### Rate law equations

Posted:

**Sun Feb 25, 2018 5:54 pm**What is the difference between the equations Rate=k x [concentration]^a and (-1/a)*(d[A]/dt)?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=145&t=28517

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Posted: **Sun Feb 25, 2018 5:54 pm**

What is the difference between the equations Rate=k x [concentration]^a and (-1/a)*(d[A]/dt)?

Posted: **Sun Feb 25, 2018 6:56 pm**

The two equations are equal to each other; therefore, you can use either one. The equation k[R]^n is just the other reaction rate equation reexpressed after doing experiments to observe d[R]/dt. The equation k[R]^n is in terms of the rate constant, k, the concentration of reactant, [R], and the order of reactant, n.

Posted: **Sun Feb 25, 2018 8:33 pm**

They are the same. They are only written using different variables but they ultimately represent the same thing.

Posted: **Sun Feb 25, 2018 9:18 pm**

I think the second one is described as the unique instantaneous rate of a reaction, and the first one as the rate law but they should calculate the same thing!