## Second Order Reactions

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

Johnathan Smith 1D
Posts: 108
Joined: Wed Sep 11, 2019 12:16 am

### Second Order Reactions

What determines a reaction as a second order reaction and not as a first order reaction?

Alice Chang 2H
Posts: 101
Joined: Fri Aug 30, 2019 12:18 am

### Re: Second Order Reactions

In a first order reaction, there will be one reactant present in the rate law. For a second order reaction, you can either have a rate law with one reactant to the second order, or with two reactants both to the first order.

Found this answer (and others) here: https://lavelle.chem.ucla.edu/forum/viewtopic.php?t=28639

Maia_Jackson_2C
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Joined: Fri Aug 30, 2019 12:17 am

### Re: Second Order Reactions

I think there would just be two reactants, so it would be bimolecular.

KarineKim2L
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Joined: Fri Aug 30, 2019 12:16 am

### Re: Second Order Reactions

One way is to graph the reaction and see which equation results in a linear graph. A linear graph that plots [R] to time is zero order, ln[R] to time is first order, and 1/[R] to time is second order.

Kaylee Sepulveda 4G
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Joined: Thu Jul 11, 2019 12:16 am

### Re: Second Order Reactions

A second-order reaction (where order = 2) has a rate proportional to the concentration of the square of a single reactant or the product of the concentration of two reactants. The formula is:

rate = k[A]2 (or substitute B for A or k multiplied by the concentration of A times the concentration of B), with the units of the rate constant M-1sec-1

For a first order reaction, the rate law would be = k[A] (or B instead of A), with k having the units of sec-1

Nathan Rothschild_2D
Posts: 131
Joined: Fri Aug 02, 2019 12:15 am

### Re: Second Order Reactions

Where in the book can we find examples of first and second order reactions?