Question: We have seen an introductory definition of an acid: An acid is a compound that reacts with water and increases the amount of hydronium ion present. In the chapter on acids and bases, we saw two more definitions of acids: a compound that donates a proton (a hydrogen ion, \({H^ + }\)) to another compound is called a Brønsted-Lowry acid, and a Lewis acid is any species that can accept a pair of electrons. Explain why the introductory definition is a macroscopic definition, while the Brønsted-Lowry definition and the Lewis definition are microscopic definitions.

Protons that are donated from one compound to another are called Bronsted-Lowry acid.

Electron pairs that are accepted by the substance are called Lewis acid.

Hence, the atomic particles or subatomic levels like protons and electrons that cannot be visible to the naked eye directly are called microscopic particles.

Since the Bronsted-Lowry acid and Lewis acid depends upon the protons and electrons, they belong to the microscopic definition.

Thus, the particles or things that can be easily seen directly by direct observations of physical properties are called macroscopic particles.

Since we can measure and calculate the change in the concentration of\(\)\({{\rm{H}}_3}{{\rm{O}}^ + }\)ion, the introductory definition of an acid belongs to the macroscopic definition.