Units k

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Madison Hurst
Posts: 62
Joined: Fri Sep 28, 2018 12:26 am

Units k

Postby Madison Hurst » Sun Mar 17, 2019 12:29 am

how do you determine units for rate constant?

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

Re: Units k

Postby Salena Chowdri 1I » Sun Mar 17, 2019 12:32 am

This would depend on the order of the reaction! It's easiest to write out the units for each individual element of the rate law and cancel out units from there. Here's a short cut though: first order: s^-1, second: mol^-1.L.s^-1, third: mol^-2.l^2.s^-1

Posts: 100
Joined: Thu Jul 11, 2019 12:17 am

Re: Units k

Postby MaggieHan1L » Sun Mar 01, 2020 12:52 pm

you're trying to get a rate of M/s so if you set up the rate calculations you can see that for first order you get k times M. Thus k would need units of s^-1 to obtain M/s. So you can calculate the units of k like this for each order. Its easier to be able to calculate then remembering.

Ashley Fang 2G
Posts: 102
Joined: Fri Aug 30, 2019 12:17 am

Re: Units k

Postby Ashley Fang 2G » Mon Mar 02, 2020 10:10 am

It depends on the rate equation.
Rate = k[A]n[B]m
So if the overall rxn order is 1 (n+m), then k would be in units of 1/s since you're trying to get the rate units to equal mol/L-s.
If the overall rxn order is 2, then k would be in units of L/mol-s, etc.
reaction rate k.png
reaction rate k.png (12.63 KiB) Viewed 89 times

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