Subject: Explain how proton balance controls pH.

An understanding of proton balance is essential to understanding and being able 
to solve any of the problems we are dealing with.  Everything is based on 
diagramming, e.g. equilibrium, distribution, alkalinity and buffer capacity, 
solubility, complex ions, etc.  Basic reading is "Aquatic Chemistry" by Werner 
Strumm and James J. Morgan.

An example of a problem we dealt with in class is: (and we STILL don't 
understand it!)

1.  Aqueous free chlorine is hypochlorous acid, HOCl, and hypochlorite ion, 
OCI(-), with the relative amounts depending on the pH of the solution.

a.  Given that pKa=7.5 for HOCl at 25 degrees C, what is the pH of a solution 
prepared by adding 10 (-3) mole of NaOCl to 1 liter of water?

b.  What is the pH at which 50 percent of the total free chlorine is present as 
HOCl?

2.  Using master variable diagramming, determine the concentrations of all 
chemical species and the pH of a 0.001 M (NH4)2 Se solution at 25C,  Consider 
ammonia gasd is toxic and odorous, how would you minimize volatilization?

Any  insight to the above problem would be greatly appreciated.

P.S. The educator worked this problem out in class, and we still are lost!

Re: Explain how proton balance controls pH.