Two 0.60 L buffer solutions are prepared at 25 °C using the same weak acid–conjugate…
CHEMISTRY · Single correct · A Level · Chemistry · Acids and bases · Acids and bases
Problem
Two 0.60 L buffer solutions are prepared at 25 °C using the same weak acid–conjugate base pair.
• Buffer C contains 0.10 mol weak acid (HA) and 0.20 mol conjugate base (A⁻).
• Buffer D contains 0.20 mol HA and 0.10 mol A⁻.
A small volume of 1.0 M HCl is to be added to one of the buffers.
Which statement is most accurate concerning the ability of the buffers to resist the pH change produced by the added HCl?
(a) Both buffers are equally effective because each contains the same total number of moles of buffering species.
(b) Buffer D is more effective because its larger amount of weak acid absorbs the added HCl.
(c) Buffer C is more effective because it contains the greater amount of conjugate base that neutralizes the added H+.
(d) Neither buffer is effective since the [A−]/[HA] ratio in each case differs from 1.0.