Chemistry · Ch 8 — Ionic Equilibrium
Arrhenius Concept
Arrhenius Concept
Svante Arrhenius's theory (one of the earliest systematic acid-base concepts) defines an acid as a substance that dissociates in water to give hydrogen ions -- for example and -- and a base as a substance that dissociates in water to give hydroxyl ions -- for example and . The bare proton does not exist free in water: it is strongly hydrated and is usually represented as the hydronium ion (the simplest hydrate being ), so and are used interchangeably to mean the same species.
Limitations of the Arrhenius concept. The Arrhenius picture works only in water: it cannot describe acid-base behaviour in non-aqueous solvents such as acetone or tetrahydrofuran, where the same reactive substances still show acid/base character without any water present to furnish or . It also cannot account for the basic nature of substances such as ammonia (), which turns litmus blue and neutralises acids even though it possesses no hydroxyl group of its own to dissociate. …
Worked out. The Arrhenius picture works only in water: it cannot describe acid-base behaviour in non-aqueous solvents such as acetone or tetrahydrofuran, where the same reactive substances still show acid/base character without any water present to furnish or . It also cannot account for the basic nature of substances such as ammonia (), which turns litmus blue and neutralises acids even though it possesses no hydroxyl group of i …
Worked out. A self-check box asking the student to classify four species as an acid or a base using the Arrhenius concept: (i) -- an acid, since it dissociates in water to give (as remains); (ii) -- a base, since it dissociates to give ; (iii) -- an acid, since it dissociates to give (as ); (iv) -- an acid, since it dissociates (partially) to give (as $C …