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:

(a) strong acid with a strong base.
(b) weak acid with a strong base.
(c) weak base with a strong acid.
(d) weak acid with a weak base.

Example reactions of each are:

I. HCl(aq) + NaOH(aq) ---> NaCl(aq) + H2O(ℓ)
II. HC2H3O2(aq) + NaOH (aq) ---> NaC2H3O2(aq) + H2O(ℓ)
III. NH3(aq) + HCl(aq) ---> NH4Cl(aq)
IV. HC2H3O2(aq) + NH3(aq) ---> NH4C2H3O2(aq)

Please note that I did not write any of the strong electrolytes as ions.


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 strong acid (the HCl just above) 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:

(a) 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.

(b) 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.

(c) 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.

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


The solutions marked (b) and (c) 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 (back two or three centuries ago), 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 opposite in behavior, the pH of the solution of a salt of a weak acid was greater than 7 (which, of course, is basic).

One final point has to do with the cations and anions produced by dissociation of strong acids and strong bases. Consider these two examples of strong acids dissociating (note arrows only going right and large Ka)

HCl + H2O ---> H3O+ + Cl¯    Ka = large
HNO3 + H2O ---> H3O+ + NO3¯    Ka = large

and these two examples of strong bases dissociating (note arrows only going right and large Kb)

NaOH ---> Na+ + OH¯    Kb = large
KOH ---> K+ + OH¯    Kb = large

The size of the Ka and Kb above are so large that all of the reactions above will go fully to the right and never really go back towards the left. So anions like Cl¯ and NO3¯ (i.e., conjugate bases of strong acids) and cations like Na+ and K+ (i.e., conjugate acids of strong bases) are spectator ions in any acid-base problem. They are present in solution but play no role.

Therefore, these cations and anions are usually deleted from both the chemical equation (resulting in a net ionic equation) and dropped from any discussion of effects on pH.

Bottom Line: In every case, except possibly for some very extreme case (which the ChemTeam has never come across, if it even exists), the anions of strong acids and the cations of strong bases will have no effect on the pH.


Go to The Hydrolysis of Salts in Water

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