Chemistry

Difference Between Order and Molecularity of Reaction

we explain that order is the sum of powers of concentration equations in a rate equation. while molecularity of a reaction is the number of moles and atoms participating in the rate-determining step. the main difference between Order and Molecularity of Reaction is that order is the sum of the powers of concentrations terms in the rate law expression and is determined experimentally. on the other hand, the molecularity of a reaction is the number of reactant species undergoing simultaneous collision and is determined by the theoretical concept. The molecularity of an elementary reaction is the number of reactant species/molecules involved in a reaction.Difference Between Order and Molecularity of Reaction

Overview

We should note here that the order of a reaction is the sum of exponents of concentrations terms in the rate equation. Order is the number of reacting substances that concentrations change during a reaction. whereas the molecularity of an elementary reaction is the number of reactants molecules that take part in a chemical reaction. in case if one molecule takes part in a reaction, then it is called unimolecular. if two molecules take part, it is the bimolecular reaction and for three molecules, it is known as a termolecular reaction.

In this post, you are going to learn about the 8 Key Differences Between Order and Molecularity of a Reaction in Tabular Form. if you want to get benefits from this post you’ll love this post.

8 Differences Between Order and Molecularity of a Reaction in Tabular Form:

Order of reaction Molecularity of reaction
It is the number of molecules whose concentration changes in a chemical reaction. Molecularity is the number of molecules involved in a chemical reaction. 
Order is the sum of exponents expressed in the rate expression. On the other hand, molecularity is the sum of moles of reactants that take part in a chemical reaction.
It is determined by experiment. It is determined by the reaction mechanism.
We get an order of reaction from kinetic theory study (i.e. speed of a reaction)  It is indicated by simply adding the molecules of the slowest step.
It can be fractional. It is always the whole number.
It may be equal to zero. It is never zero. 
It is the overall reaction and no separate steps are written to obtain the order of a reaction.  The overall molecularity of a complex reaction has no significance. It is the slowest step whose molecularity has significance to the overall reaction. 
Its maximum value may be three. Its values may be greater than three. 

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