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

Answer:

The rate constant can be defined as the rate of the reaction when the concentration of each of the reactant is taken as unity. Now, if the concentration of NO and O2 is taken to be unity, then the rate constant is found to be equal to the rate of the reaction. –1 = 1 – n => n = 2, i.e., second order reaction.

Answer 2

The rate of reaction is found to depend on α concentration of term of reactant A and β concentration term of reactant B

Then Rate of reaction ∝ [A]α [B]β

or Rate = K [A]α [B]β

This expression is called Rate law.

‘K’ in this expression is called Rate constant. Rate constant’s unit :

(i) Unit = L-1 mol s-1 → Zero order reaction

(ii) Unit = L mol-1 s-1 → Second order reaction.