# Ionisation constants

1. Mar 2, 2006

### chound

If 6.8 * 10-4 is ionisation constant(IC) of HF, what is the IC of its conjugate base.

HF +H2O -----> H3O+ +F-
So F- is the conjugate base(CB)
I figured the IC of CB would be the reciprocal of IC of HF. But the answer given is the same but multiplied by Ionic product of water i.e. 10-14

2. Mar 6, 2006

### siddharth

Ionisation of the conjugate base? Isn't it already ionised?

Perphaps you mean the basicity constant for the equilibirium
F- + H2O ----> HF + OH-

In that case, won't it be Kw/Ka?

Last edited: Mar 6, 2006
3. Mar 6, 2006

### GCT

yep, that's what is meant the ionization constant, in this problem. For the base it can also be called the hydrolysis constant, Kb