Weak acids include formic acid, acetic acid, hydrofluoric acid, hydrogen sulfide and hydrocyanic acid. These acids do not completely dissociate in water to form ions, which means substances in weak acids normally stay together as molecules rather than dissolve in water. Weak acids typically have a pH of 4 to 7.
Formic acid is found in the venom of bees and ants. Based on its chemical structure, formic acid is also known as methanoic acid, which is the simplest carboxylic acid. Formic acid is used as a preservative in feed for livestock, a tanning agent for animal hides and as a dye.
Acetic acid is the main component of vinegar. Acetic acid comes from the oxidation of ethanol and the distillation of wood fibers. This substance is also known as ethanoic acid or acetate. Acetic acid is used in the manufacture of explosives, wine, vinegar, lacquers and industrial chemicals.
Hydrogen sulfide smells like rotten eggs in lower concentrations. The acid is used for oil refining, mining, tanning and paper processing. Hydrogen sulfide occurs naturally in sewers, gas wells, volcanoes and well water. In its gaseous state, hydrogen sulfide is flammable. In higher concentrations, hydrogen sulfide is toxic to humans. Mild headaches can occur during exposure to this weak acid's fumes.