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### Know Which Order It Is

Posted: Sat Feb 18, 2017 11:07 pm
Hello! I was wandering how can we tell what kind of order the reaction is based off the rate? Thank you so much for your help!

### Re: Know Which Order It Is  [ENDORSED]

Posted: Sun Feb 19, 2017 8:51 am
One way is based off how the rate varies with concentration. If the concentration increases two-fold and the rate increases two-fold, you know that the reaction is first order. Similarly, if the concentration increases two-fold and the rate increases by a factor of 4, then you know the reaction is second order.

### Re: Know Which Order It Is

Posted: Sun Feb 19, 2017 3:49 pm
As well as this, another thing to consider is the overall order of the reaction. Depending on the amount of reactants, aA+bB=cC+dD, you must find the order of each reactant, then add the sum of the orders to get the OVERALL order. For example, let's say rate law =k[A]^2 * [B]^2, then the overall order is 2+2=4. From here, they would usually ask to find k. If given the table of values for different concentrations of A and B as well as the rate, then you would simply focus on one line, and plug in k=(rate of reaction)/[A]^2*[B]^2. Then once k is found, you have found the rate law for that reaction by plugging in the value of k to the original equation of the rate law.