A buffer has a ratio of A THA 31 How could the capacity or s

A buffer has a ratio of [A] /THA]- 3/1. How could the capacity (or strength) of the buffer be increased? Add more A to the buffer system Add more HA to the buffer system O Prepare a new buffer using a stronger acid (one with a larger Ka). Prepare a new buffer using a stronger base (one with a larger Kb)

Solution

Capacity or strength of the buffer defines the amount of added acid or base that can be neutralised by the buffer solution. Higher buffer capacity means large amount of addition of acid/base without any change in pH of the solution.

In case of acidic buffer, increase in buffer capacity requires greater dissociation of HA to produce more [H₃O⁺] which will neutralise the added base. Thus, K_a should increase.

By Henderson hasselbalch equation,

pH = pK_a + log{[A^-]/[HA]}

If K_a is increasing, so, pK_a is decreasing. To resist any change in pH of the solution, the second term log{[conjugate base]/[HA]} should increase i.e., [conjugate base] should increase.

Thus, to increase the buffer capacity, [A^-] should be added to buffer system.