What are salts?

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Salts are the non-water product of an acid base neutralization. There are four possible acid base reactions that produce salts. They are the reaction of a:

1) strong acid with a strong base.
2) weak acid with a strong base.
3) weak base with a strong acid.
4) weak acid with a weak base.

Example reactions of each are:

1) HCl + NaOH --> Na+ + Cl¯ + H2O
2) HC2H3O2 + NaOH --> Na+ + C2H3O2¯ + H2O
3) NH3 + HCl --> NH4+ + Cl¯
4) HC2H3O2 + NH3 --> NH4+ + C2H3O2¯

Please not that I only wrote the products in ionic form.

Brief Historical Note: Svante Arrhenius struggled with fitting NH3 (ammonia) into his system, which called for bases to produce OH¯ (hydroxide ion) in solution. He "solved" his problem by pronouncing that NH3, when dissolved in solution, produced NH4OH. This substance (ammonium hydroxide) was then the source of hydroxide he needed. Unfortunately for Arrhenius, ammonium hydroxide does not exist. The NH3 reacts directly with the acid via its lone electron pair and no water is produced.

The salts produced in the above four types have a characteristic pH range in water solution by themselves:

1) A salt of a strong acid and a strong base will produce a solution with pH = 7. Generally speaking, these types of solutions are mentioned, then ignored in deeper discussions.

2) A salt of a weak acid and a strong base will produce a solution with pH greater than 7. In other words, a salt of a weak acid produces a basic solution. Notice also, the mention of a strong base is usually omitted and the phrase "salt of a weak acid" is used. Of course, the strong base had to be present to make the salt, but its presence is assumed.

3) A salt of a weak base and a strong acid will produce a solution with pH less than 7. In other words, a salt of a weak base produces an acidic solution. Notice also, the mention of a strong acid is usually omitted and the phrase "salt of a weak base" is used. Of course, the strong acid had to be present to make the salt, but its presence is assumed.

4) A salt of a weak acid and a weak base produces a solution whose pH depends on the strengths of the acid and base which made the salt. Many times textbooks will show one example calculation only and then not provide any additional problems.


The second and third types of solutions just above are very, very important in chemistry. It is critical that you remember what pH range is associated with each type. Here they are again:

Salt Solutionleads topH Range
salt of a weak acid--->greater than 7 (basic)
salt of a weak base--->less than 7 (acidic)

When the ChemTeam was first learning this, he noticed that the salts produced an opposite pH to its "parent." The salt of the weak acid came from an acid (which make solutions with pH less than 7). Therefore, since salts are oppsite in behavior, the pH of the solution of a salt of a weak acid was greater than 7 (which, of course, is basic).

The last point has to do with anions of strong acids, such as Cl¯ and NO3¯, and cations of strong bases, such as Na+ and K+. They are usually deleted from both the chemical equation (resulting in a net ionic equation) and any discussion of effects on pH. In every case, except possibly for some very extreme case, they will have no effect on the pH.

Go to The Hydrolysis of Salts in Water

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