assuming order from units of k

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Emi Nakahara 3F
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Joined: Wed Sep 21, 2016 2:57 pm

assuming order from units of k

Postby Emi Nakahara 3F » Wed Feb 22, 2017 10:48 am

In questions where the order is not given but k is, is it possible to assume the order from the units of k? For example, observing that k is in units of seconds^-1 or minutes^-1 then assuming it is a first order reaction, or if k is in liters per mole per second, then it assuming it is a second order reaction.

Posts: 31
Joined: Wed Sep 21, 2016 2:56 pm

Re: assuming order from units of k

Postby Anna_Kim_2E » Wed Feb 22, 2017 1:39 pm

Yes you can figure out the order of reaction by looking at the units of k.
Because the unit of rate is M/s, if you plug the unit of rate in 0 order, 1st order, and 2nd order rate law, you will be able to get the unit of k for different orders.

For example rate=k[A]^0 for 0 order. Since you know that unit of rate is M/s and because [A]^0 with no unit, unit of k will also be M/s.

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