### 1st and 2nd order

Posted:

**Sun Mar 03, 2019 11:27 pm**How do you tell the difference of the first and second order reactions?

Created by Dr. Laurence Lavelle

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

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=145&t=43573

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Posted: **Sun Mar 03, 2019 11:27 pm**

How do you tell the difference of the first and second order reactions?

Posted: **Sun Mar 03, 2019 11:33 pm**

I think to find the order in general, you have to do the calculations. The m and n values, which are the reaction orders with respect to each reactant, are determined experimentally. The difference between the 1st and 2nd order of the overall reaction seems to be just a difference in the sum of m and n.

Now I'm wondering, Is there a notable difference outside the mere numerical difference?

Now I'm wondering, Is there a notable difference outside the mere numerical difference?

Posted: **Sun Mar 03, 2019 11:59 pm**

What would be an example of the 1st and 2nd order then? I understand that the sums are different but I don't understand how to get the values to begin with.

Posted: **Mon Mar 04, 2019 1:47 pm**

A first-order reaction will be proportional to the change in the initial reaction. So if you multiply one side by two, and the other side doubles as well, you know it's the first order. You also know because when you plug in the equation you will get a decreasing linear graph. If it's a second order, if you double one side, the other will quadruple.

Posted: **Mon Mar 04, 2019 2:22 pm**

You must calculate this by using experimental data as shown in class on Friday. This is found by comparing the reaction rates at different initial concentrations for the same reaction.

Posted: **Mon Mar 04, 2019 2:53 pm**

In addition to using data tables, it can also be determined through the usage of graphs as the example we saw today. In applying a ln(x) function to the concentration function, we can potentially determine whether it's a first or different order reaction. However, experimentally calculating it is often the most common way to determine each step.

Posted: **Mon Mar 04, 2019 3:06 pm**

A zeroth-order reaction is one whose rate is independent of concentration; its differential rate law is rate = k. In a first-order reaction, the reaction rate is directly proportional to the concentration of one of the reactants.The simplest kind of second-order reaction is one whose rate is proportional to the square of the concentration of one reactant. To distinguish between the three types, we can use differential and integrated rate laws and look at the data on a graph.