Question

The rate law of a reaction is rate = k[D][X]. What are the units of the rate constant?

Answer 1

The rate constant `k` takes on whatever units it needs to such that the units on the lefthand side are the same as on the righthand side. Supposing the units on the left are `"M/s"`, we really just have:

`"M"/"s" = (???)("M")("M")`

Solve for the `???`.

`"M"/"s" xx 1/("M" cdot "M") = ???`

Thus,

`??? = color(blue)(1/("M"cdot"s"))`

or

`color(blue)("M"^(-1)cdot"s"^(-1))`

or

`color(blue)("L"/("mol"cdot"s"))`