## Reaction orders

$\frac{d[R]}{dt}=-k; [R]=-kt + [R]_{0}; t_{\frac{1}{2}}=\frac{[R]_{0}}{2k}$

jane_ni_2d
Posts: 67
Joined: Fri Sep 28, 2018 12:23 am

### Reaction orders

How can you tell the difference between a first/second/and third order reaction?

Ashley Zhu 1A
Posts: 69
Joined: Fri Sep 28, 2018 12:16 am

### Re: Reaction orders

Dr. Lavelle said in class that we won't have to worry about third order reactions, but for first and second order reactions, you can plot the data given to you on a graph or examine the rate law. If a graph of ln[A] vs. t shows a straight line with a negative slope, you know that it is a first order reaction; by examination, when the orders of each reactant add up to 1 in the rate law, then the reaction is a first order reaction. Similarly, if a graph of 1/[A] vs. t yields a straight line with a positive slope, then the reaction is second order; if the sum of the orders of the reactants in the rate law equals 2, then the reaction is second order.

Danielle_Gallandt3I
Posts: 70
Joined: Fri Sep 28, 2018 12:24 am

### Re: Reaction orders

Another way to look at this is to consider how a rate changes as a reactant's concentration changes. If you add more of a reactant and the rate does not change it is a zero order reaction. If you double the concentration and the rate doubles, it is a first order reaction. If you double the concentration and the rate quadruples, it is a second order reaction. This pattern would then continue with any other order