Question

The unit of rate and rate constant are same for a:
A.Zero order reaction
B.First order reaction
C.Second order reaction
D.Third order reaction

Answer 1

Rate of reaction: It is defined as the rate of disappearance of reactant and the rate of appearance of the product.
Rate constant: It is proportionality constant between the rate of reaction and the concentration term.

Complete step by step solution:
First of all we read about the rate law, rate of reaction and rate constant.
Rate of reaction: It is defined as the rate of disappearance of reactant and the rate of appearance of the product. It is represented as:
For example: the reaction is as $A \to B$ i.e. the reactant $A$ is converting to the product $B$.
Then, the rate of reaction can be written as: $- \dfrac{{\Delta [A]}}{{\Delta t}}\propto [A]$. This is known as the rate of reaction. If we want to write in terms of product then it will be written as $\dfrac{{\Delta [B]}}{{\Delta t}}\propto [B]$.
Rate law: Rate law is the mathematical relation between the rate of reaction and concentration of each reactant.
For example: the reaction is as $A \to B$ i.e. the reactant $A$ is converting to the product $B$.
Then the expression for rate law will be as: $rate = - \dfrac{{\Delta [A]}}{{\Delta t}}$. And we know that the rate of disappearance of reactant is equal to the concentration of reactant (by the definition of rate of reaction). So the equation for rate law will become: $rate\propto [A]$ . To remove the proportionality sign let us take a constant $k$ which is known as rate constant. So the final equation will be as $rate = k[A]$.
Rate constant: It is proportionality constant between the rate of reaction and the concentration terms.
The unit of rate of reaction is $mol{L^{ - 1}}{s^{ - 1}}$ while the unit of rate constant depends on the order of the reaction. For example: if the order of the reaction is one then the unit of rate constant will be ${s^{ - 1}}$.
If the reaction is of zero order then the unit of rate constant and rate of reaction will be same i.e. $mol - {L^{ - 1}}{s^{ - 1}}$.

Hence, option A is correct.

Note: Order of reaction is defined as the power relation of the rate on the concentration of the reactants. For example: If the reaction is of one order then rate of the reaction is directly proportional to the single power of the concentration of that reactant.