Question

The concentrations of acid and base in buffer B are twice the concentrations of buffer A (buffer B is twice as strong as buffer A). Show that the ratio of the volume of titrant required to raise the pH of each buffer by 1 unit (V_B/V_A) is directly related to the ratio of the buffer strengths (Strength_B/Strength_A).

Answer 1

For the buffer solutions, the pH is governed by the hessley-henderbach equation

pH = pKa + log[A-/HA]

In order to increase the pH of the buffer by 1 unit, we need to make the value of log[A-/HA] to be 1, which is governed by the buffer strength of the equation.

Since buffer B is twice as strong as buffer A, hence the HA will be present in the double amount, so we need the same ration titrant (Volume of base) to make it neutralize and reduce the term. Hence the concentration of buffer term will directly affect the pH of the equation using hessley henderbach equation