Units of k

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Tinisha 1G
Posts: 69
Joined: Fri Sep 28, 2018 12:17 am

Units of k

Postby Tinisha 1G » Wed Mar 13, 2019 12:39 pm

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

Jerome Mercado 2J
Posts: 60
Joined: Tue Nov 28, 2017 3:02 am

Re: Units of k

Postby Jerome Mercado 2J » 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

Xingzheng Sun 2K
Posts: 62
Joined: Fri Sep 28, 2018 12:29 am

Re: Units of k

Postby Xingzheng Sun 2K » 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.

Joonsoo Kim 4L
Posts: 61
Joined: Fri Sep 28, 2018 12:29 am

Re: Units of k

Postby Joonsoo Kim 4L » 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.

Rhea Churi 4K
Posts: 62
Joined: Fri Sep 28, 2018 12:28 am

Re: Units of k

Postby Rhea Churi 4K » 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.

Salena Chowdri 1I
Posts: 66
Joined: Fri Apr 06, 2018 11:02 am

Re: Units of k

Postby Salena Chowdri 1I » 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!


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