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Topic: Rate Equation for Rxn Engineering  (Read 5138 times)

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Offline Gerard

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Rate Equation for Rxn Engineering
« on: November 28, 2006, 10:15:49 AM »
we are asked to derived the rate equation of
A+2B=R
yes i derived the other half which is
-ln{(M-2XA)/M(1-XA)}=CA0(M-2)KT
but then we are asked what if M=2 this is where our problem arises..
what if M=2
what will happen to the equation???further more we are also asked what are the thermodynaimc quantities that can predict whether a reaction is reversible or irreversible???
"Charles! Charles! That's it Mr. Charles Darwin get out of this room, I told you once and I told you twice not to tease your fellow Mr. Arrhenius!"

Offline Donaldson Tan

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Re: Rate Equation for Rxn Engineering
« Reply #1 on: November 28, 2006, 11:29:09 AM »
A + 2B => R

I assume XA refers to XA - the conversion of A.

This is the rate equation: Rate = - d[A]/dt = K[A][ B ]2

- d[A]/dt = - (d/dt)([A]0(1 - XA) = [A]0dXA/dt

From the stoichiometric ratio, [ B ]0XB = 2 [A]0XA

[ B ] = [ B ]0(1 - XB)
 
K[ A ][ B ]2 = K[A]0(1 - XA)([ B ]0-[ B ]0XB)2 = K[A]0(1 - XA)([ B ]0 - 2[A]0XA)2

[A]0dXA/dt = K[A]0(1 - XA)([ B ]0 - 2[A]0XA)2

dXA/dt = K(1 - XA)([ B ]0 - 2[A]0XA)2

Solving the above ODE will yield the correct reaction profile.
« Last Edit: November 28, 2006, 11:38:04 AM by geodome »
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Offline Donaldson Tan

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Re: Rate Equation for Rxn Engineering
« Reply #2 on: November 28, 2006, 12:33:48 PM »
further more we are also asked what are the thermodynaimc quantities that can predict whether a reaction is reversible or irreversible???

dG = dH - T.dS

if dG = 0, then your reaction is reversible
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

Offline Gerard

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Re: Rate Equation for Rxn Engineering
« Reply #3 on: November 30, 2006, 11:16:08 AM »
further more we are also asked what are the thermodynaimc quantities that can predict whether a reaction is reversible or irreversible???

dG = dH - T.dS

if dG = 0, then your reaction is reversible
i feel ashamed of myself! i did not took acount the gibbs free energy what ever happened to my chemical thermodynamics
thank you
a lot!
"Charles! Charles! That's it Mr. Charles Darwin get out of this room, I told you once and I told you twice not to tease your fellow Mr. Arrhenius!"

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