15.9b

[Adrienne Dang 1B]

Can someone explain to me why you are supposed to divide the units by (mol A)/L for the first-order reaction?

[Alyssa Pelak 1J]

The question asks you to express the units for rate constants when the concentrations are in moles per liter and time is in seconds. You are using the equation rate= k[A] since it is first order. Rate is stated in mol L(-1)s(-1) and concentration is in mol L(-1). Therefore, in order to find the units of k you rewrite the equation as k=rate/[A]. That would mean the units of k would be mol L(-1)s(-1)/mol L(-1) which would give you s(-1).

Hope this helps!

[snehabhargava]

That is the concentration of the reactants and you are dividing by the concentration.