[CHM 112] Burdge Chapter 17

[Andrew J. Pounds]

On 07/21/13 23:36, Mary Caroline Logan wrote:
> I have multiple questions about your solutions for these problems. But in general, I'm having trouble figuring out when to use the reaction producing OH- versus H3O+ (17.32), figuring out where/how you are coming up with various mole to mole ratios (17.30), and various Ksp values the book said was previously given and it wasn't written in your solutions (17.50).
>
> Caroline Logan
In 17.32 you have to figure out what is in solution (i.e. -- what is 
left over after the strong base and the weak acid react) before you can 
set up the equilibration.  Since the acid was completely consumed, and I 
had excess OH in solution, I had to write the equilibration reaction as 
shown.

In 17.30 they are simply doing a titration.  The only caveat is the the 
Ba(OH)2 is going to give you two OH-.

In 17.50 when I divide the mass by the molar mass to come up with the 
moles that are in solution, I finding the value of x that then has to be 
plugged into the Ksp expression.  In other words you are using the 
solubility data to find Ksp (Ksp was not given in this case).  Look back 
at my solutions -- if you plug in the value I determined for the 
solubility in moles/L as "x" in the Ksp expression you should get the 
Ksp value I listed in the solution.


-- 
Andrew J. Pounds, Ph.D.  (pounds_aj at mercer.edu)
Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627
http://faculty.mercer.edu/pounds_aj

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