WEAK ACID


A 'weak acid' is an acid that does not ionize in solution to a significant extent; that is, if the acid was represented by the general formula ''HA'', then in aqueous solution a significant amount of undissociated HA still remains. Weak acids in water dissociate as
mathrm{ HA_{(aq)} , leftrightarrow , H^+,_{(aq)} +, A^-,_{(aq)} }.
The equilibrium concentrations of reactants and products are related by the Acidity constant expression, (Ka):
mathrm{ K_a, =, rac {[H^+,][A^-,]}{[HA]} }
The greater the value of Ka, the more the formation of H+ is favored, and the lower the pH of the solution. The Ka of weak acids varies between 1.8×10-16 and 55.5. Acids with a Ka less than 1.8×10-16 are weaker acids than water. Acids with a Ka of greater than 55.5 are strong acids and almost totally dissociate when dissolved in water. The vast majority of acids are weak acids. Organic acids are a large subset of weak acids. Common household weak organic acids include acetic acid found in vinegar, and citric acid found in lemons; weak mineral acids include boric acid used as an antiseptic and eyewash and phosphoric acid that appears in many soft drinks.

Contents
See also

See also



★ Strong Acid

★ Weak base

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