consider a phosphate buffer, consisting of h2po4- and hpo42- . initially at the same ph as its pka (6.86) when concentrated sodium hydroxide is added to this buffer, the: a. ph increases more than when an equal amount of equal amount of naoh is added to unbuffered water at ph 6.86 b. ph remains constant c. ratio of [hpo42-] to [h2po4] in the buffer increases d. ph increases more than when an equal amount of naoh is added to a phosphate buffer initially at ph 5.0