| Themes > Science > Chemistry > Inorganic Chemistry > Acids and Bases > Acids and Bases > Bronsted-Lowery Concept of Acids and Bases |
The Bronsted-Lowery concept of acids and bases is that acid-base reactions can be seen as proton-transfer reactions. This results in acids and bases being able to be defined in terms of this proton (H+) transfer. According to the Bronsted-Lowery concept, acids donate a proton in a proton-transfer reactions. Bases accept the proton in a proton-transfer equation. As an example, lets look at the reaction of hydrochloric acid with ammonia. When we write it as an ionic equation we get:
which reduces to: because there is two Cl-(aq) one each side. We now have the net ionic equation after we cancel out the "spectator ions"(Cl-). What happens in this reaction in aqueous solution is a proton transfer. According to the Bronsted-Lowery concept, acids donate a proton in a proton-transfer reactions. Bases accept the proton in a proton-transfer equation. As an example, lets look at the reaction of hydrochloric acid with ammonia shown above. What happens in this reaction in aquesous solution is that a poton is transferred from H3O+ to NH3. This results in H3O+ losing a (H+), resulting in H2O. The NH3 gains the transferred proton, resulting in NH4+. We call H3O+ the proton donor, or acid. We call NH3 the proton acceptor, or base. The Bronsted-Lowery concept defines something as either an acid or base depending on its function in the acid-base (proton transfer) reaction. Some things can act as either an acid or a base. These are called amphiprotic species, they can either lose or gain a proton, depending on the other reactant. An example of an amphiprotic species would be HCO3-. In the presence of OH-, it acts as an acid. In the presence of HF it acts as a base. Water is also amphiprotic, as are most anions with ionizable hydrogens and certain solvents. Water as an amphiprotic species is very important to the acid-base reactions.
In the Bronsted-Lowery concept we have
found that: 1. A base is a species that accepts protons, while an acid is a species that dontates protons. 2. Acids and bases can be ions as well as molecular substances. 3. Some species can act as either acids or bases, depending on what the other reactant is. |
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