Question

What do you understand by the rate law and rate constant of a reaction? Identify the order of a reaction if the units of its rate constant are:

(i) L^–1 mol s^–1

(ii) L mol^–1 s^–1.

Answer 1

An experimentally determined expression which relates the rate of reaction with the concentration of reactants is called rate law while the rate of reaction when concentration of each reactant is unity in a rate law expression is called rate constant.

(i) Comparing power of mole in L^–1 mol s^–1 and (mol L^–1)^1–n s^–1,

We get

1 = 1 – n ⇒  n = 0 i.e., zero order reaction

(ii) Again comparing power of mole in L mol^–1s^–1 and (mol L^–1) ^1–n s^–1, we get

–1 = 1 – n ⇒  n = 2, i.e., second order reaction