Salts

An acid and base react to form a salt. Therefore when an acid or a base is "neutralized" a salt is formed.

Depending on the acids and bases the salt that is formed can be neutral, acidic, or basic.   This is all just a different language for what you have already learned.   For example, if formic acid is combined with sodium hydroxide, it generates a salt, sodium formate and water

\[\rm{HCOOH(aq) + NaOH(aq) \rightleftharpoons Na(HCOO)(aq) + H_2O(l)}\]

In this case, the salt is a basic salt since it contains the weak base, formate (HCOO^-) [and the spectator ion Na⁺].

In contrast, if a strong acid and a strong base are combined, like hydrochloric acid and potassium hydroxide you get a neutral salt, potassium chloride

\[\rm{HCl(aq) + KOH(aq) \rightleftharpoons KCl(aq) + H_2O(l)}\]

This is because both the strong acid and the strong base result in ions that are merely spectators.

Finally, it is possible to make acidic salts by neutralizing a weak base such as ammonia, NH₃ with a strong acid like HCl

\[\rm{NH_3(aq) + HCl(aq) \rightleftharpoons NH_4Cl(aq) + H_2O(l)}\]

Here the neutralization of NH₃ forms the ammonium ion, NH₄⁺ which is a weak acid.  Thus the ammonium chloride salt is acidic.

These salts can be isolated from solution by removing the water. This will leave behind the solid ionic compound.

What are some examples of basic salts? KCN, potassium cyanide. CN^- is the conjugate base of HCN. Na(HCOO), sodium formate. The formate ion, HCOO^- is the conjugate base of formic acid. What are some acidic salts? CH₃NH₃Cl, methylammonium chloride. Methylammonium is the conjugate acid of methylamine, CH₃NH_2.

There is a worksheet on identifying acid/base compounds on the worksheet page

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