Solving for polyprotic acids and bases

[samanthaywu]

When solving for the equilibrium concentrations of polyprotic acids and bases, do we always have to break them into individual protonations of one H+ ion released / gained for each reaction and use the Ka1, Ka1, etc.?

[Gwendolyn Hill 2F]

I think so; this method seems to work to organize the equations and show the ionization stepwise. For example, polyprotic acids like H3PO4, H2PO4-, and HPO4(2-) will always show that each ionization step is more difficult, since it's more difficult to remove H+ from a molecule as its negative charge increases. Doing the step method will show us that, with
Ka1>Ka2>Ka3

[Juwon Lim 2A]

I believe so. And to find the overall K of the reactions, we would just multiply the K values we found.

[Jiwon_Chae_3L]

Yeah, I think that we need to break the reactions down into individual protonations.

[Lisa Seidl 3H]

Yes, from what I understood from the textbook, it doesn't seem like we would need to use anything more than the first protonation for a lot of them since the later ones are negligible but that would be the easiest way to solve it if you do have to use the other values.