Determining Rate Law

[Isabelle Hales 1J]

Hi. I am still a bit confused on the basics of how you determine the rate law of a reaction (how to use different given values). Also, if you are given the rate law for the overall reaction, how would you determine the rate laws of each sub reaction? Any advice is appreciated.

[Rachael Cohen 3G]

Determining the rate law can be done in a lot of different ways. The main one that comes to mind is when we are given a table of concentrations and rates and we are asked to calculate the orders of each reactant and to calculate k so we can write the rate law. Is this what you're asking about?

[BrittneyMyint1D]

Hi! I'd recommend watching some chem videos or rewatching lectures since I'm not sure if I can explain everything, but for determining the rate law by comparing the rates of two different experiments when one of the reactant concentrations have changed. For example, for a question like 7A 17, let's try to find the order with respect to [A]:
To do this, we should compare experiments where [B] and [C] are the same but [A] is different, like experiments 1 and 2. If we set up 17.4/8.7 = (k[A1]^n[B1]^m[C1]^l)/(k[A2]^n[B2]^m[C2]^l) = (k[2.5]^n[1.25]^m[1.25]^l)/(k[1.25]^n[1.25]^m[1.25]^l), you are left with 2 = 2^n, so n =1. Therefore, A is first order. Repeat this with B and C. Hope this helps!

[Geethika Janga 1L]

As far as finding the rate laws when the table is give, you are try to observe how changing a specific reactants concentration will change the rate of the reaction. You want to make sure that the concentrations of the other reactants are constant so you know that any change to the rate is caused only by the reactant you are manipulating. Now, for example, you observe that doubling the concentration of a specific reactant also doubles the rate, then this is a first order interaction. I hope that was a little helpful :)