Question

The value of rate constant of a pseudo first order reaction _______.
(A)- depends on the concentration of reactants present in small amount
(B)- depends on the concentration of reactants present in excess
(C)- is independent of the concentration of reactants
(D)- depends only on temperature

Answer 1

Hint: Pseudo first order reaction sometimes also known by the name of unimolecular or bimolecular chemical reaction. And the rate constant of any chemical reaction always depends on the concentration of the reactants present in that reaction.

Complete step by step answer:
For giving any conclusion about the rate constant of pseudo first order reaction, first we have to know about the important points regarding this reaction and which are as follow:
-In this reaction two reactants are involved but due to the presence of any one reactant in the excess amount or in the constant concentration, rate of the whole reaction will depend on that reactant only.
-In the equation of rate constant only one reaction of reactant is written, that’s why it is called the pseudo first order reaction rather than a second order reaction.
From the above points it is clear that the value of rate constant of a pseudo first order reaction depends on the concentration of reactants which is present in excess quantity.

Hence, option (B) is correct.

Note:
Here some of you may think that option (C) is the right option because if you see the chemical reaction equation, there will be two reactants but rate constant depends only on the concentration of only one. But that assumption is wrong.