how-would-you-calculate-the-ph-at-the-isoionic-point-of-a-diprotic-acid-with-pka

Question

How would you calculate the pH at the isoionic point of a diprotic acid with pK_{a1} = 4.0 and pK_{a2} = 8.0?

Accepted Answer

Use the equation pH = 0.5(pK_{a1} + pK_{a2}) to get 6.0.

Answer

Use the equation pH = 0.5(pK_{a2} + pK_{a3}) to get 6.0.

Answer

Use the equation pH = pK_{a1} to get 4.0.

Answer

Use the equation pH = pK_{a2} to get 8.0.

How would you calculate the pH at the isoionic point of a diprotic acid with pKa1 = 4.0 and pKa2 = 8.0?