## assuming order from units of k

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

### assuming order from units of k

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.

Anna_Kim_2E
Posts: 31
Joined: Wed Sep 21, 2016 2:56 pm

### Re: assuming order from units of k

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.