Weak and strong acids and bases

It is known in the world of chemistry that one way to classify acids and bases depends on the strength of their ionization of substances in an aqueous medium. Therefore, an acid and base will be strong when fully ionized, that is, they transform into cations or positive ions and into anions or negative ions. On the other hand, an acid and a base are weak when in water they are partially ionized, giving rise to a proportion of cations, anions and also undissociated molecules.

Strong acids and basesWeak acids and bases
DefinitionIt refers to those substances that completely ionize in solution.It refers to substances that are only partially ionized in solution.
IonizationIs complete.It is biased.
ExamplesStrong acids: hydrochloric acid, sulfuric acid or perchloric acid, among others.

Strong bases: sodium hydroxide, lithium hydroxide or potassium hydroxide, among others.

Weak acids: acetic acid, nitrous acid or phosphoric acid, among others.

Weak bases: ethylamine, ammonia, benzylamine, among others.

Strong acids and bases

An acid or base are strong when in an aqueous medium they dissociate completely, since what is produced is a total ionization . Therefore, the solution will find the same concentrations of anions and cations. Here it is clearly seen that the result is not dynamic as in the case of the weak, much less reversible.

Examples of strong acids are hydrochloric acid, sulfuric acid, nitric acid, chromic acid or perchloric acid, among others. Examples of strong bases can be sodium, lithium, potassium, calcium, and aluminum hydroxide, among others.

A good example of strong ionization is given by hydrochloric acid HCl, whose formula is composed below.

Weak acids and bases

An acid or base is called weak when in an aqueous solution it is only partially ionized , this gives rise to a dynamic, reversible equilibrium, since ions but also non-ionized molecules will be present in it. In other words, they do not completely dissociate in a solution.

With the aforementioned, a rule can be said: the strength of the weak acid or base will depend on how much they dissociate and the greater this dissociation, the greater its strength will also be. This is when the dissociation constant Ka appears in the formula, which represents the equilibrium constant for the dissociation reaction of an acid.

Below we present the formula for how a weak acid or base (acetic acid CH3COOH) is ionized, in addition to the other formula that expresses the equilibrium constant in the same process.

Examples of weak acids are acetic, hypochlorous, nitrous, lactic, carbonic acid, among others. Examples of weak bases can be ammonia, aniline, ethylamine, among others.

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