Question

The units for the rate constant and rate of reaction are the same for a reaction. What will be the order of the reaction?
A.Second
B.Zero
C.First
D.Third

Answer 1

The rate constant of a reaction is the proportionality constant that expresses the relationship between the rate of a chemical reaction and the concentrations of the reactants involved in the reaction.
The order of reaction is nothing but the relationship between the rate of a chemical reaction and the concentration of the reactants involved in it.

Complete answer:
In the question it is given that units for the rate constant and rate of reaction are the same for a reaction.
We have to find the order of the reaction based on the given data.
Consider a chemical reaction where ‘n’ number of moles of A is converted into product.
nA→product
Rate of the above chemical reaction = $K{{[A]}^{n}}$
Here, K = rate constant, [A] = concentration of the reactant, and n = number of moles of the reactant.
Assume that if n = 0 in the above reaction then,
Rate of the reaction =$K{{[A]}^{0}}$= K
Therefore, the rate of the reaction is equal to K and it is only possible when n is zero. Means the order of the reaction should be zero.
Units for zero order reaction are $mol.\text{ }li{{t}^{-1}}{{\sec }^{-1}}$.
The units for the rate constant and units of reaction are the same when the order of the reaction is zero.
Therefore the order of the reaction is zero.
So, the correct option is B

Note: The order of a chemical reaction can be defined as the sum of the powers of the concentration of the reactants involved in the rate equation of a particular chemical reaction.
Consider a general reaction
$aA+bB\to cC+dD$
Rate of the above chemical reaction = $K{{[A]}^{a}}{{[B]}^{b}}$
Order of the above reaction = a+b