Weak acid
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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) <math> \leftrightarrow </math> 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.
Examples
- Phosphoric acid, H3PO4
- Acetic acid, CH3COOH
- Hydrofluoric acid, HF
- Acetylsalicylic acid, C6H4OCOCH3CO2H
- Nicotinic acid, C5H5NCOOH
- Pyruvic acid, CH3COCOOH
- Bromothymol blue, C21H15NaBr2O3S
