Weak acid
A weak acid is an acid that does not fully ionize in solution; that is, if the acid was represented by the general formula AH, then in aqueous solution a significant amount of undissolved AH still remains. HA(aq) H+(aq) + A-(aq) The equilibrium concentrations of reactants and products are related by the Acidity constant expression, (Ka)''': Ka = [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 vast majority of acids are weak acids.
ExamplesPhosphoric acid, H3PO4Acetic acid, CH3COOHHydrofluoric acid, HFAcetylsalicylic acid, C6H4OCOCH3CO2HNicotinic acid, C5H5NCOOHPyruvic acid, CH3COCOOHBromothymol blue, C21H15NaBr2O3S
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