Kinetics of homogeneous reaction

CHAPTER 2

IDEAL REACTORS HAVE THREE IDEAL FLOW OR CONTACTING PATTERNS.

We know that:

-rA= f [temperature depend term, concentration depend term]

As an example:

-RA=-1/V (DNA/DT)=(AMOUNT OF A DISAPPEARED)/(VOLUME*TIME)= [MOL/(M3.S)]

ELEMENTARY REACTION

NONELEMENTARY REACTIONWE ASSUME THAT A SEQUENCE OF ELEMENTARY

REACTION OCCURRING BUT WE CANNOT MEASURE OR OBSERVE THE INTERMEDIATE FORMED!

FREE RADICALS/ IONS AND POLAR SUBSTANCE /TRANSITION

COMPLEXES / NON CHAIN AND CHAIN REACTIONS MOLECULES

Search for the reaction mechanism

TESTING KINETIC MODELS (WE HAVE TWO LIMITATIONS)HYPOTHESIZE THE EXISTENCE OF EITHER OF TWO TYPES OF

INTERMEDIATES: 1. STEADY STATE APPROXIMATION D[X]/DT=0

2. THE INTERMEDIATE IS IN EQUILIBRIUM WITH ITS REACTANTS

Activated energy (E) has related with temperature. The temperature dependency of reactions is determined by the activated energy and temperature level of the reaction as

illustrated in fig. (1-1).

ARRHENIUS LAW R1=F1(TEMP.).F2(COMP.)=KF2(COMP.)

ARREHENIUS LAW: K=K0E-E/RT [E]=JOULE/MOLE

ACTIVATED ENERGY AND TEMPERATURE DEPENDENCY

THERE ARE THREE AREAS OF INVESTIGATION OF A REACTION, THE STOICHIOMETRY, THE KINETICS AND THE MECHANISM.- STOICHIOMETRY CAN TELL WHETHER WE HAVE A SINGLE

REACTION OR NOT .- STOICHIOMETRY CAN SUGGEST WHETHER A SINGLE

REACTION IS ELEMENTARY OR NOT, THERE IS NO ELEMENTARY REACTIONS WITH MOLECULARITY GRATER THAN THREE.

N2+3H2 2NH3- USING PRINCIPLE OF MICROSCOPIC REVERSIBILITY.

- FOR MULTIPLE REACTIONS WITH INCREASING TEMP.

PREDICTABILITY OF REACTION RATE FROM THEORY - CONCENTRATION-DEPENDENT TERM

EXPERIMENTALLY FOUND RATE EXPRESSION IS OFTEN USED TO INVESTIGATE THE ENERGIES OF THE

INTERMEDIATE OF THE REACTION.- TEMPERATURE-DEPENDENT TERM

WITH ASSUMPTION THAT WE KNOW THE MECHANISM AND WHETHER OR NOT IT IS ELEMENTARY WE MAY THEN PREDICT ACTIVATED ENERGY, BUT THIS PROCEDURE HAS A LOT ERROR!

- USE OF PREDICTED VALUE IN DESIGN

FOR ENGINEERING DESIGN, EXPERIMENTALLY FOUND RATE SHOULD BE USED IN ALL CASES.