MurphyClox
Bluelighter
- Joined
- Mar 26, 2008
- Messages
- 1,416
1st deprotonation:Question: what's the pKb of carbonate (the *diprotonated* conjugate base of carbonic acid)? I confess I am in a depressive funk right now and have forgotten how to look up pKb's of conjugate bases of weak diprotic acids.
H2CO3 + H2O ---> HCO3- + H3O+
pKa = 3.88; But because the equilibrium CO2 + H2O -> H2CO3 lies very much on the left side (H2CO3 is unstable!), the first equation and the hydrolysis are usually combined to give a pKa = 6.5
2nd deprotonation:
HCO3- + H2O ---> carbonate + H3O+
pKa = 10.33
The relation between pKa & pKb is as follows:
pka + pkb = 14
Peace! - Murphy
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