3 posts / 0 new
Last post
Adam R. Johnson, Harvey Mudd College
Offline
Last seen: 2 weeks 6 days ago
Joined: 11/17/2007 - 10:55am

pKa prediction for oxyacids (oxoacids?)

I have in my notes from 9 years ago, this handy equation for prediction of pKa's for oxyacids.  I was using Huheey at the time, and the equation isn't there.  In fact, I can't find it ANYWHERE.  I am certain that I did not develop this equation.... Does anyone recognize it?  Where is it from?  And which electronegativity values does it use?

 

pKa ~ 10.5 -5n - (chi)X

for

(HO)mX(O)n;  chi is the electronegativity of the central atom X, n is the number of oxos.

I have found several other equations, but none of them take into account the central element...

 

its driving me crazy!

Adam

Nancy Scott Burke Williams, Scripps College, Pitzer College, Claremont McKenna College
Offline
Last seen: 3 days 15 hours ago
Joined: 11/17/2007 - 10:57am

Well, not exactly Pauling's per se, but his textbook popularized this one. It's Eqn. 9.46 on p. 329 of Huheey, Keiter, and Keiter, 4th Ed.

Adam R. Johnson, Harvey Mudd College
Offline
Last seen: 2 weeks 6 days ago
Joined: 11/17/2007 - 10:55am

ok, I looked through HKK since that was the book I was using at the time, and totally missed it.  That MUST be where I got it.  thanks!

Feeling old,

Adam