## 6th edition 15.17

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

Helen Zhao 1F
Posts: 31
Joined: Fri Sep 28, 2018 12:20 am

### 6th edition 15.17

For 15.17 from the 6th edition, why did we use the 2nd and 4th experiment to find the order of A? Why couldn't we use the 1st and 2nd or 3rd and 4th? And how do we know C is independent from the rate.

Grace Kim 1J
Posts: 60
Joined: Fri Sep 28, 2018 12:18 am
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### Re: 6th edition 15.17

When you want to figure out the reaction order of one reactant (for example: for A), choose the two experiments in which the initial concentrations of the other reactants (B in this case) stay the same. For the two experiments that you choose to compare to find the order with respect to A, only the initial concentrations of A should be different. The same rule applies for figuring out the reaction orders of the other reactants.

If you compare experiments 1 and 4, you see that the initial concentration of C changes, whereas A & B stay the same, but the initial rate doesn't change. Therefore, the reaction is zero order with respect to C, meaning it is independent of the rate. Therefore, we would not include it in our rate of reaction equation.

Hope this helped!