Acid–Base Reactions: Neutralization Reactions
When a strong acid and a strong base solution are mixed,
a neutralization reaction occurs, and the products do not have characteristics
of either acids or bases. Instead, a neutral salt and water are
formed. Look at the reaction below:
HCl(aq) + NaOH(aq)
H2O(l) +
NaCl(aq)
The anion from the acid (Cl–)
reacts with the cation from the base (Na+)
to give a salt, and a salt is defined as any compound
formed whose anion came from an acid and whose cation came from
a base.
When a strong acid and a weak base are mixed, the resulting
salt will be acidic; likewise, if a strong base and a weak acid
are mixed, the resulting salt will be basic. If on the SAT II Chemistry
test you are asked to determine if a salt formed in a particular
reaction is neutral, acidic, or basic, first ask yourself, Which
acid reacted with which base to form this salt? Next ask
yourself, Was the acid strong or weak? and then, Was
the base strong or weak? Consider K2CO3.
K2CO3 is formed when
the base, potassium hydroxide (which is strong since potassium is
a 1A metal), reacts with the acid, H2CO3 (which
is weak since it isn’t one of our six strong acids). Since this
is a combination of a strong base and a weak acid, the salt formed
will be basic.
The good news is that for the SAT II Chemistry exam, you
needn’t worry about weak-weak combinations. Now try some problems
on your own.
Example
Classify each of the salts listed below as acidic, basic,
or neutral.
Explanation
-
Fe(NO3)3—This
salt was formed from the reaction of a weak base, iron (III) hydroxide,
with a strong acid, nitric acid. This means that the salt will be acidic.
- MgSO4—This
salt was formed from the reaction of a strong base, magnesium hydroxide,
with strong acid, sulfuric acid. This reaction results in a neutral
salt.
- Ni(ClO4)2—This
salt was formed from the reaction of a weak base, nickel (II) hydroxide,
with a strong acid, perchloric acid. This is an acidic salt.
