15.4 : Acid Strength and the Acid Ionization Constant ACID STRENGTH: HA(aq) + H2O(l) H3O+(aq) + A-(aq) (HA is the acid, while A- is the conjugate base)A strong acid completely ionizes in solution. (represented by )A weak acid only partially ionizes in solution. (represented by ) Acids can be classified according to the number of protons it has: Monoprotic Acid : HA (can give off one proton) Diprotic Acid: H2A (can give off two protons) Triprotic Acid : H3A (can give off three protons)*Stronger acids give off protons easily, while weaker acids don’t give off protons very easily. This indicates that the conjugate base of a stronger acid is weaker than the conjugate base of a weaker acid. ACID IONIZATION CONSTANT: KaKa= [H3O + ] [A - ] [HA]Ka provides information about the strength of the acid. It is a general rule that any acid with a Ka less than 1 is a weak acid, and any acidwith a Ka greater than 1 is a strong acid. The smaller the Ka the weaker the acid. The larger the Ka the stronger the acid. *So if you are looking at two weak acids, the one with the larger Ka values will the be stronger of the two. Remember it is not a STRONG acid, it is just the stronger of the two weak
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