Question

A solution of phosphate buffer at a pH of 6.82 with a pK2 = 6.82 would have more capacity to buffer the addition of

a) Hydrochloric acid
b) Sodium hydroxide
c) Acetic acid
d) Ammonia

Answer 1

The phosphate buffer at pH 6.82 will have the most capacity to buffer the addition of hydrochloric acid (HCl) because it can absorb the hydrogen ions released by the strong acid. The option (A) is correct.

Step-by-step explanation:

The question is about a phosphate buffer at a pH of 6.82, where the pK2 of the buffer system is also 6.82. At this optimal buffering point (pH = pK2), the buffer has equal amounts of its conjugate acid and base forms (HPO42- and H2PO4-). Buffers resist changes in pH when small amounts of an acid or a base are added.

Considering the given options, the buffer would have more capacity to buffer against the addition of:

1. Hydrochloric acid (HCl), because it is a strong acid and the buffer has an optimal capacity to soak up hydrogen ions (H+) added or generated by strong acids.

Adding a base to the buffer would result in a decrease in the buffer capacity relative to the addition of an acid, due to the consumption of HPO42- ions. Therefore, option (A) is correct.