[CHM 112] Burdge Problem

[Andrew J. Pounds]

On 04/14/2013 04:29 PM,  wrote:
> On chapter 16, question 104, the equation set up was F- + H2O --> OH- 
> + HF. Why is it not HF --> H+ + F-?
>
> "What is the pH of 0.082M NaF, Ka for HF is 7.1E-11."

Because you were only given a compound (NaF) that contained the 
conjugate base (F-) of the Weak acid (HF).  There is no HF initially in 
the solution -- you form it as a result of the system establishing 
equilibrium.


  In this type of "hydrolysis" problem you write the equilibrium so that 
you make OH- and the weak acid HF.  This also requires that you modify 
the Ka value and convert it to a Kb.


-- 
Andrew J. Pounds, Ph.D.  (pounds at theochem.mercer.edu)
Associate Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://theochem.mercer.edu/pipermail/chm112/attachments/20130414/6f343d3b/attachment.html>