chemistry acid help???

Question

paraperiodic acid (H5IO6) is a diprotic which k1=2.8*10^-9 and k2= 5.3*10^-9

Compare ka and kb for H4IO6- to determine whether a solution containg that ion is acidic or basic?

Use values k1&k2 to estimate the PH at the first equvialence point in titration of a solution of paraperodic acid with NaOH. Does this PH agree with the answer in part A?

Thanks so much to anyone who helps/

Answer 1

Divide the first Ka into 10-14 to get Kb for the (H4IO6)- ion, 3.57 x 10-6.

Ka for this ion is about 1,000 times smaller, implying that the ion is a stronger base than it is an acid, and will be alkaline in solution.

the pH at first equivalence point can be estimated by looking at pH=pKa for the two Ka values given, and taking a half-way value. This is half way between 8.5 and 8.2, which certainly agrees with what I've written above.