Acid Strength

This animation demonstrates the difference between a strong acid, hydrochloric acid, and a weak acid, hydrofluoric acid. Click on one of the buttons to see hydrochloric acid, HCl or hydrofluoric acid, HF, dissolved in water.

Hydrochloric acid is a strong acid. Strong acids are strong electrolytes, which, for most purposes, are assumed to ionize completely in water. In this case, HCl ionizes completely to hydrogen ions, H+ and chloride ions, Cl-. The reaction is better represented as hydrochloric acid donating an H+ to water, producing hydronium ion, H3O+, and chloride ion. The role of water in this reaction was not shown to simplify the animation. You can think of H+ as a shorthand representation of H3O+.

Hydrofluoric acid is a weak acid. Weak acids are weak electrolytes, which only ionize to a limited extent in water. At equilibrium, a hydrofluoric acid solution contains mostly non-ionized acid molecules, HF, and a small amount of hydrogen ions H+, and the conjugate base ions F-. This reaction is better represented as hydroflouric acid donating a proton to water, producing hydronium H3O+ and a flouride ion. Remember that weak acids only partially ionize in water. The role of water in this reaction was not shown to simplify the animation. You can think of H+ as a shorthand representation of H3O+.


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