Some examples of acid salts are:
Acid salts are salts resulting from partial neutralization of a polyprotic acid (acid with more than one ionizable hydrogen ion. They can behave as either an acid or a base. In the presence of a strong enough acid an acid salt will gain back a proton (H+), and in the presence of a strong enough base it will give up a proton. Acid salts can be acidic or basic in solution. In general a salt will be acidic if it forms from a strong acid and weak base, because the conjugate acid can hydrolyze water, and it will be basic if it forms from a strong base and weak acid because in this case the conjugate base can hydrolyze water.
Acid salts are the salts that are formed as a result of incomplete replacement of hydrogen ions from an acid. Since some protons are still there that can be replaced, such salts can serve as both acids or bases. When these salts will react with strong acids, they can get protonated and become acids. When they react with a strong base, they can add hydroxyl ions to neutralize the proton and work as a base. An example of acid salt is sodium bicarbonate (NaHCO3). It is formed when a weak acid, carbonic acid, reacts with a strong base, sodium hydroxide.
NaOH + H2CO3 -> NaHCO3 + H2O
It can further react with a strong acid and gain a proton to convert back to carbonic acid or react with a strong base to lose this proton and become sodium carbonate.
Hope this helps.