## 3rd order?

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

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### 3rd order?

What is the units for third order rxns?

Betty Tesfaye 2G
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Joined: Fri Sep 25, 2015 3:00 am

### Re: 3rd order?

1/M^2s

Michael Lee 2I
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### Re: 3rd order?

I agree

204918982
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### Re: 3rd order?

If you don't remember the units for k for certain orders you can always just divide the rate by the concentration. For 3rd order reactions, the units are (M/s)(1/M^3) which simplifies to (1/M^2)s

Cam Bear 2F
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### Re: 3rd order?

What would we be asked about third order reactions other than their units?

Fatima_Iqbal_2E
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### Re: 3rd order?

If you want to write the units of K in terms of molarity, it would be $M^{-2}/s$, but if you wanted to write it in terms of moles and liters, it would be $L^{2}/(mol^{2}s)$.

Pooja Nair 1C
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### Re: 3rd order?

If you look at first order and second order reactions, when you increase the order, you raise the power of the L and the mol in the units. Thus as you increase the order further, the power continues to rise.

Rachel Wang
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Joined: Fri Sep 29, 2017 7:04 am

### Re: 3rd order?

It's very rare for 3rd order rxns to occur unless it's the overall rxn's order. The units are 1/M^2.s