text: is the following true or false? the units of the rate constant, k, are always the same. it's false.  the units of the rate constant depend on the order of the reaction. a first order reaction would have units of 1/s (one over seconds, often stated as "per second") a second order reaction would have units of 1/(m*s) (one over molarity times seconds, often stated as "per molar per second") you can, of course, use other units of time.