Common weak acids include formic, acetic, hydrofluoric, hydrocyanic, citric and trichloroacetic acids. Some weak bases include ammonia, trimethyl ammonia, pyridine, sodium bicarbonate and ammonium hydroxide. Weak acids and bases do not completely dissociate, or ionize, in water. Calculating the pH of weak acids and bases is more complicated than that of stronger varieties because of this lack of dissociation.
Most weak acids and bases dissociate only 1 percent to 5 percent of their potential ions into water, meaning most of the source of the acid or base stays out of solution as a solid salt. This makes weak acids and weak bases easier to dilute. Weak acids and weak bases often come in a buffer solution, which is a combination of the acid and its resulting salt. The weak solution has some, but not all, of the ions from the salt dissolved in water.
Many weak acids and bases are important to the biochemistry of living things. Acetic acid is a main component of vinegar. Citric acid contains vitamin C, an important antioxidant in human nutrition. Ammonia is a common cleaning solvent. A weak acid forms in the lungs because of the presence of carbon dioxide, which leads to respiration among animals with lungs. Blood pH regulates many processes regarding nutrition and the elimination of waste.