textbook problem 6E.1

[Essence Moua 2C]

When calculating for polyprotic acids, how do we know which form to calculate it for? How do we know to calculate the pH for in the equation HSO4- instead of H2SO4?

[Julia_Belysheva_3K]

When looking at the polyprotic acid H2SO4, the first dissociation is for that of a strong acid so the hydrogen ion concentration is the same as the concentration of H2SO4 since this strong acid dissolved completely. For the following dissociation, HSO4- is now a weak acid so a RICE table should be used to find the concentration of H+ (use the concentration of H+ from the first dissociation and add on the new H+ for the weak acid dissociation). From here, the pH of the polyprotic acid can be calculated using pH=-log[H+]