Chapter 8 Self Test


Sketch XEB versus T

For an adiabatic reaction with and , sketch the conversion, XEB as a function of temperature for:

a. an exothermic reaction


Hint 1: What is the adiabatic energy balance?

Full Solution


b. an endothermic reaction


Full Solution


c. give XMB=f(T) using the combined mole balance, rate law, and stoichiometry for a first order irreversible reaction



i.e. show how to locate the steady state conversion and temperature

Full Solution

 


 

 

 

 

 

 

Hint 1

Energy Balance to Determine XEB=f(T)

Back to Problem



 

 

 

 

 

 

 

 

 

 

 

 

For and adiabatic reaction with and , sketch conversion as a function of temperature.

Solution: Part A


Energy Balance to Determine XEB=f(T)

For an exothermic reaction,ΔHRX is negative,[ e.g., ΔHRX= -100 kJ/mole A]. Therefore, [-ΔHRX] is a positive number.

X increases with increasing T.

Back to Problem

 

 

 

 

 

 

 

 

 

 

Solution: Part B

For an endothermic reaction, ΔHRX is positive (+), XEB increases with decreasing T. [e.g. ΔHRX=100 kJ/mol A] And therefore [-ΔHRX] is a negative number.


Back to Problem

 

 

 

 

 

 

 

 

 

 

 

 

Solution: Part C

Mole Balance to Determine XMB=f(T)

For a first order reaction


rearranging...

At the intersection of XMB vs. T and XEB vs. T both the mole balance and the energy balances are satisfied. The steady-state conditions (XSS,TSS) occur here.

       

        Endothermic Reaction                                Exothermic Reaction

Both the mole and energy balances are satisfied when XMB=XEB. The steady state temperature and conversion are TSSand XSS respectively for an entering temperature TO.


Back to Chapter 8