was discussed in Chapter 7. When an electric current is passed through a
saltwater solution, hydrogen, chlorine, and sodium hydroxide are the products.
The formula for this equation is:
Broader Acid–Base Theories
Besides the common Arrhenius Theory of acids and bases discussed for aqueous
solutions, two other theories, the Brønsted-Lowry Theory and the Lewis Theory,
are widely used.
The Brønsted-Lowry Theory (1923) defines acids as proton donors and
bases as proton acceptors. This definition agrees with the aqueous solution
definition of an acid giving up hydrogen ions in solution, but goes beyond to other
cases as well.
An example is the reaction of dry HCl gas with ammonia gas to form the
white solid NH 4 Cl.
HCl(g) + NH 3 (g) → NH 4 Cl(s)The HCl is the proton donor or acid, and the ammonia is a Brønsted-Lowry
base that accepts the proton.
Conjugate Acids and Bases
In an acid–base reaction, the original acid gives up its proton to become a
conjugate base. In other words, after losing its proton, the remaining ion is
capable of gaining a proton, thus qualifying as a base. The original base accepts a
proton, so it now is classified as a conjugate acid since it can release this newly
acquired proton and thus behave like an acid.
Some examples are given below:
Strength of Conjugate Acids and Bases
The extent of the reaction between a Brønsted-Lowry acid and base depends on
the relative strengths of the acids and bases involved. Consider the following