How do you classify Bronsted acids and bases?

1 Answer

Bronsted acids and bases are classified by their ability to donate or accept a proton.
An acid is a proton donor, and a base is a proton acceptor .


A Bronsted-Lowry acid, very similar to an Arrhenius acid, is a compound that donates an #H^+# to another substance.

The only difference is that the other substance does not have to be water.

So, technically, we can still leverage the Arrhenius model for classification of the acids.

You just don't have to limit the other substance to water in the Brønsted-Lowry model (e.g. ammonia, alcohol, or anything else).

On the base side, the Bronsted-Lowry and Arrhenius definitions differ.

An Arrhenius base refers specifically to the hydroxide #OH^-)# ion, while a Bronsted-Lowry base refers to any atom or ion capable of accepting or bonding to a proton.

Let use an example: Consider Nitric Acid and Ammonia :

#HNO_3 + NH_3 -> N H_4^+ + NO_3^-#

Nitric acid donates an #H^+# to #NH_3#.

Notice that, in the Arrhenius model, it is the water that picks up the proton.

When ammonia picks up the #H^+#, it acts as a proton-acceptor.

#NH_3# is the Bronsted-Lowry base in this example.

Notice there is no reference to #OH^-#.