consider the following titration curve for a diprotic acid, h2a: a titration curve showing p h on the y axis and volume of n a o h on the x axis has two areas of steep increase in between areas of more gradual increase. the midway point of the first steep increase is at p h 5.0. the midway point of the gradual increase afterwards is at p h 7.5. the midway point of the next steep increase is at p h 9.5. what is the value of pka1 for the diprotic acid?