posted by mie on .
make 300.0 mL of a pH 5.30 buffer from 0.500 M acetic acid and 0.500 M sodium acetate. Calculate the volume of 0.500 M acetic acid and the volume of 0.500 M sodium acetate required to make 300.0 mL of a buffer solution with pH = 5.30.
(The Ka for acetic acid at 298 K is 2.00 x 10-5)
pH = pKa + log (base)/(acid)
5.30 = 4.699 + log(b/a)
b/a = 3.99 for one equation.
Second equation is
mLbase x 0.5M = mLacid x 0.5M
The 0.5M divides out. Substitute base 3.99*acid in the above and
solve for mL base and subtract from 300 to obtain mL acid. You should get something close to 120 and 31 but those aren't exact.