

1. Group unknown parameters/values on the same

side of the equation

example: [unknowns] = [knowns]

2. Look for a Case 1 and a Case 2 (usually two

data points) to make intermediate calculations

3. Take ratios of Case 1 and Case 2 to cancel as

many unknowns as possible

4. Carry all symbols to the end of the manipulation

before evaluating, UNLESS THEY ARE ZERO

4

5

8.5CK

X2 =Total moles reacted at Point 2

Mole fed to first reactor

Knowns: Intermediate Conversion, X1, KC, and W1 = W2

Unknowns: FA0, W1, CA0

P5-17B California Professional Exam Problem

A B

P. E. Example

6

1) Mole Balances

2) Rate Laws

3) Stoichiometry

Liquid, = 0

XCXFF

C

XCXFF

C

K

CCkr

F

r

dW

dX

AAB

B

AAA

A

C

BAA

A

A

0

0

0

0

0

0

0

0

0

11

P. E. Example

2

1 111

111

1

11

1

0

02

00

01

21

0

0

0

0

X

X

C

A

AX

C

A

A

CA

A

A

A

C

AA

XK

dX

kC

FW

XK

dX

kC

FW

WW

XKF

kC

F

r

dW

dX

K

XXkCr

7

4) Combine

5) Evaluate

P. E. Example

745.0

11

1111

111

111

ln1

1

1

111

1ln

11

1

2

2

1

2

2

1

0

0

1

0

01

X

K

XK

X

XK

XK

K

kC

F

XKK

kC

FW

C

C

C

C

C

A

A

CC

A

A

8

Cancel unknowns FA0, k and CA0

Substitute X1 = 0.55 and KC = 5.8

P. E. Example

9

Part 2

Conversion ¢ X 2 based on FA1

212 1 XFF AA

0

20

A

AAoverall

F

FFX

P. E. Example

2

01

0

1

1 12

00

0 2

1 2

1 0 1

1

21

1

1 1ln

1 11 1 1

1ln

11 111 1 1 1

1

1 1ln 1 ln

111 11 1

0.55

A

A

C C

XA A

A

A

CC C

A A

CC

FW

kCX

K K

F FdXW

kCkCX X

KK K

W W

F F X

X

XXKK

X

5.8CK 10

Substitute for FA1 and cancel FA0, CA0, k

P. E. Example

11

2

2

0.768

X

X

One equation and one unknown

Solving for

P. E. Example

0 1 2 0 0 1 20 2

0 0 0

1 1 1A A A AA Aoverall

A A A

F F X F F X XF FX

F F F

1 21 1 1 0.895X X

0.895overallX

Mole Balance

Rate Laws

Stoichiometry

Isothermal Design

Heat Effects

12

End of Lecture 7

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