Conjugate Acids and Bases

Moderators: Chem_Mod, Chem_Admin

Prina Patel 1H
Posts: 62
Joined: Fri Sep 25, 2015 3:00 am

Conjugate Acids and Bases

Postby Prina Patel 1H » Fri Nov 20, 2015 8:16 pm

I don't understand why the conjugate of a strong acid has to be a weak base and visa versa...Why is it like that?

Ronald Yang 2F
Posts: 86
Joined: Fri Sep 25, 2015 3:00 am

Re: Conjugate Acids and Bases

Postby Ronald Yang 2F » Fri Nov 20, 2015 9:56 pm

If an acid is a strong acid, it can easily donate a proton (Ka is big, since products favored). Thus, when you look at it's conjugate base, the conjugate base would not likely accept a proton, as it wouldn't want the H+ back that it so readily gave up. Think of it this way. An acid would technically disassociate into a proton and its conjugate base. If it's a strong acid, the reaction would favor the formation of that proton and that conjugate base. Thus, if we were to flip the equation so that the conjugate base and proton are now the reactants, the reaction would not favor the formation of that strong acid; it would favor the reverse reaction (thus the conjugate base's Kb would be small, since reactants favored). This is why the conjugate of a strong acid is a weak base, and vice versa.

Dulshan Jayasekera 3I
Posts: 20
Joined: Fri Sep 25, 2015 3:00 am

Re: Conjugate Acids and Bases

Postby Dulshan Jayasekera 3I » Fri Nov 20, 2015 10:18 pm

We also know that Ka x Kb = Kw, with Kw being a constant of 1.0X10^14. So according to this equation, increasing Ka would mean Kb needs to decrease and vice versa, so if you have a strong acid, you automatically get a weaker conjugate base. Hope this helps


Return to “Conjugate Acids & Bases”

Who is online

Users browsing this forum: No registered users and 2 guests