## Units

$aR \to bP, Rate = -\frac{1}{a} \frac{d[R]}{dt} = \frac{1}{b}\frac{d[P]}{dt}$

ClaireHW
Posts: 60
Joined: Fri Sep 29, 2017 7:07 am
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### Units

When dealing with rate laws, is it always necessary to convert all units into moles, liters, or seconds?
If not, when can we use difference units?

Thanks!

(Claire Woolson Dis 1K)

Andrea ORiordan 1L
Posts: 52
Joined: Fri Sep 29, 2017 7:04 am
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### Re: Units

Rate laws involve concentrations, so you will need to use moles per liter or mmols per liter. However, some rates use seconds, some use minutes, some use hours. You just have to be consistent while solving an equation in terms of what units you use.

kaushalrao2H
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### Re: Units

since the unit for rate is mol/(liters*seconds), you'd want to ideally use those units for the calculations.

Nicole Jacobs 1C
Posts: 59
Joined: Thu Jul 13, 2017 3:00 am

### Re: Units

use the units for k requested in the question because sometimes it asks per second and sometime it asks per minute

Charles Ang 1E
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Joined: Thu Jul 13, 2017 3:00 am

### Re: Units

When working with rate laws, it is not necessary to convert to Si units immediately but is done to simplify/ make the answer more relevant. If you choose not to, just make sure to properly perform dimensional analysis to give your answer the proper units.

Sophie 1I
Posts: 51
Joined: Fri Sep 29, 2017 7:04 am

### Re: Units

The most important thing is to make sure that all of your units are consistent, and to see if the problem asks you for specific units.

AnuPanneerselvam1H
Posts: 52
Joined: Fri Sep 29, 2017 7:07 am

### Re: Units

While these are common units for these types of problems, it does not have to be these units specifically. Use whatever is consistent with the problem.

Jaewoo Jo 2L
Posts: 31
Joined: Fri Sep 29, 2017 7:06 am

### Re: Units

your units just have to be consistent, unless the questions state otherwise.

Michael Lee 2I
Posts: 51
Joined: Fri Sep 29, 2017 7:05 am

### Re: Units

Just make sure all of your units are consistent.

Sarah 2F
Posts: 33
Joined: Fri Sep 29, 2017 7:06 am

### Re: Units

Do the units that are most consistent with your problem (after canceling out and such)

Joyce Gu 1E
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Joined: Tue Nov 24, 2015 3:00 am

### Re: Units

i think it helps to just be consistent with the problem! i notice that i sometimes get lost along the way when i don't convert and forget what to cancel out

Troy Tavangar 1I
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

### Re: Units

Since the units which you generally deal with are mols per liter per second, you probably should.