Chem
posted by Sean on .
A buffer contains 1.0mol CH3CO2H and 1.0mol CH3CO2^ diluted with water to 1.0L. How many moles of NaOH are required to increase the pH of the buffer to 5.10? (pKa oof Ch3CO2H=4.74)

You want to use the HendersonHasselbalch equation,
pH = pKa + log (base/acid)
First, plug in 5.10 for pH and 4.74 for pKa, and solve the HH equation for B/A ratio.
Then look at the equation if you add OH^ to the buffer solution. It will neutralize acid to produce more acetate at the expense of CH3COOH.
CH3COOH + OH^ ==> CH3COO^ HOH
Here is what I would do.
Let x = moles OH^ to be added which is what the problem asks for.
You are starting with 1 mole CH3COOH and 1 mole CH3COO^
At the end of x moles OH^, the concns are
1x for CH3COOH (acid) and 1+x for CH3COO^ (base).
Now plug those into the B/A you solved for above and solve for x.
Then to make sure you are right, plug B and A back into the HH equation and see if you end up with pH of 5.01. Post your work if you get stuck. It may sound complicated but it really is straight forward.