Question

The rate law for the reaction below is given by the expression $k\left[ A \right]\left[ B \right]$
$A + B \to P$
If the concentration of B is increased from $0.1$ mol to $0.3$ mol keeping the value of A at $0.1$ mol the rate constant will be:
A.$3K$
B.$\dfrac{K}{3}$
C.$9K$
D.$K$

Answer 1

Then for this on putting the concentration values we find that the rate of the reaction gets changed with the change in the concentration of the reactant but most importantly the rate constant does not get affected by it .

Complete step-by-step answer: Talking firstly we should know what is rate law
So rate law states that the rate of a reaction depends upon the concentration terms of the reaction and this is experimentally observed.
As stated in the question which for sure true that the rate law expression is given by $k\left[ A \right]\left[ B \right]$
We are further given that the concentration of B changes from from $0.1$ mol to $0.3$ mol keeping the value of A at $0.1$ mol the rate constant will be:
Then for this on putting the concentration values we find that the rate of the reaction gets changed with the change in the concentration of the reactant but most importantly the rate constant does not get affected by it .
Now you must be thinking why
Then answer to this is just remember the Arrhenius equation. Which states that the rate constant only changes with the change in temperature. We can further state that it also changes with the addition of the catalyst . you must know that the catalyst is nothing but the intermediates which make the speed of the reaction higher.
Hence the last option is correct in which the rate constant remains unchanged.

Note: The rate of a chemical reaction when concentration of each reactant is unity. The rate constant is also called the specific rate of a reaction.