Products and Rate Law

$aR \to bP, Rate = -\frac{1}{a} \frac{d[R]}{dt} = \frac{1}{b}\frac{d[P]}{dt}$

Emily Glaser 1F
Posts: 156
Joined: Thu Jul 27, 2017 3:01 am

Products and Rate Law

Let's say you were given a table of concentrations (reactants and products) at some point in a reaction. When product is produced, it inhibits the reactionn.

The equation is A + B --> C

A & B are each first order, and C is negative one order.

Would the rate law be:
Rate=k[A]1[B]1[C]-1

Is this correct? Is this allowed?

Posts: 58
Joined: Fri Sep 29, 2017 7:06 am
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Re: Products and Rate Law

No you wouldn't include C because it is a product. Your rate law is dependent on your reactants.

Isabella Sanzi 2E
Posts: 54
Joined: Thu Jul 13, 2017 3:00 am

Re: Products and Rate Law

Based on the structure we have been following in class, this does not match up with what we have been doing. In class, Dr. Lavelle has been focusing on the method of initial rates, meaning that we use the initial concentrations of the reactants and examine the rate of reaction based on those initial concentrations. Since your reaction cannot go from C --> A + B (it is not reversible as indicated by your single arrow), I do not think that the initial concentration of C would be relevant to the rate in this case, meaning we would exclude it from the rate law. However, some more clarification would be helpful for this question.

Jakob von Morgenland 2C
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Joined: Sat Jul 22, 2017 3:00 am
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Re: Products and Rate Law

I'd like to point everyone's attention to page 621 in the textbook, there is a possibility for orders to be negative numbers (you can see the example that they provided of the decomposition of ozone to oxygen to understand it better). So yes, that would be the right rate law, according to the textbook (although they write the negative order in the denominator to make it positive).