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Strong electrolyte: concept, characteristics, examples

The most representative example of an electrolyte is common salt, sodium chloride, NaCl. In aqueous solution, the NaCl crystals dissociate in their entirety to produce Na + and Cl  ions , which end up surrounding themselves with water molecules. A salt is then said to behave as a strong electrolyte when its solubility is very high in water.

Somewhat similar is the case of acids and bases. When these are strong, their solutions in water produce the maximum possible amount of H 3 O + or OH  ions , so the pH changes are abrupt. Examples of strong acids and bases are nitric acid, HNO 3 , and potassium hydroxide, KOH, respectively.

Characteristics of strong electrolytes

Solubility

Strong electrolytes are characterized by being extremely soluble substances in water. Whether they are solid or gas, when it comes into contact with water it should not take too long to completely dissolve. If a salt, for example, is poorly soluble in water, it can be discarded as a strong electrolyte.

Ionic conductivity

Strong electrolytes are not only very soluble in water, but they also generate a large number of ions. Thanks to the electrical charges of these ions, electrons can comfortably travel through solutions. This is reflected in an increase in ionic conductivity with respect to pure water. This is why ionic solutions conduct electricity very well.

Salt neutrality

Many strong saline electrolytes, when dissolved in water, do not produce any pH change. This means that the solutions of these salts are neither acidic nor basic, but neutral, with a pH close to 7.

However, there may be acidic or basic salts that dissolve easily in water, and also generate ions completely. For example, sodium carbonate, Na 2 CO 3 , dissolves to generate Na + and CO 2- ions , but the pH of the solution is basic.

Examples of strong electrolytes

Sodium chloride is the most representative example of a strong electrolyte. Source: Cristian V. / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

Strong electrolytes, being so many, are divided into three classifications: strong acids, strong bases, and soluble salts product of the neutralizations among the first two.

Strong acids when dissolved in water, without any problem, must produce the maximum possible amount of H 3 O + , so the acid must be completely ionized; that is, it must not exist as a neutral molecule with unreleased acidic protons.

Examples of these acids are:

-HCl, hydrochloric acid, releases H 3 O + and Cl  ions

-HF, hydrofluoric acid, releases H 3 O + and F  ions

-HNO 3 , nitric acid, releases H 3 O + and NO  ions

-HClO 4 , perchloric acid, liberates ions H 3 O + and ClO 

-HIO 4 , periodic acid, liberates ions H 3 O + and IO 

-H 2 SO 4 , sulfuric acid, liberates ions H 3 O + and SO 2-

The reason why the hydronium ion, H 3 O + , is always present (in one way or another) is because the hydrogen they donate is received by a water molecule:

HCl + H 2 O → H 3 O + + Cl 

The reaction is direct and irreversible. This is a characteristic of a strong acid, which in turn is a strong electrolyte because of its complete ionization in water.

Strong bases

Strong bases, when dissolving in water without any problem, must release OH  ions from their own crystals, or irreversibly deprotonate a water molecule to generate them.

Many strong bases consist of ionic and non-molecular solids. Some examples of these bases that behave like strong electrolytes are:

-LiOH, lithium hydroxide, releases OH  and Li + ions

-NaOH, sodium hydroxide, releases OH  and Na + ions

-RbOH, rubidium hydroxide, releases OH  and Rb + ions

-Ca (OH) 2 , calcium hydroxide, releases OH  and Ca 2+ ions

-Sr (OH) 2 , strontium hydroxide, releases OH  and Sr 2+ ions

-Ba (OH) 2 , barium hydroxide, releases OH  and Ba 2+ ions

-NaH, sodium hydride, releases OH  ions and hydrogen gas, H 2

-NaNH 2 , sodium amide, liberates OH  ions and ammonia gas, NH 3

You go out

Strong saline electrolytes when dissolved in water must ionize completely. Many of them do not produce pH changes. This is because its ions are very stable, so they do not participate in hydrolysis equilibria to change the nature of the water. Examples of these salts are:

-NaCl, sodium chloride, releases Na + and Cl  ions

-AgNO 3 , silver nitrate, releases Ag + and NO  ions

-NaNO 3 , sodium nitrate, releases Na + and NO  ions

-K 2 SO 4 , potassium sulfate, releases K + and SO 2- ions

-MgCl 2 , magnesium chloride, releases Mg 2+ and Cl ions 

-CuSO 4 , cupric sulfate, liberates ions Cu 2+ and SO 2-

-KBr, potassium bromide, releases K + and Br  ions

-NH 4 Cl, ammonium chloride, releases NH + , Cl  , H 3 O + ions and ammonia gas

-NaCN, sodium cyanide, releases Na + and CN  ions

-Na 3 PO 4 , sodium phosphate, releases Na + and PO 3- ions

-CrCl 3 , chromic chloride, releases Cr 3+ and Cl  ions

-AuBr 3 , auric bromide, releases Au 3+ and Br  ions

-SnSO 4 , stannous sulfate, releases Sn 2+ and SO 2- ions

NH 4 Cl is a contradictory example: it ionizes completely, but at the same time generates neutral ammonia molecules because it is an acidic salt.

Differences between strong and weak electrolyte

Although the differences between a strong and a weak electrolyte have been indirectly established, these will be discussed below as a conclusion:

-Strong electrolytes are very soluble in water; weak electrolytes are not.

-The ionization of a weak electrolyte is partial, which means that there may be neutral molecules in solution. In contrast, strong electrolytes exist in solution exclusively as ions.

-Weak acids and bases, which in turn are weak electrolytes, do not dissociate completely in water, so they generate fewer H 3 O + or OH  ions than might be expected.

-Strong saline electrolytes hardly hydrolyze compared to weak electrolytes. Therefore, the solutions of the former tend to be neutral, except for acidic or basic salts.

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