Strengths of acids and bases in aqueous solution

We have referred somewhat vaguely above to the relative strengths of acids and bases. It is now necessary to give quantitative significance to such terms. The strengths of acids for a particular solvent are measured and expressed with respect to a chosen standard/or that solvent. Thus, for water, the standard is the acid-base pair H3OVH2O. The strength of some other acid. A, may then be defined with respect to the reaction 

B being the conjugate base of the acid A. The equilibrium constant for this reaction is then a measure of the strength of A in that it defines the extent to which the reaction proceeds to the left or right, i.e., 

It is usual to express the equilibrium constant for this case as 

Then the greater the strength of A and the smaller that of B, the higher is the value of K and the smaller the value of jK. 

Since the above treatment is not generally adopted, we shall also consider the more conventional definition of base strength in terms of the hydroxyl ions produced in water, e.g., for the reaction 

---