When the pH of a solution of a weak acid, HA, is equal to the pKa, the ratio of the concentrations of the salt and the acid (/) is which one of the following?: (A) 0, (B) 1, (C) 2, (D) 3
Answer is B. The pKa is the pH at which the functional group is 50% dissociated, which in this case is the pH at which = The Henderson-Hasselbalch equation, pH=pKa +log10/, gives the relationship between these parameters. If pH=pKa , log10/=0,and/=1