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Author Topic: H2+Br2  (Read 6683 times)

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AhmedEzatAlzawalaty

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H2+Br2
« on: March 19, 2007, 08:53:02 AM »

the order of the reaction H2+I2=2HI is second order.The order of the raection H2+Br2=2HBr is 1.5
how the rate of the latter couldnt be like the rate of the former rections?
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Yggdrasil

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Re: H2+Br2
« Reply #1 on: March 19, 2007, 09:25:25 AM »

The two reactions probably proceed through different reaction mechanisms.
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AhmedEzatAlzawalaty

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Re: H2+Br2
« Reply #2 on: March 19, 2007, 09:59:24 AM »

do you know what that mechanism is?
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Yggdrasil

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Re: H2+Br2
« Reply #3 on: March 19, 2007, 12:34:32 PM »

Unfortunately, no.  Sorry.
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AhmedEzatAlzawalaty

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Re: H2+Br2
« Reply #4 on: March 20, 2007, 02:11:17 AM »

Does any one know what the mechanism is?
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ARGOS++

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Re: H2+Br2
« Reply #5 on: March 20, 2007, 02:00:31 PM »

Dear ahmedezat,
Mr. Bodenstein found by his experiments, that the following Formula
for the Reactiontime holds for Br2:

     d[HBr]  / dt    = [/sub]   k’  *  [H2] * [Br2]½    
                               k’’ + [HBr] / [Br2]

YES, what surprise:  [Br2]½  !!!

As the reaction is Light induced to build first radicals:
                     0.)   Br2          <?>   2Br.            (fast! )
Next Steps:     A.)  Br.  +  H2    ?>   HBr  + H.     (slow!)
                     B.)   H.  +  Br2   ?>   HBr  + Br.     (fast! )

That’s telling you, that reaction A.)  is relevant for the reaction speed,
and the whole "thing" is a so called "chain-reaction" ,
so in this case, (for H2 + Cl2 too, but NOT for H2 + I2!), it means,
you have to use:
   
           d[HBr] / dt    =    k’ * [H2 ] * [Br.]        from A.)
                                                  ________
From 0.) it follows, that:   [Br.]  =  ? K * [Br2]   ,  and combined:

           d[HBr] / dt    =     k’ * K½  * [H2] * [Br2]½         

Now, may be all clear?
Good Luck!
                   ARGOS++


« Last Edit: March 24, 2007, 11:34:52 AM by ARGOS++ »
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Formulas, in its best sense,  ARE ONLY Recipes for “A Picture”,  —
     If you DON’T catch “The Picture”, you are lost, - for ever!      (A++)

There is ONLY one correct Formula for the “Hydrogen”:  —
     The Atom/Molecule, ITSSELF!                          (Dr. R. Mory  1968)

"Make it AS SIMPLE AS possible,  — BUT NEVER SIMPLER!"  (A. Einstein)

AhmedEzatAlzawalaty

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Re: H2+Br2
« Reply #6 on: March 21, 2007, 02:37:09 AM »

Thank u vey much, ARGOS++
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