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Topic: Writing Reaction Rates  (Read 3269 times)

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Offline DutchGirl13

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Writing Reaction Rates
« on: November 16, 2011, 02:47:51 PM »
For my PChem class, I have to write reaction rates in terms of the disappearance of reactant and appearance of product. Here are the reactions:
a). 3O2 :rarrow: 2O3
b). C2H6 :rarrow: C2H4+H2
c). ClO-+Br- :rarrow: BrO-+Cl-
d).(CH3)3CCl+ H2O :rarrow:(CH3)3COH + H+ + Cl-
e). 2AsH3 :rarrow: 2As + 3H2

These are my tentative answers:
a). rate= -3k1[O2]3/sub] + 2k-1[O3]3
b). rate= -k1[C2H6]+k-1[C2H4][H2]
c). rate= -k1[ClO-][Br-]+k-1[BrO-][Cl-]
d). rate= -k1[(CH3)3CCl][H2O]+k-1[(CH3)3COH] [H+][Cl-]
e). rate= -2k1[AsH3]2+k-1[H2]3[As]2

Would someone please offer guidance to me on how to write rate laws in this fashion? Where does water belong in a rate law? When do I need to use coefficients, and when do I need to use exponents? Part e) is especially thorny on this.  Where can I find some more practice problems of this sort and ones where I have find the differential amount of a reactant or product?

Thanks for any help you can offer. I want to understand this general concept, not just solve these problems. If this is in the wrong forum, please move it.

Offline juanrga

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Re: Writing Reaction Rates
« Reply #1 on: November 16, 2011, 03:22:54 PM »
Start from considering

aA  :rarrow: bB

$$ rate = - \frac{1}{a} \frac{d[A]}{dt} = \frac{1}{b} \frac{d[ B]}{dt} /$$

I do not understand your other questions.
« Last Edit: April 03, 2012, 08:59:36 AM by Borek »
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Offline faizan

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Re: Writing Reaction Rates
« Reply #2 on: November 17, 2011, 11:22:38 AM »
first make it clear that either u want to write rate of these reactions or rate expressions for these reactions?

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