Plz explain Lewis concept Utility and its limitations:

Utility of Lewis Concept:

* This concept includes those reactions in which no protons are involved.

* Lewis concept is more general than the Bronsted-Lowry concept(i.e protonic concept) in that acid-base behaviour is not dependent on the presence of one particulr element or on the presence or absence of a solvent.

* It explains the long accepted basic properties of metallic oxides and acidic properties of non-metallic oxides.

* This theory also includes many reactions such as gas phase, high temperature and non-solvent reaction as neutralization process.

* The Lewis approach is, however, of great value in case where the protonic concept is non-applicable, for example, in reaction between acidic and basic oxides in the fused state.

Limitations:

* Since the strength of Lewis acids and bases is found to depend on the type of reaction, it is not possible to arrange them in any order of their relative strength.

* According to the phenomenological criteria, an acid-base reaction should be a rapid reaction. There are, however, many Lewis acid-base reactions which are slow.