Is acetic acid a weak acid or strong acid? Why?

Acids are classified as either strong or weak, based on their ionization in water . A strong acid is an acid which is completely ionized in an aqueous solution. Hydrogen chloride (HCl) ionizes completely into hydrogen ions and chloride ions in water .

HCl(g)→H+(aq)+Cl−(aq)

A weak acid is an acid that ionizes only slightly in an aqueous solution. Acetic acid (found in vinegar) is a very common weak acid because it doesn’t dissociate very much in solution Its ionization is shown below.

CH3COOH(aq)⇄H+(aq)+CH3COO−(aq)

Thus, it is less capable at donating protons.

The ionization of acetic acid is incomplete, and so the equation is shown with a double arrow. The ionization for a general weak acid, HA, can be written as follows:

HA(aq)→H+(aq)+A−(aq)

Because the acid is weak, an equilibrium expression can be written. An acid ionization constant (Ka) is the equilibrium constant for the ionization of an acid.

Ka=[H+][A−]/[HA]

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