Posted by **elvis** on Saturday, February 18, 2012 at 9:19pm.

The units of a rate constant for zero, first and second order reactions are given in the textbook. If the time units are minutes, what would you expect the units to be for a third order reaction?

a. 1/min3 b. mol2/L2-min c. L/mol-min2 d. L2/mol2-min e. L2/mol2-min2

help help!

chemistry - DrBob222, Friday, February 17, 2012 at 10:25pm

rate laws:

zero order is rate = k so units are M/s or moles/l*s

1st order is rate = k*(A)

k = rate/(A) = moles/L*ws/(moles/L) = 1/s or s^-1.

Here is a site that will give you the units of zero, 1st, 2nd, and a formula for calculating any order units for k. Just scroll to that part of the site.

guessing B?

- chemistry -
**DrBob222**, Saturday, February 18, 2012 at 10:00pm
You shouldn't guess. You should KNOW. Either I forgot to give you the link that I said I gave you or you didn't look at it. Anyway, here is the link. C-mon. Figure it out.

rate = k(A)^3

k = rate/(A)^3

rate has units of M/min (in this problem) and (A) has units of M so

k = M/min divided by M.

M = moles L. Now the units are k are ??

http://en.wikipedia.org/wiki/Rate_equation

- chemistry -
**Rick**, Sunday, February 19, 2012 at 1:28pm
I get L^2/mol^2 -min. Is that correct?

- chemistry -
**DrBob222**, Sunday, February 19, 2012 at 2:07pm
yes

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