### Units of k

Posted:

**Wed Mar 13, 2019 12:39 pm**Can someone show how to derive the units of k for zero, 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=146&t=44378

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Posted: **Wed Mar 13, 2019 12:39 pm**

Can someone show how to derive the units of k for zero, first, and second order reactions?

Posted: **Wed Mar 13, 2019 12:43 pm**

A Khan Academy video best explains how to derive K without memorization:

https://www.khanacademy.org/science/che ... constant-k

https://www.khanacademy.org/science/che ... constant-k

Posted: **Thu Mar 14, 2019 10:04 pm**

The unit of k for a zero-order reaction is mol L-1 s-1; for a first-order reaction is s-1; For a second-order reaction is L mol-1 s-1.

Posted: **Thu Mar 14, 2019 10:41 pm**

since the equation for rate law is rate=k[A]^n, and the units for rate is mol/(L*s) and the units for [A]^n is (mol/L)^n, you can derive the units for k just by solving for units depending on the value of n.

Posted: **Thu Mar 14, 2019 10:58 pm**

Zero-order reaction is mol L-1 s-1

First-order reaction is s-1

Second-order reaction is L mol-1 s-1.

First-order reaction is s-1

Second-order reaction is L mol-1 s-1.

Posted: **Sun Mar 17, 2019 12:57 am**

we know that the units for rate are mol.L-1.s-1

Zero order: rate =k[A]^0

so units of k have to be the same as the units for the rate

First order: rate =k[A]

the multiplication of the units of k and units of concentration of A (i.e mol.L-1) should result in the units for the rate; thus, units of k is s^-1

You can do the same for second order and so on!

Zero order: rate =k[A]^0

so units of k have to be the same as the units for the rate

First order: rate =k[A]

the multiplication of the units of k and units of concentration of A (i.e mol.L-1) should result in the units for the rate; thus, units of k is s^-1

You can do the same for second order and so on!